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Negative dysphotopsia: Causes and rationale for prevention and treatment
Abstract
Purpose
To determine the cause of negative dysphotopsia using standard ray-tracing techniques and identify the primary and secondary causative factors.
Setting
Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.
Design
Experimental study.
Methods
Zemax ray-tracing software was used to evaluate pseudophakic and phakic eye models to show the location of retinal field images from various visual field objects. Phakic retinal field angles (RFAs) were used as a reference for the perceived field locations for retinal images in pseudophakic eyes.
Results
In a nominal acrylic pseudophakic eye model with a 2.5 mm diameter pupil, the maximum RFA from rays refracted by the intraocular lens (IOL) was 85.7 degrees and the minimum RFA for rays missing the optic of the IOL was 88.3 degrees, leaving a dark gap (shadow) of 2.6 degrees in the extreme temporal field. The width of the shadow was more prominent for a smaller pupil, a larger angle kappa, an equi-biconvex or plano-convex IOL shape, and a smaller axial distance from iris to IOL and with the anterior capsule overlying the nasal IOL. Secondary factors included IOL edge design, material, diameter, decentration, tilt, and aspheric surfaces.
Conclusions
Standard ray-tracing techniques showed that a shadow is present when there is a gap between the retinal images formed by rays missing the optic of the IOL and rays refracted by the IOL. Primary and secondary factors independently affected the width and location of the gap (or overlap). The ray tracing also showed a constriction and double retinal imaging in the extreme temporal visual field.
... One theory states that the IOL does not focus light at considerable visual angles because it is much smaller than the natural crystalline lens it replaces [2,3]. Ray-tracing optical modeling, especially Holladay's extensive work in this field, proposed that there is "a shadow when there is a gap between the retinal images formed by rays missing the optic of the IOL and rays refracted by the IOL" [4]. An experimental model in phakic eyes that simulates what happens in pseudophakic eyes with an annular opaque contact lens supports the hypothesis of light obstruction from the far temporal field [5]. ...
... It has been reported that IOL tilt and decentration do not cause dysphotopsia [13], and most authors agree that ND is invariably associated with in-the-bag IOLs [14]. Table 1 includes primary and secondary factors known to increase the risk of ND, as reported by Holladay and Simpson [4]. There have been several strategies reported for the treatment of negative dysphotopsia, like intraocular lens optic truncation [15], sulcus-fixated IOL implantation [12], dedicated IOLs designed to treat ND [12,16], or ring implantation [17]. ...
... Persistent ND has been treated successfully or reduced with procedures like anterior optic capture, sulcus IOL placement, and neodymium:yttrium-aluminum-garnet nasal capsulotomy, among others [12,15,16,20,21]. Studies have established several factors that influence the incidence of ND, like pupil size or the power or design of IOLs [4]. Since controlling all variables in a clinical study on this topic is not feasible, we decided to focus on a strategy that would not alter the refractive objective or surgical plan of phacoemulsification and, therefore, minimize any unnecessary risks derived from the study. ...
Phacoemulsification is the standard of care in cataract surgery in the developed world, with patients having high expectations regarding visual results. Postoperative dissatisfaction due to negative dysphotopsia (ND) ranges from rare to very frequent; its etiology is unclear, and it affects postoperative satisfaction. Since one of the most frequently used strategies to avoid ND is related to intraocular lens (IOL) haptic orientation, we conducted a prospective interventional study that enrolled 197 patients who underwent standard phacoemulsification. All patients had a one-piece hydrophobic acrylic IOL implanted; in one group, the haptics were placed in any meridional axis except inferotemporal (IT) meridians, and in the other group, the IOL was implanted with the haptics in an IT position. Our results showed no statistically significant differences between groups when analyzing the correlation between the position of IOL haptics and the presence of ND in week one and month one. Also, pupillary diameter showed no statistically significant differences between patients with or without ND. Despite some studies claiming that haptic orientation prevents ND, we found that haptic orientation does not correlate with ND incidence and that ND decreases from day 1 to month 1. Our results support previous findings on the decrease in ND over time and that haptic orientation should not be considered an intraoperative strategy to avoid this unwanted phenomenon.
... Рівнодвоопуклі ІОЛ (рис.2 Б) з вищою діоптричною силою створюють підвищений ризик негативної дисфотопсії [21]. ...
... 3. З'ясовано значення впливу квадратного краю оптики ІОЛ на розвиток негативної дисфотопсії. Holladay J. T. також підтримує точку зору Osher і Cooke про те, що "постійна негативна дисфотопсія, схоже, має відношення до контуру оптики ІОЛ, -перш за все, до її усіченого квадратного краю або до показника заломлення цього краю" [21]. Скарги хворих на негативну дисфотопсію після факоемульсифікації вікової катаракти з імплантацією ІОЛ стали частіше з'являтися в 1990-х роках. ...
... Певний вплив на розвиток негативних дисфотопсій має розмір переднього капсулорексису. Крім цього, дослідження виявили, що відбиття від краю переднього капсулорексису проектується на носові відділи периферії сітківки, при цьому якщо відбувається покриття оптичної частини ІОЛ передньої капсулою, то скарги на НД виникають набагато Рис. 2. Схема світлорозсіювання при опукло-плоских (А), двояко-опуклих(Б) і плоско-опуклих (В) ІОЛ [21] Рис. 3. Хід променів через квадратний край і частково закруглений край оптики ІОЛ [22]: 1 -промені, що проходять уздовж поверхні ІОЛ; 2 -промені, що проходять через передній край лінзи, відхиляються назад; 3 -промені, що проходять через задній край лінзи, відхиляються вперед. Тінь утворюється між променями 2 і 3 (а): промінь 2, що проходить через точку Р, визначає задню, а промінь 3, що проходить через точку А, -передню межу тіні. ...
Modern technologies of examining cataract patients and phacoemulsification with implantation of the posterior chamber intraocular lens (IOL) commonly allow achieving the desired anatomical outcome and a high functional outcome after surgery. The development of postoperative dysphotopsias in patients with a posterior chamber IOL, however, requires a separate consideration. Dysphotopsia can develop practically in any eye with the IOL after cataract surgery and in some cases can affect postoperative vision, which hinders the patient from resuming working life as usual. Clear systemic guidelines for preventing postoperative dysphotopsia are still to be developed.
... Currently, there are no specific objective tests available to diagnose ND, although it is accompanied by demonstrable far peripheral visual field changes on Goldmann kinetic testing [4]. The prevailing understanding suggests that ND arises from a complicated interaction between IOL optics and the anatomical predisposition of the eye [5]. Notable primary risk factors for developing ND include smaller photopic pupils, larger positive angle ĸ, nasal anterior capsule overlying the in-the-bag IOL, and higher dioptric IOL power [5]. ...
... The prevailing understanding suggests that ND arises from a complicated interaction between IOL optics and the anatomical predisposition of the eye [5]. Notable primary risk factors for developing ND include smaller photopic pupils, larger positive angle ĸ, nasal anterior capsule overlying the in-the-bag IOL, and higher dioptric IOL power [5]. In recent years, supplementary IOL implantation in the sulcus has become more popular to treat ND. ...
... An angle ĸ value higher than 3.26 degrees was considered abnormally high [12]. A standard approximation conversion of 7.5 degrees to 1 mm was used; converting a Chang-Waring chord length value above 0.44 mm as abnormally high [5]. ...
Negative dysphotopsia (ND) refers to the subjective perception of an arc-shaped darkness or shadow in the temporal field of vision. This condition occurs after uneventful cataract surgery with an in-the-bag intraocular lens (IOL). To address this issue, supplementary implantation of conventional three-piece IOLs in the sulcus or dedicated supplementary Rayner Sulcoflex® IOL have been used successfully. The aim of this retrospective case series was to assess the effectiveness of resolving ND using a supplementary 1stQ AddOn® (Medicontur) IOL. The 1stQ AddOn® has a different design and optic size compared to the Rayner Sulcoflex®. Patients experiencing severe and persistent ND underwent supplementary implantation of the 1stQ AddOn® IOL. The primary outcome measure was the resolution of dysphotopsia. Nine eyes received the 1stQ AddOn® IOL, with complete symptom resolution observed in 6 eyes, partial improvement in 1 eye, and no change in 2 eyes. This indicates that supplementary implantation of the 1stQ AddOn® IOL can effectively and safely treat ND, performing equally well as the Rayner Sulcoflex®. The positive impact of sulcus-fixated supplementary IOLs seems to be related to the interaction between the central optic and the pupil margin.
... Recent evaluations of bothersome "dark shadows" that are seen by some intraocular lens (IOL) patients in the far periphery [5,6] have led to questions about far peripheral vision. The use of IOLs has increased in recent decades, and an evaluation of one county in Minnesota found that about 7% of the entire population had at least one IOL, mostly in an older age group, with about 50% of those aged over 75 having at least one IOL [7]. ...
... This is consistent with surgical cases exceeding 3.5 million per year in the US. Recent theoretical calculations indicate that all eyes with an IOL (often called pseudophakic eyes) probably have a difference in vision in the far periphery compared to their own earlier phakic eye, whether or not they see bothersome shadows [5,6], though IOL patients rarely report changes. ...
... Optical modeling of the pseudophakic eye very clearly demonstrates, however, that it is simply not possible for light to pass through the optical portion of a conventional IOL and reach the far periphery because the light is vignetted at the IOL edge [6,25]. IOLs had never specifically been designed to provide vision over the complete range of visual angles, and even when negative dysphotopsia became a concern it seemed likely initially that the issue might be something to do with the corneal incision, or the lens itself, or capsular opacification, or some other unknown variable, rather than to be something related to the size of the IOL and to the far periphery [5,26]. ...
Vision is rarely evaluated scientifically at very large visual angles, despite being used continuously in everyday life. Furthermore, raytrace calculations indicate that peripheral optical properties are different for a pseudophakic eye, and even though this is rarely noted by patients, it is probably the cause of bothersome “negative dysphotopsia.” Simplified paraxial parameters that characterize the basic properties of phakic and pseudophakic eyes are collected together here as a baseline, and then raytracing is used to show that input angles of about 60°, which correspond to obstruction by the nose, eyebrow, and cheek, illuminate a retinal hemisphere. At larger angles in the temporal direction, the image with an intraocular lens (IOL) reaches a limit due to vignetting at about a 90° input angle to the optical axis, in comparison to 105° with the Gullstrand–Emsley eye model, and 109° for the most realistic gradient index crystalline lens model. Scaling the far peripheral vision region more accurately may lead to benefits relating to intraocular lenses, diseases of the peripheral retina, widefield fundus images, and myopia prevention.
... The etiology of ND is not clearly defined, and the cause seems to be multifactorial. Holladay and Simpson categorized the risk factors for ND development into three groups: anatomic characteristics (pupil size, hyperopia, and angle kappa), IOL properties (IOL surface steepness, edge design, dioptric power, and refraction index), and surgical technique for cataract removal (optic-haptic junction orientation and position of nasal anterior capsule to the IOL surface) [34]. There is also a possibility that central nervous system adaptation mechanisms could be involved in the ND development, although they are not yet clearly understood [35,36]. ...
... The most supported working theory for temporal visual field shadow occurrence in pseudophakic patients with ND is the illumination gap of the nasal retina [34]. The illumination gap is caused by different refraction of rays that hit the IOL optic periphery to those that miss the IOL (Figure 3) [3,7,34]. ...
... The most supported working theory for temporal visual field shadow occurrence in pseudophakic patients with ND is the illumination gap of the nasal retina [34]. The illumination gap is caused by different refraction of rays that hit the IOL optic periphery to those that miss the IOL (Figure 3) [3,7,34]. The illumination gap is bounded posteriorly by the rays refracting on IOL optic periphery and anteriorly by the rays missing the IOL which are not refracted [7,34,37]. ...
Dysphotopsias are unwanted visual phenomena that occur after cataract surgery. They represent some of the most common reasons for patient dissatisfaction after uncomplicated surgery for cataract phacoemulsification with in-the-bag intraocular lens (IOL) implantation. Depending on the form of the optical phenomenon and the effect it poses on vision, dysphotopsias are divided into positive and negative type. Positive dysphotopsias are usually described by patients as glare, light streaks, starbursts, light arcs, rings, haloes, or flashes of light. Negative dysphotopsias are manifested as an arc-shaped shadow or line usually located in the temporal part of the visual field, similar to a temporal scotoma. In addition to their different clinical manifestations, positive and negative dysphotopsia also have different risk factors. Even though up to 67% of patients may experience positive dysphotopsia immediately after surgery, only 2.2% of the cases have persistent symptoms up to a year postoperatively. Surgical intervention may be indicated in 0.07% of cases. The incidence of negative dysphotopsias is up to 26% of all patients; however, by one year postoperatively, the symptoms usually persist in 0.13 to 3% of patients. For both types of dysphotopsia, preoperative patients’ education, accurate preoperative diagnostics, and use of an appropriate IOL design and material is mandatory. Despite all these measures, dysphotopsias may occur, and when noninvasive measures fail to improve symptoms, a surgical approach may be considered.
... Recent efforts to model the eye in the far periphery have led to re-evaluating optical parameters that are useful for all lenses. The starting point was an evaluation into why the nodal point can be a useful reference for scaling the retinal image at very large angles, even though the nodal point of a lens system is a paraxial property [1][2][3]. The earlier work was for a "pseudophakic" eye, where an intraocular lens (IOL) had been implanted during cataract surgery. ...
... The earlier work on IOLs came about because some patients see bothersome dark shadows in their far peripheral vision. This led to finding that the far periphery had never been modeled for the eye and that, when it was modeled in raytrace software with an IOL, the main focused image is vignetted at large angles, leading to the primary image going totally dark [2,4]. However, light can also miss the IOL and illuminate the retina directly, and it is likely that these characteristics are the cause of bothersome shadows with small pupils, though there is still no consensus about this as the cause of "negative dysphotopsia," as it is called clinically [2,[5][6][7][8]. ...
... This led to finding that the far periphery had never been modeled for the eye and that, when it was modeled in raytrace software with an IOL, the main focused image is vignetted at large angles, leading to the primary image going totally dark [2,4]. However, light can also miss the IOL and illuminate the retina directly, and it is likely that these characteristics are the cause of bothersome shadows with small pupils, though there is still no consensus about this as the cause of "negative dysphotopsia," as it is called clinically [2,[5][6][7][8]. Matching retinal locations to visual angles in the far periphery is problematic because there is a double image effect. ...
Nodal points are defined using parallel object and image rays at very small angles to the optical axis, and Johann Listing described them when characterizing the eye in 1845. They are only distinct from principal points when there is a refractive index difference, but Reginald Clay used the term “nodal slide” in 1904 for equipment that uses lens rotation when measuring a lens focal length in air. Over time, sketches of nodal rays at large angles have become common, and these perhaps appear to support observations that input angles to the eye match image angles measured to the nodal point. Raytrace calculations confirm that this is correct for very large angles, but the relationship comes from the cornea curving around, towards incoming light, angles being rescaled at the exit pupil by a constant factor, and then the retina curving around to meet the image rays. The eye has high linearity, with 1:1 angular scaling occurring at approximately the nodal point, but ray bundles passing through the pupil center, rather than paraxial nodal rays, define the optical properties.
... (12) Holladay, en un primer artículo publicado en el año 2012, atribuyó la DN a la sombra que se forma entre los rayos refractados por el borde anterior y posterior de un LIO de bordes truncados, al ser proyectados en diferentes lugares de la retina nasal, dejando un espacio no iluminado entre ellos (llamada sombra Tipo 3 este artículo). (3) Posteriormente, un artículo publicado en 2016 por Holladay y Simpson, (13) con una metódica similar basada en análisis de trazado de rayos usando un modelo óptico con una abertura pupilar de 2,5 mm, Revista Cubana de Oftalmología 2021;34(2):e1006 5 Esta obra está bajo una licencia: https://creativecomons.org/licenses/by-nc/4.0/deed.es_ES sugirieron que la causa más probable de la sombra era el espacio no iluminado, delimitado por delante por los rayos que pasan por la pupila sin alcanzar el borde del LIO, y por detrás por los rayos refractados por la cara posterior nasal del lente (Fig. 1). ...
... Hay un grupo de factores que aumentan el riesgo de aparición de la DN, los que han sido divididos en factores primarios y secundarios. (13) Pensamos que para su mejor comprensión es preferible agruparlos en 3 grupos de factores: asociados al paciente, al lente intraocular y a la cirugía de catarata. ...
... Ángulo kappa (k) y descentrado de la pupila: El ángulo formado entre el eje visual (línea que conecta el punto de fijación con la fóvea) y el eje pupilar (línea a través del centro de la pupila perpendicular a la córnea) se denomina ángulo kappa. Se sabe que un valor elevado de este ángulo, en donde el ojo gira temporalmente (más frecuente en hipermétropes), aumenta la exposición de la retina nasal y contribuye a la aparición de la DN. (13) Por otro lado, la pupila está desplazada nasalmente unos 2,6 grados (0,3 mm en la córnea) en promedio, por lo que está más cerca del borde nasal del LIO y altera el ángulo visual retinal. La exposición de la retinal nasal es mayor respecto a la temporal. ...
Negative disfotopsia is an important cause of patient´s dissatisfaction after an uncomplicated cataract surgery. The affected individuals perceive a dark shadow on the temporal visual field, in the form of a crescent or arc, that transforms in frustrating a postsurgical result otherwise considered as successful. Given the several articles published on this topic, this review hopes to summarize the most up-to-date literature about this optic phenomenon considering its causes, associated factors, diagnosis and current treatment.
... An evaluation of why a small number of patients with intraocular lenses (IOLs) see bothersome dark shadows in the far periphery (negative dysphotopsia) involved modeling the eye at very large visual angles [1][2][3][4]. During this work, it was found that the intersection angle of the chief ray with the retina was substantially the same as the input visual angle over a very large range when it was calculated relative to the optical axis from the second nodal point (NP2) [2,5]. ...
... An evaluation of why a small number of patients with intraocular lenses (IOLs) see bothersome dark shadows in the far periphery (negative dysphotopsia) involved modeling the eye at very large visual angles [1][2][3][4]. During this work, it was found that the intersection angle of the chief ray with the retina was substantially the same as the input visual angle over a very large range when it was calculated relative to the optical axis from the second nodal point (NP2) [2,5]. This would be expected for small angles, but it was not clear why that would also be the case for angles as large as 70-90 • , and that is evaluated here. ...
... An average pseudophakic model eye that has been described before [2] was evaluated using the Zemax raytrace software (Zemax, Kirkland, WA, USA). It had been found previously that phakic and pseudophakic eye models had broadly similar behavior, and retinal scaling for a phakic eye model had been used to evaluate a pseudophakic eye [2,3,14]. The model eye was also simplified to be rotationally symmetric by removing the decentration of the IOL and using the optical axis as the reference (which is typically rotated 5 • from the visual axis (Figure 1)). ...
Angles subtended at the second nodal point of the eye (NP2) are approximately the same as input visual angles over a very large angular range, despite the nodal point being a paraxial lens property. Raytracing using an average pseudophakic eye showed that the angular nodal point criterion was only valid up to about 10°, and that the linear relationship was due instead to the cornea and lens initially creating chief ray angles at the exit pupil that are about 0.83 times input values for this particular eye, and then by the retina curving around to meet the rays in a manner that compensates for increasing angle. This linear relationship is then also maintained when retinal intersections are calculated relative to other axial points, with angles rescaled approximately using the equation R/(R + delta), where delta is the axial distance from the center of a spherical retina of radius R. Angles at NP2 approximately match the input angles, but the terminology is misleading because this is not a paraxial property of the eye. Chief rays are used with finite raytracing to determine the actual behavior.
... Many potential factors of influence have been proposed, including pupil size, angle k, size of the capsular overlap, diffusiveness of the capsular bag, position of the intraocular lens (IOL) about the iris, design of the IOL, and extent of the functional nasal retina. 2,5,9,10,[14][15][16][17] For most of these factors, clinical validation based on evaluations of larger patient groups has not yet been reported. Recently, we combined multiple optical evaluations to establish clinical support for a smaller pupil size, a more temporally displaced pupil center, a stronger temporally tilted iris, and a difference in peripheral refraction in patients with ND compared with pseudophakic patients without complaints. ...
... 18 Because the result of this study showed that the IOL is aligned with the iris, it strengthens the idea that the complete eye of patients with ND is rotated more toward the temporal side of the head instead of solely the iris, which is in line with the thought that patients with ND might have a larger angle between the optical and visual axis. 14,18 The retinal shape, quantified by the radii of a fitted ellipse in AP and LR directions, showed comparable radii in both patients with ND and pseudophakic controls, which were, on average, larger in the LR direction in both groups (Table 3 and Figure 5). These radii correlated significantly with the axial length, which correspond to the earlier described correlations of similar measurements with refraction and of axial length with refraction. ...
... [8][9][10][11][12][13] Furthermore, they could include the proposed optical effects caused by the lens capsule, although this should not exclude clinical measurements confirming their presence in the ND population. 14,16 Because MRI, computed tomography, and ultrasound are generally not sensitive to these optical changes of the tissue, an optical imaging modality, capable of assessing the edge of the IOL, is probably required. ...
Purpose:
Assessment of potential relationships of intraocular lens (IOL) position and retinal shape in Negative Dysphotopsia.
Setting:
Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.
Design:
Case-control study.
Methods:
High-resolution ocular MRI scans were performed in thirty-seven patients with negative dysphotopsia (ND) and twenty-six pseudophakic controls and used to determine the displacement and tilt of the in-the-bag IOL with respect to the pupil and iris. Additionally, anterior segment tomography was used to assess the iris-IOL distance. Furthermore, the retinal shape was quantified from the MRI-scans by fitting an ellipse to the segmented inner boundary of the retina. Both the IOL position and retinal shape were compared between groups to assess their potential role in the etiology of ND.
Results:
The average displacement and tilt of the IOL were below 0.1 mm and 0.5 degrees, respectively, in both groups and all directions. The corresponding average iris-IOL distance was 1.1 mm in both groups. Neither of these values differed significantly between groups (all p-values > 0.6). The retinal shape showed large variations but was not significantly different between the groups in both the left-right (p=0.10) and the anterior-posterior (p=0.56) direction.
Conclusions:
In this study, we showed that the in-the-bag IOL position and retinal shape are not significantly different between patients with ND and the general pseudophakic population. Given the large variation in retinal shape between subjects, however, it could still be an important factor in a multifactorial origin of ND.
... Some authors tried different simulations in different eye models to find a cause for ND. Holladay et al found in one eye model, that a shadow is present when some rays miss the optic of the IOL [14]. Besides, Holladay et al found that a small pupil, an axial space behind the iris, and a sharp optic edge are predisposing factors for ND, as well as the angle kappa and the nasal location of the pupil relative to the optical axis [4]. ...
... (Table 2) The iris -IOL distance was also slightly smaller in our ND group, but due to the larger spreading of the data, there was no statistically significant difference (Table 2), which can be due to the fact that the imaging of the lens behind the iris is not so precise with the Pentacam as measuring the anterior chamber depth through the pupil, because Scheimpflug cameras don`t provide direct visualization of the lens behind the iris [20]. Altogether, our finding is in accordance with the theory of Holladay et al [14], who suggested that a smaller Iris-IOL-distance is a factor associated with negative dysphotopsia. ...
Purpose : To describe the incidence and characteristics of negative dysphotopsia (ND) as well as the risk factors contributing to it. Methods : For this retrospective study, data from patients who underwent cataract surgery between January 2018 and December 2019 at our department (Department of Ophthalmology, Hietzing Hospital, Vienna, Austria) was analyzed. A total of 8122 eyes had cataract surgery performed. Three different intraocular lenses (IOLs) have been used (EyeCee® One by Bausch + Lomb, TECNIS® by Johnson & Johnson, HOYA Vivienx ™ by HOYA). Data from patients who postoperatively complained about ND as well as data from a gender and age-matched control group (34 eyes in each) was further analyzed: pupil size, axial length, anterior chamber depth, angle kappa, IOL power and other biometrical factors. The scotomas were depicted on a Harms tangent screen. Results : An incidence of 1.99% of ND was found, of which 1.58% was transient and 0.42% persistent. The average duration of the symptoms was 5.40 (±6.15) weeks in the transient ND group. In the total cohort of 8122 eyes, there was no difference in the distribution of implanted IOL types or IOL power; neither played the surgeon a significant role in the development of ND. There was no significant difference between ND and control eyes regarding pupil size, axial length, and angle kappa. The anterior chamber was significantly shallower in the ND group: 5.1±0.58mm vs. 5.41±0.61mm (p=0.03). Conclusion : According to our findings, a shallower anterior chamber poses a risk to the development of ND.
... It usually represents with dark crescent shaped shadow in temporal peripheral visual field. Holladay et al. [58] demonstrated through ray tracing method that far peripheral retinal image beyond 80 • of visual field angle is contributed by two optical paths; the rays refracted by intraocular lens itself and those missed by the IOL. The negative photopsia results from the gap between these two retinal images. ...
... They found the IOL decentration and tilt to be one of the secondary factors contributing towards this visual phenomenon alongside IOL material, diameter, edge design and aspheric surfaces. However, the primary contributory factors were observed to be smaller pupil size, larger angle kappa, a bi-convex or plano-convex IOL shape with smaller iris-to-IOL distance and anterior capsule overlying nasal IOL edge [58]. ...
Tilt and decentration of intraocular lenses (IOL) may occur secondary to a complicated cataract surgery or following an uneventful phacoemulsification. Although up to 2-3 • tilt and a 0.2-0.3 mm decentration are common and clinically unnoticed for any design of IOL, larger extent of tilt and decentration has a negative impact on the optical performance and subsequently, the patients' satisfaction. This negative impact does not affect various types of IOLs equally. In this paper we review the methods of measuring IOL tilt and decentration and focus on the effect of IOL tilt and decentration on visual function, in particular visual acuity, dysphotopsia, and wavefront aberrations. Our review found that the methods to measure the IOL displacement have significantly evolved and the available studies have employed different methods in their measurement, while comparability of these methods is questionable. There has been no universal reference point and axis to measure the IOL displacement between different studies. A remarkably high variety and brands of IOLs are used in various studies and occasionally, opposite results are noticed when two different brands of a same design were compared against another IOL design in two studies. We conclude that <5 • of inferotemporal tilt is common in both crystalline lenses and IOLs with a correlation between pre-and postoperative lens tilt. IOL tilt has been noticed more frequently with scleral fixated compared with in-the-bag IOLs. IOL decentration has a greater impact than tilt on reduction of visual acuity. There was no correlation between IOL tilt and decentration and dysphotopsia. The advantages of aspheric IOLs are lost when decentration is >0.5 mm. The effect of IOL displacement on visual function is more pronounced in aberration correcting IOLs compared to spherical and standard non-aberration correcting aspherical IOLs and in multifocal versus monofocal IOLs. Internal coma has been frequently associated with IOL tilt and decentration, and this increases with pupil size. There is no correlation between spherical aberration and IOL tilt or decentration. Although IOL tilt produces significant impact on visual outcome in toric IOLs, these lenses are more sensitive to rotation compared to tilt.
... As to the previous second erroneous assertion-the rationale that light cannot enter from the side-the answer is simply that the cornea protrudes in the eyeball so that light from the side gets refracted enough to enter the pupil. Figure 8A shows a ray-trace model by Holladay and Simpson (2017). With both a 2.5-mm and 5-mm pupil, the model predicts a maximum horizontal angle of 109 eccentricity. ...
... (A) Ray-trace model of how light enters the eye at the maximum angle for a 5-mm pupil(Holladay & Simpson, 2017, Figure 3A). (B) Pupil as seen from an angle of 80 on the temporal side(Mathur et al., 2013, Figure 5). ...
Crowding has become a hot topic in vision research, and some fundamentals are now widely agreed upon. For the classical crowding task, one would likely agree with the following statements. (1) Bouma’s law can be stated, succinctly and unequivocally, as saying that critical distance for crowding is about half the target’s eccentricity. (2) Crowding is predominantly a peripheral phenomenon. (3) Peripheral vision extends to at most 90° eccentricity. (4) Resolution threshold (the minimal angle of resolution) increases strongly and linearly with eccentricity. Crowding increases at an even steeper rate. (5) Crowding is asymmetric as Bouma has shown. For that inner-outer asymmetry, the peripheral flanker has more effect. (6) Critical crowding distance corresponds to a constant cortical distance in primary visual areas like V1. (7) Except for Bouma’s seminal article in 1970, crowding research mostly became prominent starting in the 2000s. I propose the answer is “not really” or “not quite” to these assertions. So should we care? I think we should, before we write the textbook chapters for the next generation.
... We explained this dilemma to the patient, and he opted for the SSF-IOL without the implantation of an artificial iris. Typical rigid poly methyl methacrylate (PMMA) IOL designed for suspension has superior long-term stability and relatively larger optics, which could cause minimal dysphotopsia [7][8][9]. According to the IOL-master biometer (Carl Zeiss Meditec AG, Jena, Germany), the + 22.5 D CZ70BD (Alcon Laboratories, Fort Worth, TX, USA) was selected for the patient. ...
Background
A modified surgical technique of sutured scleral fixated intraocular lens (SSF-IOL) was applied in a patient with post-traumatic aniridia and aphakia.
Case presentation
A 51-year-old man was referred to our clinic with decreased vision (finger count) in his right eye. This patient had previously undergone primary repair of the ruptured globe and pars plana vitrectomy to manage ocular trauma in the same eye. On presentation, the best corrected visual acuity in his right eye was 20/40. The slit lamp examination of his right eye revealed loss of total iris and lens. Corneal endothelial cell density was 1462 cells/mm². Fundoscopic examination of the right eye revealed a retinal attachment. For IOL implantation, a rigid poly methyl methacrylate IOL was used with a 2-point scleral fixation performed using a polypropylene suture. One year postoperatively, the uncorrected distance visual acuity was 20/32, and the manifest refraction was − 0.5/–1.5 × 130 (20/20). Pentacam revealed that the astigmatism of the anterior corneal surface and the total cornea was 1.1 D (axis: 59.8°) and 1.0 D (axis: 35.6°), respectively. The horizontal (3°–183°) cross-section image displayed an IOL with a 1° tilt and 0.425 mm decentration. The patient reported no dysphotopsia or photophobia and was satisfied with the visual results. OPD-scan III revealed that higher-order aberrations in the right eye were slightly higher than those in the left eye. No suture-related or other serious complications were observed.
Conclusion
The modified SSF-IOL technique can offer improved visual quality for patients with aniridia and aphakia by ensuring proper IOL positioning and reducing astigmatism.
... This condition appears to be more common in the cases of narrow pupils and long eyes. [45] Pupils that are too large determine an increase in HOAs, which favor the onset of halos, glare, and positive dysphotopsia. On the contrary, pupils that are too narrow favor negative dysphotopsia and the "starburst" phenomenon caused by the diffraction of light rays that hit the pupillary edge. ...
Purpose
To estimate the pupil size (at the iris plane) under photopic (P PH ) and scotopic (P S ) conditions after phacoemulsification with intraocular lens (IOL) implantation.
Methods
This retrospective observational cohort study included 190 virgin eyes from 190 patients who underwent cataract surgery with IOL implantation. Data collected with Aladdin (Topcon), AS-OCT MS-39 (CSO), and iTrace (Tracey) were SimK, mean pupillary power at 6 mm (MPP), anterior chamber depth (ACD), lens thickness (LT), axial length (AL), lens rise (LR), P PH and P S before and after surgery at 30 days, dysfunctional lens index, and opacity grade. The position of the postoperative iris plane (PIP) was measured manually with MS-39, and a multivariate regression formula was developed to predict it. Statistical analysis was performed using Statistical Package for Social Science (SPSS) (IBM).
Results
The mean and standard deviations were 42.61 ± 3.20 D for MMP at 6 mm, 3.35 ± 0.37 mm for ACD, 3.89 ± 0.18 mm for PIP ( P < 0.01), 4.55 ± 0.42 mm for LT, 0.43 ± 0.24 mm for LR, and 25.91 ± 3.03 mm for AL. The mean preoperative and postoperative topographic pupil magnification was 12% and 14.22%, respectively ( P < 0.01). Despite an increase in magnification, the postoperative pupil was smaller than the preoperative one both for scotopic and photopic conditions: The larger the preoperative pupil, the more it tends to reduce in the postoperative period.
Conclusions
Analysis of the preoperative topographic pupil alone is not sufficient for a correct indication of the optical zone and total diameter of IOL to be implanted but must be correlated with biometric data. The topographic pupil, therefore, undergoes a change in magnification from the preoperative period to the postoperative period. Furthermore, the real pupil presents a modification and, in most cases, tends to be smaller postoperatively in both photopic and scotopic conditions.
... In a study using the standard ray-tracing technique, it has been reported that a shadow is formed between retinal images when a gap occurs between the rays that miss the IOL and the rays that are reflected from the IOL. In another study, it was suggested that if the kappa angle is wide, the light enters the eye through different diffraction rings, and thus negative photic phenomena can occur (20). There was no statistically significant difference in terms of overall satisfaction, spectacle requirement, and photic phenomena according to the groups in our study. ...
Aim: This study aimed to investigate the relationship between photic phenomena and the kappa angle after trifocal lens implantations.
Material and Methods: Fifty eyes of 35 cases, 17 female and 18 male, were included in the study. The kappa angle was calculated with the Lenstar LS900 low-coherence interferometry device using the pupil barycenter parameter. It was also calculated by using the iris barycenter parameters. According to the calculations using the pupil barycenter distance, the patients were divided into two groups with the preoperative pupil barycenter distance below 0.4 mm and above 0.4 mm. A questionnaire was applied to the patients to evaluate complaints and satisfaction in the postoperative period.
Results: The mean preoperative pupil barycenter distance was 0.38±0.12 mm and 52.0% (n=26) of the measurements were below 0.40 mm, while the mean preoperative iris barycenter distance was 0.40±0.15 mm and 46.0% (n=23) of the measurements were below 0.40 mm. No significant correlation was found between the preoperative pupil barycenter distance and the preoperative iris barycenter distance (rs=0.086, p=0.553). Additionally, there was no statistically significant difference between the two groups concerning symptoms such as halo and glare (p=0.948).
Conclusion: When considering a kappa angle upper limit of 0.6 mm, there is no discernible difference in the frequency of occurrence of photic phenomena. We believe that both iris barycenter parameters and pupil barycenter parameters, utilized for kappa angle calculations, can be effectively employed to determine the deviation distance.
... If a line is drawn through the paraxial nodal point that is parallel to the input beam, it approximately identifies the image location on the retina over a range of more than 90 • [1,2] (with 60 • just used here as an illustration). This characteristic of the eye is generally known, and similar behavior has been shown for other eye models that have a gradient refractive index lens [13], and an IOL [2], but this is due to the optical design of the eye rather than to the paraxial properties of the nodal point. ...
The focal length is often called the effective focal length, or efl instead, and although this is acceptable for a lens in air, it is not otherwise correct. The eye is used as an example here for an optical system where the object is in air and the image is in fluid. Welford, Aberrations of Optical Systems (1986) has paraxial equations that are consistent with historical use while also clearly defining efl. These are based on power at a surface having to be the same for light traveling in both directions ( n ′ / f ′ ). The focal length f ′ is the actual physical distance from the 2nd principal point to the paraxial focus, and the equivalent focal length, or efl, is the focal length divided by the image index ( f ′ / n ′ ). Separately, when the object is in air, the efl is shown to act at the nodal point, with the lens system represented by either an equivalent thin lens at the principal point with a focal length or a different equivalent thin lens in air at the nodal point with an efl. The rationale for using effective instead of equivalent for efl is unclear, but efl is used more as a symbol than as an acronym.
... 5,6 One year post-operatively, 3.2% of pseudophakic patients still report negative dysphotopsia. 6,7 Although many potential factors of influence have been identified, 4,6,[8][9][10][11] the exact origin of negative dysphotopsia is still not fully understood. Various treatment options have been proposed for negative dysphotopsia, including intraocular lens exchange, piggyback intraocular lens implantation, and reverse optic capture, but none of these treatments have shown to be successful in all cases. ...
Significance:
There is a clinical need for a quantitative test to objectively diagnose negative dysphotopsia, especially because the diagnosis is generally assessed using patients' subjective descriptions. In the search of a clinical test to objectify the shadow experienced in negative dysphotopsia, this study excludes static perimetry as suitable evaluation method.
Purpose:
This study aimed to evaluate the value of static perimetry in the objective assessment and follow-up of negative dysphotopsia.
Methods:
Peripheral 60-4 full-threshold visual field tests were performed in 27 patients with negative dysphotopsia and 33 pseudophakic controls. In addition, 11 patients with negative dysphotopsia repeated the test after an intraocular lens exchange. Both the total peripheral visual field and the averaged peripheral visual field from 50 to 60° eccentricity were compared between patients and controls, and pre-operatively and post-operatively in patients who had an intraocular lens exchange.
Results:
The peripheral visual fields from 30 to 60° did not show significant differences between patients with negative dysphotopsia and pseudophakic controls. Analysis of the peripheral visual field from 50 to 60° showed a median [Q1, Q3] of 20.0 [17.1, 22.5] dB in the negative dysphotopsia group compared with 20.1 [15.5, 21.3] dB in the control group (P = .43). Although 82% of patients treated with an intraocular lens exchange subjectively reported improvement of their negative dysphotopsia complaints post-operatively, there were no significant differences in their total peripheral visual field or averaged peripheral visual field from 50 to 60° (P = .92).
Conclusions:
Full-threshold static perimetry with a Goldmann size III stimulus up to 60° eccentricity does not show significant differences between patients with negative dysphotopsia and pseudophakic controls or between measurements before and after intraocular lens exchange. Therefore, this type of static perimetry cannot be used as a quantitative objective test for diagnosis or follow-up of patients with negative dysphotopsia.
... It is accepted that patients with angle kappa of less than 0.3 mm had a very low risk for IOL decentration and dissatisfaction [9]. Patients with angle kappa more than 0.4 mm had a high risk of halos and glare after the implantation of diffractive MIOLs [13]. Patients with angle kappa of more than 0.5 mm decreased visual quality with a trifocal IOL [2]. ...
Background
To assess postoperative changes in angle alpha, and to evaluate the postoperative visual quality of patients with different angle alpha values after implantation of extended depth of focus (EDOF) intraocular lenses (IOLs).
Methods
Seventy-nine eyes of 79 patients who had phacoemulsification with EDOF IOLs implantation were enrolled. A cut-off value of 0.3 mm, 0.4 mm, and 0.5 mm in preoperative angle alpha was chosen to divide eyes into groups. Distance, intermediate, and near visual acuities, modulation transfer function (MTF), and aberrations were recorded during a 6-month follow-up. A patient questionnaire was completed.
Results
There were no significant differences in angle alpha postoperatively compared to preoperatively. No significant differences were found in visual acuity and MTF between all groups. With 5 mm pupil diameter, there were significant differences of higher-order aberrations and spherical aberration in ocular aberration and internal aberration between angle alpha<0.4 mm and angle alpha≥0.4 mm. Additionally, significant differences of coma were also added in cut-off value of 0.5 mm. When the value of angle alpha is 0.4 mm or higher, there were significant differences in the score of halos and glare.
Conclusions
Angle alpha did not affect visual acuity, but the value of 0.4 mm or higher in angle alpha affected the visual quality under scotopic conditions and occurrence of halos and glare. For patients with 0.4 mm or higher in angle alpha, the choice to implant a EDOF IOL should be carefully considered.
... These findings may also be of interest to those investigating "negative dysphotopsia", a subjective perception of dark shadows in the periphery typically experienced by pseudophakes post cataract surgery due to focussing of image through the periphery of intraocular artificial lens. 15,16 Given that restricted eye movements are known to be associated with degenerative changes, the findings of this study may also be used to understand any neurological deficits based on further evidence. ...
Purpose
This pilot study aimed to investigate the maximum extension of foveal fixation in the horizontal direction among young adults in both emmetropes and myopes.
Methods
35 participants (28 emmetropes and 7 myopes) were included. Participants with restricted extra-ocular mobility, end gaze nystagmus, and/or any other ocular pathology were excluded. Visual acuity (VA) was used as a surrogate measure of foveal fixation. VA was determined using a staircase procedure with 8 reversals. The average of the last 5 reversals was taken as the thresholds. VA acuity was measured at different gaze eccentricities along nasal and temporal visual field meridian. The eccentricity at which VA drops significantly was taken as the maximum extent of foveal fixation. A bilinear fit regression model was used to investigate the drop in the VA in both nasal and the temporal direction.
Results
Emmetropes can foveate up to 35 ± 2° in nasal and 40 ± 3° in temporal direction and myopes can foveate up to 38° in both nasal and temporal directions. Paired student t-test showed a significant difference in foveal fixation between nasal and temporal direction for emmetropes (P<0.001) but not in myopes (P = 0.168). An unpaired student t-test showed a significant difference in foveal fixation for nasal direction between myopes and emmetropes (P = 0.01). However, no statistically significant difference was found in foveal fixation for temporal direction between myopes and emmetropes (P = 0.792).
Conclusion
The eye rotation does not necessarily match with the extent of foveal fixation at extreme eye rotation. Eyes can fixate only up to 35° nasally and 40° temporally maintaing their maximum visual acuity.
... For the shape of posterior corneal surface was difficult to measure, the Q of the posterior corneal surface was calculated according to the schematic corneal SA and corneal thickness (obtained from various previous experimental investigations), which led to a narrow selection window of Q. [13] Considering all the aspects, it was proved that the Liou-Brennan model eye had smaller corneal SA than the human eye [40]. According to the results of Holladay, angle κ was simulated by decentering the aperture surface in Zemax software [41]. The simulated angle κ of the model eye is still different from that of the human eye, whereas, the Liou-Brennan model eye was still enough for our research, though not perfect. ...
Intraocular lens (IOL) misalignment and angle κ have had significant negative impact on post-operative quality of vision. ZEMAX software has been used to imitate the optical performance of pseudophakic eyes with different IOL surface designs at different orientations of IOL misalignment (decentration of 0.4 mm and tilt of 7°, and with the existence of 0.5 mm angle κ ). We found that an aspheric balanced curve optic surface maintained better optical performance via inducing less coma aberration. Coma aberration played an unexpectedly important role in the optical performance. With angle κ , the impact of IOL misalignment on visual quality was associated with the orientation of decentration and tilt, indicating that the coma compensation also took effect in pseudophakic eyes. Due to the high incidence of post-operative IOL misalignment, our results provide evidence of the importance of considering personalized angle κ before cataract surgery for patients.
... It is accepted that patients with angle kappa of less than 0.3 mm had a very low risk for IOL decentration and dissatisfaction [9]. Patients with angle kappa more than 0.4 mm had a high risk of halos and glare after the implantation of diffractive MIOLs [11]. Patients with angle kappa of more than 0.5 mm decreased visual quality with a trifocal IOL [2]. ...
Background: To assess postoperative changes in angle alpha, and to evaluate the postoperative visual quality of patients with different angle alpha values after implantation of extended depth of focus (EDOF) intraocular lenses (IOLs).
Methods: Seventy-nine eyes of 79 patients who had phacoemulsification with EDOF IOLs implantation were enrolled. A cut-off value of 0.3 mm, 0.4 mm, and 0.5 mm in preoperative angle alpha was chosen to divide eyes into groups. Distance, intermediate, and near visual acuities, modulation transfer function (MTF), and aberrations were recorded during a 6-month follow-up. A patient questionnaire was completed.
Results: There were no significant differences in angle alpha postoperatively compared to preoperatively. No significant differences were found in visual acuity and MTF between all groups. With 5mm pupil diameter, there were significant differences of higher-order aberrations and spherical aberration in ocular aberration and internal aberration between angle alpha＜0.4 mm and angle alpha≥ 0.4 mm. Additionally, significant differences of coma were also added in cut-off value of 0.5 mm. When the value of angle alpha is 0.4 mm or higher, there were significant differences in the score of halos and glare.
Conclusions: Angle alpha did not affect visual acuity, but the value of 0.4 mm or higher in angle alpha affected the visual quality under scotopic conditions and occurrence of halos and glare. For patients with 0.4 mm or higher in angle alpha, the decision to implant a EDOF IOL should be carefully considered.
... Average right eye from above for input visual angles of 0, 30, 60, and 90 degrees, with thin iris and 2.5 mm actual pupil diameter. 2 The main focused image reaches a limit and goes dark due to vignetting at about 90 degrees, yet the phakic eye is believed to image to 105 degrees. Light at about 90 degrees illuminates 2 different retinal regions. ...
... Negative dysphotopsia can occur with any type of IOL placed within the capsular bag. One of the major factors associated with this phenomenon is when the anterior capsule overlaps the anterior IOL edge [23], [24]. Procedures used to treat these symptoms include nasal anterior capsulotomy [25], [26] and reverse optic capture [24]. ...
Purpose: to evaluate dysphotopsias, patient satisfaction and posterior capsulotomy rate in patients undergoing phacoemulsification and implantation with Hoya iSert 250 monofocal intraocular lens (IOL). Design: retrospective cohort study. Setting-Teaching unit at a District General Hospital, UK. Methods: patients were implanted with the hydrophobic acrylic Hoya iSert 250 monofocal IOL through a 2.2mm clear corneal/ limbal incision. For dysphotopsia data, patients responded to a telephone questionnaire describing any visual symptoms and their satisfaction. Nd:YAG laser capsulotomy data were collected retrospectively from electronic medical records, paper notes and laser records. Eyes from patients (mean age 73.6 range 64-93 years) undergoing cataract surgery with implantation of Hoya iSert 250 IOL during the period January 1, 2014 and July 31, 2014, and 2-year follow-up were analysed. Main outcome measures: dysphotopsia rate, patient satisfaction and posterior capsulotomy rate. Results: 106 patients had the Hoya iSert 250 lenses implanted over a seven month period in 2014. 88 patients were contacted at 24 months post-operatively. 18 had passed away or were not contactable. 61 patients completed the survey. 15 patients (24.5%) reported transient positive dysphotopsias. One patient (1.6%) reported negative dysphotopsia. 95% were either very satisfied or satisfied with their vision (59% 'very satisfied' and 36% 'satisfied'). 3 patients (4.9%) had a YAG laser capsulotomy within 24 months post-operatively. Conclusions: the Hoya iSert 250 monofocal IOL was associated with low dysphotopsia and posterior capsulotomy rates with the majority of patients being 'Very Satisfied' with their vision at 24 months. Posterior capsulotomy rate and dysphotopsias following implantation of Hoya iSert 250 monofocal intraocular lens: 24 month study.
Purpose
We aimed to elucidate the factors related to effective lens position (ELP), tilt, and decentration of scleral fixed intraocular lenses (IOLs) with a flanged haptic technique in an artificial eye model using anterior segment optical coherence tomography (AS-OCT).
Methods
Two bent 27-gauge needles were passed through a 1.0- or 2.0-mm scleral tunnel, 2.0 mm posterior to the limbus and 180° apart. Both haptics of a 3-piece IOL were docked with guide needles and externalized. Factors related to the IOL position were analyzed using AS-OCT and a stereomicroscope.
Results
The 1.0-mm scleral tunnel induced a significantly longer ELP than the 2.0-mm tunnel and suture fixation (p<0.05 and p<0.01, respectively). Discrepancy in scleral tunnel length induced higher decentration of the optic to the opposite side of the haptic-embedded shorter tunnel and tilt perpendicular to the fixed axis than that in the scleral tunnel of the same length (p<0.001 and p<0.05, respectively). If the scleral fixation points of both haptics are not exactly 180° apart, the IOL may become decentered and tilted (p<0.01 and p<0.05, respectively).
Conclusion
In the flanged haptic technique, the length, balance, and position of both scleral tunnels determine IOL ELP, tilt, and decentration.
Purpose
To evaluate efficacy and safety of Negative Dysphotopsia(ND) Ring ( CareGroup SS ) implantation for treating and preventing ND.
Setting
Multicentric Tertiary Eye Hospitals
Study Design
Prospective Interventional Cohort study
Method
22 patients with ND were enrolled. Eyes with other ocular structural pathologies (corneal, macular, optic nerve head, retinal, neuro-ophthalmological) were excluded. In 15 eyes, the ring was implanted to treat ND (Therapeutic group ) and in 7 eyes it was implanted during cataract surgery of the fellow eye as a prophylactic measure ( Prophylactic group ) to prevent the occurrence of ND. Pre-operative evaluation included videographic recording of the patients’ complaints besides complete eye examination. Post-operatively, patients were interviewed to confirm resolution of complaints related to ND. The intra-operative difficulties and the post-operative adverse events were recorded. A minimum follow-up of 1 year was completed for all eyes.
Results
In therapeutic group, 14/15(93.3%) eyes reported complete resolution of ND on first post-operative day, while one patient reported persistence of a smaller and lighter temporal shadow. No ND was reported in any of the 7 eyes treated prophylactically. No significant adverse intra-operative event was recorded, however vitreous up-thrust was noted in 2/22(9.0%) eyes. No permanent drop in visual acuity was recorded in therapeutic group.
Conclusion
The Negative Dysphotopsia Ring implantation is an easy, safe and effective approach for both treating and preventing ND.
Purpose
To assess whether intraocular lens (IOL) implantation induces shifts in the peripheral visual field.
Setting
Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.
Design
Ray tracing study.
Methods
Non-sequential ray tracing simulations were performed with phakic and pseudophakic versions of the same eye model to assess potential shifts in the visual field after IOL implantation. Two different IOL designs were evaluated and for each design 5 different axial positions and 7 different intrinsic powers were tested. The relation between the physical position of the light source and the location where the retina was illuminated was determined for each eye model. Subsequently, these relations were used to calculate whether the visual field shifts in pseudophakic eyes.
Results
The pseudophakic visual field shift was below 1 degree for central vision in all evaluated models. For peripheral vision, the light rays in the pseudophakic eyes were refracted to a more central retinal location compared to phakic eyes, resulting in a central shift of the peripheral visual field. The magnitude of the shift depended on the IOL design and its axial position, but could be as high as 5.4 degrees towards central vision.
Conclusion
IOL implantation tends to have little effect on the central visual field but can induce an over 5 degrees shift in the peripheral visual field. Such a shift can affect the perception of peripheral visual complaints.
Optical phenomena can have a great impact on the subjective visual quality of life. In this chapter, the forms of dysphotopsia and the methods for testing dysphotopsia by means of questionnaires and simulations will be discussed.KeywordsDysphotopsiaPositive dysphotopsiasNegative dysphotopsiasOptical quality
Patients can be unhappy after lens surgery. In this chapter the most important reasons and strategies to help the patient will be discussed.KeywordsDissatisfaction after lens surgeryMultifocal IOL
Purpose:
To explore the distribution of lens volume (VOL) and its associated factors in non-cataract adolescents and adults, and cataract patients in a Chinese population.
Setting:
Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Design:
Cross-sectional study.
Methods:
A total of 1674 eyes from 1674 Chinese participants (690 adolescents and 363 adults without cataract, and 621 cataract patients) aged from 7 to 90 years were included. Lens thickness (LT) and lens diameter (LD) were measured using swept-source anterior segment optical coherence tomography (SS-AS OCT) to calculate VOL. Axial length (AL) was measured by IOL-Master 700. Pearson correlation analysis and multivariable linear regression models were used to evaluate the potential associated factors of lens dimensions.
Results:
The mean VOL was 167.74±12.18 mm3 in non-cataract adolescents, 185.20±14.95 mm3 in non-cataract adults, and 226.10±49.25 mm3 in cataract patients. VOL had no significant correlation with AL in cataract patients (P > 0.05), neither in non-cataract adolescents nor non-cataract adults, when adjusted with LT, LD, age, and gender (P > 0.05). On the other hand, eyes with longer ALs tended to have smaller LTs and larger LDs in all groups (all P-trend<0.05). Larger VOL was associated with older age in all groups (all P<0.001).
Conclusions:
A dataset of VOLs in Chinese eyes over a wide age range was presented. It is inaccurate to predict VOL, LT, and LD solely according to AL. The direct measurement and calculation of VOL in vivo and the establishment of the normal range of VOL, could help predict the size of lens capsular bag and plan cataract surgery.
Purpose:
To assess the effect of ocular anatomy and intraocular lens (IOL) design on negative dysphotopsia (ND).
Setting:
Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.
Design:
Ray-tracing study based on clinical data.
Methods:
Ray-tracing simulations were performed to assess the effect of anatomical differences and differences in IOL design on the peripheral retinal illumination. To that end, eye models that incorporate clinically measured anatomical differences between eyes of patients with ND and eyes of pseudophakic controls were created. The anatomical differences included pupil size, pupil centration, and iris tilt. The simulations were performed with different IOL designs, including a simple biconvex IOL design and a more complex clinical IOL design with a convex-concave anterior surface. Both IOL designs were analyzed using a clear edge and a frosted edge. As ND is generally considered to be caused by a discontinuity in peripheral retinal illumination, this illumination profile was determined for each eye model and the severity of the discontinuity was compared between eye models.
Results:
The peripheral retinal illumination consistently showed a more severe discontinuity in illumination with ND-specific anatomy. This difference was the least pronounced, 8%, with the frosted edge clinical IOL and the most pronounced, 18%, with the clear edge biconvex IOL.
Conclusions:
These results show that small differences in the ocular anatomy or IOL design affect the peripheral retinal illumination. Therewith, they can increase the severity of ND by up to 18%.
Purpose
We investigated the relationship between the refractive index of intraocular lenses and optical phenomena such as leading dysphotopsia.Methods
A modified Liou–Brennan model including an intraocular lens (IOL) was used to analyze the illumination from off-axis incident light; the IOL was a biconvex single-focus spherical IOL at 20 D with three refractive indices set as 1.413 (low refractive index), 1.458 (medium refractive index), and 1.550 (high refractive index). Pupil diameters were analyzed for three different diameters, 3.0 mm, 5.0 mm, and 7.0 mm. Illumination optic simulations were performed using the optical illumination simulation program for LightTools ver. 9.1.1 (Synopsis Inc. California, USA).ResultsFor off-axis incident light at 80–90°, a bimodal peak was observed. Higher refractive index IOLs resulted in higher peak values for both peaks and larger peak-to-valley. This was more pronounced at larger pupil diameters and peak values closer to the fovea.Conclusion
Off-axis incident light consists of light passing between the iris and IOL, through the IOL to the sides of the IOL, and through the anterior and posterior surfaces of the IOL. These results suggest that the occurrence of optical phenomena can be reduced using IOLs with a low refractive index.
Peripheral dark shadows seen by some intraocular lens patients have led to evaluations of “far peripheral vision”. Angular scaling to the second nodal point has been found to be highly linear for the chief ray.
Purpose:
To evaluate whether orientation of the optic-haptic junction of an intraocular lens (IOL) during cataract surgery could decrease the incidence and/or severity of positive and negative dysphotopsia.
Design:
Prospective, randomized controlled trial.
Methods:
163 patients (326 eyes) in a private practice scheduled to have bilateral implantation of a Tecnis monofocal IOL (ZCB00) (Johnson & Johnson Vision, Santa Ana, CA) were randomly assigned to have the optic-haptic junction positioned vertically, horizontally, superonasally or inferonasally. Patients with known visual field defects or best corrected vision less than 20/80 were excluded. Patients were surveyed for positive and negative dysphotopsia symptoms at 1 week and 4-6 weeks after surgery. Patients were blinded to the orientation while researchers were not. Data was analyzed to compare the differences in positive and negative dysphotopsia incidence and severity.
Results:
IOL oriented vertically in 82 eyes (25.2%), horizontally in 72 eyes (22.1%), superonasally in 94 eyes (28.8%), and inferonasally in 78 eyes (23.9%). Significant difference noted between orientations in incidence of negative dysphotopsia at 1 week postoperatively (p = 0.019) and 4-6 weeks postoperatively (p = 0.002). Patients in the superonasal group had the worst outcome at both time periods, and the horizontal group had the best outcome at 4-6 weeks. No differences were noted for positive dysphotopsia incidence or severity.
Conclusions:
The orientation of the optic-haptic junction of a monofocal IOL was significantly associated with incidence of negative dysphotopsia after surgery, with the horizontal orientation performing best at 4-6 weeks.
Purpose of Review
To explore the etiology and incidence of pseudophakic positive dysphotopsia (PD) and negative dysphotopsia (ND) and summarize strategies to prevent and treat its occurrence.
Recent Findings
PD is managed with intraocular lens (IOL) exchange for lower refractive index or treated edge lenses or by use of photochromic contact lenses. PD related to presbyopia-correcting IOL designs is prevented with patient screening and education and mitigated post-operatively by optimizing visual acuity, treating ocular surface disease, and facilitating neuroadaptation through virtual augmentation. Consider IOL exchange if these measures fail. ND is managed with manipulation of the optic and the anterior nasal capsule through multiple surgical and procedural techniques. New IOL design and peripheral ring contact lenses are promising treatments.
Summary
Pseudophakic PD and ND are unique entities presenting independently of one another and demanding individualized prevention and treatments. A multifaceted approach will cater itself to the best treatment per patient.
Purpose:
To use optical modeling to compare 6.0 mm and 7.0 mm intraocular lens (IOL) optic diameters on peripheral retinal illumination with implications for negative dysphotopsia.
Setting:
Mayo Clinic, Rochester, MN, and Simpson Optics LLC, Arlington, TX.
Design:
Model eye.
Methods:
Ray-trace software was used to simulate retinal illumination from an extended light source for a pseudophakic eye with in-the-bag biconvex IOLs (Refractive Index [n] 1.46 and 1.55) and a 2.5 mm pupil. Ray-tracing diagrams and simulated retina illumination profiles were compared using 6.0 mm and 7.0 mm optic diameter IOLs. Retinal locations were scaled to relative visual angles from 70° - 110° horizontally.
Results:
A 7.0 mm optic (n 1.46) expands the image field by 2.8° compared to a 6.0 mm optic. High angle input light misses a 7.0 mm optic at a larger visual angle than a 6.0 mm optic, shifting illumination of the peripheral retina by this light anteriorly by 5.6°. Consequently, a region of non-illuminated peripheral nasal retina is enlarged and shifted peripherally using a 7.0 mm optic (visual angle, 86.3°- 96.3°) compared to a 6.0 mm optic (visual angle, 83.5°- 90.7°). Similar illumination changes were seen modeling a 1.55 n IOL.
Conclusions:
A narrow dark region in the nasal retina when using a 6.0 mm optic is changed to a broader, more peripheral dark region when using a 7.0 mm optic. An extended, more peripheral dark nasal region may make a temporal shadow less bothersome and explain lower ND rates using a 7.0 mm optic.
Aim
This study aimed to compare the performance of two monofocal Intraocular Lenses (IOL) platforms.
Background
The Clareon® Intraocular Lens (IOL) is a relatively new monofocal lens platform designed to improve postoperative results compared to other monofocal platforms.
Objective
This study aimed to assess and compare the visual and refractive outcomes, and incidence of YAG capsulotomy of the Clareon® IOL and a standard non-preloaded AcrySof® monofocal IOL following contralateral implantation in patients undergoing cataract surgery.
Methods
A total of 20 patients (40 eyes; 12 female, average age 72.8±6.4 years) who had undergone contralateral implantation of an AcrySof® IQ monofocal lens (SN60WF or SN6AT; Alcon; Texas, USA) and a Clareon®monofocal lens (CNAOT0; Alcon; Texas, USA) were selected. Uncorrected Distance Visual Acuity (UDVA), Contrast Sensitivity (CS), kinetic perimetry, and refraction were measured 1 month following the second surgery and subjective vision was measured 6 months following the second surgery using a quality-of-life questionnaire.
Results
There was no difference in postoperative UDVA (P=0.94), CS (P>0.05), or refraction (P=0.64) between eyes that received the Clareon® and AcrySof® IQ lenses. Clareon® eyes had a higher incidence of glare/haloes and positive dysphotopsia while AcrySof® IQ eyes had a higher incidence of negative dysphotopsia. Patient satisfaction was similar between the groups (P=0.86), although 25% of patients reported more clarity in the eye that received the Clareon® lens. The incidence of posterior capsular opacification was low for both groups.
Conclusion
Clareon® and AcrySof® IQ lenses perform similarly, providing good refractive, visual, and subjective outcomes. Clareon® is available as a preloaded lens option and may reduce PCO and the need for Nd: YAG capsulotomy.
Purpose
To specify a keratoprosthesis (KPro) power value for use with an intraocular lens (IOL).
Methods
Raytracing software was used to determine the imaging properties of both the natural cornea and conceptual KPro designs, and IOL power calculation methods were reviewed. Traditional calculations use ‘thick lens’ models for the overall eye, while also using ‘thin lens’ approximations for the cornea and IOL. The power of the natural cornea acts approximately at the apex, although this is unlikely to be the case for a KPro. The IOL location is determined using an empirical adjustment that is calculated from clinical results for natural eyes.
Results
The use of a KPro has a similar optical effect to corneal refractive surgery, where the cornea no longer matches the original eye. A modification of the ‘double-K’ calculation method can be used by specifying the KPro effective power at the original corneal apex, but still estimating the postoperative IOL location using the original corneal power. The KPro power is measured by assembling the KPro with fluid and a window to simulate the way it is used, recording the best focus power at room temperature with a 3 mm diameter aperture, rescaling to the in situ power at 35°C using refractive index changes, and then rescaling again to the power expected relative to the original corneal apex. When expressed as a K value, a keratometer refractive index of 1.332 is proposed. If necessary, clinical results may be used later to make empirical adjustments to the calculation method.
Conclusions
A KPro power can be specified relative to the expected location of the original corneal apex using a keratometer index of 1.332. A double-K calculation can then be used to determine the correct KPro and IOL power values for a pseudophakic eye.
Purpose:
To determine the impact of IOL with 7.0 mm optic and plate haptic design on incidence of dysphotopsiae and visual functions after cataract surgery.
Setting:
Day-care clinic.
Design:
A prospective monocentric randomized patient-blinded comparative clinical study.
Methods:
Following preoperative measurements, patients underwent cataract surgery with implantation of two IOL designs - with 7.0 mm optic and plate haptics (group 1) or with 6.0 mm optic and C-loop haptics (group 2). In month 1, 3 and 12 follow-ups patients were examined, answered a questionnaire regarding satisfaction, spectacle dependence, frequency and extent of positive and negative dysphotopsiae, and underwent contrast sensitivity, mesopic vision and glare sensitivity testing. The data were analyzed as nominal, ordinal and metric with Chi-Square, Mann-Whitney-U, Wilcoxon and t-tests.
Results:
Group 1 comprised 57 eyes (43 patients) and group 2 comprised 63 eyes (43 patients). Corrected distance visual acuity was the same between groups throughout the study. Group 1 showed significantly lower incidence of positive and negative dysphotopsiae in month 1 follow-up (p=0.021 and 0.015, respectively) and a higher satisfaction rate in month 3 follow-up (p=0.006). Mean contrast sensitivity and mesopic vision with and without glare were the same in both groups. Positive dysphotopsiae cases in month 12 follow-up revealed lower photopic contrast sensitivity (p=0.005, 0.036 and 0.047, respectively), longer AL and greater preoperative pupil dynamics (p=0.04 and 0.06).
Conclusions:
The IOL design with 7.0 mm optic diameter and plate haptics reduces dysphotopsiae, provides good visual acuity, contrast sensitivity, mesopic vision with and without glare and high patient satisfaction.
Purpose:
To describe a patient with negative dysphotopsia who underwent a novel non-invasive technique that uses the Nd:YAG laser to induce nasal light scattering through targeted lens pitting.
Methods:
Case report.
Results:
Symptoms of negative dysphotopsia resolved after targeted lens pitting.
Conclusions:
Targeted lens pitting with Nd:YAG laser is a potential technique that may help treat negative dysphotopsia in a manner that preserves intraocular anatomy. Further study is warranted to explore targeted lens pitting in both patients with and without prior retinal surgery as a treatment for negative dysphotopsia. [J Refract Surg. 2021;37(3):212-214.].
Purpose:
To describe the distribution of angle alpha and angle kappa in a population with cataract in Shanghai.
Setting:
Eye and Ear, Nose, Throat Hospital, Fudan University, Shanghai, China.
Design:
Hospital-based, cross-sectional study.
Methods:
We included 15,127 eyes of 15,127 cataract patients in this study. Angle alpha, angle kappa, and other ocular biometric parameters were determined by IOLMaster 700 (Carl Zeiss Meditec AG, Germany). The distributions of angle alpha and angle kappa and their associations with systemic and ocular parameters were assessed.
Results:
The mean angle alpha and angle kappa values were 0.45 ± 0.21 mm and 0.30 ± 0.18 mm, respectively. Angle alpha and angle kappa were both predominantly located temporal to the visual axis. A greater angle alpha or angle kappa was associated with older age, lower corneal power, shorter white-to-white distance, and shallower anterior chamber depth (all P < 0.05). Angle alpha correlated positively with angle kappa. With increasing axial length (AXL), angle alpha gradually decreased in a nonlinear way and shifted to the nasal side of the visual axis, whereas angle kappa decreased in eyes with AXL < 27.5 mm but increased again in eyes with longer AXL.
Conclusions:
Angle alpha and angle kappa, both predominantly located temporal to the visual axis, are influenced by multiple anterior segment parameters. As AXL increases, the changes in angle alpha and angle kappa are nonlinear, and their locations gradually shift from the temporal to the nasal side of the visual axis.
We reviewed the literature concerning Positive and Negative Dysphotopsia with regard to etiology, incidence, and clinical/surgical management; in addition, we summarized our surgical experienced in managing dysphotopsia. A PubMed review, limited to English language, yielded 149 citations; multifocal (diffractive optic) and phakic IOL dysphotopsia were excluded. Overall 39 articles were determined to be relevant for the objectives of this investigation.
Regarding Positive Dysphotopsia (PD), 7 articles corroborated that the etiology of PD is primarily related to internal reflection of oblique light-rays that strike the square (truncated) edge of the IOL and are reflected onto the retinal surface. No round edged foldable IOLs are available in the US at this time, although IOLs modified with a round anterior edge and a square posterior edge show a trend toward decreased incidence of PD. High Index of Refraction (I/R), surface reflectivity and IOL optic design are additional causative factors for PD. Regarding the authors’ surgical experience, changing the optic material to a lower I/R, improved PD symptoms in the large majority of cases.
The etiology of Negative Dysphotopsia (ND) appears to be multifactorial and less well understood with some disparity between clinical and laboratory findings. Four articles, employing ray tracing optical modeling, suggested an “illumination gap” where some temporally incident light rays to the nasal retina pass anterior to the IOL and some are refracted posteriorly by the IOL, resulting in a “gap” and resultant temporal shadow. However, clinically ND is associated invariably with well centered “in the bag” IOLs. Other implicating factors include nasal anterior capsule override, haptic orientation, large angle kappa, and high hyperopia. Persistent ND has been successfully treated or reduced with reverse (anterior) optic capture, sulcus IOL placement, piggyback IOLs, and Nd:YAG nasal capsulectomy. Two articles reference a new optic edge designed to capture the anterior capsulotomy, mimicking reverse optic capture.
Persistent dysphotopsia following cataract surgery is a significant cause for patient dissatisfaction. Etiology and management of both ND and PD are of significance and new IOL designs and alternative surgical strategies may help mitigate these unintended side effects of IOL implantation.
At very large visual angles, vignetting can occur at the edge of an intraocular lens (IOL), because it is much smaller than the natural crystalline lens that it replaces. Ray trace calculations show that, by 80–90 deg of input visual angle, it is possible that about half the light is no longer focused by the IOL. This may create curved, peripheral, shadowlike regions, which are a clinical characteristic of negative dysphotopsia. The imaging characteristics for this “far peripheral vision” region are different from those of a phakic eye, whether or not negative dysphotopsia is experienced.
Purpose:
To evaluate patient satisfaction with multifocal intraocular lens (MIOL) implants (AcrySof Restor) in relation to the size of angle kappa and precise centration of the MIOL.
Methods:
Fifty-two eyes of 26 patients were included in this study. All patients underwent bilateral phacoemulsification and multifocal intraocular lens implantation (AcrySof Restor) from January 2008 to April 2010. Preoperative and postoperative examinations included slit lamp biomicroscopy, near and distance uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity and measurement of angle kappa. Precise centration of the IOL with respect to the centre of the pupil was evaluated postoperatively. Subjective photic phenomena were evaluated separately for each eye and the patients were asked to compare the perception between the right and left eye.
Results:
Angle kappa was positive in all cases, ranging from +1° to +7°. The mean angle kappa was 2.78° and 2.10° in the right and left eye, respectively. The IOL was centred exactly to the centre of the pupil in 40 eyes. In twelve eyes there was a slight decentration of the IOL (3 nasal, 4 temporal, 2 superotemporal, 2 superior, 1 inferior). Different subjective perception of photic phenomena between the two eyes was recorded only in five patients. All these patients were among those with a decentred IOL. Temporal and superotemporal decentration of the IOL caused pronounced photic phenomena in five cases - in four cases there was a greater angle kappa of +3° to +4°. In one case of temporal decentration and a small angle kappa (+1°), the patient failed to observe a difference between both eyes. In the cases of inferior, superior and nasal decentration of the IOL, no difference between both eyes was seen.
Conclusion:
According to our results, temporal decentration of the IOL is associated with the greatest risk in multifocal IOL implantation, particularly in cases with a higher angle kappa. An evaluation of angle kappa should be a part of preoperative examination before MIOL implantation. Patients with a high angle kappa should be excluded because of a higher risk of postoperative photic phenomena. Key words: angle kappa, multifocal intraocular lens, photic phenomena.
To evaluate the visual acuity and quality-related satisfaction of patients implanted with a refractive design multifocal intraocular lens (IOL), and evaluate the factors predicting it including angle kappa.
Dr Agarwal's Eye Hospital and Eye Research Centre, Chennai.
In this prospective trial, 50 eyes of 44 consecutive patients were included. All patients underwent phacoemulsification with multifocal IOL implantation (Rezoom IOL, Abbott Medical Optics). The preoperative and postoperative assessment included slit lamp biomicroscopy, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and kappa angle assessment. At 1 year, 37 patients (43 eyes), who finished follow-up, were asked to rate their symptoms on a graded questionnaire (0-5 for five queries).
The decimal scores for UCVA and BCVA were 0.38±0.21 and 0.47±0.17 (preoperative), and 0.75±0.22 and 0.99±0.11 (postoperative), respectively. Symptom scores were haloes 0.98±1.7, glare 0.69±1.48, blurred distance 1.0±1.7, intermediate 1.34±1.6, near 1.06±1.8. On regression analysis haloes depended on angle kappa and distance UCVA (R (2)=0.26, P=0.029), and glare on angle kappa (R (2)=0.26, P=0.033). Poor satisfactions with distance, intermediate, and near vision were linked with distance UCVA (R (2)=0.17, P=2.3 × 10(-4)), distance UCVA (R (2)=0.1, P=0.04), and near UCVA (R (2)=0.12, P=0.03), respectively. The strongest predictor, however, for overall visual discomfort was distance UCVA (R (2)=0.1, P=0.04).
Our study suggests that there may be a role of misalignment between the visual and pupillary axis (angle kappa) in the occurrence of photic phenomenon after refractive multifocal IOL implantation.
To identify factors which affect mesopic pupil diameter in refractive surgery patients.
This retrospective study was performed at the 1st Ophthalmology Clinic in Ankara Ataturk Training and Research Hospital, Ankara, Turkey.
Medical records of 412 refractive surgery candidates who applied between 2006 and 2008 were reviewed. Detailed ophthalmological examination data were obtained from medical records. Pupil size measurements were performed with a COAS Ocular Wavefront analyzer in mesopic conditions. Relationship between mesopic pupil diameter and age, sex, spherical refractive error (D), magnitude of astigmatism (D), type of astigmatism, spherical equivalent, and average keratometry were analyzed by means of univariate and multivariate regression analyses.
Mean mesopic pupil diameter was 6.19 +/- 0.88 mm. Mean pupil diameter (mean +/- standard deviation) was 5.70 +/- 1.01 in hypermetropia, 6.04 +/- 0.79 mm in mixed astigmatism, and 6.33 +/- 0.82 mm in myopia. The difference in mean mesopic pupil diameters between myopes and hypermetropes was statistically significant (p = 0.001). However, differences with regard to mean pupil diameters between myopes and mixed astigmatism (p = 0.660) and between hypermetropes and mixed astigmatism (p = 0.109) were not significant. Mean pupil diameter was 6.00 +/- 0.99 mm in against the rule astigmatism, 5.96 +/- 0.84 mm in oblique astigmatism, and 6.27 +/- 0.84 mm in with the rule astigmatism. Mean mesopic pupil diameter in with the rule astigmatism group was higher than oblique astigmatism group. Spherical refractive error (r = -0.213, p = 0.001), cylindrical refractive error (0.197, p = 0.001), and age (r = -0.341, p = 0.001) showed correlation with pupil diameter.
This study showed that age and magnitude of both spherical and cylindrical refractive error are the most determinative factors on mesopic pupil size.
The addition of edetic acid (EDTA) or trypsin to the infusion during a simulated extracapsular cataract extraction on cadaver eyes facilitates the removal of lens epithelial cells from the anterior capsule. Modification of the chemical composition of infusions used during extracapsular surgery may maximise lens epithelial cell removal and hence reduce the incidence of opacification of the posterior capsule after cataract extraction.
There is a need for a schematic eye that models vision accurately under various conditions such as refractive surgical procedures, contact lens and spectacle wear, and near vision. Here we propose a new model eye close to anatomical, biometric, and optical realities. This is a finite model with four aspheric refracting surfaces and a gradient-index lens. It has an equivalent power of 60.35 D and an axial length of 23.95 mm. The new model eye provides spherical aberration values within the limits of empirical results and predicts chromatic aberration for wavelengths between 380 and 750 nm. It provides a model for calculating optical transfer functions and predicting optical performance of the eye.
To determine and compare the shapes of the retinas of emmetropic and myopic eyes.
Nonrotationally symmetrical ellipsoids were mathematically fitted to the retinal surfaces of 21 emmetropic and 66 myopic eyes (up to -12 D) of participants aged 18 to 36 years (mean, 25.5) using transverse axial and sagittal images derived from magnetic resonance imaging.
The shapes of the ellipsoids varied considerably between subjects with similar refractive errors. The shapes were oblate (steepening toward the equator) in most of the emmetropic eyes (i.e., the axial dimensions of the ellipsoids were smaller than both the vertical and horizontal dimensions). As myopia increased, all ellipsoid dimensions increased with the axial dimension increasing more than the vertical dimension, which in turn increased more than the horizontal dimension (increases in approximate ratios 3:2:1). The relative difference in the increase of these dimensions meant that as the degree of myopia increased the retinal shape decreased in oblateness. However, few myopic eyes were prolate (flattening toward the equator). Independent of myopia, the ellipsoids were tilted about the vertical axis by 11 degrees +/- 13 degrees , and ellipsoid centers were decentered horizontally by 0.5 +/- 0.4 mm nasally and 0.2 +/- 0.5 mm inferiorly, relative to the fovea.
In general both emmetropic and myopic retinas are oblate in shape, although myopic eyes less so. This finding may be relevant to theories implicating the peripheral retina in the development of myopia.
To obtain normative values of angle kappa in a normal population by synoptophore and Orbscan II and to compare the reliability of these devices.
Three hundred consecutive healthy individuals were enrolled in the study. A complete orthoptic and ophthalmologic examination was performed. Synoptophore and Orbscan II corneal topography were used to measure angle kappa. To evaluate the association of the angle kappa and refraction measures, individuals were further classified according to the degree of myopia and hyperopia. The spherical equivalent error measures were grouped into six categories: > or = -3.00 diopters (D); -2.75 to -1.50 D; -1.25 to -0.50 D; +0.50 to +1.25 D; +1.50 to +2.75 D; and > or = +3.00 D. Paired t test and Pearson's correlation test were used for statistical analysis.
The mean age of the individuals was 28.74 +/- 1.63 years (range: 20 to 40 years). The angle kappa values obtained by synoptophore and Orbscan II were normally distributed. In the myopic group, angle kappa values decreased significantly towards negative refractive errors. In contrast, a correlation existed between large positive angles and positive refractive errors in the hyperopic group. Angle kappa values obtained by Orbscan II were significantly higher in all groups when compared to synoptophore (P < .0001). A significant correlation was noted between synoptophore and Orbscan II measurements (r = 0.932, P < .0001).
A significant correlation exists between positive refractive errors and large positive angle kappa values. Refractive surgeons must take into account angle kappa, especially in hyperopic patients, to avoid complications related to decentration of the ablation zone.
We measured optical and biometric parameters of emmetropic eyes as a function of age. There were approximately 20 subjects each in age groups 18-29, 30-39, 40-49, 50-59, and 60-69 years with similar male and female numbers. One eye was tested for each subject, having spherical equivalent in the range -0.88 D to +0.75 D and <or=0.50 D astigmatism. Despite considerable data scatter, we found significant age changes: anterior chamber depth decreased 0.011 mm/year, lens central thickness increased 0.024 mm/year, anterior segment depth increased 0.013 mm/year, eye length increased 0.011 mm/year, anterior lens radius of curvature decreased 0.044 mm/year, and lens equivalent refractive index decreased 0.0003/year. Males had higher anterior corneal radii of curvature (0.16 mm), lower lens equivalent refractive index (0.006), longer vitreous lengths (0.51 mm), and longer axial lengths (0.62 mm) than females. Superficially, the results suggest that eyes get bigger as they age. However, results can be related to refraction patterns in which refraction is stable in 20s to 40s and then moves in the hypermetropic direction. It is likely that several young subjects will become hypermetropic as they age, and it is possible that some of the older subjects were myopic when younger.
Purpose:
To compare the extension of peripheral visual fields in phakic and pseudophakic patients and to evaluate whether Goldmann kinetic perimetry can be used as an objective measure of negative dysphotopsia.
Setting:
University Eye Clinic, Maastricht University Medical Centre, Maastricht, the Netherlands.
Design:
Prospective and case-control study.
Methods:
Kinetic perimetry was performed with V4e and I4e stimuli. Visual fields were assessed in the following 4 quadrants: superior temporal, superior nasal, inferior temporal, and inferior nasal. In the control group, patients were evaluated before and 1 month after cataract surgery. Biometric and perimetric data in the control group were compared with data in the patients with negative dysphotopsia (study group).
Results:
Each group comprised 10 patients. In the control group, the extension of visual field did not change after surgery. Patients in the study group had a significantly shorter axial length and higher intraocular lens powers than those in the control group. The inferior temporal and inferior nasal quadrants were, respectively, 10 degrees and 6 degrees (P < .05) smaller in the study group than in the control group. In 3 patients with negative dysphotopsia, a shadow was drawn in the superior temporal and the inferior temporal quadrants during perimetry and the position of this shadow matched their subjective description of negative dysphotopsia.
Conclusions:
The peripheral visual field did not change after cataract surgery in patients without negative dysphotopsia. Kinetic perimetry can be used for objective evaluation of patients with negative dysphotopsia because these patients had constricted peripheral visual fields or a relative temporal scotoma corresponding to the position of the shadow.
Financial disclosure:
Proprietary or commercial disclosures are listed after the references.
PURPOSE: To evaluate whether positioning the intraocular lens (IOL) to decrease the entry of inferotemporal
light would decrease the incidence of negative dysphotopsia.
SETTING: Private practices, Boston and Chelmsford, Massachusetts, USA.
DESIGN: Prospective randomized case study.
METHODS: Patients had cataract surgery with implantation of either a silicone IOL inferotemporally
or vertically (randomly assigned) or a 1-piece acrylic IOL with the optic–haptic junction
inferotemporally or vertically (randomly assigned). Other patients received acrylic IOLs bilaterally
and inferotemporally without randomization. Patients were asked about negative dysphotopsia
symptoms postoperatively. Data were analyzed using the z test and a chi-square test for
comparing the incidence of negative dysphotopsia between the 3 groups.
RESULTS: The study comprised 305 patients (418 eyes). A silicone IOL was implanted inferotemporally
in 39 eyes and vertically in 60 eyes. An acrylic IOL was implanted with the optic–haptic junction
inferotemporally in 163 eyes and with the junction vertical in 114 eyes. Forty-two eyes had
bilateral inferotemporal implantation of an acrylic IOL. For the acrylic IOL on the first
postoperative day, the incidence of negative dysphotopsia was smaller for the inferotemporal
IOL orientation (6%) than in the control group (14%) (P Z .026). The rate of persistent negative
dysphotopsia decreased in both groups over time, and the difference 1 month after surgery was
no longer statistically significant. The negative dysphotopsia rate for the silicone IOL was 0%.
CONCLUSIONS: Positioning the optic–haptic junction of an acrylic IOL inferotemporally resulted in
a 2.3-fold decrease in the incidence of negative dysphotopsia after cataract surgery. When
implanted in the vertical position, Acrylic IOLs seemed to lead to a higher incidence of negative
dysphotopsia than silicone IOLs.
A healthy 51-year-old woman with life-long history of diminished visual capacity has noted significantly reduced functional vision over the past several years. A long-standing high hyperope, she had prophylactic laser iridotomies for narrow angles. She has been warned "never to have cataract surgery." Although corneal diameters are 11.2 mm, she has visibly small eyes, clear corneas, and shallow anterior chambers with imperforate prior laser iridotomies and extraordinarily dense nuclear cataracts in both eyes. The optic nerve in the right eye is apparently healthy, but no structures are visible in the left eye's posterior segment. Confrontation visual Add analysis is seemingly normal. A-scan ultrasonography reveals extremely short eyes. How would you manage the patient?
The objective of this review was to provide a summary of the peer-reviewed literature on the etiologies of negative dysphotopsia that occurs after routine cataract surgery. A search of PubMed, Google Scholar, and Retina Medical identified 59 reports. Negative dysphotopsia has been associated with many types of intraocular lenses (IOLs), including hydrophobic and hydrophilic acrylic, silicone, and 1-piece and 3-piece designs. Proposed etiologies include edge design, edge smoothness, edge thickness, index of refraction of the IOL, pupil size, amount of functional nasal retina, edema from the clear corneal incision, distance between the iris and IOL, amount of pigmentation of the eye, corneal shape, prominent globe and shallow orbit, and interaction between the anterior capsulorhexis and IOL. Treatments include a piggyback IOL, reverse optic capture, dilation of the pupil, constriction of the pupil, neodymium:YAG capsulotomy of the nasal portion of the anterior capsule, IOL exchange with round-edged optics, and time alone. This review summarizes the findings. Financial Disclosure Dr. Henderson is a consultant to Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Bausch & Lomb, and Genzyme Corp. Neither author has a financial or proprietary interest in any material or method mentioned.
Purpose:
The aim of this study was to correlate different biometric dimensions of the eye as measured from ocular magnetic resonance imaging (MRI) scans to predict the lens diameter.
Methods:
High-resolution ocular MRI scans of 100 eyes of 100 patients were reviewed. Various anatomical variables of the eye such as the axial length, the globe diameter, and the lens dimensions were measured. Also, the distances between the ciliary sulcus and angle-to-angle were measured. A partial least square (PLS) regression model was built to analyze which variables influence the model regarding the lens dimensions.
Results:
Sixty-two eyes of 62 patients were included in the final analysis. The lens diameter ratio (horizontal to vertical) was 0.93 (SD: 0.04; 0.83-1.00). The partial least square regression showed a significant connection (P < 0.001) between the horizontal and vertical diameter. The partial least square regression model that included the globe diameter and the axis length resulted in the best prediction for the horizontal lens diameter. Similar to the horizontal lens diameter, globe diameter was the best predictor for the vertical lens diameter followed by the distance of the ciliary sulcus. White-to-white distance, distance of the ciliary sulcus, and axial eye length were found to have a high influence on the angle-to-angle distance.
Conclusions:
The introduced models may serve as tools to predict the capsular bag biometry in a preoperative setting for cataract surgery or lens refilling procedures.
Purpose
To describe the inconsistencies in definition, application, and usage of the ocular reference axes (optical axis, visual axis, line of sight, pupillary axis, and topographic axis) and angles (angle kappa, lambda, and alpha) and to propose a precise, reproducible, clinically defined reference marker and axis for centration of refractive treatments and devices.
Design
Perspective
Methods
Literature review of papers dealing with ocular reference axes, angles, and centration
Results
The inconsistent definitions and usage of thecurrent ocular axes, as derived from eye models, limit their clinical utility. With a clear understanding of Purkinje images and a defined alignment of the observer, light source/fixation target, and subject eye, the subject-fixated coaxially sighted corneal light reflex can be a clinically useful reference marker. The axis formed by connecting the subject-fixated coaxially sighted corneal light reflex and the fixation point, the subject-fixated coaxially sighted corneal light reflex axis, is independent of pupillary dilation and phakic status of the eye. The relationship of the subject-fixated coaxially sighted corneal light reflex axis to a refined definition of the visual axis without reference to nodal points, the foveal-fixation axis, is discussed. The displacement between the subject-fixated coaxially sighted corneal light reflex and pupil center is described not by an angle, but by a chord, here termed chord mu. The application of the subject-fixated coaxially sighted corneal light reflex to the surgical centration of refractive treatments and devices is discussed.
Conclusion
As a clinically defined reference marker, the subject-fixated coaxially sighted corneal light reflex avoids the shortcomings of current ocular axes for clinical application and may contribute to better consensus in the literature and improved patient outcomes.
C.V. Mosby Company; St. Louis 1985, pp654, Third Edition ($135.45: Review Copy courtesy of CIG Medishield)
Purpose:
To determine whether intraocular lens (IOL) exchange with insertion of a sulcus-fixated IOL is an effective treatment for the management of pseudophakic negative dysphotopsia.
Setting:
Department of Ophthalmology, Stoke Mandeville Hospital, Buckinghamshire, United Kingdom.
Design:
Case series.
Methods:
Participants in the study were recruited prospectively from the clinic at the time of diagnosis or retrospectively from the operating room logs by identifying all patients who had IOL exchanges over a 4-year period (2009 to 2012).
Results:
Five eyes of 5 women with negative dysphotopsia were treated with IOL exchange and replacement with a 3-piece IOL (Acrysof MA60AC) inserted in the ciliary sulcus. All patients had a resolution of the negative dysphotopsia symptoms. One patient had primary insertion of a sulcus IOL in the fellow eye and did not develop negative dysphotopsia symptoms.
Conclusion:
Intraocular lens exchange with insertion of a 3-piece IOL in the ciliary sulcus appears to be a safe and effective treatment for the management of pseudophakic negative dysphotopsia.
Financial disclosure:
Neither author has a financial or proprietary interest in any material or method mentioned.
This report describes 6 cases in which neodymium:YAG (Nd:YAG) laser anterior capsulectomy achieved limited success in treating negative dysphotopsia. In 5 eyes with the Akreos AO MI60L posterior chamber intraocular lens (PC IOL), the dysphotopsia symptoms resolved completely (3 eyes) and partially (2 eyes) depending on the extent of the Nd:YAG laser anterior capsulectomy. In 1 eye with the Acrysof IQ toric PC IOL, the symptoms did not improve. Success with this procedure in patients with the Akreos AO MI60L PC IOL supports the role of the anterior capsule in the etiology and mechanism of negative dysphotopsia. Because the anterior capsulectomy did not resolve the symptoms in the patient with the Acrysof IQ toric PC IOL, the anterior capsule should be considered an optical risk factor for negative dysphotopsia and important in the manifestation of symptoms in only some patients. Other primary optical factors that have been described can presumably manifest negative dysphotopsia symptoms independent of light scatter from the anterior capsule.
The author has no financial or proprietary interest in any material or method mentioned.
To evaluate factors that may affect mesopic pupil size in refractive surgery candidates.
Medical records of 13,959 eyes of 13,959 refractive surgery candidates were reviewed, and one eye per subject was selected randomly for statistical analysis. Detailed ophthalmological examination data were obtained from medical records. Preoperative measurements included uncorrected distance visual acuity, corrected distance visual acuity, manifest and cycloplegic refraction, topography, slit lamp examination, and funduscopy. Mesopic pupil size measurements were performed with Colvard pupillometer. Relationship between mesopic pupil size and age, gender, refractive state, average keratometry, and pachymetry (thinnest point) were analyzed by means of ANOVA (+ANCOVA) and multivariate regression analyses.
Overall mesopic pupil size was 6.45 ± 0.82 mm, and mean age was 36.07 years. Mesopic pupil size was 5.96 ± 0.8 mm in hyperopic astigmatism, 6.36 ± 0.83 mm in high astigmatism, and 6.51 ± 0.8 mm in myopic astigmatism. The difference in mesopic pupil size between all refractive subgroups was statistically significant (p < 0.001). Age revealed the strongest correlation (r = -0.405, p < 0.001) with mesopic pupil size. Spherical equivalent showed a moderate correlation (r = -0.136), whereas keratometry (r = -0.064) and pachymetry (r = -0.057) had a weak correlation with mesopic pupil size. No statistically significant difference in mesopic pupil size was noted regarding gender and ocular side. The sum of all analyzed factors (age, refractive state, keratometry, and pachymetry) can only predict the expected pupil size in <20% (R = 0.179, p < 0.001).
Our analysis confirmed that age and refractive state are determinative factors on mesopic pupil size. Average keratometry and minimal pachymetry exhibited a statistically significant, but clinically insignificant, impact on mesopic pupil size.
To determine the cause of negative dysphotopsia and the location, appearance, and relative intensity of such images in pseudophakic eyes.
Baylor College of Medicine, Houston, Texas, USA.
Reporting available data addressing a specific clinical question.
Negative dysphotopsia was simulated using the Zemax optical design program. The nominal values for the pseudophakic eye model were as follows: IOL power, 20.0 diopters (D); corneal power, 43.5 D; Q value, -0.26; axial IOL depth behind pupil, 0.5 mm; external anterior chamber depth (corneal vertex to iris plane), 4.0 mm; optic diameter, 6.0 mm; pupil diameter, 2.5 mm.
From the first ray-tracing simulation, analysis of the image for the nominal parameters showed 2 annuli (ring-shaped) shadows. The inner annulus shadow was located from a retinal visual field angle of 86.0 to 100.0 degrees (width 14.0 degrees), and the outer annular shadow was located from 105.9 to 123.3 degrees (width 17.4 degrees). Superimposing the inner annulus on the human visual field showed that the shadow would be apparent only temporally, where it is within the limits of the visual field and functional retina. The patient would perceive this as a temporal dark crescent-shaped partial shadow (penumbra).
Primary optical factors required for negative dysphotopsia are a small pupil, a distance behind the pupil of 0.06 mm or more and 1.23 mm or less for acrylic, a sharp-edged design, and functional nasal retina that extends anterior to the shadow. Secondary factors include a high index of refraction optic material, angle α, and the nasal location of the pupil relative to the eye's optical axis.
Drs. Zhao and Reisin are employees of and Dr. Holladay is a consultant to Abbott Medical Optics, Inc. No author has a financial or proprietary interest in any material or method mentioned.
The improved designs of intraocular lenses (IOLs) implanted during cataract surgery demand understanding of the possible effects of lens misalignment on optical performance. In this review, we describe the implementation, set-up and validation of two methods to measure in vivo tilt and decentration of IOLs, one based on Purkinje imaging and the other on Scheimpflug imaging. The Purkinje system images the reflections of an oblique collimated light source on the anterior cornea and anterior and posterior IOL surfaces and relies on the well supported assumption of the linearity of the Purkinje images with respect to IOL tilt and decentration. Scheimpflug imaging requires geometrical distortion correction and image processing techniques to retrieve the pupillary axis, IOL axis and pupil centre from the three-dimensional anterior segment image of the eye. Validation of the techniques using a physical eye model indicates that IOL tilt is estimated within an accuracy of 0.261 degree and decentration within 0.161 mm. Measurements on patients implanted with aspheric IOLs indicate that IOL tilt and decentration tend to be mirror symmetric between left and right eyes. The average tilt was 1.54 degrees and the average decentration was 0.21 mm. Simulated aberration patterns using custom models of the patients eyes, built using anatomical data of the anterior cornea and foveal position, the IOL geometry and the measured IOL tilt and decentration predict the experimental wave aberrations measured using laser ray tracing aberrometry on the same eyes. This reveals a relatively minor contribution of IOL tilt and decentration on the higher-order aberrations of the normal pseudophakic eye.
To evaluate capsular bag size and accommodative movement before and after cataract surgery using ultrasound biomicroscopy (UBM) and anterior segment optical coherence tomography (AS-OCT).
Ophthalmology Unit, Fabia Mater Clinic, Rome, Italy.
Cohort study.
Eyes having cataract surgery and monofocal intraocular lens (IOL) implantation were studied using UBM. The following parameters were measured preoperatively and 1, 2, and 12 months postoperatively: anterior chamber depth (ACD) (also by AS-OCT), capsular bag thickness, capsular bag diameter, ciliary ring diameter, sulcus-to-sulcus (STS) diameter, ciliary process-capsular bag distance, ciliary apex-capsular bag plane, and IOL tilting. The preoperative and postoperative capsular bag volumes were calculated at 12 months. The results were compared with the changes during accommodation.
The study comprised 24 eyes. With the exception of the ciliary apex-capsular bag plane, which appeared to be unmodified postoperatively, all measured parameters showed significant variation after IOL implantation. Only the ACD did not change significantly during accommodation.
After cataract surgery, the capsular bag stretched horizontally and with reduced vertical diameter as a result of adaptation to the implanted IOL. The capsular bag-IOL complex filled all available space, compressing the zonular fibers and almost abolishing the space between the ciliary apex and the capsular bag. There was anterior chamber deepening and a decrease in the ciliary ring diameter and STS diameter. In the absence of zonular fiber tension, the shape of the ciliary processes may be modified.
No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.
To determine the reproducibility of intraocular lens (IOL) decentration and tilt measurements with a new Purkinje meter instrument.
Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
After pupil dilation, images of pseudophakic eyes with a plate-style IOL (Akreos Adapt) were obtained using a recently developed Purkinje meter. Intraocular lens decentration and tilt were evaluated by analyzing the captured images using a semiobjective method by marking the reflexes in the images and automatic calculation using a dedicated software program. In study 1, examiner 1 examined the eyes first followed by examiner 2. Ten minutes later, examiner 1 performed a second measurement, after which the intraexaminer and interexaminer reproducibility were determined. In study 2, a Purkinje meter was used to measure pseudophakic eyes with slitlamp finding of clinical IOL decentration, IOL tilt, or both. The results were compared with retroillumination photographs and slitlamp findings.
In study 1, there was high intraexaminer reproducibility for decentration (r = 0.95) and tilt (r = 0.85) and high interexaminer reproducibility for decentration (r = 0.84) and tilt (r = 0.75). In study 2, even in extreme cases of decentration and/or tilt, the Purkinje meter measurements were possible and appeared to correlate well with slitlamp findings.
Acquisition of images in pseudophakic eyes with the Purkinje meter was simple and rapid. The method was highly reliable for 1 examiner and between 2 examiners.
to evaluate the results of intraocular lens (IOL) exchange in cases of severe negative dysphotopsia and to measure the distance between the iris and the IOL optic using ultrasound biomicroscopy (UBM).
Szent Rókus Hospital and Eye Clinic, Semmelweis University, Budapest, Hungary.
Data of patients with major negative dysphotopsia symptoms after phacoemulsification with IOL implantation were reviewed retrospectively. In cases in which IOL exchange was performed to diminish the symptoms, the distance between the iris and the anterior surface of the IOL optic was measured by UBM and compared with that in a group of nonsymptomatic pseudophakic patients (control group).
in 3806 cataract procedures, 5 eyes (4 patients) had severe negative dysphotopsia symptoms. Intraocular lens exchange was performed in 3 cases. In 1 case, the secondary IOL was implanted in the reopened capsular bag and the symptoms persisted. In 2 cases, the secondary IOL was implanted in the ciliary sulcus and the symptoms resolved. On UBM, the mean iris-optic distance was 0.45 mm +/- 0.07 (SD) in the symptomatic group, 0.59 +/- 0.29 mm in the control group (n = 21) (P = .353), and 0.00 mm in the sulcus-fixated group.
The iris-optic distance was not statistically significantly different between eyes with severe negative dysphotopsia symptoms and nonsymptomatic eyes. However, when IOL exchange reduced the iris-IOL distance, the severe negative dysphotopsia symptoms resolved.
To study the incidence, course, and common factors of patients with negative dysphotopsia and consider the possible role of the corneal incision in cases in which symptoms are transient.
Private practice and the University of Cincinnati, College of Medicine, Cincinnati, Ohio, USA.
Phacoemulsification with implantation of a single-piece acrylic intraocular lens (IOL) was performed in 250 consecutive routine cataract procedures. Patients were asked whether they noticed a temporal shadow on the day after surgery and were followed by serial evaluations for 3 years. Evaluations included subjective questionnaires and objective testing.
The incidence of negative dysphotopsia was 15.2% on the first postoperative day, decreasing to 3.2% after 1 year, then 2.4% after 2 and 3 years. Common findings included a shallow orbit, prominent globe, space greater than 0.45 mm between the iris and IOL by ultrasound biomicroscopy, and perimetric comet-shaped light in the area corresponding to the shadow. Slitlamp revealed a transparent peripheral capsule and a shadow sign in which a linear shadow on the iris became curvilinear as the light from the slit beam was projected through the incision toward the pupil.
Two groups of patients experienced negative dysphotopsia that rapidly resolved or remained unchanged from the first postoperative day. It is hypothesized that the corneal edema associated with a beveled temporal incision contributes to transient negative dysphotopsia.
In 22 patients (23 eyes), who had undergone an uncomplicated cataract extraction with implantation of a posterior chamber lens in otherwise normal eyes 11 to 44 weeks previously, the intra-ocular light scatter was measured with an IOI stray light meter. All the eyes examined had little or no after-cataract. A regression curve for stray light values in normal eyes as function of age was used as reference. The measurements show that the intra-ocular light scatter in pseudophakic eyes with little or no after-cataract increases by a factor 2. This increase must be caused by the combination implant lens-posterior capsule.
A series of direct photographic measurements of corneal reflex positions was taken to reconcile discrepant interpretations of the Hirschberg test. A value of 21 prism diopters per millimeter was obtained for the conversion factor relating ocular rotations to reflex displacement, valid over a range of 200 prism D. Quantitative interpretation of routine clinical photographs of strabismic patients can thus be easily obtained by including a millimeter scale in each picture. This value for the conversion factor is in agreement with a simple optical model for the corneal reflex. The discrepancy with the traditional value (about 14 prism D/mm) appears to arise from an attempt of most observers to measure reflex displacement from the corneal apex along the surface of the cornea, rather than to project the reflex and pupil onto a true frontal plane, as is done in a photograph.
To report the incidence, management, and prevention of patient reports of glare and streaks around a point source of light or a dark shadow in the temporal field of vision after acrylic intraocular lens (IOL) implantation.
A private practice.
Cases in which patients complained vigorously of dysphotopsia were catalogued prospectively during the implantation experience in 6668 consecutive eyes having surgery between January 1995 and June 1999. The techniques of topical-intracameral anesthesia, temporal clear corneal incisions, and phacoemulsification were used in all cases. Alternate IOL styles were selected for use from July 1999 to April 2000.
Fourteen cases (0.2%) were identified. The complaints resolved in 1, were diminished in 1, and were tolerated without change in 7. Five eyes of 4 patients required IOL exchange with capsular bag placement of a poly(methyl methacrylate) (PMMA) or silicone lens for resolution of symptoms. Selecting alternate IOL styles reduced the incidence of dysphotopsia.
Glare and streaks from a point source of light represent positive photic expressions of dysphotopsia, and temporal dark shadows represent similar negative photic expressions. Both appear to be associated with shiny square-edge optics made of high-refractive-index acrylic polymer. Intraocular lenses of PMMA and silicone with rounded edges, along with square-edge acrylic IOLs with nonreflective edges, appear less likely to cause clinically significant pseudophakic dysphotopsia.
To evaluate the role of posterior optic edge design and the effect of anterior capsule polishing on peripheral fibrotic posterior capsule opacification (PCO).
Department of Ophthalmology, University of Vienna, Vienna, Austria.
This randomized prospective study comprised 144 eyes of 72 patients with bilateral age-related cataract. Each patient had standardized cataract surgery in both eyes by the same surgeon. Group 1 (46 patients) received a round-edged hydrophobic acrylic IOL (AMO Sensar AR40) in 1 eye and a sharp-edged hydrophobic acrylic IOL (AMO Sensar OptiEdge AR40e) in the other eye. Group 2 (26 patients) received a silicone IOL (Pharmacia CeeOn 911A) with a truncated optic in both eyes. In this group, the anterior capsule was extensively polished in 1 eye and was left unpolished in the other eye. Digital slitlamp photographs were taken 1 year postoperatively using a standardized photographic technique for fibrotic PCO. The intensity of PCO was subjectively graded (score 0 to 4) by 2 masked examiners.
Subjective PCO scores correlated well between the 2 examiners (r = 0.88). In Group 1, the mean PCO score was 0.26 for the OptiEdge AR40e IOL and 0.90 for the AR40 IOL (P<.01). In Group 2, the mean PCO score was 0.24 in eyes with a polished capsule and 0.17 in eyes in which the capsule was not polished (P =.31).
The sharp-edged OptiEdge AR40e IOL led to significantly less peripheral fibrotic PCO 1 year postoperatively than the round-edged AR40 IOL. In eyes with the sharp-edged silicone 911A IOL, anterior capsule polishing caused no significant difference in fibrotic PCO.
To determine whether lens edge design or anterior capsule overlap on the intraocular lens (IOL) has greater effect on posterior capsule opacification (PCO).
Retrospective cohort clinical study.
Retrospective.
Academic clinical practice.
The patient population consisted of 259 uncomplicated surgical patients (259 eyes) with no confounding comorbidity and at least 1 year of follow-up after surgical placement of a silicone or hydrophobic acrylic lens.
Digital retroilluminated photographs were taken to ascertain PCO, anterior capsular opacification (ACO), previous neodymium:YAG capsulotomy and degree of anterior capsule overlap on the IOL optic.
PCO, ACO, YAG capsulotomy rate, and anterior capsule overlap on the IOL optic.
One hundred forty-eight digital images (74 silicone and 74 acrylic) were measurable for both anterior capsule overlap and PCO. Complete 360 degrees of anterior capsule overlap on the IOL was associated with decreased PCO (P = <.001). A significant negative correlation was found between the degree of anterior capsule overlap and PCO (P = <.001). Evaluation of PCO, and YAG capsulotomy rates were similar between acrylic and silicone lenses. Minimal anterior capsule overlap may also be associated with PCO prevention.
Implanting a lens with complete anterior capsule overlap on the IOL was found to significantly reduce PCO, which advantage appeared to be greater than PCO prevention by a truncated, sharp edge IOL design.
To determine the shape and astigmatism of the posterior corneal surface in a healthy population with age, using Scheimpflug photography corrected for distortion due to the geometry of the Scheimpflug imaging system and the refraction of the anterior corneal surface.
Scheimpflug imaging was used to measure in six meridians the cornea of the right eye of 114 subjects, ranging in age from 18 to 65 years.
The average radius of the anterior corneal surface was 7.79+/-0.27 (SD) mm and the average radius of the posterior corneal surface was 6.53+/-0.25 (SD) mm. Both surfaces were found to be flatter horizontally than vertically. The cylindrical component of the posterior surface of 0.33 mm is twice that of the anterior surface (0.16 mm). The asphericity of both the anterior and the posterior surface was independent of the radius of curvature at the vertex, refractive error and gender. In contrast with that of the anterior corneal surface, the asphericity of the posterior corneal surface varied significantly between meridians. With age, the asphericity of both the anterior and the posterior corneal surface changes significantly, which results in a slight peripheral thinning of the cornea.
On average, the astigmatism of the posterior corneal surface (-0.305 D) compensates the astigmatism of the anterior corneal surface (0.99 D) with 31%. The results show that the effective refractive index is 1.329, which is lower than values commonly used. There is no correlation between the asphericity of the anterior and the posterior corneal surface. As a result, the shape of the anterior corneal surface provides no definitive basis for knowing the asphericity of the posterior surface.
Cataract surgical problem. In: Masket S, ed, Consultation section.
- Vamosi
Cataract surgical problem. In: Masket S, ed, Consultation section.
- Weinstein
Refractive error may influence mesopic pupil size.
- Cakmak
Proceedings of the Physiological Society 1919
- H Hartridge
Hartridge H. The limit to peripheral vision. Proceedings of the Physiological
Society 1919. Published in J Physiol 1920; 53:xvii-xviii. Available at: http://
onlinelibrary.wiley.com/doi/10.1113/jphysiol.1920.sp001894/pdf.
Accessed December 26, 2017
Intraocular lens exchange in patients with negative dysphotopsia symptoms
- P V Amosi
- Cs Ak Any
V amosi P, Cs ak any B, N emeth J. Intraocular lens exchange in patients with
negative dysphotopsia symptoms. J Cataract Refract Surg 2010; 36:418-424
Intraocular lens alignment from Purkinje and Scheimpflug imaging
- P Rosales
- De Castro
- Jim Enez-Alfaro
Rosales P, De Castro A, Jim enez-Alfaro I, Marcos S. Intraocular lens alignment from Purkinje and Scheimpflug imaging. Clin Exp Optom 2010;
93:400-408. Available at: http://onlinelibrary.wiley.com/doi/10.1111/j.
1444-0938.2010.00514.x/epdf. Accessed December 27, 2016
Management of Dysphotopsias following Cataract Surgery
- Other Cited Material A
- J T Holladay
OTHER CITED MATERIAL
A. Holladay JT, "Management of Dysphotopsias following Cataract Surgery,"
presented on Cornea day at the ASCRS Symposium on Cataract, IOL and
Refractive Surgery, April 2014