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Evaluation of the Mechanical Properties of the Anterior Lens Capsule Following Femtosecond Laser Capsulotomy at Different Pulse Energy Settings
Abstract
To evaluate and compare the mechanical properties of anterior capsule opening performed with femtosecond laser capsulotomy at different energy settings in ex vivo porcine anterior lens capsule specimens.
Twenty-five fresh porcine eyes per group were included in the study. Femtosecond laser capsulotomy was performed with three different pulse energy levels: 2 µJ (low energy group), 5 µJ (intermediate energy group), and 10 µJ (high energy group). The capsule openings were stretched with universal testing equipment until they ruptured. The morphologic profile of the cut capsule edges was evaluated using scanning electron microscopy.
The high energy group had significantly lower rupture force (108 ± 14 mN) compared to the intermediate energy group (118 ± 10 mN) (P < .05) and low energy group (119 ± 11 mN) (P < .05), but the difference between the intermediate energy and low energy groups was not significant (P = .9479). The high energy group had significantly lower circumference stretching ratio (144% ± 3%) compared to the intermediate energy group (148% ± 3%) (P < .05) and low energy group (148% ± 3%) (P < .05), but the difference between the intermediate energy group and low energy group was not significant (P = .9985). Scanning electron microscopy images showed that the edge was only serrated with low and intermediate energy, but additional signs of collagen melting and denaturation were observed at high energy.
Anterior capsule openings created at a high energy level were slightly weaker and less extensible than those created at low or intermediate levels, possibly due to the increased thermal effect of photo-disruption. [J Refract Surg. 2015;31(3):153-157.].
Copyright 2015, SLACK Incorporated.
... The use of a higher energy setting in FLACS may also have negative implications 29,38,39 . Previous studies have suggested that the application of higher energy can denature and melt the collagen fibrils, causing adherence of the capsule and an increased risk of anterior-capsular tags 29 . ...
... The use of a higher energy setting in FLACS may also have negative implications 29,38,39 . Previous studies have suggested that the application of higher energy can denature and melt the collagen fibrils, causing adherence of the capsule and an increased risk of anterior-capsular tags 29 . However, these studies were performed with a higher energy FLACS system (LenSx (Alcon Laboratories, Inc., Forth Woth, TX) 29 . ...
... Previous studies have suggested that the application of higher energy can denature and melt the collagen fibrils, causing adherence of the capsule and an increased risk of anterior-capsular tags 29 . However, these studies were performed with a higher energy FLACS system (LenSx (Alcon Laboratories, Inc., Forth Woth, TX) 29 . Contrary to most FSL platforms, the LDV Z8 is a low energy (nanojoule range) high-frequency FSL system 2,40,41 . ...
The introduction of femtosecond laser-assisted cataract surgery is an alternative approach to conventional cataract surgery. Our study aimed to determine the effectiveness of femtosecond laser-assisted capsulotomy in the presence of different ophthalmic viscoelastic devices (OVDs) in the anterior chamber. Fresh porcine eyes (n = 96) underwent LDV Z8-assisted anterior capsulotomy, either in the presence of an OVD (Viscoat, Provisc, Healon, Healon GV or HPMC) or without, using 90% and 150% energies respectively. Following that, the capsule circularity, tag’s arc-length, tag-length, tag-area and rupture strength (mN) of the residual capsular bag were evaluated. We found that increasing energy from 90 to 150% across the OVD sub-groups improved the studied capsulotomy parameters. Amongst the 90% energy sub-groups, the circularity and tag-parameters were worse with Viscoat and Healon GV, which have higher refractive index and viscosity compared to the aqueous humour. Using 150% energy, Healon GV showed a significantly worse total arc-length (p = 0.01), total tag-length (p = 0.03) and total tag-area (p = 0.05) compared to the control group. We concluded that; an OVD with a refractive index similar to aqueous humour and lower viscosity, such as Healon or Provisc, as well as a higher energy setting, are recommended, to enhance the efficacy of laser capsulotomy.
... 127 Using a porcine model, Sandor and colleagues evaluated the mechanical rupture force for anterior capsulotomy specimens created using different energy settings. 140 They found that the high energy group (10 mJ) had a significantly lower rupture force (108 AE 14 mN) compared to the intermediate energy (5 mJ) group (118 AE 10 mN) (P < 0.05) and low energy (2 mJ) group (119 AE 11 mN) (P < 0.05), but the difference between the intermediate energy and low energy groups was not significant (P ¼ 0.9). 140 Using scanning electron microscopy, they observed a serrated capsulotomy edge with no thermal damage at low and intermediate energy levels, whereas there was melting of the serrated edge and coagulation of the collagen fibers without significant collateral damage at the higher 10 mJ energy setting. ...
... 140 They found that the high energy group (10 mJ) had a significantly lower rupture force (108 AE 14 mN) compared to the intermediate energy (5 mJ) group (118 AE 10 mN) (P < 0.05) and low energy (2 mJ) group (119 AE 11 mN) (P < 0.05), but the difference between the intermediate energy and low energy groups was not significant (P ¼ 0.9). 140 Using scanning electron microscopy, they observed a serrated capsulotomy edge with no thermal damage at low and intermediate energy levels, whereas there was melting of the serrated edge and coagulation of the collagen fibers without significant collateral damage at the higher 10 mJ energy setting. 140 Scanning electron microscopy demonstrates that the laser created capsulotomy edge surfaces are more irregular compared with a manually created capsulorhexis. ...
... 140 Using scanning electron microscopy, they observed a serrated capsulotomy edge with no thermal damage at low and intermediate energy levels, whereas there was melting of the serrated edge and coagulation of the collagen fibers without significant collateral damage at the higher 10 mJ energy setting. 140 Scanning electron microscopy demonstrates that the laser created capsulotomy edge surfaces are more irregular compared with a manually created capsulorhexis. 12 The capsule edge irregularity increases with increasing laser power. ...
... Для оценки биомеханической «устойчивости» края передней капсулы после разных методов капсулотомии использовали кадаверные свиные [15][16][17][18] и человеческие глаза [19][20][21][22]. Сравнительный анализ этих исследований, представленный нами в опубликованном ранее обзоре литературы, позволил сделать следующие основные выводы [23]: ...
... При применении тестов, предполагающих заполнение капсульного мешка желатином или гиалуроновой кислотой, и последующем растяжении с помощью ретракторов край капсулы после лазерного воздействия оказался достоверно прочнее, чем при мануальной технике [15,16]. При растяжении же изоли-Результаты механических испытаний образцов передней капсулы хрусталика после разных методов капсулотомии а/a б/b рованных, периферических, кольцевидных образцов передней капсулы был получен результат противоположного характера: средняя сила, регистрируемая при разрыве, оказалась достоверно выше после мануальной капсулотомии (155 мН против 119 мН), причем этот показатель снижался по мере увеличения энергии лазерного излучения (в среднем со 119 до 108 мН) [17,18]. Не исключено, что в первом случае на результаты могло повлиять применение желатина и гиалуроновой кислоты в процессе проведения механических испытаний. ...
Purpose:
To comparatively evaluate the mechanical stability of the edge of central fragment of anterior lens capsule after manual and femtolaser capsulotomy.
Material and methods:
The mechanical tests were performed on the central fragments of the anterior lens capsules obtained intraoperatively after manual and femtolaser capsulotomy (15 and 13 samples, respectively). The conditions of the developed method of mechanical testing are as close to in vivo as possible. The method allows evaluation of the mechanical response mainly from the edge of the sample, reception of the averaged response from the four edges of the capsule, and almost eliminates the effect of additional edge notches in samples obtained by manual capsulotomy.
Results:
After manual capsulotomy, the maximum force and elongation of the anterior capsule sample at maximum tensile strength were significantly higher than similar characteristics of the samples after femtolaser capsulotomy.
Conclusion:
The obtained results correspond with the morphological studies of capsule edge structure after manual and femtolaser capsulotomy. The edge of the anterior capsule after femtolaser capsulotomy has form, in rough approximation, close to one of a postage stamp perforation, which is the consequence of micro-irregularities (microfractures) in the areas irradiated by pulsed laser, and wider area of deepithelization compared to the manual technique.
... Although the probability of achieving a complete capsulotomy increases when 150% of energy is used, as indicated by results of the previous study, 21 an increase in laser energy can adversely affect capsulorhexis, such as capsular adhesion and an increased risk of anterior-capsular tags. 22 Therefore, it is important to increase laser energy appropriately through accurate calculations. Moreover, considering the results of this study, power attenuation due to absorption must be included in the calculation. ...
Purpose:
In femtosecond laser-assisted cataract surgery (FLACS), capsulorhexis can be performed with an ophthalmic viscosurgical device (OVD) filled in the anterior chamber. We aimed to investigate changes in the laser properties in various optical aspects, such as focal shifting, reflection, and absorption associated with OVD.
Methods:
Simulation was achieved by calculating the laser power attenuation due to reflection and spot size change using the Gullstrand eye model. Additionally, we calculated the absorption coefficient by measuring the laser power passing through the OVD with a laser meter and evaluated the effect of absorption by the OVD.
Results:
In our simulation, power attenuation due to reflection was a maximum of 0.07%, and power attenuation was 0.08% even when considering the change according to the incident angle. Power attenuation due to the change of the spot size at the focus was 0.005%. Owing to the absorption of the OVD, a power increase of up to 13.5% was required for an anterior chamber depth of 3.0 mm to obtain the same effect as the aqueous humor.
Conclusions:
The main reason for laser power attenuation associated with OVD was laser absorption through the OVD, and could also be caused by laser cavitation bubbles. To complete a safe capsulotomy during FLACS, the laser power should be increased appropriately, considering the absorption by the OVD in the anterior chamber.
Translational relevance:
The study results can be applied to calculate the optimal femtosecond laser energy to achieve complete capsulotomy during FLACS in the presence of anterior chamber OVD.
... A problem with FLC is the strength of the capsular edge, which was shown to decrease with increasing laser energy levels. 30,32 Even with optimized energy settings, FLC presents lower stress resistance and higher propensity for anterior radial tears compared with manual CCC. 33 An experimental study on human cadaver eyes showed that the fracture strength of the FLC is lower than in manual CCC by a factor of 1.28. ...
Introduction
Since the introduction, femtosecond laser-assisted cataract surgery was believed to revolutionize cataract surgery. However, the judgment of clinical benefit was found to be far more complex than initially might have been thought. The aim of this review was to analyze the benefits and drawbacks of femtosecond laser-assisted cataract surgery compared with traditional phacoemulsification cataract surgery.
Methods
PubMed and the Web of Science were used to search the medical literature. The following keywords were searched in various combinations: femtosecond laser, femtosecond laser-assisted cataract surgery, phacoemulsification cataract surgery, FLACS.
Results
The benefits of femtosecond laser-assisted cataract surgery include lower cumulated phacoemulsification time and endothelial cell loss, perfect centration of the capsulotomy, and opportunity to perform precise femtosecond-assisted arcuate keratotomy incisions. The major disadvantages of femtosecond laser-assisted cataract surgery are high cost of the laser and the disposables for surgery, femtosecond laser-assisted cataract surgery–specific intraoperative capsular complications, as well as the risk of intraoperative miosis and the learning curve.
Conclusion
Femtosecond laser-assisted cataract surgery seems to be beneficial in some groups of patients, that is, with low baseline endothelial cell count, or those planning to receive multifocal intraocular lens. Nevertheless, having considered that the advantages of femtosecond laser-assisted cataract surgery might not be clear in every routine case, it cannot be considered as cost-effective.
... A sejtek meglehetősen hosszú élettartamúak, azonban a folyamatos oxidatív és egyéb károsító folyamat apoptózist okozhat, amely a cataractaképződés egyik központi elemének számít, így a lencsehámsejtek vizsgálata szürke hályog esetén kiemelt jelentőségű [23]. Kutatócsoportunk korábbi tanulmányaiban már sikeresen vizsgált lencsehámsejteket transzmissziós elektronmikroszkóppal, de azok a vizsgálatok az elülső lencsetok mechanikai tulajdonságaira irányultak [24,25]. Jelen tanulmányunkkal a szürke hályogos lencseepithelsejtek morfológiai eltéréseit kerestük. ...
Inrtoduction: Caveolae are flask shaped with 50-100 nm size, non-clathrin associated invaginations of the plasmamembrane. The main membrane protein of the structures is caveolin-1. Caveolae play an important role in numerous cellular functions including vesicular transport and cell-cycle regulation, and create platforms for classical and alternative signaling pathways. According to international studies, caveolae may influence the physiology and pathology of lens epithelial cells.
Aim:
The aim of the study was to examine and compare the morphology of caveolae and the immunohistochemical difference of caveolin-1 in control (myopic and hyperopic) lens epithelial cells and human lens epithelial cells affected by cataract. Authors investigated whether caveolae might have a role in cataractogenesis.
Method:
Anterior lens capsules were obtained by capsulorhexis during surgery of senile cataract and refractive surgery of the clear lens. Ultra-fine sections have been studied by transmission electron microscopy, and semi-fine samples were labelled for immunohistochemistry with polyclonal caveolin-1 and cavin-1 antibodies.
Results:
By immunohistochemistry, in the control group, significant caveolin-1 label with low cavin-1 signal were measured in the lens epithelial cells. In the cataract group high cavin-1 and caveolin-1 expression was detected. In the control group, caveolae were not observed, but in the lens epithelial cells with cataract, increased number of caveolae have been detected by electron microscopy.
Conclusions:
For the development and maintenance of the specific caveolae shape, caveolin-1 is needed to be accompanied by cavin-1. Therefore, it is presumable that the increased expression of cavin-1 could explain the higher number of caveolae in the cataract group. These results might suggest that caveolae might play a role in cataractogenesis. Orv Hetil. 2019; 160(8): 300-308.
... В своей следующей работе G. Sandor и соавт. [22] провели оценку механических свойств передней капсулы хрусталика после фемтосекундной капсулотомии в зависимости от мощности лазерных импульсов. Фемтосекундную лазерную капсулотомию выполняли в трех группах (по 25 свиных глаз в каждой) при разных режимах мощности -2, 5 и 10 нДж (условно низкая, средняя и высокая энергетические группы соответственно) и использовали выше описанную методику механических испытаний [19]. ...
This paper reviews studies on biomechanical properties of the anterior lens capsule. Early experiments in this field were more fundamental. Later studies were aimed mainly at assessing the mechanical stability of the capsule edge after manual or femtosecond laser capsulorhexis (capsulotomy) - an important step in modern minimally invasive phaco surgery. For biomechanical tests, ex vivo samples of human and animal anterior capsules were used. The results of the studies presented here are quite heterogeneous, which suggests the necessity of gaining further insight into the issue.
... Secondly, we used a consistent femtosecond laser setting for the current experiment. Several reports showed that FLCs with high energy lead to an irregular cutting edge and that they decrease maximum stretch forces [21,22]. Furthermore, future studies should evaluate the effect of laser energy or spot/layer separation settings on capsule stretch forces. ...
The current study reports comparing the postoperative mechanical properties of the anterior capsule between femtosecond laser capsulotomy (FLC) and continuous curvilinear capsulorhexis (CCC) of variable size and shape in porcine eyes. All CCCs were created using capsule forceps. Irregular or eccentric CCCs were also created to simulate real cataract surgery. For FLC, capsulotomies 5.3 mm in diameter were created using the LenSx® (Alcon) platform. Fresh porcine eyes were used in all experiments. The edges of the capsule openings were pulled at a constant speed using two L-shaped jigs. Stretch force and distance were recorded over time, and the maximum values in this regard were defined as those that were recorded when the capsule broke. There was no difference in maximum stretch force between CCC and FLC. There were no differences in circularity between FLC and same-sized CCC. However, same-sized CCC did show significantly higher maximum stretch forces than FLC. Teardrop-shaped CCC showed lower maximum stretch forces than same-sized CCC and FLC. Heart-shaped CCC showed lower maximum stretch forces than same-sized CCC. Conclusively, while capsule edge strength after CCC varied depending on size or irregularities, FLC had the advantage of stable maximum stretch forces.
... Earlier literature with higher energy FLACS platforms suggested a higher rate of anterior tags and the reporting of adherence of the capsule to the underlying lens material. These changes have been supported with evidence of collagen melting and denaturation at higher energy settings 31 . The rate of anterior capsule tears however has been a source of some controversy with rates varying from 0.1% (Catalys platform) to 1.8% (Technolas), 1.84% (Catalys), 5.3% (Lensar) 20,32-35 . ...
The introduction of femtosecond laser assisted cataract surgery (FLACS) is a paradigm changing approach in cataract surgery, the most commonly performed surgical procedure. FLACS has the potential to optimize the creation of an anterior lens capsulotomy, a critical step in accessing the cataractous lens. The merits of using a laser instead of a manual approach include a potentially more circular, consistent, and stronger aperture. In this study we demonstrated for the first time in both a porcine and human experimental setting that with a low energy, high repetition FLACS system, that a circular, smooth and strong capsulotomy was achievable. While there was no demonstrable difference in the resistance to rupture before or after the removal of the nucleus, larger capsulotomies had an increase in tensile strength. The LDV Z8 system appeared to create circular, rupture-resistant and smooth capsulotomies in both porcine and more importantly human globes.
Ophthalmology is always at the forefront of LASER (Light Amplification by Stimulated Emission of Radiation) use first place. Meyer-Schwickerath reported first in 1949 to coagulate the retina in diabetes mellitus with specially focused sunshine [1]. Not much later appeared the first laser kind machine with a huge size to photocoagulate the retina indoors under planned circumstances, not depending on sunshine. The most important feature of ophthalmic (medical) lasers is that they emit specific wavelengths of electromagnetic light via stimulated emission. In ophthalmology, the wavelength, energy, pulse pattern, spot size, and repetition rate are the most crucial factors of a successful treatment due to the delicate anatomical structures of the eye. Usually, thermal effects cause changes in pigmented tissues; on the contrary, there are lasers that do not operate with heat effects. Tissue evaporation and non-thermal effects are also important in laser–tissue interaction.
Anterior capsule contraction syndrome is a specific complication of continuous circular capsulorhexis in various phacoemulsification techniques. Surgical, laser and combined methods have been proposed for its treatment. All approaches in the treatment of anterior capsule contraction syndrome have some advantages, as well as certain problems and difficulties. This review presents the current state of this problem of cataract surgery and possible prospects for improving the treatment.
Studies devoted to the assessment of lens capsule biomechanics can be divided into fundamental and applied. The former are oriented towards analysis of various indicators characterizing elasticity of the capsule as a basal membrane that maintains and changes the shape of the lens, and the latter deal with widespread introduction of modern microinvasive methods of phaco surgery into clinical practice.
Purpose:
To assess age-related changes in lens capsule biomechanics based on atomic force microscopy (AFM).
Material and methods:
The study included 50 central fragments of the anterior capsule of the human lens obtained intraoperatively during ultrasonic phacoemulsification by continuous circular capsulorhexis. The measurements were carried out in the Fast Force Volume (FFV) mode. The force curves were processed in the Nanoscope Analysis software (Bruker, USA) using the Hertz model that allows calculating the Young's modulus of the capsule sample based on the dependence of the force on the puncture depth.
Results:
There was no statistically significant difference in the «stiffness» of the inner and outer surfaces before and after removal of the subcapsular epithelium (p=0.25). In all cases, the inner surface of the capsule turned out to be «harder» than the outer one. In this case, the ratio of Young's modulus of the inner and outer surfaces has a significant dependence on age (p<0.001). With an increase in age from 50 to 90 years, this ratio decreased from ~7 to ~1.5. This was due to a simultaneous change in Young's modulus of the opposite nature: an increase in the stiffness of the outer surface and its decrease in the inner one.
Conclusion:
It is possible to assess lens capsule biomechanics using AFM if the subcapsular epithelium is present. In this case, the objects of study are the areas of the capsule free of epithelium, and the epithelial cells themselves can be used to identify the inner surface of the capsule. Regardless of age, the stiffness of the inner surface of the anterior lens capsule significantly exceeds that of the outer surface.
Purpose:
To compare the efficacy and safety of femtosecond laser-assisted cataract surgery (FLACS) with conventional cataract surgery (CCS).
Setting:
Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany.
Design:
Meta-analysis.
Methods:
PubMed, Cochrane Library, and EMBASE were systematically searched for studies comparing FLACS and CCS. Outcomes were efficacy and safety parameters. The effect measures were weighted mean differences or odds ratios with 95% CIs.
Results:
A total of 73 studies (25 randomized controlled, 48 observational) were reviewed with a total of 12,769 eyes treated with FLACS and 12,274 eyes treated with CCS. In eyes treated with FLACS, uncorrected and corrected distance visual acuity and spherical equivalent after 1 to 3 months (P=0.04, P=0.005, P=0.007) were better, total and effective phacoemulsification times were shorter (P<0.001 respectively), cumulative dissipated energy was less (P<0.001), circularity was more accurate (P<0.001), central corneal thickness after 1 day and 1 to 3 months was less (P<0.001, P=0.004), and endothelial cell loss after 3 to 6 weeks and 3 months was less (P=0.002, P<0.001) compared to CCS. Anterior capsule ruptures occurred more often with FLACS. No significant differences among groups were found in visual acuity at 1 week and after 6 months, or in posterior capsule rupture rates and endothelial cell loss after 6 months.
Conclusions:
Both FLACS and CCS are effective and safe. FLACS required less ultrasound energy and a more precise treatment. However, mid-term visual acuity did not show any difference between both methods.
The lens capsule, a thin specialized basement membrane that encloses the crystalline lens, is essential for both the structural and biomechanical integrity of the lens. Knowing the mechanical properties of the lens capsule is important for understanding its physiological functioning, role in accommodation, age-related changes, and for providing a better treatment of a cataract. In this review, we have described the techniques used for the lens capsule biomechanical testing on the macro- and microscale and summarized the current knowledge about its mechanical properties.
Purpose:
To evaluate and compare the mechanical resistance to tearing of the anterior lens capsule opening after staining with different concentrations of trypan blue in ex vivo porcine eyes.
Setting:
Semmelweis University, and Budapest University of Technology and Economics, Budapest, Hungary.
Design:
Experimental study.
Methods:
The study comprised 75 porcine eyes. The capsule was unstained in the Control Group (n = 25 eyes), 0.06% trypan blue was used to stain the capsule in Stained 1 Group (n = 25 eyes), and 0.1% trypan blue was used to stain the capsule in Stained 2 Group (n = 25 eyes). After capsulorhexis, the capsule openings were stretched with custom-designed testing equipment until they ruptured. The rupture force (RF), circumference stretching ratio (CSR), and secant modulus at 10 mN (SM10mN) and 50 mN (SM50mN) were evaluated.
Results:
In total, 75 eyes were enrolled. There were no statistically significant differences in the RF (P = .8924) or CSR (P = .3876) among the groups. There were no statistically significant differences in the SM10mN (P = .8215) or SM50mN (P = .4184) among the groups.
Conclusions:
In this porcine eye model, the trypan blue concentrations that are routinely used in cataract surgery had no effect on capsular rim stability.
Objective:
To evaluate the application of femtosecond laser technology in the management of subluxated lens.
Methods:
We retrospectively analyzed the data of the patients with subluxated lens undergoing femtosecond laser- assisted surgery at the Cataract Center of Guangzhou Aier Eye Hospital between March, 2017 and May, 2019. The LenSx femtosecond laser-assisted cataract surgery system was used to perform capsulotomy and lens fragmentation. According to the patients' eye condition, anterior vitrectomy was performed and capsular retractors was used. After phacoemulsification, I/A and insertion of the tension rings, the intraocular lens (IOL) was implanted into the capsular bag. The perioperative data, complications, visual acuity and intraocular pressure after the operation were recorded, and the stability of the capsular bag and IOLs were assessed.
Results:
We analyzed the data of 25 cases (29 eyes) of subluxated lens, including 16 (16 eyes; 55.17%) as the result of traumatic lens subluxation, 5 (9 eyes; 31.03%) of Mafan syndromes, 1 case (1 eye; 3.45%) of high myopia and 3 cases (3 eyes; 10.34%) of unknown causes. Thirteen 13 eyes (44.83%) showed mild subluxation, 7 (24.14%) had moderate subluxation, and 9 (31.03%) had severe subluxation. Femtosecond laser- assisted capsulorhexis, lens fragmentation and phacoemulsification were successfully completed for 29 eyes, of which 28 eyes (96.55%) retained the complete capsular bag and with successful implantation of the capsular tension devices and IOLs. Nine eyes (31.03%) were treated with anterior segment vitrectomy; iris hooks were used for 2 eyes (6.90%) and capsular bag hooks for 9 eyes (31.03%). The best corrected visual acuity was significantly improved in 29 eyes after operation (P < 0.05). At 1 month after the surgery, 26 eyes (89.66%) showed stably centered IOLs, 2 eyes (6.90%) showed slight tilt of the IOLs, and 3 eyes (10.34%) had anterior capsular contraction. The intraoperative complications included subconjunctival hemorrhage (75.87%), incomplete capsulotomy (17.24%) and contracted pupils (13.79%).
Conclusions:
The application of femtosecond laser assisted technology enhances the surgical safety and effectiveness for subluxated lens, facilitates the choice of individualized surgical options, and promotes maximum recovery of the patients' visual function.
Purpose
To compare the anterior capsulotomy edge tear strength created by manual continuous curvilinear capsulorhexis (CCC), femtosecond laser-assisted capsulotomy (FLACS), and selective laser capsulotomy (SLC).
Setting
Singapore National Eye Centre, Singapore and Excel-Lens, Livermore, California, USA.
Design
Three armed study in paired human eyes.
Methods
Capsulotomies were performed in 60 cadaver eyes of 30 donors using CCC, Victus Femtosecond Laser, (Bausch & Lomb, Rochester, New York, USA) or CAPSULaser, (Excel-Lens, Los Gatos, California, USA). Three pairwise study groups each involved 10 pairs of eyes. Study group 1: SLC eyes compared with fellow eyes with CCC. Study group 2: CCC eyes compared with fellow eyes with FLACS. Study group 3: FLACS eyes compared with fellow eyes with SLC.
A shoe-tree method was used to apply load to the capsulotomy edge, and Instron tensile stress instrument measured distension and threshold load applied to initiate capsule fracture. Relative fracture strengths and distension of CCC, FLACS and SLC were determined. Scanning electron microscopy (SEM) of capsule edges were reviewed
Results
Anterior capsulotomies behave as non-linear elastic (elastomeric) systems when exposed to an external load. The pairwise study demonstrated that the SLC fracture strength was superior to that of CCC by a factor of 1.46-fold with SLC 277±38 mN versus CCC with 190±37 mN. Furthermore, CCC fracture strength was superior to that of FLACS by a factor of 1.28-fold with CCC 186 + 37 mN versus FLACS 145 ± 35 mN (p < 0.001). This was determined by statistical analysis utilising the Wilcoxon matched-pairs signed-ranks test and in accordance with the Consolidated Standards of Reporting Trials guidelines. The capsule edge of SLC on SEM demonstrated a rolled over edge anteriorly and an alteration of collagen.
Conclusions
The strength of the capsulotomy edge for SLC was significantly stronger than that of CCC which and both were significantly stronger than FLACS. The relative strengths can be explained by SEM of each type of capsulotomy.
This book presents the most modern and innovative techniques in ocular surgery currently utilized by experts in the field. All aspects of ocular surgery from the front to the back of the eye are covered in this resource, with all surgeries demonstrated as ‘recipes’ with first the ingredients and then the surgical techniques with step-by-step instructions. The surgeries are illustrated with photographs, drawings and videos for practical application, and the step-by-step presentation allows for quick and easy access to the most appropriate techniques in ocular surgery.
Since its introduction in 2009 femtosecond laser-assisted cataract surgery (FLACS) has promised to revolutionize cataract surgery. Despite its promise, the assessment of FLACS's perceived benefits has proven to be far more complicated than initially might have been thought. Most studies to date have not provided validation of FLACS technology as a clinically significant advancement on our current techniques. We review FLACS technology and outcomes including detailed analysis of safety, efficacy, cost effectiveness and future prospects using data from the literature and our own published clinical experience.
Purpose:
To compare histological analyses of capsulotomies from different laser systems with regard to tissue alteration, laser spot formation, and energy settings.
Methods:
Four femtosecond laser platforms approved for cataract surgery were evaluated: LenSx (Alcon Laboratories, Inc., Fort Worth, TX), Catalys (Abbott Medical Optics, Santa Ana, CA), Victus (Tecnolas/Bausch & Lomb, Munich, Germany), and LensAR (Topcon, Gamagori, Japan). Ten human anterior lens capsulotomy disks from each laser system were analyzed: five by means of light microscopy and five by transmission electron microscopy (TEM). TEM was used especially to examine the cellular and stromal changes at the cutting edges. The cellular demarcation line was measured at 15 points along the rim and statistically compared with the findings from all laser platforms. Three capsules of each laser platform were prepared for TEM to evaluate the cellular and tissue edges of the laser cuttings.
Results:
All capsulotomies revealed a circular demarcation zone of different sizes along the cutting edges. Light microscopy showed a radial tissue damage of 36.0 ± 12.3 μm after Victus laser capsulotomy, 8.9 ± 2.9 μm after Catalys laser capsulotomy, 25.2 ± 5.6 μm after LensAR laser capsulotomy, and 39.8 ± 5.1 μm after LenSx laser capsulotomy. Differences between the damaged tissue zones correlated with the laser systems and their energy settings.
Conclusions:
The use of less energy and larger spot separation led to smaller collateral damaged tissue areas along the cutting edges. The aberrant laser spots along the cutting edge may result in weakening of the remaining tissue, thereby enhancing the risk for capsular ruptures during surgery. [J Refract Surg. 2017;33(10):670-675.].
Ophthalmology always had a pioneer role in use of lasers (Light Amplification by Stimulated Emission of Radiation). A great variety of lasers have been employed since the first laser appeared within the ophthalmic armamentarium for more than 50 years. The German ophthalmologist Meyer-Schwickerath applied the first laser for photocoagulation in the retina in 1949 [1]. A laser is a special surgical device which emits specific electromagnetic light via stimulated emission. Ophthalmic lasers operate at one specific fixed wavelength, pulse pattern, energy, duration, repetition rate, spot size and causing most of the time thermal effects, but photocoagulation, evaporation and non-thermal effects also important, regarding laser-tissue interaction.
Purpose:
To assess the role of femtosecond laser technology in the management of severely subluxated cataracts DESIGN: Retrospective, interventional case series METHODS: All eyes with subluxated cataract seen between July 2012 and June 2015 were assessed for suitability for femtosecond laser assisted cataract surgery, with the use of capsular tension devices. Participants with subluxated cataracts of at least 6 clock hours of zonular weakness were included in the study. Data collected included patient demographics, pre and post-operative best corrected visual acuity (BCVA), nuclear density, extent of zonular weakness, completeness of capsulotomy and complications. Poor visual outcome was defined as BCVA of worse than 20/40. Main outcome measure was the retention of the capsular bag.
Results:
Of the 72 eyes with subluxated cataracts undergoing surgery during the study period, 47 eyes of 47 patients were eligible for analysis. Mean age of the patients was 60.7 years old (standard deviation [SD] 13.2 years). The majority were male (32, 68.1%) and Chinese (38, 80.8%). The mean duration of follow up was 8 months (SD 5.6). The main identifiable cause of lens subluxation was trauma (11 eyes). Almost two-thirds (30 eyes) had more than 9 clock hours of zonular weakness. Seventy percent of cataracts (33) were nuclear sclerosis grade 3 and above. The capsular bag was preserved in 43 eyes (91.5%). The intraocular lens was stable and centered at the last follow up in all these 43 eyes. An anterior capsule tear occurred in 6 eyes, all of which had cataracts of nuclear sclerosis grade 3 and above, with posterior extension occurring in 3 eyes. Primary posterior capsule rupture occurred in one eye. At one month 37 eyes (80.4%) had a BCVA of 20/40 or better. There was significant improvement in BCVA at one month [mean of 0.92 logMAR units (SD 0.88) to 0.22 (SD 0.38) (P<0.001, paired samples T-test)] which was maintained at 1 year.
Conclusions:
Selected cases of severely subluxated cataracts may be managed using femtosecond laser technology to perform the capsulotomy and nuclear fragmentation, with successful preservation of the capsular bag in 90% of eligible cases especially in eyes with soft cataracts.
Purpose:
To investigate the effect of femtosecond laser-assisted cataract surgery (FLACS) on aqueous humour and lens capsule.
Methods:
This prospective randomized comparative study enrolled 19 eyes that underwent FLACS as the trial group and 20 eyes that underwent conventional phacoemulsification as the control group. The femtosecond laser platform (LLS-fs 3D; LensAR, Orlando, FL, USA) was used to generate capsulotomy (laser energy 8 μJ) and lens fragmentation (laser energy 10 μJ). Morphology of the cutting edge and cells of anterior capsule was assessed by light microscopy. The proteins in the aqueous humour were identified by mass spectrometry (Ultraflex III TOF/TOF; Bruker Dalton, Bremen, Germany). Electrolyte in the aqueous humour was detected by a chemistry analyzer (Aeroset Clinical Chemistry Analyzer; Abbott Laboratories, Abbott Park, IL, USA).
Results:
The cutting edge of anterior capsule was saw-tooth-shaped under magnification of 200× and 400× in the trial group, while it was smooth in the control group. Intact cells were found in the boundary area next to the cutting edge of anterior capsule in both groups. β-Crystallin B1, γ-crystallin S and transferrin were detected in the aqueous humour in the trial group. The concentrations of K(+) , Na(+) and Cl(-) in the aqueous humour in the trial group differed significantly from those in the control group (p = 0.02, 0.03 and 0.04, respectively).
Conclusion:
Femtosecond laser-assisted cataract surgery (FLACS) causes release of transferrin and crystallin from lens to aqueous humour and results in significant changes in the concentrations of K(+) , Na(+) and Cl(-) in aqueous humour. However, these changes due to FLACS have no clinical significance or toxicity.
Over the last decade, femtosecond lasers have emerged as an important tool to perform accurate and fine dissections with minimal collateral damage in biological tissue. The most common surgical procedure in medicine utilizing femtosecond laser is LASIK. During the femtosecond laser dissection process, the corneal collagen fibers inevitably undergo biomechanical and thermal changes on a sub-micro- or even a nanoscale level, which can potentially lead to post-surgical complications. In this study, we utilized helium ion microscopy, complemented with transmission electron microscopy to examine the femtosecond laser-induced collagen fibrillar damage in ex vivo human corneas. We found that the biomechanical damage induced by laser etching, generation of tissue bridges, and expansion of cavitation bubble and its subsequent collapse, created distortion to the surrounding collagen lamellae. Femtosecond laser-induced thermal damage was characterized by collapsed collagen lamellae, loss of collagen banding, collagen coiling, and presence of spherical debris. Our findings have shown the ability of helium ion microscopy to provide high resolution images with unprecedented detail of nanoscale fibrillar morphological changes in order to assess a tissue damage, which could not be resolved by conventional scanning electron microscopy previously. This imaging technology has also given us a better understanding of the tissue-laser interactions in a nano-structural manner and their possible effects on post-operative wound recovery.
The purpose of the study was to investigate the influence of age on the biomechanical properties of the human anterior lens capsule.
The material comprised 67 lens capsules obtained from human donors ranging in age from 7 months to 98 years. Test specimens were prepared from the anterior lens capsule as tissue rings by means of excimer laser technique using a metal ring (mask) to shape the laser output (outer diameter = 3.2 mm, width = 100 microns). Capsular thickness was measured under microscope as the difference in focus between microspherules placed on the outer and inner surfaces of the capsule. The rings were slipped over two pins connected to a motorized micropositioner and a force transducer, respectively, and stretched at constant speed until rupture, with continuous recording of load and elongation.
Capsular thickness was associated significantly with age of the donors and increased gradually (1.2% per year) until age 75, after which a slight decrease was observed. The elastic response curves showed a high degree of nonlinearity and were influenced markedly by age. Ultimate strain decreased 0.5% per year (range, 108% to 40%). Ultimate tensile strength decreased 1% per year (range, 17.5 N/mm2 to 1.5 N/mm2), and ultimate elastic stiffness (tangent modulus) decreased 0.9% per year (range, 44.8 N/mm2 to 4.4 N/mm2), whereas elastic stiffness corresponding to a specific strain level (30%) increased until age 35, after which a slight decrease was observed.
Aging of the human anterior lens capsule is associated with a progressive loss of mechanical strength. The young capsule is strong, tough, and highly extensible, whereas the older, thicker capsule is less extensible and much more brittle, and it has a markedly reduced breaking strength.
Objective:
To quantify the biomechanical properties of the capsulotomy edge following continuous-tear circular capsulorhexis (CTCC) or radiofrequency (RF) diathermy capsulotomy.Methods:
A test apparatus was constructed that allowed controlled stretching of capsulotomy edges following CTCC or RF diathermy capsulotomy. The lens contents were removed by phacoemulsification to permit the implantation of probes that exerted a test force on the capsulotomy edge and were moved in diametrically opposite directions using computer-controlled stepping motors. The magnitude of the force was measured during the capsule stretch, which allowed precise determination of the degree of capsular distention at the time of capsular rupture. Selected capsular edges were subsequently examined by scanning electron microscopy.Results:
The capsulotomy edge produced by CTCC was significantly stronger (P<.001) than that following RF. The mean (±SD) force to achieve capsule rupture was 0.15±0.06 N with CTCC compared with 0.02±0.01 N with RF. The mean (±SD) increase in the capsulotomy circumference was significantly greater with CTCC at 53%±14.5% compared with RF at 18%±8.5% (P<.001). Scanning electron microscopy disclosed a smooth edge for the CTCC capsulotomy. In contrast, multiple irregularities were seen in the edge following RF.Conclusions:
Continuous-tear circular capsulorhexis provides a stronger capsulotomy and is the preferred method in routine cataract surgery. However, RF diathermy capsulotomy may have a useful role in conditions unfavorable to the safe completion of CTCC.
Purpose:
To evaluate and compare the mechanical properties of anterior capsule openings performed with the continuous curvilinear capsulorhexis (CCC) technique and femtosecond laser capsulotomy (FLC) in ex vivo porcine lens capsule specimens.
Methods:
Fresh porcine eyes were included in the study (CCC group, n = 50; FLC group, n = 30). The capsule openings were stretched with universal testing equipment until they ruptured. The rupture force and circumference stretching ratio were evaluated. The morphologic profile of the cut capsule edges was evaluated using scanning electron microscopy (SEM).
Results:
The average rupture force was higher in the CCC group (median: 155 mN; interquartile range [IQR]: 129 to 201 mN; range: 71 to 294 mN) than in the FLC group (median: 119 mN; IQR: 108 to 128 mN; range: 91 to 142 mN) (P < .01, Mann-Whitney U test). The average circumference stretching ratio in the CCC group was greater (median: 150%; IQR: 146% to 156%; range: 136% to 161%) than in the FLC group (median: 148%; IQR: 145% to 150%; range: 141% to 154%) (P = .0468, Mann-Whitney U test). When less than 71 mN, no capsular tear occurred in either group. When less than 91 mN, no capsular tear occurred in the FLC group, whereas at 91 mN, the probability of capsular tears was 9% for the CCC group. SEM examination found that the CCC group had smooth edges, whereas those of the FLC group were gently serrated.
Conclusions:
According to the current results in a porcine eye model, FLC had less average resistance to capsule tear than CCC, but the weakest openings were seen in the CCC group.
Purpose:
To compare histologically the size and appearance of capsule disks after femtosecond laser-assisted cataract surgery and conventional cataract surgery.
Methods:
In 100 eyes of 100 patients with visually significant cataracts, a femtosecond laser capsulotomy or a capsulorhexis with an aimed diameter of 5.0 mm was performed by one experienced surgeon. The diameter, area, circularity, and cut quality was histologically examined with light microscopy and scanning electron microscopy.
Results:
The mean diameter of the manual and the femtosecond laser capsule disk group were not statistically significantly different (manual 4.91 ± 0.34; femtosecond: 4.93 ± 0.03; p = 0.58). The mean area of the capsule disks was 18.85 ± 2.69 mm2 in the manual and 19.03 ± 0.26 mm2 in the femtosecond group (p = 0.64). The capsules of the femtosecond group (0.95 ± 0.02) were significantly more circular than the ones of the manual group (0.81 ± 0.07; p<0.0001). The femtosecond laser capsule disks displayed a more saw blade-like structure created through the single laser spots. The histologic examination combined with prospective video analysis revealed respiratory movement of the eye during the capsulotomy as a potential risk factor for redial tears.
Conclusions:
Femtosecond laser can perform a capsulotomy with high reliability. In comparison to a highly experienced cataract surgeon, the achieved results in size are similar. In terms of circularity, the femtosecond laser was superior the manual procedure. Better refractive outcomes based on a 360°-degree optic overlap seem to be possible, especially for less experienced surgeons.
Purpose:
To perform a morphological comparison of capsulotomy edges generated by commercially available femtosecond lasers with manual capsulorhexis.
Setting:
Private clinic.
Design:
Experimental study.
Methods:
Capsules were collected using the following laser platforms and software versions: Lensx pre-soft-fit (version 2.16), Lensx post-soft-fit (version 2.20), Victus I (version 2.5), Victus II (version 2.7SP2), Catalys (version 2.15.13), and 10 manual. Scanning electron microscopy images were analyzed for the coefficient of variation (CoV) of pixilation along the capsule edge and homogeneity using gray-level co-occurrence matrix analysis. A qualitative assessment for anomalies, such as tags, was also made.
Results:
The mean CoV values from the regression analysis showed the manual edge (n = 10) (101.6% ± 0.6% [SD]) was smoother than the edges created with Lensx pre-soft-fit (105.2% ± 1.2%) (P<.001), Lensx post-soft-fit (102.7% ± 1.4%) (P=.04), Victus I (104.9% ± 0.9%) (P<.001), Catalys (104.5% ± 1.6%) (P<.001), and Victus II (104.7% ± 1.6%) platforms. All lasers (0.19 to 0.23) (P<.001) except the Lensx post-soft-fit (0.25 ± 0.03) (P=.23) generated less homogenous capsulotomies than the manual technique (0.27 ± 0.04). Tags occurred with Lensx pre-soft-fit (5/10), Lensx post-soft-fit (1/10), Victus I (1/4), and Victus II (3/10) platforms. Misdirected pulses were seen with the Catalys (4/10) and Victus II (4/10) platforms, which used fluid interfaces.
Conclusions:
Laser capsulotomies are approaching the smoothness of the manual capsulorhexis. The Lensx post-soft-fit platform showed the least anomalies and the smallest difference for the CoV and homogeneity metrics compared with the manual method.
Financial disclosure:
No author has a financial or proprietary interest in any material or method mentioned.
To evaluate cell death and ultrastructural effects on capsulotomy specimens derived from femtosecond laser-assisted cataract surgery.
In 26 eyes an anterior capsulotomy was performed using the LenSx femtosecond laser. In 10 eyes (group 1) the laser-pulse energy was set to 15 μJ using a rigid curved interface and in another 10 eyes (group 2) to 5 μJ using a curved interface combined with a soft contact lens. The control group (6 eyes, group 3) underwent manual anterior capsulorhexis using forceps. All extracted capsule specimens underwent cell death analysis using the terminal uridine-deoxynucleotidyl transferase-dUTP nick end labeling (TUNEL) kit, ultrastructural analyses using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Counterstaining was performed with 4',6-diamidino-2-phenylindol (DAPI) and hematoxylin-eosin (HE).
Cell death was found in all capsule specimens along the cutting edge but was significantly more pronounced in group 1. DAPI and HE staining showed regular epithelial cell distribution with a demarcation line along the cutting edge of both laser groups which was more pronounced in group 1. In AFM analysis laser spot size showed no significantly deviation in the femtosecond laser groups based on preoperative planned size (p<0.01). Cutting edges in SEM observations were smoother and in a more round shaped using 5 μJ (group 2).
Cutting edges of femtosecond laser performed capsulotomies are precise and laser spot lesions are within planned size. Cell death reaction depends on the laser pulse energy settings and can be reduced to the level observed in a manual capsulorhexis.
To ascertain the morphological changes in the edge structure of femtosecond laser-derived capsulotomy specimens using varying patient interfaces and different laser pulse energies.
In this experimental clinical study femtosecond laser-assisted capsulotomies were performed in 30 eyes using the LenSx femtosecond laser (LenSx, Alcon, Fort Worth, TX, USA). Surgery was performed using either a rigid curved contact interface (group 1, 15 eyes) or a curved interface with a soft contact lens between cornea and interface (group 2, 15 eyes). The laser pulse-energy was set to 15 μJ in group 1 and to 5 μJ in group 2. After the removal of the anterior capsule, half of the specimens from each group underwent either further staining for light microscopy (LM) or scanning electron microscopy (SEM). Cell configuration, capsule shape, and edge abnormalities were analysed on a morphological basis.
LM showed continuous anterior capsular incisions with a prominent demarcation line along the cutting edge, as well as tags and bridges, which were more pronounced in group 1. SEM revealed further smaller microgrooves and sawtooth patterns in both groups, and a more regular demarcation line configuration in group 2.
A soft contact lens interface with a subsequent laser pulse energy of 5 μJ resulted in fewer tags and bridges, smoother edges, and a more regular and thinner demarcation line on specimens edges of femtosecond laser-performed capsulotomies compared to a rigid curved 15 μJ interface application.
To compare the incidence of anterior capsular tears after femtosecond laser-assisted cataract surgery (FLACS) versus phacoemulsification cataract surgery (PCS) and to assess the ultrastructural features of anterior capsulotomy specimens (FLACS and PCS) using electron microscopy.
Prospective, multicenter, comparative cohort case series.
Consecutive patients undergoing FLACS or PCS.
A prospective cohort study of all patients (n = 1626) undergoing FLACS or PCS by 2 surgeons from centers A and B was undertaken to compare the incidence of anterior capsule tears. Anterior lens capsules were collected by 4 surgeons from centers A, B, C, and D using 3 different commercially available femtosecond platforms, each with latest version upgrades. Lens capsule tissue was prepared for scanning electron microscopy (SEM) using a total of 10 samples for patients undergoing PCS, and 40 samples for patients undergoing FLACS.
Incidence of anterior capsule tear and comparative ultrastructural features of capsular samples from both PCS and FLACS cases.
There was a significantly increased rate of anterior capsule tears in the FLACS group (15/804 [1.87%]) when compared with the PCS group (1/822 [0.12%]; P = 0.0002, Fisher exact test). In 7 cases, the anterior capsule tear extended to the posterior capsule. Because all cases had occurred in complete capsulotomy, the integrity of the anterior capsule was questioned in the FLACS group. Subsequent SEM sampling showed irregularity at the capsule margin, as well as multiple apparently misplaced laser pits in normal parts of the tissue. Aberrant pits were approximately 2 to 4 μm apart and occurred at a range of 10 to 100 μm radially from the capsule edge.
Laser anterior capsulotomy integrity seems to be compromised by postage-stamp perforations and additional aberrant pulses, possibly because of fixational eye movements. This can lead to an increased rate of anterior capsule tears, and extra care should be taken during surgery after femtosecond laser pretreatment has been performed. A learning curve may account for some of the increased complication rate with FLACS. However, the SEM features raise safety concerns for capsular integrity after FLACS and warrant further investigation.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Purpose:
To study the microanatomic edge structures of anterior lens capsule specimens derived from manual and femtosecond laser-assisted capsulotomies.
Setting:
Department of Ophthalmology, Goethe-University, Frankfurt, Germany.
Design:
Experimental study.
Methods:
Of 60 eyes with lens removal and intraocular lens implantation, 30 received a manual capsulotomy and 30 received a femtosecond laser-assisted capsulotomy (Lensx, rigid curved interface, pulse energy 15 μJ, spot separation 4 μm, layer separation 3 μm). After anterior capsule removal, tissues were immediately fixed in 4.5% formalin. Approximately 30 minutes after fixation, the tissues were removed from the fixation containers and air dried for at least 2 hours. Fifteen capsules in each group had further staining for light microscopy (LM). The surface of the capsulotomy edge was the primary focus of LM and scanning electron microscopy (SEM). Cell configuration, capsule shape, and abnormalities were evaluated.
Results:
Subjective LM and SEM analysis showed smooth edges at all magnifications, no cell destruction, and cells up to the cutting edge in the manual capsulotomy group. Light microscopy demonstrated almost continuous anterior capsule incisions of the femtosecond laser-assisted capsulotomy, a prominent demarcation line along the cutting edge, and several tags and bridges. Scanning electron microscopy showed microgrooves and valley- and mountain-like structures as signs of the photodisruption process.
Conclusion:
Compared with manual procedures, curved, rigid interface femtosecond laser-assisted capsulotomy specimens using 15 μJ pulse energy showed tags, bridges, rougher edges, and demarcation lines on the capsulotomy edges on SEM but subjectively estimated a more round shape on LM.
Financial disclosures:
Mr. Klaproth received travel reimbursements and/or lecture fees from Alcon Laboratories, Inc., Rayner Intraocular Lenses Ltd., and Oculus GmbH. Dr. Kohnen received travel reimbursements, grant support, and/or lecture fees from Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Bausch & Lomb, Carl Zeiss Meditec AG, Neoptics AG, Rayner Intraocular Lenses Ltd., and Schwind eye-tech-solutions GmbH and Co. KG; he is a consultant to Alcon Laboratories, Inc., Carl Zeiss Meditec AG, Rayner Intraocular Lenses Ltd., and Schwind eye-tech-solutions GmbH and Co. KG. No other author has a financial or proprietary interest in any material or method mentioned.
To use scanning electron microscopy (SEM) to evaluate capsulorhexis-cut quality obtained during femtosecond laser-assisted cataract surgery at different energy settings and evaluate whether there are differences between this technique and a standard manual technique.
Ophthalmology Clinic, Department of Medicine and Science of Ageing, University G. D'Annunzio Chieti-Pescara, Chieti, Italy.
Prospective nonrandomized single blinded study.
Sixty capsulorhexes obtained using the conventional manual technique and the femtosecond laser with different laser energy settings were divided into 5 groups as follows: Group 1 (12 capsulorhexes) obtained with the manual technique and Groups 2 to 5 (each with 12 capsulorhexes) obtained with the femtosecond laser at 7.0 μJ, 13.5 μJ, 14.0 μJ, and 15.0 μJ, respectively. All samples were evaluated using SEM to compare the thickness along the capsulorhexis edge and the overall irregularity of the cut surface.
Capsulorhexes obtained with the femtosecond laser at all energy settings were perfectly circular with negligible deformation. Group 1 and Group 2 had a significantly higher thickness and lower thickness, respectively, of the capsulorhexis edge than the other 3 groups (P<.001). There was also a statistically significant correlation between the degree of irregularity and increasing energy (P<.001).
The use of the femtosecond laser in cataract surgery resulted in better capsulorhexis geometry and circularity than the manual capsulorhexis. The cut surface was smoother in the manual group. In the femtosecond laser groups, the degree of irregularity was higher at increasing energy settings.
No author has a financial or proprietary interest in any material or method mentioned.
Type I collagen is a major extracellular matrix component and its hierarchical structure plays an essential role in the regulation of cellular behavior. Here, we have analyzed the changes in the morphological, chemical, and mechanical properties of collagen fibrils induced by acidic and thermal treatments and the influence on the cellular response of MC3T3-E1 cells. Morphological changes induced by the disintegration of the fibrillar structure of collagen were observed using atomic force microscopy. The changes in the surface chemistry due to the disassembly of native collagen fibrils were observed using time-of-flight secondary ion mass spectroscopy (ToF-SIMS). ToF-SIMS spectra were very sensitive to changes in the molecular configuration of the collagen fibrils induced by acidic and thermal treatments due to the extreme surface specificity. In addition, ToF-SIMS showed clear and reproducible changes in the surface amino acid composition corresponding to the acidic and thermal treatments of collagen fibrils. Based on the quantitative map of surface elastic modulus measured by contact-resonance force microscopy, acid and thermally treated collagen showed a lower elastic modulus than native collagen fibrils. Compared with native collagen fibrils, reduced cell spreading and decreased viability of MC3T3-E1 cells were observed on both the acid and thermally treated collagen.
To evaluate a femtosecond laser system to create the capsulotomy.
Porcine and cadaver eye studies were performed at OptiMedica Corp., Santa Clara, California, USA; the human trial was performed at the Centro Laser, Santo Domingo, Dominican Republic.
Experimental and clinical study.
Capsulotomies performed by an optical coherence tomography-guided femtosecond laser were evaluated in porcine and human cadaver eyes. Subsequently, the procedure was performed in 39 patients as part of a prospective randomized study of femtosecond laser-assisted cataract surgery. The accuracy of the capsulotomy size, shape, and centration were quantified and capsulotomy strength was assessed in the porcine eyes.
Laser-created capsulotomies were significantly more precise in size and shape than manually created capsulorhexes. In the patient eyes, the deviation from the intended diameter of the resected capsule disk was 29 μm ± 26 (SD) for the laser technique and 337 ± 258 μm for the manual technique. The mean deviation from circularity was 6% and 20%, respectively. The center of the laser capsulotomies was within 77 ± 47 μm of the intended position. All capsulotomies were complete, with no radial nicks or tears. The strength of laser capsulotomies (porcine subgroup) decreased with increasing pulse energy: 152 ± 21 mN for 3 μJ, 121 ± 16 mN for 6 μJ, and 113 ± 23 mN for 10 μJ. The strength of the manual capsulorhexes was 65 ± 21 mN.
The femtosecond laser produced capsulotomies that were more precise, accurate, reproducible, and stronger than those created with the conventional manual technique.
To evaluate femtosecond laser lens fragmentation and anterior capsulotomy in cataract surgery.
Anterior capsulotomy and phacofragmentation procedures performed with an intraocular femtosecond laser (LenSx Lasers Inc) were initially evaluated in ex vivo porcine eyes. These procedures were then performed in an initial series of nine patients undergoing cataract surgery. In addition to standard intraoperative assessments (including capsulotomy diameter accuracy and reproducibility), optical coherence tomography was used to evaluate human procedures.
For an intended 5-mm capsulorrhexis in porcine eyes, average achieved diameters were 5.88+/-0.73 mm using a standard manual technique and 5.02+/-0.04 mm using the femtosecond laser. Scanning electron microscopy revealed equally smooth cut edges of the capsulotomy with the femtosecond laser and manual technique. Compared to control porcine eyes, femtosecond laser phacofragmentation resulted in a 43% reduction in phacoemulsification power and a 51% decrease in phacoemulsification time. In a small series of human clinical procedures, femtosecond laser capsulotomies and phacofragmentation demonstrated similarly high levels of accuracy and effectiveness, with no operative complications.
Initial results with an intraocular femtosecond laser demonstrate higher precision of capsulorrhexis and reduced phacoemulsification power in porcine and human eyes.
The development of the continuous circular capsulorhexis (CCC) technique has contributed significantly to the safety and effectiveness of cataract extraction and intraocular lens implantation. This technique facilitates every size of smooth, circular, capsular opening, and it produces a strong capsular rim that resists tearing even when stretched during lens material removal or lens implantation. Maintaining the general integrity of the eye and facilitating such procedures as hydrodissection, endolenticular phacoemulsification, capsule polishing, and safe lens implantation in both adults and children are some of the advantages of CCC. This procedure can be performed in several ways, and it has been proven to be consistently reproducible by experienced surgeons.
Capsulorhexis using radio-frequency endodiathermy may confer some advantages over continuous tear curvilinear capsulorhexis (CTCC) in certain clinical situations. It is unclear whether a capsulorhexis produced in this fashion has the clinically advantageous elasticity and resistance to tearing that a CTCC has been demonstrated to have. To investigate this, a test of capsular elasticity was carried out on pairs of eyes obtained from an eye bank, 42 eyes of 21 patients in total, using modified digital vernier calipers. One eye of each pair had a CTCC, the other a diathermy capsulorhexis (DC). The elasticity of the capsule in both groups was expressed by comparing the circumference of the capsulotomy at rest with its circumference at rupture. The mean capsular elasticity of the CTCC group was significantly greater than that of the DC group (p < 0.001). The capsular edge in both groups was examined using scanning electron microscopy, and the difference in morphology appears to be the source of the difference in elasticity.
To compare the mechanical quality of a capsulotomy opening performed by diathermy with that made by capsulorhexis (tearing).
Department of Ophthalmology, Vejle Hospital, Denmark.
This study included 12 pairs of human cadaver eyes and 20 pairs of pig eyes. One in each pair was randomly selected for one capsulotomy technique. The capsulotomy edge was stretched in a materials testing machine until break; force and elongation values were continuously recorded.
In humans, the extensibility of the diathermic capsulotomy edge was approximately half that of the capsulorhexis edge (mean 38% +/- 4 [SD] versus 68% +/- 6), and the force required to break the edge was reduced by a factor of five (26 +/- 8 mN versus 134 +/- 36 mN).
The mechanical quality of the diathermic capsulotomy edge is significantly less than that of the capsulorhexis edge, which indicates that the diathermic capsulotomy edge would withstand less surgical manipulation.
We compared the postoperative characteristics of the anterior capsule edges produced by two incision techniques: continuous curvilinear capsulorhexis (CCC) and diathermy capsulorhexis (DC). We examined the incised rims of human and animal capsules histologically and also compared the configuration and strength of the rims produced in animal experimentation. Histological examination of rabbit lenses revealed that 0.5 seconds was sufficient for coagulation of the anterior capsule: longer times caused deeper cortical tissue damage. Experimentally produced small capsulorhexis (3.5 mm diameter) with DC produced edges were less elastic than with CCC when tension was applied.
To compare the tear resistance of anterior capsulotomies using manual continuous curvilinear capsulorhexis (CCC) and vitrector-cut capsulotomy (vitrectorhexis) techniques in an animal model of the pediatric eye and in 2 pairs of human infant eyes.
Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.
Continuous curvilinear capsulorhexis and automated vitrectorhexis capsulotomy techniques were performed in 20 pig eyes, 10 with each technique. The capsules were then stretched until they ruptured. The forces required for rupture after each technique were compared. The forces required for rupture of the pig eye lens capsule were also compared with those required for the human infant eye lens capsule. Scanning electron microscopy was performed in each group following intraocular lens (IOL) insertion.
All capsules stretched adequately for IOL insertion. The percentage of stretch prior to rupture was higher in the capsulorhexis group (mean 157%, range 147% to 169%) than in the vitrectorhexis group (mean 135%, range 124% to 147%) (P < .001). The percentage of stretch in the human infant eyes was not statistically different from that in the porcine eyes (P > .05).
The manual CCC offered greater resistance to capsule tearing than the vitrectorhexis and also revealed a more smooth, regular edge. It therefore remains the gold standard. However, the vitrectorhexis displayed more than adequate resistance to unwanted anterior capsule tears when used for IOL insertion through capsulotomy sizes currently used in clinical practice.
To compare the extensibility and scanning electron microscopy (SEM) of 5 currently used pediatric anterior capsulotomy techniques: vitrectorhexis, manual continuous curvilinear capsulorhexis (CCC), can-opener, radio frequency diathermy, and plasma blade in a porcine model.
Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.
Extensibility was determined by stretching each capsulotomy until it ruptured and measuring it by calculating the mean stretch-to-rupture circumference of each capsulotomy (20 eyes per technique) as a percentage of its baseline circumference. Edge characteristics were evaluated using SEM.
The mean extensibility of each technique tested (vitrectorhexis 161%, CCC 185%, can opener 149%, radio frequency 145%, plasma blade 170%) was significantly different (P<.001, 1-way analysis of variance). The SEM examination found that the vitrectorhexis had a scalloped edge with the whole edge rolled over, presenting a smooth surface toward the inside of the capsulotomy; the manual CCC produced the smoothest edge, with no irregularities noted; the can-opener edge was irregular, showing each puncture of the needle had created a small arc, with occasional regions of the edge rolled over in a "hit-and-miss" fashion; the radio-frequency diathermy capsulotomy edge was ragged, rough, and irregular; and the plasma blade capsulotomy edge was rougher than the manual CCC, but there were fewer irregularities than the radio-frequency diathermy edge had.
The manual CCC technique produced the most extensible porcine capsulotomy, followed by the plasma blade, vitrectorhexis, can-opener, and radio-frequency techniques, in a porcine model. The manual CCC technique also produced the smoothest anterior capsulotomy edge according SEM evaluation.