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The volume visual field: A basis for functional perimetry

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This paper introduces the concept of the volume visual field (VVF) map in the linear horizontal, vertical, and distance coordinates of environmental space, as a basic construct on which to build a theory of the functional visual field. A number of conditions under which both finite and infinite volume scotomas, or volumes of space within which objects cast their images onto scotomatous or occluded retina, are identified for both normal and diseased eyes. Convergence position and direction of gaze have marked effects on the VVFs of normal individuals, and on those with visual field defects. The functional impact of such effects is discussed. Methods for construction of the VVF from two conventional monocular field maps are outlined.
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... Mapping of volume scotomas in the linear three-dimensional space is referred to as volume perimetry. 10 The magnitude and location of the volume scotomas varies with the instantaneous fixation distance or the convergence of eyes. It has been argued that since the volume VF (VVF) takes into account depth in space, it yields the closest approximation of a person's real field of view. ...
... It has been argued that since the volume VF (VVF) takes into account depth in space, it yields the closest approximation of a person's real field of view. 10 Complete VVF testing, however, is impractical in standard clinical practice. There is no report on performing a complete volume perimetry for distances ranging from very close (e.g., 14 cm) to very far (e.g., 1000 cm and beyond). ...
... One previous study outlined the methods for constructing IVF by superimposing two monocular field maps with successive transverse sectional views and referred to these maps as retinocentric binocular field maps. 10 Although theoretical computation of depth-dependent IVF (DD-IVF) from two monocular VF results is possible, to the best of our knowledge, there is no existing simulation program available in the public domain that reads standard clinically measured monocular VFs and estimates how these two disparate, inhomogeneous VFs can be combined to produce a single IVF as a function of depth. ...
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Purpose: Visual fields (VF) are measured monocularly at a single depth, yet real-life activities require people to interact with objects binocularly at multiple depths. To better characterize visual functioning in clinical vision conditions such as glaucoma, analyzing visual impairment in a depth-dependent fashion is required. We developed a depth-dependent integrated VF (DD-IVF) simulation and demonstrated its usefulness by evaluating DD-IVF defects associated with 12 glaucomatous archetypes of 24-2 VF. Methods: The 12 archetypes included typical variants of superior and inferior nasal steps, arcuate and altitudinal defects, temporal wedge, biarcuate, and intact VFs. DD-IVF simulation maps the monocular 24-2 VF archetypes to binocular ones as a function of depth by incorporating three parameters of fixation, object, and interpupillary distances. At each location and depth plane, sensitivities are linearly interpolated from corresponding locations in monocular VF and returned as the higher value of the two. Results: The simulation produced 144 DD-IVFs for multiple depths from combinations of 12 glaucomatous archetypes. The DD-IVFs are included as a Shiny app in the binovisualfields package. The number of impaired locations in the DD-IVFs varied according to the overlap of VF loss between eyes. Conclusions: Our DD-IVF program revealed binocular functional visual defects associated with glaucomatous archetypes of the 24-2 pattern and is designed to do the same for empirically measured VFs. The comparison of identified visual impairments across depths may be informative for future empirical exploration of functional visual impairments in depth in glaucoma and other conditions leading to bilateral VF loss. Translational relevance: Our DD-IVF program can reveal depth-dependent functional visual defects for clinical vision conditions where 24-2 test patterns are available.
... Thus, it ignores the potential change in alignment of the eyes during pursuit in 2 or 3 dimensions (depth). Arditi (1988) has shown previously that the binocular scotoma is a 3-dimensional volume that depends on vergence angle. Our estimate of the static scotoma is similar to previous methods of mapping the binocular scotoma with an eye tracker (e.g. ...
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When the scotoma is binocular in macular degeneration (MD), it often obscures objects of interest, causing individuals to miss information. To map the binocular scotoma as precisely as current methods that map the monocular scotoma, we propose an iterative eye-tracker method. Study participants included nine individuals with MD and four age-matched controls. We measured the extent of the monocular scotomata using a scanning laser ophthalmoscope/optical coherence tomography (SLO/OCT). Then, we precisely mapped monocular and binocular scotomata with an eye tracker, while fixation was monitored. Participants responded whenever they detected briefly flashed dots, which were first presented on a coarse grid, and then at manually selected points to refine the shape and edges of the scotoma. Monocular scotomata measured in the SLO and eye tracker are highly similar, validating the eye-tracking method for scotoma mapping. Moreover, all participants used clustered fixation loci corresponding to their dominant preferred fixation locus. Critically, for individuals with binocular scotomata, the binocular map from the eye tracker was consistent with the overlap of the monocular scotoma profiles from the SLO. Thus, eye-tracker-based perimetry offers a reliable and sensitive tool for measuring both monocular and binocular scotomata, unlike the SLO/OCT that is limited to monocular viewing.
... 39 Previously, volume perimetry was used to consider the volume scotoma (including tunnel scotomas) of patients with binocular central field loss, which varies with convergence between the two eyes. 40,41 In the multiplexing prism, a similar volume scotoma can occur between see-through and shifted views, but the angular separation of the two views in the multiplexing prism remains constant with effective prism power (unlike the convergence in binocular central field loss). Therefore, the apical scotoma with the multiplexing prism results in a volume scotoma. ...
Article
Significance: Acquired monocular vision (AMV) is a common visual field loss. Patients report mobility difficulties in walking due to collisions with objects or other pedestrians on the blind side. Purpose: The visual field of people with AMV extends more than 90° temporally on the side of the seeing eye but is restricted to approximately 55° nasally. We developed a novel field expansion device using a multiplexing prism (MxP) that superimposes the see-through and shifted views for true field expansion without apical scotoma. We present various designs of the device that enable customized fitting and improved cosmetics. Methods: A partial MxP segment is attached (base-in) near the nose bridge. To avoid total internal reflection due to the high angle of incidence at nasal field end (55°), we fit the MxP with serrations facing the eye and tilt the prism base toward the nose. We calculated the width of the MxP (the apex location) needed to prevent apical scotoma and monocular diplopia. We also consider the effect of spectacle prescriptions on these settings. The results are verified perimetrically. Results: We documented the effectivity of various prototype glasses designs with perimetric measurements. With the prototypes, all patients with AMV had field-of-view expansions up to 90° nasally without any loss of seeing field. Conclusions: The novel and properly mounted MxP in glasses has the potential for meaningful field-of-view expansion up to the size of normal binocular vision in cosmetically acceptable form.
... Binocular disparity of objects in different depth planes drives vergence, which will alter the overlap of scotomas in the two eyes resulting in a change in the binocular scotoma. 73 This result has consequences for avoiding diplopia in remapped images. Diplopia also is a concern for magnification within a region of interest centered on the preferred retinal locus because angular magnification (pixel magnification) is used, which also magnifies binocular disparity. ...
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Significance: Head-mounted video display systems and image processing as a means of enhancing low vision are ideas that have been around for more than 20 years. Recent developments in virtual and augmented reality technology and software have opened up new research opportunities that will lead to benefits for low vision patients. Since the Visionics low vision enhancement system (LVES), the first head-mounted video display LVES, was engineered 20 years ago, various other devices have come and gone with a recent resurgence of the technology over the past few years. In this article, we discuss the history of the development of LVESs, describe the current state of available technology by outlining existing systems, and explore future innovation and research in this area. Although LVESs have now been around for more than two decades, there is still much that remains to be explored. With the growing popularity and availability of virtual reality and augmented reality technologies, we can now integrate these methods within low vision rehabilitation to conduct more research on customized contrast-enhancement strategies, image motion compensation, image-remapping strategies, and binocular disparity, all while incorporating eye-tracking capabilities. Future research should use this available technology and knowledge to learn more about the visual system in the low vision patient and extract this new information to create prescribable vision enhancement solutions for the visually impaired individual.
... 12 In particular, daily activities involving driving and mobility skills are dependent on the status of the binocular visual field. 9,10 There are also significant implications for binocular visual field characteristics and disability determinations. However, clinical perimetry is per-formed for each eye separately, and perimeters are not designed to perform binocular visual field testing. ...
Article
Purpose. To determine whether monocular visual field results can predict binocular visual field sensitivity in glaucoma patients, and to evaluate which model for combining monocular data provides the best estimate of binocular field sensitivity. Methods. Monocular and binocular (both eyes open, centered on the bridge of the nose) visual field measures (Humphrey 30-2 Full Threshold) were obtained in 112 glaucoma patients with varying levels of visual field sensitivity in both eyes. Four models of combining monocular visual field data were evaluated: ( 1 ) BeslEye Binocular sensitivity determined by the best eye [based on Mean Deviation], (2) Best Location - Binocular sensitivity determined by the most sensitive visual field location of the two eyes, (3) Average - Binocular sensitivity determined by an average of the two eyes at each location, and (4) Probability Summation - Binocular sensitivity determined by probability summation of the two eyes at each location. Results. The average difference between actual and predicted binocular sensitivity is presented in the table below, along with the standard deviation and range of measures, and the number of times that the model gave the closest prediction. Probability Summation and Best Location gave good predictions, while Best Eye and Average gave poorer predictions and underestimated binocular sensitivity. MODEL MEAN Dir F STDDEv RANGE BEST PREP. Best Eye 1.49 dB 1.85 dB 7.58 to -2.57 24/112(2f%T Best Location 0.05 dB 1.53 dB 4.73 to -4.34 33/112(27%) Average 3.70 dB 2.29 dB 10.39 to -0.67 8/112(7%) Prob Summation -0.40 dB 1.51 dB 4.37 to -4.67 50/112(45%) Conclusions. Binocular visual field sensitivity in glaucoma patients can be accurately predicted in most cases by probability summation of monocular fields at each location, or the most sensitive location between the two eyes.
... In spite of this limitation, the authors presumably were able to differentiate between a central field deficit and a field constriction. A preferred method for calculating binocular visual fields was described by Arditi (1988), in which a "map" of the volume of visual fields may be constructed to determine the functional visual field, as was used in a later study by Szlyk et al. (1993). ...
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The authors conducted a systematic review to examine whether vision-related assessments can predict the driving performance of individuals who have low vision. The results indicate that measures of visual field, contrast sensitivity, cognitive and attention-based tests, and driver screening tools have variable utility for predicting real-world driving performance.
... While we confirmed these findings with standard perimetric tests, at least for experienced bioptics users, we also demonstrated that when patients with central VF loss use monocular bioptic telescopes they may have a binocular central scotoma 30 due to the overlap of the ring scotoma with the disease-related scotoma in the other eye. 31 It is not known whether, in more complex visual environments, such as those encountered when driving, it will still be possible for the fellow eye to usefully detect potential hazards when the driver is viewing through a monocular telescope. ...
... In paper III the visual fields were examined before and after prolonged DA (24 h) in selected cases. In paper V, binocular visual field maps were produced by merging the monocular fields of each subject via the method described by Arditi (Arditi, 1988). The visual field areas were then measured and analyzed by a computer. ...
... This volume scotoma may have some impact on the functionality of patients with bitemporal hemianopia. [4][5][6] The effect, however, is limited to conditions where the fixation plane itself does not block the view behind it (e.g., fixating on a small object or on a transparent surface such as the windshield of the car). While the peripheral and post-fixation field losses are rarely presented symptomatically, patients with bitemporal hemianopia frequently present with binocular vision symptoms. ...
Article
Bitemporal hemianopic visual field impairment frequently leads to binocular vision difficulties. Patients with bitemporal hemianopia with pre-existing exophoria complain of horizontal diplopia, sometimes combined with vertical deviation (with pre-existing hyperphoria). The symptoms are a result of the phoria decompensating into a tropia (hemi-slide) due to the lack of retinal correspondence between the remaining nasal fields of both eyes. We measured these effects using a dichoptic perimeter. We showed that aligning the eyes with prisms could prevent diplopia if the bitemporal hemianopia is incomplete. We also describe the successful use of a novel fusion aid - the 'stereo-typoscope' - that utilizes midline stereopsis to prevent diplopia resulting from hemi-sliding in patients with complete bitemporal hemianopia.
... Par conséquent, les zones centrales importantes du champ visuel sont représentées par de petites unités, les zones périphériques par des larges unités. D'autres auteurs ont essayé d'intégrer l'effet de profondeur sur le champ visuel (Arditi, 1988). Mais, tous ces essais ne concernaient que le seul niveau du champ visuel. ...
Article
The term visual field corresponds to the angular field of view that is seen by the eyes when they are fixed on a point straight-ahead. In neurological patients - e.g. stroke, trauma, or tumour patients - visual field function can be restricted, depending on lesion site and size. In contrast, the term “functional visual field” describes the area of visual field responsiveness under more ordinary viewing conditions. The visual exploration, i.e. the capacity to explore and analyze our visual world, is dependent on the integrity of the visual system and the oculomotor system which has to move the fovea from one object of interest to the next. In this paper, we present a new method to assess the functional visual field, conceptualized as the area that a patient actively scans with eye movements to detect predefined targets placed on everyday scenes. This method allows us to compare three levels of visual field function: a) the spatial distribution of successful search (hits, i.e. which targets did the patient find?), b) the spatial distribution of fixations (i.e. where did the patient preferentially search for targets?), and c) the retinotopic level (i.e. the visual field assessed by perimetry). By integrating these three levels, one can evaluate functional outcomes of visual field disorders. Of particular importance is the question of how a patient compensates for a visual field loss with appropriate eye movements. A further clinical application of this method is the comparison of pre- with post-treatment data. Patients with visual field disorders usually undergo specific exploration trainings, aimed at enhancing the number and amplitude of saccades towards the region of the visual field deficit. The first experiences and clinical application with this method are presented here.
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One of the consequences of the noncoincidence of the nodal point and the center of rotation of the eye is the disappearance of targets near the limit of the nasal visual field when the monocular gaze is directed towards them. This ocular parallax phenomenon, which we measured in six adult subjects, is discussed in terms of its usefulness in demonstrating ocular parallax in a classroom situation. Also, a possible laboratory exercise is suggested.
Chapter
This report1 is a critical survey of different systems and of different national regulations which are or have been used for the percentage evaluation of functional impairment due to visual field losses. The scores of these several systems vary greatly. The new Esterman binocular system is the one which is recommended, with certain precautions.
Chapter
This second portion of the official report from the IPS Task Committee on the Functional Visual Field describes the effects of age, refractive error and its correction, ocular and neuro-ophthalmic disease, hypoxia, drugs, physical exercise, environmental lighting and noise on the functional visual field. Relationships between the functional visual field and ergonomics are also discussed, particularly with regard to driving, piloting an airplane, control tasks, illumination engineering, optical instruments, visual display units, and the design of spectacles and other devices that partially obstruct or interfere with peripheral vision. A third section examines visual field loss as a form of visual impairment, especially with regard to the definitions of visual disability, low vision and blindness, the prediction of functional capabilities, and the design of treatment regimens. Relationships between visual field properties and job fitness are discussed in a fourth section, with an emphasis on existing regulations and how they might be improved for driving, aviation and other areas. The last report section consists of technical notes pertaining to testing distance, measurement of eye and head movements, assessment of the dynamic functional visual field, and detection of visual field defects within the context of industrial medicine and automobile driver licensing requirements. The report was intended only as a review of the present knowledge about an interdisciplinary topic. It suggests lines along which progress may be directed, but does not include actual practical recommendations.
Chapter
Esterman’s grid for visual field scoring is both well known and widely accepted as a valid system for evaluating perimetric defects. However, it does not offer a completely precise functional assessment, because the threshold inside the visual field areas studied is not evaluated. In order to overcome this drawback we studied a new scoring method based on the position of 100 points strategically placed on the perimetric diagram. This method permits the quantitative analysis of the results of manual or automatic perimetric examination performed utilizing four targets: IV/4, I/4, I/3 and I/2. The points arrangement has been studied on the basis of the physiological visual field width of elderly subjects. A correction index must be used with younger subjects. Our method evaluates not only the defect’s extention but also its depth. In such a manner a better quantification of the functional damage, useful for medical-legal and insurance purposes, is obtained.
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Although the 'filling in' of each blind spot by healthy retina in the other eye has long been described as an adaptive property of the spatial arrangement of the optic disks, an explanation of why the disks are specifically located where they are has yet to be proposed. A rationale for their horizontal position in humans is offered that is based on the projections of the blind spots in visual space in relation to fixation distance and to the protrusion of the bony facial occlusion of the nose bridge.