Peripheral Binocular Imbalance in Anisometropic and Strabismic Amblyopia.

Purpose: Individuals with amblyopia experience central vision deficits, including loss of visual acuity, binocular vision, and stereopsis. In this study, we examine the differences in peripheral binocular imbalance in children with anisometropic amblyopia, strabismic amblyopia, and typical binocular vision to determine if there are systematic patterns of deficits across the visual field. Methods: This prospective cohort study recruited 12 participants with anisometropic amblyopia, 10 with strabismic amblyopia, and 10 typically sighted controls (age range, 5-18 years). Binocular imbalance was tested at 0°, 4°, and 8° eccentricities (4 angular locations each) using band-pass filtered Auckland optotypes (5 cycles per optotype) dichoptically presented with differing contrast to each eye. The interocular contrast ratio was adjusted until the participant reported each optotype with equal frequency. Results: Participants with anisometropic and strabismic amblyopia had a more balanced contrast ratio, or decreased binocular imbalance, at 4° and 8° eccentricities as compared with central vision. Participants with strabismic amblyopia had significantly more binocular imbalance in the periphery as compared with individuals with anisometropic amblyopia or controls. A linear mixed effects model showed a main effect for strabismic amblyopia and eccentricity on binocular imbalance across the visual field. Conclusions: There is evidence of decreased binocularity deficits, or interocular suppression, in the periphery in anisometropic and strabismic amblyopia as compared with controls. Notably, those with strabismic amblyopia exhibited more significant peripheral binocular imbalance. These variations in binocularity across the visual field among different amblyopia subtypes may necessitate tailored approaches for dichoptic treatment.

Patient-Reported Outcome Measures (PROMs) with Refractive and Diffractive Extended Depth of Focus (EDOF) Intraocular Lenses.

BACKGROUND: Extended depth of focus intraocular lenses (EDOF-IOLs) provide unaided far- and mid-range vision. Refractive IOLs, in contrast to diffractive designs, are associated with a lower depth of focus and absence of dysphotopsia. The aim of this study was to assess spectacle independence for far-range, mid-range, and near-vision activities in patients after implantation of refractive or diffractive EDOF-IOLs using patient-reported outcome measures (PROMs) in a real-world setting. PATIENTS AND METHODS: In 2021 and 2022, all patients in a single center referred for bilateral cataract surgery were assigned to 7 experienced cataract surgeons who either bilaterally implanted only a diffractive EDOF-IOL (Carl Zeiss Meditec AG, AT LARA Jena, Germany, three surgeons) or refractive EDOF-IOL (Johnson & Johnson Vision Inc., Tecnis Eyhance Irvine, California, USA, four surgeons) at the surgeon's discretion, with the aim of bilateral emmetropia. Six months after both cataract surgeries, all patients were contacted by telephone and asked to report their outcomes using a structured questionnaire investigating their spectacle usage for various daily activities and their experience with night glare or halos. Inclusion criteria were a normal postoperative visual potential based on the preoperative examination and completion of the questionnaire regarding postoperative visual experience. RESULTS: Of the patients, 514 underwent bilateral cataract surgery aiming for bilateral emmetropia with the implantation of EDOF-IOLs (422 with Tecnis Eyhance and 92 with AT LARA). A complete questionnaire was obtained from 472 (92%) patients, who were included in the study (393 vs. 79). Comparing Tecnis Eyhance with AT LARA IOL, 54 vs. 57% patients were able to perform most of their daily activities without spectacles, 9 vs. 19% reported not being dependent on spectacles at all, 25 vs. 29% reported using their smartphones without spectacles, 15 vs. 49% patients reported experiencing glares or halos at night, and 1 vs.15% with driving disturbance. Overall, 95 vs. 93% patients described themselves as "satisfied" or "highly satisfied" with their IOL. CONCLUSIONS: With both types of EDOF-IOLs, the majority of patients could perform most of their daily activities without spectacles, except reading, and were highly satisfied with their IOLs. Patients with diffractive Zeiss AT LARA EDOF-IOLs were more likely to accomplish unaided near-range visual tasks; however, they were also at a higher risk of experiencing glares or halos at night.

Real-World Clinical Results with the Hoya Vivinex Impress Intraocular Lens with Enhanced Depth of Focus.

BACKGROUND: In cataract surgery, intraocular lenses (IOLs) with enhanced depth of focus are an option to correct presbyopia. The purpose of this quality assurance analysis was to evaluate visual acuity and patient satisfaction after implantation of the Hoya Vivinex Impress IOL. METHODS: The Hoya Vivinex Impress IOL was implanted in patients undergoing cataract surgery at the Pallas Klinik, Olten, Switzerland. Five weeks postoperatively, a clinical examination and a survey on patient satisfaction were conducted. RESULTS: A total of 17 eyes (9 patients; mean age 64 years) underwent cataract surgery with implantation of a Hoya Vivinex Impress IOL. Five weeks postoperatively, mean uncorrected distance visual acuity (UDVA) was 0.2 logMAR, uncorrected intermediate visual acuity (UIVA) was 0.0 logMAR, and uncorrected near visual acuity (UNVA) was 0.2 logMAR. The mean distance-corrected visual acuity results were 0.0 logMAR, 0.1 logMAR, and 0.3 logMAR, respectively. Reading the newspaper without glasses was possible for 33.4% of patients. Visual disturbances such as halos and glares were not reported. CONCLUSION: Cataract surgery with Hoya Vivinex Impress IOL implantation revealed good distance and intermediate vision and, in some patients, functional near vision as well as a high patient satisfaction.

Toward a theory of perspective perception in pictures.

This paper reviews projection models and their perception in realistic pictures, and proposes hypotheses for three-dimensional (3D) shape and space perception in pictures. In these hypotheses, eye fixations, and foveal vision play a central role. Many past theories and experimental studies focus solely on linear perspective. Yet, these theories fail to explain many important perceptual phenomena, including the effectiveness of nonlinear projections. Indeed, few classical paintings strictly obey linear perspective, nor do the best distortion-avoidance techniques for wide-angle computational photography. The hypotheses here employ a two-stage model for 3D human vision. When viewing a picture, the first stage perceives 3D shape for the current gaze. Each fixation has its own perspective projection, but, owing to the nature of foveal and peripheral vision, shape information is obtained primarily for a small region of the picture around the fixation. As a viewer moves their eyes, the second stage continually integrates some of the per-gaze information into an overall interpretation of a picture. The interpretation need not be geometrically stable or consistent over time. It is argued that this framework could explain many disparate pictorial phenomena, including different projection styles throughout art history and computational photography, while being consistent with the constraints of human 3D vision. The paper reviews open questions and suggests new studies to explore these hypotheses.

Pictorial depth cues always influence reaching distance.

We report five experiments to test the influence of pictorial depth on reaching. Our core method is to project a wide-field background of linear perspective and/or texture gradient onto a tabletop, and to measure the amplitude of reaches made to targets within it. In 63 healthy participants performing immediate open-loop reaches across Experiments 1-4, we observed a clear effect of pictorial depth. This effect was driven specifically by the convergence of the background pattern at the target position: for each additional degree of pictorial convergence, reaching distance increased by half a millimetre. In the individual experiments, we applied manipulations that might be expected to modify the influence of pictorial depth. We found no evidence that the effect was modified with monocular viewing, or when participants responded with the left hand, or if a memory delay was inserted before the response. Nor did participants become less susceptible to pictorial depth when visual feedback of terminal reaching errors was provided, although visual feedback during the reach did mitigate the influence of pictorial depth. Finally, the visual form agnosic patient DF showed an entirely normal effect of pictorial depth cues, which leads us to question the idea that this effect emanates from visual analyses of size and shape in the ventral stream, rather than from the dorsal stream, or from earlier stages of visual processing.

Virtual reality for assessing stereopsis performance and eye characteristics in Post-COVID.

In 2019, we faced a pandemic due to the coronavirus disease (COVID-19), with millions of confirmed cases and reported deaths. Even in recovered patients, symptoms can be persistent over weeks, termed Post-COVID. In addition to common symptoms of fatigue, muscle weakness, and cognitive impairments, visual impairments have been reported. Automatic classification of COVID and Post-COVID is researched based on blood samples and radiation-based procedures, among others. However, a symptom-oriented assessment for visual impairments is still missing. Thus, we propose a Virtual Reality environment in which stereoscopic stimuli are displayed to test the patient's stereopsis performance. While performing the visual tasks, the eyes' gaze and pupil diameter are recorded. We collected data from 15 controls and 20 Post-COVID patients in a study. Therefrom, we extracted features of three main data groups, stereopsis performance, pupil diameter, and gaze behavior, and trained various classifiers. The Random Forest classifier achieved the best result with 71% accuracy. The recorded data support the classification result showing worse stereopsis performance and eye movement alterations in Post-COVID. There are limitations in the study design, comprising a small sample size and the use of an eye tracking system.

Relationship Between Suppression Scotomas and Stereoacuity in Anisometropic Amblyopia With Successfully Treated Visual Acuity.

Purpose: The purpose of this study was to investigate the relationship among suppression scotoma size, stereoacuity, and four-prism base-out test (4ΔBOT) results in anisometropic amblyopia with successfully treated visual acuity. Methods: We included 103 cases of anisometropic amblyopia successfully treated for visual acuity without strabismus. Stereoacuity was measured using a Randot Stereotest. The size of the suppression scotomas was measured using a new device, the polarized four dot (P4D) test. This is a modification of the Worth 4 dot test (W4D) device. The patients were divided into three groups based on the 4ΔBOT results: normal (group A = 29 cases), subnormal (group B = 48 cases), and abnormal (group C = 26 cases) response groups. The horizontal diameter of the suppression scotomas and stereoacuity in logarithmic values with a base of 20 seconds of arc (″) were compared among the 3 groups. Results: The mean age at P4D testing was 8.4 ± 2.1 years. The average horizontal diameters of the suppression scotomas were 0.35 ± 0.79Δ, 2.01 ± 0.82Δ, and 5.50 ± 2.72Δ in groups A, B, and C, respectively, showing significant differences (A versus B: P < 0.0001, A versus C: P < 0.0001, and B versus C: P < 0.0001; 1-way ANOVA). The average logarithmic stereoacuity were 1.07 (24.95″), 1.22 (38.84″), and 1.47 (82.79″) in groups A, B, and C, respectively, thereby showing significant differences between the groups (A versus B: P < 0.0001, A versus C: P < 0.0001, and B versus C: P < 0.0001; 1-way ANOVA). Stereoacuity and horizontal diameter of the suppression scotoma were strongly correlated (r = 0.732, P < 0.0001). Conclusions: The suppression scotoma size measured using P4D correlated significantly with stereoacuity and the 4ΔBOT results.

Qualitative perception of 3D shape from patterns of luminance curvature.

A new source of information is proposed for the perception of three-dimensional (3D) shape from shading that identifies surface concavities from the curvature of the luminance field. Two experiments measured the abilities of human observers to identify concavities on smoothly curved shaded surfaces depicted with several different patterns of illumination and several different material properties. Observers were required to identify any apparent concavities along designated cross sections of the depicted objects and to mark each concavity with an adjustable dot. To analyze the results, we computed both the surface curvature and the luminance curvature along each image cross section. The results revealed that most responses were in concave regions of the luminance profiles, although they were often shifted in phase relative to the curvature of the depicted surfaces. This pattern of performance was surprisingly robust over large changes in the pattern of illumination or surface material properties. Our analysis predicts that observers should make false alarm responses in regions where a luminance concavity does not correspond to a surface concavity, and our empirical results confirm that prediction.

The horopter: Old and new.

The horopter's history may partly be responsible for its ambiguous psychophysical definitions and obscured physiological significance. However, the horopter is a useful clinical tool integrating physiological optics and binocular vision. This article aims to help understand how it could come to such different attitudes toward the horopter. After the basic concepts underlying binocular space perception and stereopsis are presented, the horopter's old ideas that influence today's research show their inconsistencies with the conceptualized binocular vision. Two recent geometric theories of the horopter with progressively higher eye model fidelity that resolve the inconsistencies are reviewed. The first theory corrects the 200-year-old Vieth-Müller circle still used as a geometric horopter. The second theory advances Ogle's classical work by modeling empirical horopters as conic sections in the binocular system with the asymmetric eye model that accounts for the observed misalignment of optical components in human eyes. Its extension to iso-disparity conics is discussed.

Contribution of the stereoscopic representation of motion-in-depth during visually guided feedback control.

Considerable studies have focused on the neural basis of visually guided tracking movement in the frontoparallel plane, whereas the neural process in real-world circumstances regarding the influence of binocular disparity and motion-in-depth (MID) perception is less understood. Although the role of stereoscopic versus monoscopic MID information has been extensively described for visual processing, its influence on top-down regulation for motor execution has not received much attention. Here, we orthogonally varied the visual representation (stereoscopic versus monoscopic) and motion direction (depth motion versus bias depth motion versus frontoparallel motion) during visually guided tracking movements, with simultaneous functional near-infrared spectroscopy recordings. Results show that the stereoscopic representation of MID could lead to more accurate movements, which was supported by specific neural activity pattern. More importantly, we extend prior evidence about the role of frontoparietal network in brain-behavior relationship, showing that occipital area, more specifically, visual area V2/V3 was also robustly involved in the association. Furthermore, by using the stereoscopic representation of MID, it is plausible to detect robust brain-behavior relationship even with small sample size at low executive task demand. Taken together, these findings highlight the importance of the stereoscopic representation of MID for investigating neural correlates of visually guided feedback control.

Context-based modulations of 3D vision are expertise dependent.

An object's identity can influence depth-position judgments. The mechanistic underpinnings underlying this phenomenon are largely unknown. Here, we asked whether context-dependent modulations of stereoscopic depth perception are expertise dependent. In 2 experiments, we tested whether training that attaches meaning (i.e. classification labels) to otherwise novel, stereoscopically presented objects changes observers' sensitivity for judging their depth position. In Experiment 1, observers were randomly assigned to 3 groups: a Greeble-classification training group, an orientation-discrimination training group, or a no-training group, and were tested on their stereoscopic depth sensitivity before and after training. In Experiment 2, participants were tested before and after training while fMRI responses were concurrently imaged. Behaviorally, stereoscopic performance was significantly better following Greeble-classification (but not orientation-discrimination, or no-) training. Using the fMRI data, we trained support vector machines to predict whether the data were from the pre- or post-training sessions. Results indicated that classification accuracies in V4 were higher for the Greeble-classification group as compared with the orientation-discrimination group for which accuracies were at chance level. Furthermore, classification accuracies in V4 were negatively correlated with response times for Greeble identification. We speculate that V4 is implicated in an expertise-dependent, object-tuning manner that allows it to better guide stereoscopic depth retrieval.

The gender-based facing bias in 3-D biological motion perception.

In biological motion perception, movements of several point lights can evoke a vivid impression of living animals, including humans. Recent studies have reported that male point-light walkers tend to be perceived as facing toward the viewer more than female walkers, and have hypothesized that the gender-based facing bias arises from motion signals. The purpose of this study was to test this hypothesis under experimental conditions where binocular disparity was added to biological motion stimuli. In the two experiments reported here, participants were presented with disparity-defined female and male point-light figures facing toward or away from the viewer. In Experiment 1, we measured "facing-the-viewer" responses in upright and inverted walker configurations. It was found that the facing bias was greater for the male walker than for the female walker in most disparity magnitudes, regardless of walker inversion. In Experiment 2, the walker stimuli were replaced by static snapshots of the walkers. The results showed that the facing bias did not differ between the female and male static figures. These results suggest that motion signals play an important role in producing the gender-based facing bias, even when binocular disparity is added to biological motion stimuli.

Validity and repeatability of contour-based visotec distance stereoacuity test.

CLINICAL RELEVANCE: The clinical assessment of distance stereoacuity is important in some ocular conditions. Given the different neurophysiological mechanism for crossed and uncrossed stereoacuities, evaluation of both may provide additional insight into binocular vision disorders. BACKGROUND: Clinical devices measuring distance crossed and uncrossed stereopsis are not readily available. Visotec Distance Stereo Test (VDST) is a contour-based device designed to measure both forms of distance stereoacuity. This study assesses the validity and test-retest reliability of the device in comparison to the random dot-based Randot Distance Stereo Test (RDST). METHOD: VDST and RDST were administered to a total of 107 children, that included 51 'normal' and 56 'abnormal' (37 intermittent exotropia and 19 amblyopia) between the ages of 5 and 15 years. Two examiners retested stereoacuities in a sub-set of 62 randomly selected subjects. Stereoacuity was transformed to log scale. 95% limits of agreement were calculated for test-retest reliability. The Bland-Altman plot was used to demonstrate the agreement between the tests and the examiners. RESULTS: The mean ± SD crossed distance stereoacuities using VDST in normal, intermittent exotropia and amblyopic children were 93.1 ± 43.8, 161.9 ± 89.8 and 236.3 ± 122.4 arcseconds, respectively. For uncrossed stereoacuity, these were 104.7 ± 54.0, 187.6 ± 89.6 and 265.5 ± 144.0 arcseconds, respectively. Crossed stereoacuity was significantly better than uncrossed stereoacuity. 95% limits of test-retest agreement for crossed and uncrossed stereoacuities using the VDST were 0.27 and 0.30, respectively. An exact test-retest match using VDST was 84% in normals and 77% in abnormals for crossed and 83% in normal and 74% in abnormal for uncrossed stereoacuities. CONCLUSION: VDST is a reliable, valid and easy-to-administer distance crossed and uncrossed stereoacuity measuring device. Further studies are required to establish the clinical importance of assessing these two forms stereoacuities in relation to various binocular vision disorders.

Cortical Deficits are Correlated with Impaired Stereopsis in Patients with Strabismus.

In this study, we explored the neural mechanism underlying impaired stereopsis and possible functional plasticity after strabismus surgery. We enrolled 18 stereo-deficient patients with intermittent exotropia before and after surgery, along with 18 healthy controls. Functional magnetic resonance imaging data were collected when participants viewed three-dimensional stimuli. Compared with controls, preoperative patients showed hypoactivation in higher-level dorsal (visual and parietal) areas and ventral visual areas. Pre- and postoperative activation did not significantly differ in patients overall; patients with improved stereopsis showed stronger postoperative activation than preoperative activation in the right V3A and left intraparietal sulcus. Worse stereopsis and fusional control were correlated with preoperative hypoactivation, suggesting that cortical deficits along the two streams might reflect impaired stereopsis in intermittent exotropia. The correlation between improved stereopsis and activation in the right V3A after surgery indicates that functional plasticity may underlie the improvement of stereopsis. Thus, additional postoperative strategies are needed to promote functional plasticity and enhance the recovery of stereopsis.

From pictures to reality: modelling the phenomenology and psychophysics of 3D perception.

The dominant inferential approach to human 3D perception assumes a model of spatial encoding based on a physical description of objects and space. Prevailing models based on this physicalist approach assume that the visual system infers an objective, unitary and mostly veridical representation of the external world. However, careful consideration of the phenomenology of 3D perception challenges these assumptions. I review important aspects of phenomenology, psychophysics and neurophysiology which suggest that human visual perception of 3D  objects and space is underwritten by distinct and dissociated spatial encodings that are optimized for specific regions of space. Specifically, I argue that 3D perception is underwritten by at least three distinct encodings for (1) egocentric distance perception at the ambulatory scale, (2) exocentric distance (scaled depth) perception optimized for near space, and (3) perception of object shape and layout (unscaled depth). This tripartite division can more satisfactorily account for the phenomenology, psychophysics and adaptive logic of human 3D perception. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

Cortical Deficits are Correlated with Impaired Stereopsis in Patients with Strabismus / 神经科学通报·英文版

In this study, we explored the neural mechanism underlying impaired stereopsis and possible functional plasticity after strabismus surgery. We enrolled 18 stereo-deficient patients with intermittent exotropia before and after surgery, along with 18 healthy controls. Functional magnetic resonance imaging data were collected when participants viewed three-dimensional stimuli. Compared with controls, preoperative patients showed hypoactivation in higher-level dorsal (visual and parietal) areas and ventral visual areas. Pre- and postoperative activation did not significantly differ in patients overall; patients with improved stereopsis showed stronger postoperative activation than preoperative activation in the right V3A and left intraparietal sulcus. Worse stereopsis and fusional control were correlated with preoperative hypoactivation, suggesting that cortical deficits along the two streams might reflect impaired stereopsis in intermittent exotropia. The correlation between improved stereopsis and activation in the right V3A after surgery indicates that functional plasticity may underlie the improvement of stereopsis. Thus, additional postoperative strategies are needed to promote functional plasticity and enhance the recovery of stereopsis.

Effects of virtual target size, position, and parallax on vergence-accommodation conflict as estimated by actual gaze.

Due to the increased utilization of stereoscopic displays, the scope of the vergence-accommodation conflict has been studied extensively to reveal how the human visual system operates. The purpose of this work was to study the phenomenon of vergence-accommodation conflict by comparing the theoretical eye vergence angle (vergence response) and gaze-based eye vergence angle (vergence stimulus) based on eye tracker gaze data. The results indicated that the gaze-based eye vergence angle was largest at the greatest parallax. The result also revealed that the eye vergence angle accuracy was significantly highest at the nearest parallax. Generally, accuracy improves when virtual objects are put in the middle and close to participants' positions. Moreover, the signed error decreases significantly when the virtual object is in the middle. Based on the results of this study, we can gain a greater understanding of the vergence-accommodation conflict in the stereoscopic environment.

Strong tuning for stereoscopic depth indicates orientation-specific recurrent circuitry in tree shrew V1.

Neurons in the primary visual cortex (V1) are tuned to specific disparities between the two retinal images, which form the neural substrate for stereoscopic vision. We show that V1 neurons in tree shrews, but not in mice, display highly selective responses to narrow ranges of disparity in random-dot stereograms. Surprisingly, V1 neurons in both species show similarly strong tuning to gratings of varying interocular phase differences. This stimulus-dependent dissociation of disparity tuning can be explained by a network model that combines both feedforward and recurrent connections. The features of the model connections are supported by cortical organizations specific to each species. We validate this model by identifying putative inhibitory neurons and confirming their predicted disparity tuning in both species. Together, our studies establish a foundation for using tree shrews in studying binocular vision and raise an exciting possibility of how cortical columns could be uniquely important in computing stereoscopic depth.

Ernst Wilhelm Brücke on stereoscopic vision.

In the early 19th century the doctrine of identical retinal points, linked with the Vieth-Müller circle, was a pillar of German physiological optics. It was challenged by Wheatstone's observations of stereoscopic depth perception announced in 1838; he also advanced a cognitive theory of binocular vision that attacked physiological interpretations. In 1841 Brücke mounted a defense of the doctrine by questioning Wheatstone's observations and offering an alternative interpretation in terms of the integration over time of a rapid sequence of convergence eye movements. The theory could not be sustained because of evidence that stereoscopic depth occurred without eye movements. Brücke also questioned Wheatstone's observations that with some stereoscopic displays stimulation of identical retinal points could result in double vision. The binocular combination of circles differing in size was accounted for by differentially dissociating accommodation in opposite directions for each eye from convergence. Despite the negative reaction to Brücke's proposals, his speculations about the nature of rapid eye movements and of their neural basis were ahead of his time.

Cognitive penetrability of scene representations based on horizontal image disparities.

The structure of natural scenes is signaled by many visual cues. Principal amongst them are the binocular disparities created by the laterally separated viewpoints of the two eyes. Disparity cues are believed to be processed hierarchically, first in terms of local measurements of absolute disparity and second in terms of more global measurements of relative disparity that allow extraction of the depth structure of a scene. Psychophysical and oculomotor studies have suggested that relative disparities are particularly relevant to perception, whilst absolute disparities are not. Here, we compare neural responses to stimuli that isolate the absolute disparity cue with stimuli that contain additional relative disparity cues, using the high temporal resolution of EEG to determine the temporal order of absolute and relative disparity processing. By varying the observers' task, we assess the extent to which each cue is cognitively penetrable. We find that absolute disparity is extracted before relative disparity, and that task effects arise only at or after the extraction of relative disparity. Our results indicate a hierarchy of disparity processing stages leading to the formation of a proto-object representation upon which higher cognitive processes can act.