Collective plasticity of binocular interactions in the adult visual system.

Binocular visual plasticity can be initiated via either bottom-up or top-down mechanisms, but it is unknown if these two forms of adult plasticity can be independently combined. In seven participants with normal binocular vision, sensory eye dominance was assessed using a binocular rivalry task, before and after a period of monocular deprivation and with and without selective attention directed towards one eye. On each trial, participants reported the dominant monocular target and the inter-ocular contrast difference between the stimuli was systematically altered to obtain estimates of ocular dominance. We found that both monocular light- and pattern-deprivation shifted dominance in favour of the deprived eye. However, this shift was completely counteracted if the non-deprived eye's stimulus was selectively attended. These results reveal that shifts in ocular dominance, driven by bottom-up and top-down selection, appear to act independently to regulate the relative contrast gain between the two eyes.

Continuous psychophysics shows millisecond-scale visual processing delays are faithfully preserved in movement dynamics.

Image differences between the eyes can cause interocular discrepancies in the speed of visual processing. Millisecond-scale differences in visual processing speed can cause dramatic misperceptions of the depth and three-dimensional direction of moving objects. Here, we develop a monocular and binocular continuous target-tracking psychophysics paradigm that can quantify such tiny differences in visual processing speed. Human observers continuously tracked a target undergoing Brownian motion with a range of luminance levels in each eye. Suitable analyses recover the time course of the visuomotor response in each condition, the dependence of visual processing speed on luminance level, and the temporal evolution of processing differences between the eyes. Importantly, using a direct within-observer comparison, we show that continuous target-tracking and traditional forced-choice psychophysical methods provide estimates of interocular delays that agree on average to within a fraction of a millisecond. Thus, visual processing delays are preserved in the movement dynamics of the hand. Finally, we show analytically, and partially confirm experimentally, that differences between the temporal impulse response functions in the two eyes predict how lateral target motion causes misperceptions of motion in depth and associated tracking responses. Because continuous target tracking can accurately recover millisecond-scale differences in visual processing speed and has multiple advantages over traditional psychophysics, it should facilitate the study of temporal processing in the future.

Extraction of three-dimensional shapes in glaucoma patients in response to monocular depth cues.

PURPOSE: To assess the impact of glaucoma on perceiving three-dimensional (3D) shapes based on monocular depth cues. STUDY DESIGN: Clinical observational study. METHODS: Twenty glaucoma patients, subjected to binocular visual-field sensitivity (binocular-VFS) tests using a Humphrey Visual Field Analyzer, and 20 age-matched healthy volunteers, underwent two tasks: identifying the nearest vertex of a 3D shape using monocular shading (3D-SfS), texture (3D-SfT), or motion (3D-SfM) cues, and distinguishing elementary one-dimensional (1D) features of these cues. The association of the visual-field index (VFI) of binocular-VFS with 3D shape perception in glaucoma patients was also examined. RESULTS: Glaucoma patients demonstrated reduced accuracy in distinguishing 1D luminance brightness and a larger "error-in-depth" between the perceived and actual depths for 3D-SfM and 3D-SfS compared to healthy volunteers. Six glaucoma patients with a 100% VFI for binocular-VFS exhibited a similar error-in-depth to the other fourteen glaucoma patients; they had a larger error-in-depth for 3D-SfM compared to healthy volunteers. No correlation between the error-in-depth values and the VFI values of binocular-VFS was observed. CONCLUSIONS: The 3D shape perception in glaucoma patients varies based on the depth cue's characteristics. Impaired 1D discrimination and larger thresholds for 3D-SfM in glaucoma patients with a 100% VFI for binocular-VFS indicate more pronounced perceptual deficits of lower-level elementary features for 3D-SfS and higher-level visual processing of 3D shapes for 3D-SfM. The effects of the location and degree of binocular visual-field defects on 3D shape perception remain to be elucidated. Our research provides insights into the 3D shape extraction mechanism in glaucoma.

Surround masking reveals binocular adding and differencing channels.

Recent studies suggest that binocular adding S+ and differencing S- channels play an important role in binocular vision. To test for such a role in the context of binocular contrast detection and binocular summation, we employed a surround masking paradigm consisting of a central target disk surrounded by a mask annulus. All stimuli were horizontally oriented 0.5c/d sinusoidal gratings. Correlated stimuli were identical in interocular spatial phase while anticorrelated stimuli were opposite in interocular spatial phase. There were four target conditions: monocular left eye, monocular right eye, binocular correlated and binocular anticorrelated, and three surround mask conditions: no surround, binocularly correlated and binocularly anticorrelated. We observed consistent elevation of detection thresholds for monocular and binocular targets across the two binocular surround mask conditions. In addition, we found an interaction between the type of surround and the type of binocular target: both detection and summation were relatively enhanced by surround masks and targets with opposite interocular phase relationships and reduced by surround masks and targets with the same interocular phase relationships. The data were reasonably well accounted for by a model of binocular combination termed MAX (S+S-), in which the decision variable is the probability summation of modeled S+ and S- channel responses, with a free parameter determining the relative gains of the two channels. Our results support the existence of two channels involved in binocular combination, S+ and S-, whose relative gains are adjustable by surround context.

Unusual and Rare Causes of Monocular Elevation Deficit.

INTRODUCTION: To study the rare and unusual causes of monocular elevation deficit. METHODS: Five patients presenting to us with diplopia and elevation deficit were thoroughly examined and were found to have monocular elevation deficit due to rare causes. OBSERVATIONS: All five were found to have different underlying etiologies - iatrogenic, sphenoid wing meningioma, cysticercosis, sarcoidosis and mid brain infarct, and were managed appropriately. DISCUSSION: Monocular Elevation Deficit can occur due to a variety of causes. Having a high index of suspicion for the more serious etiologies is of utmost importance. Thorough clinical examination and imaging help clinch the diagnosis.

Long-term Results after Bilateral Implantation of Extended Depth of Focus Intraocular Lenses with Mini-Monovision.

PURPOSE: To assess long-term clinical results following bilateral Tecnis Symfony ZXR00 intraocular lens implantation with mini-monovision. METHODS: The medical records of cataract patients who underwent bilateral implantation of ZXR00 with intended mini-monovision (target refraction of -0.3 diopters [D] in dominant eye and -0.6 D in nondominant eye) between April 2019 and March 2021 were assessed. Postoperative uncorrected distance visual acuity (UDVA), corrected distance VA (CDVA), uncorrected intermediate VA (UIVA), uncorrected near VA (UNVA), and rate of spectacle dependence for near distance were investigated at 3 months and 2 years after surgery. RESULTS: This study included 61 patients (122 eyes) with average age of 61.8 ± 7.7 years. At 2 years postoperatively, binocular logarithm of the minimum angle of resolution UDVA, UIVA, UNVA, and CDVA were 0.086 ± 0.094, 0.056 ± 0.041, 0.140 ± 0.045, and 0.012 ± 0.024, respectively. The monocular manifest refraction spherical equivalent was -0.31 ± 0.38 in the dominant eye and -0.53 ± 0.47 in the nondominant eye at 3 months postoperatively, and -0.38 ± 0.43 in the dominant eye and -0.61 ± 0.54 in the nondominant eye at 2 years postoperatively. Eight out of 61 patients (13.1%) needed glasses 3 months after surgery, and nine out of 61 patients (14.8%) needed glasses 2 years after surgery. CONCLUSIONS: The bilateral implantation of ZXR00s with mini-monovision allows for a good VA at wide range of distance from far to near, thereby resulting in high rate of spectacle independence. These results have held up well even after 2 years after surgery.

Daily dose-response from short-term monocular deprivation in adult humans.

Short-term monocular deprivation (MD) shifts sensory eye balance in favour of the previously deprived eye. The effect of MD on eye balance is significant but brief in adult humans. Recently, researchers and clinicians have attempted to implement MD in clinical settings for adults with impaired binocular vision. Although the effect of MD has been studied in detail in single-session protocols, what is not known is whether the effect of MD on eye balance deteriorates after repeated periods of MD (termed 'perceptual deterioration'). An answer to this question is relevant for two reasons. Firstly, the effect of MD (i.e., dose-response) should not decrease with repeated use if MD is to be used therapeutically (e.g., daily for weeks). Second, it bears upon the question of whether the neural basis of the effects of MD and contrast adaptation, a closely related phenomenon, is the same. The sensory change from contrast adaptation depends on recent experience. If the observer has recently experienced the same adaptation multiple times for consecutive days, then the adaptation effect will be smaller because contrast adaptation exhibits perceptual deterioration, so it is of interest to know if the effects of MD follow suit. This study measured the effect of 2-h MD for seven consecutive days on binocular balance of 15 normally sighted adults. We found that the shift in eye balance from MD stayed consistent, showing no signs of deterioration after subjects experienced multiple periods of MD. This finding shows no loss of effectiveness of repeated daily doses of MD if used therapeutically to rebalance binocular vision in otherwise normal individuals. Furthermore, ocular dominance plasticity, which is the basis of the effects of short-term MD, does not seem to share the property of 'perceptual deterioration' with contrast adaptation, suggesting different neural bases for these two related phenomena.

Perception of visual variance is mediated by subcortical mechanisms.

Variance characterizes the structure of the environment. This statistical concept plays a critical role in evaluating the reliability of evidence for human decision-making. The present study examined the involvement of subcortical structures in the processing of visual variance. To this end, we used a stereoscope to sequentially present two circle arrays in a dichoptic or monocular fashion while participants compared the perceived variance of the two arrays. In Experiment 1, two arrays were presented monocularly to the same eye, dichopticly to different eyes, or binocularly to both eyes. The variance judgment was less accurate in different-eye condition than the other conditions. In Experiment 2, the first circle array was split into a large-variance and a small-variance set, with either the large-variance or small-variance set preceding the presentation of the second circle array in the same eye. The variance of the first array was judged larger when the second array was preceded by the large-variance set in the same eye, showing that the perception of variance was modulated by the visual variance processed in the same eye. Taken together, these findings provide evidence for monocular processing of visual variance, suggesting that subcortical structures capture the statistical structure of the visual world.

Visual performance and photic disturbances with diffractive and nondiffractive EDOF intraocular lenses using mini-monovision: randomized trial.

PURPOSE: To compare visual performance and photic visual disturbances of patients implanted with 2 different extended depth-of-focus (EDOF) intraocular lenses (IOLs) using mini-monovision. SETTING: Ambulatory surgical center at the University of São Paulo in Ribeirão Preto, Brazil. DESIGN: Prospective, examiner-masked, randomized clinical trial. METHODS: Patients were assigned to either a bilateral Symfony (SYM) or Vivity (VIV) IOL group, with 1 eye targeted for myopia (-0.75 diopter [D]). Defocus curve, contrast sensitivity (Pelli-Robson), Patient-Reported Spectacle Independence Questionnaire, and Quality of Vision questionnaire were recorded at 3 months postoperatively. RESULTS: A total of 126 patients finished the follow-up: group SYM: n = 60 and group VIV: n = 66. Regarding near visual acuity, 80% of patients in the SYM group and 84% of patients in the VIV group achieved J2 or better on the near-planned eye ( P = .3840). No significant differences were found between groups for distance visual acuity, defocus profiles, PRISC, contrast sensitivity, or reading speed ( P > .05). Notably, significant between-group differences were observed for bothersome visual disturbances ( P = .0235), with 45% of patients in the SYM group with a score of 0 for bothersome disturbances compared with 66% in the VIV group. CONCLUSIONS: Mini-monovision using these EDOF IOLs was well-tolerated in the patient cohort. No significant differences were found for visual performance tests between the VIV and SYM groups. However, the data suggest that Vivity IOL is associated with a lower probability of bothersome visual disturbances compared with Symfony IOL.

Monocular and binocular mechanisms detect modulations of dot density and dot contrast.

Strong reciprocity has been demonstrated between (1) spatial modulations of dot density and modulations of dot luminance, and (2) modulations of dot density and modulations of dot contrast, in textures. The latter are much easier to detect when presented in phase with one another than when presented 180° out of phase, although out-of-phase modulations can also be detected given sufficient amplitude. This result supports the existence of two detection mechanisms: one that is excited by both density modulations and contrast modulations (quiescent when those modulations are presented 180° out of phase) and another that is relatively insensitive to either density modulations or contrast modulations (thus remaining stimulated regardless of phase angle). We investigate whether the mechanism responsible for detecting out-of-phase modulations depends on high-level computations (downstream from the confluence of monocular signals) or whether both mechanisms are situated at the monocular level of visual processing. Specifically, density-modulated and/or contrast-modulated stimuli were presented monocularly (i.e., to the same eye) or dichoptically (i.e., to opposite eyes). Out-of-phase modulations of density were much easier to detect when presented dichoptically. A dichoptic advantage was also found for out-of-phase density and contrast modulations. These dichoptic advantages imply conscious access to a mechanism at the monocular level of processing. When density modulations were presented dichoptically, 180° out of phase, detection thresholds were highest. Consequently, a mechanism with binocular input must also contribute to the detection of these modulations. We describe a minimal, image-based model for these results that contains one monocular computation and one binocular computation.

Clinical results after binocular implantation of a unique nondiffractive enhanced monofocal intraocular lens designed for enhanced monovision to increase the depth of focus.

PURPOSE: To provide the reports of a pilot study to assess the visual acuity (VA) and contrast sensitivity with RayOne enhanced monovision (EMV), a unique nondiffractive enhanced monofocal intraocular lens (IOL) to increase the range of focus. METHODS: A retrospective case series study was conducted by analyzing 25 patients (50 eyes) who had bilateral implantation of EMV IOL after cataract surgery. Data collected included biometry, spherical equivalent (SE), and VA for near, intermediate, and distance. Patients were reviewed at 1 day, 1 week, and 1 month after surgery. Contrast sensitivity (CS) was checked at 1 month. RESULTS: The study included 14 males (56%). Age of participants was 61.4 ± 7.4 years. Uniocular uncorrected near and distance VA improved from 0.33 ± 0.13 to 0.05 ± 0.07 and from 0.63 ± 0.31 to 0.05 ± 0.10 log of minimum angle of resolution (logMAR) at 1 month (P < 0.001 for both). Binocular uncorrected near and distance VA improved from 0.09 ± 0.18 and 0.14 ± 0.27 to 0.05 ± 0.06 and 0.00 ± 0.09 logMAR, respectively (P < 0.001). SE changed from - 0.23 ± 2.55 to - 0.33 ± 0.46. CS at 3 months was 1.74 ± 0.21. At 1 month, 48 eyes (96%) achieved uncorrected intermediate VA 6/15 (0.4 logMAR) or better. When comparing eyes that had uncorrected intermediate vision of ≥ 0.2 (6/9 or better) to eyes that had < 0.2 logMAR at 1 month, there was no difference between groups with respect to baseline parameters. CONCLUSION: The pilot study shows that the nondiffractive EMV IOL is safe, effective, and stable, providing excellent distance and intermediate vision and good near vision.

Gaze behaviour during multiple object tracking is dependent on binocular vision integrity.

INTRODUCTION: Despite the critical importance of binocular vision integrity in daily activities, there exists limited understanding of how alterations in binocular vision integrity impact gaze behaviour during dynamic, complex psychomotor skills. This study aimed to measure how alterations in binocular vision integrity, created by Bangerter filters (BF), affect gaze behaviour during multiple object tracking (MOT). METHODS: During the experiment, 22 volunteers completed the MOT task under three different visual conditions. The first condition involved natural binocular viewing, while the second and third conditions used 0.4 and 0.2 neutral density BF, respectively, resulting in monocular blur in the sensorially dominant eye. During the MOT task, participants were instructed to track three of eight balls for 10 s, and the speed was adjusted using a staircase procedure. Throughout the task, the following gaze parameters were recorded: fixation duration, saccade duration, amplitude and frequency as well as blink rate. RESULTS: During MOT execution, participants employed three gaze strategies regardless of viewing conditions: saccadic movements were predominant, followed by maintaining fixation on a central location throughout the trial and to a lesser extent, smooth pursuit eye movements. There was a significant effect of manipulating viewing conditions on the MOT scores (p = 0.046, η2 = 0.09). As the viewing conditions became more difficult, we observed a decrease in fixation duration (p = 0.004, η2 = 0.16) and blink rate (p < 0.001, η2 = 0.20) and an increase in saccadic amplitude (p < 0.001, η2 = 0.29). CONCLUSIONS: The results support the notion that perceptual-cognitive skills depend on the integrity of binocular vision, underscoring the sensitivity of gaze behaviours to any impairment of binocular function.

Yield of Investigations in Young Patients Presenting With Transient Monocular Vision Loss: A Prospective Study.

PURPOSE: It is unclear whether transient monocular vision loss (TMVL) warrants the same thorough systemic evaluation for potential embolic sources in young adults as it does in older adults. The objective of the present study was to evaluate the yield of investigations in patients under 45 years of age presenting with TMVL. DESIGN: Prospective cohort study. METHODS: Young adult patients with TMVL presenting to a university-affiliated neuro-ophthalmology clinic were included. All included patients were referred for neuroimaging (computed tomography or magnetic resonance angiography of entire carotid tree and magnetic resonance imaging of the brain) and cardiac investigations (transesophageal echocardiography and 2 weeks of Holter monitoring). RESULTS: A total of 20 participants with TMVL were included in the study. The mean age was 33.1 ± 8.2 years, and 16 of the 20 participants were women. The most common finding on past medical history was migraines, in 5 of 20 cases (25%), and 25% of patients had headaches during their visual loss. Of 17 participants who completed neuroimaging, 1 had fibromuscular dysplasia (this patient also experienced headaches during their symptoms). Two of 13 patients who completed echocardiography had patent foramen ovale. Overall, 3 of 20 participants (15%, 95% CI 3%-38%) had abnormal findings associated with their TMVL. Aspirin treatment was initiated in 2 of 3 patients following investigations. CONCLUSION: In our cohort of young patients presenting with TMVL, 15% of patients had abnormal findings on further investigations. We recommend that young patients presenting with TMVL be referred for neuroimaging and cardiac workup so that appropriate treatments can be initiated to prevent future complications. Headaches during vision loss may not always indicate a benign cause, and retinal migraine should be a diagnosis of exclusion.

The effect of different depth planes during a manual tracking task in three-dimensional virtual reality space.

Unlike ballistic arm movements such as reaching, the contribution of depth information to the performance of manual tracking movements is unclear. Thus, to understand how the brain handles information, we investigated how a required movement along the depth axis would affect behavioral tracking performance, postulating that it would be affected by the amount of depth movement. We designed a visually guided planar tracking task that requires movement on three planes with different depths: a fronto-parallel plane called ROT (0), a sagittal plane called ROT (90), and a plane rotated by 45° with respect to the sagittal plane called ROT (45). Fifteen participants performed a circular manual tracking task under binocular and monocular visions in a three-dimensional (3D) virtual reality space. As a result, under binocular vision, ROT (90), which required the largest depth movement among the tasks, showed the greatest error in 3D. Similarly, the errors (deviation from the target path) on the depth axis revealed significant differences among the tasks. Under monocular vision, significant differences in errors were observed only on the lateral axis. Moreover, we observed that the errors in the lateral and depth axes were proportional to the required movement on these axes under binocular vision and confirmed that the required depth movement under binocular vision determined depth error independent of the other axes. This finding implies that the brain may independently process binocular vision information on each axis. Meanwhile, the required depth movement under monocular vision was independent of performance along the depth axis, indicating an intractable behavior. Our findings highlight the importance of handling depth movement, especially when a virtual reality situation, involving tracking tasks, is generated.

Psychophysics may be the game-changer for deep neural networks (DNNs) to imitate the human vision.

Psychologically faithful deep neural networks (DNNs) could be constructed by training with psychophysics data. Moreover, conventional DNNs are mostly monocular vision based, whereas the human brain relies mainly on binocular vision. DNNs developed as smaller vision agent networks associated with fundamental and less intelligent visual activities, can be combined to simulate more intelligent visual activities done by the biological brain.

Effect of binocular vision during target shooting in archery.

PURPOSE: This study aimed to evaluate the difference between binocular and monocular vision and eye movements during the competition using video-oculography (VOG). METHODS: Experiment 1 included 14 participants to evaluate differences in arrow convergence. Then, seven participants in Experiment 1 were randomly selected and included in Experiment 2, which evaluated eye movements during archery using VOG. The target used an 80-cm waterproof target face and was set at a distance of 30 m. All players shot the target 36 times using their bows and arrows. Experiments 1 and 2 evaluated the distribution of arrows in each score and the number of focus points, respectively, between binocular and monocular conditions. RESULTS: The arrows, which include the area of 9 points, were significantly greater in the binocular condition (11.85 ± 5.04 shots) than in the monocular condition (9.36 ± 5.41 shots) in Experiment 1 (P = 0.047). The players focused on the target under both binocular and monocular conditions, although the players were switching off fixation between the target and shooting sight under the binocular condition in Experiment 2. CONCLUSION: These behaviors indicated that the players were trying to accurately shoot the target by exploring the distance between themselves and the target as a cue for depth perception.

Effects of alcohol consumption on driving performance in the presence of interocular differences simulated by filters.

The role of interocular differences simulated by filters (fog filter and Bangerter foil) on visual and driving performance in alcohol users was assessed. We found that the binocular visual function deteriorates significantly in terms of contrast sensitivity (from 6 to 18 cpd). Additionally, driving performance is significantly impaired under these conditions as evidenced by increased mean speed, standard deviation of the lateral position, distance traveled outside the lane, reaction time and number of collisions. Furthermore, we found that interocular differences due to intraocular scattering and straylight are directly related to an overall reduction in visual and driving performance. This provided a comprehensive perspective from which to understand the relationship between binocular visual function, interocular differences, and driving performance. In practice, our findings contribute to the understanding of the importance of limiting interocular differences, which can be common among presbyopes corrected using the monovision technique, as well as in cases of cataract or other ocular pathology affecting only one eye, or even in cases of cataract surgery of the first eye. These interocular differences can have an adverse impact on road safety, especially when combined with moderate alcohol consumption.

Clinical Reasoning: A Woman With Progressive Painless Sequential Monocular Vision Loss.

A 68-year-old woman with a history of diabetes mellitus type 2, depression, and migraines presented with painless, acute, consecutive vision loss affecting the right eye for 1 week and the left eye for 2 weeks. Neuro-ophthalmic examination was notable for visual acuities of finger-counting peripherally, a central scotoma, anterior uveitis, vitritis, and placoid macular pigmentary changes in each eye (OU). Proprioception was diminished in the bilateral lower extremities. Optical coherence tomography (OCT) revealed hyper-reflectivity and attenuation of the outer retina OU with normal inner retinal architecture and reflectivity. Fluorescein angiography (FA) demonstrated normal filling of the central retinal arteries with patchy choroidal perfusion in the right eye and targetoid punctate foci of leakage in the macula OU. Before the recognition of intraocular inflammation and findings on OCT and FA, the patient was treated for presumed central retinal artery occlusion at an outside hospital. Additional diagnostic testing at our institution revealed an alternate diagnosis. This case highlights a rare presentation of a well-known disease entity and underscores the importance of avoiding diagnostic anchoring in clinical practice.