Vergence Responses Research Articles

Vergence eye movements during figure-ground perception

Figure-ground, that is the segmentation of visual information into objects and their surrounding backgrounds, provides structure for visual attention. Recent evidence shows a novel role of vergence eye movements in visual attention. In the present work, vergence responses during figure-ground segregation tasks are psychophysically investigated. We show that during a figure-ground detection task, subjects convergence their eyes. Vergence eye movements are larger in figure trials than in ground trials. In detected figures trials, vergence are stronger than in trials where the figure went unnoticed. Moreover in figure trials, vergence responses are stronger to low-contrast figures than to high-contrast figures. We argue that these discriminative vergence responses have a role in figure-ground.

Comparison of Visual Performance according to the Design Difference of Simultaneous Vision Multifocal Contact Lenses for Presbyopia

Purpose : To compare the visual performance of myopic presbyopia with low addition after wearing center-near and center-distance simultaneous vision multifocal contact lenses Methods : Visual performance of 13 subjects (46.92±5.91 years) was evaluated for accommodative lag, stray light, stereoacuity, horizontal phoria, near vergence and subjective vision satisfaction after wearing center-near and center-distance simultaneous vision multifocal contact lenses, respectively. Results : There were no significant differences in accommodative lag, stray light, stereoscopic acuity, horizontal phoria, near vergence and subjective vision satisfaction between center-near and center-distance simultaneous vision multifocal contact lenses with low addition in myopic presbyopes. Conclusion : There were no significant differences in visual performance related to visual quality, accommodative and vergence response after wearing center-near and center-distance simultaneous vision multifocal contact lenses with low addition in myopic presbyopes. Therefore, it is thought that it can be useful as a reference when selecting multifocal contact lenses.

Altered Vergence Eye Movements and Pupil Response of Patients with Alzheimer's Disease and Mild Cognitive Impairment During an Oddball Task.

Alzheimer's disease (AD) is characterized by progressive deterioration of cognitive functions and may be preceded by mild cognitive impairment (MCI). Evidence shows changes in pupil and vergence responses related to cognitive processing of visual information. Here we test the hypothesis that MCI and AD are associated with specific patterns in vergence and pupil responses. We employed a visual oddball task. In the distractor condition (80%of the trials), a blue stimulus was presented whereas in the target condition (20%of trials) it was red. Participants (23 Controls, 33 MCI patients, and 18 AD patients) were instructed to press a button when a target appeared. Participants briefly converged their eyes 200 ms after stimulus presentation. In controls, this transient peak response was followed by a delay response to targets but not to distractor stimuli. In the patient groups, delay responses to distractors were noticed. Consequently, the differential vergence response was strong in the control group, weak in the MCI group, and absent in the AD group. Pupils started to dilate 500-600 ms after the appearance of a target but slightly contracted after the presentation of a distractor. This differential pupil response was strongest in the AD group. Our findings support the idea of a role of vergence and pupil responses in attention and reveal altered responses in MCI and AD patients. Further studies should assess the value of vergence and pupil measurements as an objective support tool for early diagnosis of AD.

Accommodative and binocular disorders in preteens with computer vision syndrome: a cross-sectional study.

To assess computer vision syndrome (CVS) in a preteen population through an adult-validated CVS questionnaire and to evaluate how digital devices affect accommodative and binocular vision, we enrolled 309 preteens in this cross-sectional study. An adult-validated CVS questionnaire adapted to preteens was used for all subjects. Visual acuity testing, unilateral and alternate cover tests, and tests for accommodative and vergence responses were performed for all preteens. The mean age was 10.75 ± 0.67 (10-12) years. Subjects were divided into two groups: the mild CVS group with a mean CVS score ≤2 and the severe CVS group with a mean CVS score >2. Between the mild and severe CVS groups, statistically significant differences were found in near point of convergence break and recovery (P=0.03 and P=0.02, respectively) and distance negative fusional vergence break and recovery (P=0.02 and P < 0.01, respectively). More children with severe CVS developed vergence disorders than those with mild CVS. Optometric clinical screening assessments could reduce ocular symptomatology and prevent long-term effects. However, poor optometric findings might have occurred first, and the poor convergence skills resulted in the symptoms reported while using devices.

Symptoms of convergence and accommodative insufficiency predict engagement and cognitive fatigue during complex task performance with and without automation

Deficits in the accommodative and/or vergence responses have been linked with inattentive behavioral symptoms. While using automated systems (e.g., self-driving cars, autopilot), operators (e.g., drivers, pilots, soldiers) visually monitor displays for critical changes, making deficits in the accommodative and/or vergence responses potentially hazardous for individuals remaining actively engaged in the task at hand. The purpose of this study was to determine if symptoms of accommodative-vergence deficits predict an individual's level of task engagement and cognitive fatigue while performing a flight simulation task with or without automation. Eighty-four participants performed a flight simulation task with or without automation. Prior to task completion, self-report accommodative-convergence deficit symptoms were assessed with the Convergence Insufficiency Symptom Survey (CISS). Before and after the flight simulation task participants rated their task engagement and cognitive fatigue. Electroencephalographic activity (EEG) was recorded concurrently during task performance. Results showed that higher scores on the CISS were related to increased feelings of fatigue and decreased ratings of task engagement. The CISS was also positively related to parietal-occipital fast alpha power during the last 10 min of the task for participants using automation, suggesting increased cortical idling. CISS scores did not predict performance. Results have implications for optimizing operator cognitive states over extended task performance.

Reflexive Fusional Vergence and Its Plasticity Are Impaired in Convergence Insufficiency.

PurposeWe compared the adaptive capacities of reflexive fusional convergence and divergence in 10 participants with untreated convergence insufficiency (CI) to 10 age-matched binocularly normal controls (BNCs) in an effort to elucidate the functional basis of CI.MethodsVergence responses were monitored binocularly at 250 Hz using video-based infrared oculography, while single and double-step disparity stimuli were viewed dichoptically. The double-step stimuli were designed to induce an adaptive increase in the convergence or divergence reflexive fusional response dynamics.ResultsAs expected, convergence responses in the CI population were significantly slower at baseline (BNC 12.0 ± 1.8°/s vs. CI 7.4 ± 2.5°/s; P < 0.001), but divergence response velocities were similar between groups (P = 0.38). Critically, we observed an impaired adaptive change in convergence peak velocities in the CI group when compared to BNCs (–18.2% ± 27.3% vs. 25.4% ± 9.8%; P < 0.001). Adaptive changes in reflexive fusional divergence responses were similar between groups (P > 0.5) and significantly less robust when compared to BNC convergence.ConclusionsThe results support the hypothesis that the adaptive capacities of vergence are related to the strength of the underlying reflexive fusional response. Combined, the evidence suggests that the clinical condition of convergence insufficiency is underpinned by an underdeveloped or perturbated reflexive fusional vergence response mechanism. We relate these observations to different clinical guidelines for the management and treatment of this condition.

Spasm of Near Reflex: Objective Assessment of the Near-Triad.

PurposeTo characterize binocular steady-state accommodation, pupil and convergence responses (near triad) in spasm of near reflex (SNR) before and after optical and pharmacological intervention. To identify the putative source of SNR in the neural control schema of accommodation-vergence interaction using controls-engineering modeling.MethodsNear-triad of 15 patients with SNR (9 to 23 years) was recorded using an infrared photorefractor at 2m viewing distance for 120s during clinical presentation, after optical fogging intended to relieve spasm, with cycloplegia, post-cycloplegia and long-term follow-up visits. Data were also collected without cycloplegia in 15 age-matched controls. Schor (1999) model was used to computationally simulate accommodation and vergence responses of controls and SNR.ResultsBoth eyes of SNR exhibited significant myopia and refraction fluctuations (<1.0Hz) during clinical presentation [median (25th to 75th IQR) refraction: −1.7D (−3.2 to −0.8D); root mean squared (RMS) deviation: 1.1D (0.5 to 1.5D)], relative to controls [0.8D (−0.03 to 1.4D); 0.2D (0.1 to 0.3D)] (p < 0.001). These decreased after optical fogging, largely eliminated with cycloplegia and partially re-appeared in the post-cycloplegia and follow-up visits. SNR responses could be modeled by increasing the gain and decay time of tonic accommodation, vis-à-vis, controls. Pupil and convergence responses in SNR were similar to controls at all visits (p > 0.1).ConclusionsExaggerated fluctuations of steady-state accommodation may be a signature feature of SNR, even while their pupil and convergence responses may remain unaffected. These fluctuations may arise from the tonic accommodation controller, the properties of which could be potentially altered after optical fogging to relieve the disorder.

Vergence and accommodation disorders in children with vertigo: A need for evidence-based diagnosis

BackgroundPrevious clinical evaluations have demonstrated a difference in eye movements in healthy children compared to children with vertigo without vestibular pathology. It has also been previously shown that accommodation and vergence responses can be measured with remote haploscopic photo refractor (RHP) devices. We have developed a method, called REMOBI (patent US8851669, WO2011073288) that allows us to test eye movements in three-dimensional space without decoupling vergence and accommodation.[1]. MethodsWe compared standard clinical testing of vergence and accommodation responses separately, with laboratory simultaneous measurement of vergence and accommodation in healthy children, 31 with vertigo (mean age 11 SD +/- 3.02), and 53 without (mean age 10 SD +/- 3.29). Children diagnosed with vertigo then underwent orthoptic rehabilitation for vergence and accommodation disorders and were re-evaluated twice using laboratory testing: once after 12 sessions and once 3-months after completing the sessions. FindingsUsing the clinical tests, significant differences were found between the vertigo and healthy groups: D’ (break point of divergence near), D2 (second measurement of divergence after convergence far), D2’ (second measurement of divergence after convergence near), C (break point of convergence far), and C’ (break point of convergence near). However, no significant differences in accommodation or vergence were seen between the two groups using laboratory tests (RHP and REMOBI). Further, there was no difference in laboratory measurements in children with vertigo before, after, and 3 months after clinical rehabilitation. InterpretationWe postulate the difference in these two tests is because the laboratory tests are more accurate and more realistic because they measure accommodation and vergence simultaneously, as it incorporates a stronger binocular coordination response not appreciated by current clinical measurements. Further studies should be conducted to evaluate whether clinicians should consider adding objective measurements, such as using a RHP device, when diagnosing patients with vergence and accommodation disorders, to avoid prescribing costly and timely rehabilitation programs that do not improve accommodative and vergence movements. FundingWe thank the Fulbright Foundation, along with the University of California, San Francisco, for the research fellowship to Lindsey M Ward. This study is part of the PHRC VERVE, hospital research program, run at the hospital Robert Debré and supported by Direction de la Recherche Clinique, Assistance Publique, France. The funding sources had no involvement in the study design; collection, analysis, and interpretation of data; writing of the manuscript; and in the decision to submit the manuscript for publication.

Vergence Eye Movements: From Basic Science to Clinical Application - Foreword to the Special Issue.

The abstract book of the last European Conference on Eye Movements [1] lists abstracts of 373 presentations, but less than five percent investigate vergence eye movements, i.e. the coordination of the right and left eye. Why then a special issue on this neglected issue? Human vision under natural conditions involves both eyes in coordination controlled by interacting processes subsumed under the concept of vergence.. Further, vergence is important for people in their daily lives since disorders of vergence can have serious consequences: ophthalmologists deal with squinting patients on the basis of heterophoria and heterotropia testing, eye strain or visual complaints can be related to impaired vergence dynamic or less accurate static vergence, remediation by optometrist includes vergence training or prism eye glasses, etc.

Eye vergence responses in children with and without reading difficulties during a word detection task

Vergence eye movements are movements of both eyes in opposite directions. Vergence is known to have a role in binocular vision. However recent studies link vergence eye movements also to attention and attention disorders. As attention may be involved in dyslexia, it is sensible to guess that the presence of reading difficulties can be associated with specific patterns in vergence responses. Data from school children performing a word-reading task have been analysed. In the task, children had to distinguish words from non-words (scrambled words or row of X’s), while their eye positions were recorded. Our findings show that after stimulus presentation eyes briefly converge. These vergence responses depend on the stimulus type and age of the child, and are different for children with reading difficulties. Our findings support the idea of a role of attention in word reading and offer an explanation of altered attention in dyslexia.

Zone of Clear Single Binocular Vision in Myopic Orthokeratology.

To examine the zone of clear single binocular vision (ZCSBV) in myopic children and young adults after 12 months of orthokeratology (OK) wear, in comparison with single-vision soft contact lens (SCL) wear. Twelve children (8-16 years) and 8 adults (18-29 years) were assessed with a series of near-point binocular vision tests when myopia was corrected using single-vision SCLs and again after 1 and 12 months of OK wear, and axial length was measured. The ZCSBV was constructed for baseline SCL wear and after 12 months of OK wear. After 1 month of OK wear, increased accommodative responses were noted in children (C) and adults (A) as increased binocular amplitude (C:P=0.03, A:P=0.04) and reduced accommodative lag (C:P=0.01, A:P=0.01). Divergence reserves improved after 1 month in both groups (P<0.04), and a near exophoric shift was evident at 12 months (C:P=0.01, A:P=0.04). All changes at 1 month maintained stability at 12 months. An increase in accommodation and vergence responses without reduction in range resulted in an expansion of the ZCSBV in both age groups. Axial length did not significantly change in either children (P=0.25) or adults (P=0.72). In both pediatric and young adult myopes, the ZCSBV expands toward a more divergent, increased accommodation response in OK compared with SCL wear. This occurs without a corresponding loss of convergence or accommodation deactivation, indicating improved depth of focus. These findings are relevant to visual acceptance and possible mechanisms of OK's efficacy for myopia control.

Eye Vergence Responses During an Attention Task in Adults With ADHD and Clinical Controls

Objective: ADHD patients show poor oculomotor control and recent studies show that attention-related eye vergence is weak in ADHD children. We aimed to assess vergence as a potential diagnostic biomarker for ADHD in adults. Method: We assessed the modulation in the angle of vergence while performing an attention task (N = 144), comparing the results for adults previously diagnosed with ADHD (N = 108) with age-matched clinical controls (N = 36). Results: Significant differences in eye vergence response modulation between clinical controls and ADHD patients were documented. Diagnostic test accuracy was 79%. Conclusion: In combination with an attention task, eye vergence responses could be used as an objective marker to support the clinical diagnosis of adult ADHD.

Target eccentricity and form influences disparity vergence eye movements responses: A temporal and dynamic analysis

This study sought to investigate whether stimulation to the fovea or the parafovea with different color combinations influenced the temporal and dynamic features of 4° disparity vergence step responses. Twelve unique types of stimuli were displayed within a haploscope presented along the participant’s midsagittal plane. Vergence eye movement responses from fifteen naïve participants were recorded using video-based infrared eye tracking instrumentation. Latency and peak velocity from left and right eye movement responses were quantified. Results show that the type of stimulus projection (foveal versus parafoveal) significantly (p<0.001) influences the vergence response latency but did not impact peak velocity. Vergence responses to eccentric circles with 6° eccentricity targeting the parafovea resulted in a significantly faster response latency compared to vergence responses to a cross with 2° eccentricity stimuli targeting the fovea. Results have implications for the stimulus design of a variety of applications from virtual reality to vision therapy interventions.

Dynamics of the disparity vergence fusion sustain component

The stereotypical vergence response to a step stimulus consists of two dynamic components: a high velocity fusion initiating component followed by a slower component that may mediate sustained fusion. The initial component has been well-studied and is thought to be controlled by an open-loop mechanism. Less is known about the slow, or fusion sustaining component except that it must be feedback controlled to achieve the positional precision of sustained fusion. Given the delays in disparity vergence control, a feedback control system is likely to exhibit oscillatory behavior. Vergence responses to 4 deg step changes in target position were recorded in eight subjects. The slow component of each response was isolated manually using interactive graphics and the frequency spectrum determined. The frequency spectra of all isolated slow vergence movements showed a large low frequency peak between 1.0 and 2.0 Hz and one or more higher frequency components. The higher frequency components were found to be harmonics of the low frequency oscillation. A feedback model of the slow component was developed consisting of a time delay, an integral/derivative controller and an oculomotor plant based on Robinson’s model. Model simulations showed that a direction dependent asymmetry in the derivative element was primarily responsible for the higher frequency harmonic components. Simulations also showed that the base frequencies are primarily dependent on the time delay in the feedback control system. The fact that oscillatory behavior was found in all subjects provides strong support that the slow, fusion sustaining component is mediated by a feedback system.

A differential role for the posterior cerebellum in the adaptive control of convergence eye movements

IntroductionThe vergence oculomotor system possesses two robust adaptive mechanisms; a fast “dynamic” and a slow “tonic” system that are both vital for single, clear and comfortable binocular vision. The neural substrates underlying these vergence adaptive mechanisms in humans is unclear. MethodsWe investigated the role of the posterior cerebellum in convergence adaptation using inhibitory continuous theta-burst repetitive transcranial magnetic stimulation (cTBS) within a double-blind, sham controlled design while eye movements were recorded at 250hz via infrared oculography. ResultsIn a preliminary experiment we validated our stimulation protocols by reproducing results from previous work on saccadic adaptation during the classic double-step adaptive shortening paradigm. Following this, across a series of three separate experiments we observed a clear dissociation in the effect of cTBS on convergence adaptation. Dynamic adaptation was substantially reduced while tonic adaptation was unaffected. Baseline dynamic fusional vergence response were also unaffected by stimulation. ConclusionsThese results indicate a differential role for the posterior cerebellum in the adaptive control of convergence eye movements and provide initial evidence that repetitive transcranial magnetic stimulation is a viable tool to investigate the neurophysiology of vergence control. The results are discussed in the context of the current models of implicit motor adaptation of vergence and their application to clinical populations and technology design in virtual and augmented head mounted display architectures. Significance statementThe cerebellum plays a critical role in the adaptive control of motor systems. Vergence eye movements shift our gaze in depth allowing us to see in 3D and exhibit two distinct adaptive mechanisms that are engaged under a range of conditions including reading, wearing head-mounted displays and using a new spectacle prescription. It is unclear what role the cerebellum plays in these adaptive mechanisms. To answer this, we temporarily disrupted the function of the posterior cerebellum using non-invasive brain stimulation and report impairment of only one adaptive mechanism, providing evidence for neural compartmentalization. The results have implications for vergence control models and applications to comfort and experience studies in head-mounted displays and the rehabilitation of clinical populations exhibiting vergence dysfunctions.

Reflexive vergence responses to absolute disparity stimuli in 3- and 5-year old children

Reflexive vergence responses to absolute disparity stimuli in 3- and 5-year old children

Eye vergence responses to novel and familiar stimuli in young children

Eye vergence is the slow movement of both eyes in opposite directions enabling binocular vision. Recently, it was suggested that vergence could be involved in orienting visual attention and memory having a role in cognitive processing of sensory information. In the present study, we assessed whether such vergence responses are observed in early childhood. We measured eye vergence responses in 43 children (12–37 months of age) while looking at novel and repeated object images. Based on previous research, we hypothesized that visual attention and Visual Short-Term Memory (VSMT) would be evidenced by differential vergence responses for both experimental conditions, i.e. repeated (familiar) vs. novel items. The results show that attention related vergence is present in early childhood and that responses to repeated images differ from the ones to novel items. Our current findings suggest that vergence mechanisms could be linking visual attention with short-term memory recognition.

Patterns of Pupillary Activity During Binocular Disparity Resolution.

This study examined the dynamic coordination between disconjugate, vergence eye movements, and pupil size in 52 normal subjects during binocular disparity stimulation in a virtual reality display. Eye movements and pupil area were sampled with a video-oculographic system at 100 Hz during performance of two tasks, (1) fusion of a binocular disparity step (±1.5° of visual angle in the horizontal plane) and (2) pursuit of a sinusoidally varying binocular disparity stimulus (0.1 Hz, ±2.6° of visual angle in the horizontal plane). Pupil size data were normalized on the basis of responses to homogeneous illumination increments ranging from 0.42 to 65.4 cd/m2. The subjects produced robust vergence eye movements in response to disparity step shifts and high fidelity sinusoidal vergence responses (R2 relative to stimulus profile: 0.933 ± 0.088), accompanied by changes in pupil area. Trajectory plots of pupil area as a function of vergence angle showed that the pupil area at zero vergence is altered between epochs of linear vergence angle—pupil area relations. Analysis with a modified Gath-Geva clustering algorithm revealed that the dynamic relationship between the ocular vergence angle and pupil size includes two different transient, synkinetic response patterns. The near response pattern, pupil constriction during convergence and pupil dilation during divergence, occurred ~80% of the time across subjects. An opposite, previously undescribed synkinetic pattern was pupil constriction during divergence and pupil dilatation during convergence; it occurred ~15% of the time across subjects. The remainder of the data were epochs of uncorrelated activity. The pupil size intercepts of the synkinetic segments, representing pupil size at initial tropia, had different relationships to vergence angle for the two main coordinated movement types. Hippus-like movements of the pupil could also be accompanied by vergence movements. No pupil coordination was observed during a conjugate pursuit task. In terms of the current dual interaction control model (1), findings suggest that the synkinetic eye and pupillary movements are produced by a dynamic switch of the influence of vergence related information to pupil control, accompanied by a resetting of the pupil aperture size at zero-vergence.

Comparison of Vergence and Accommodation Responses of Strabismic and Non-strabismic hyperopic, and emmetropic children

Comparison of Vergence and Accommodation Responses of Strabismic and Non-strabismic hyperopic, and emmetropic children

Quantitative Approach for the Analysis of Fusional Convergence Using Eye-Tracking and SacLab Toolbox.

Fusional vergence is a disjunctive movement of the eyes that is made in order to obtain single vision. The aim of the study was to provide a quantitative and objective approach for analyzing the fusional convergence response using eye tracking (ET) technology and automatic data analysis provided by the intuitive SacLab toolbox previously developed by our group. We evaluated the proposed approach in a population of 26 subjects with normal binocular vision, who were tested with base-out prisms (magnitudes 4Δ, 6Δ, and 10Δ) in order to elicit fusional convergence response. Eye movements were recorded using the Viewpoint ET and analyzed using SacLab. Parameters describing both the vergence and the version components of the fusional response (convergence duration, CD; peak convergence velocity, PCV; number of intrusive saccades, NS; and mean saccadic amplitude, MSA) were automatically calculated and provided to clinicians for an objective evaluation. Results showed that the number of subjects achieving fusional convergence decreased with prism magnitude. For subjects achieving fusion CD and PCV increased significantly (p < 0.05) when increasing the prism magnitude. For NS and MSA, there were no significant changes when passing to 6Δ, but a significant increase resulted when passing to 10Δ (p < 0.05). Noninvasive ET associated with the intuitive SacLab toolbox may represent a valid option to objectively characterize the fusional vergence response in clinical setting. The analysis may be extended to patients with vergence disorders.