Vergence Measurements Research Articles

Diurnal Variation in Accommodation, Binocular Vergence, and Pupil Size.

Our results show significant diurnal variations in accommodative function and the magnitude of the phoria. Therefore, when comparing visual measures in clinical or laboratory settings, performing the visual examination at the same time of day (±1 hour) is encouraged. The aim of this study was to evaluate the accommodation, binocular vergence, and pupil behavior on three different times during the day. Twenty collegiate students (22.8 ± 2.1 years) participated in this study. Participants visited the laboratory on three different days at 2-hourly intervals (morning, 9:00 to 11:00 am ; afternoon, 2:00 to 4:00 pm ; evening, 7:00 to 9:00 pm ). The binocular vergence and accommodative function were measured using clinical optometric procedures, and the accommodative response and pupil function were evaluated in binocular conditions using the WAM-5500 autorefractometer. The accommodative amplitude for the right and left eyes showed statistically significant differences for the time interval ( P = .001 and P = .02, respectively), revealing higher accommodative amplitude in the morning and afternoon in comparison with the evening. Participants were more esophoric when assessed in the morning in comparison with the evening at far and near ( P = .02 and P = .01, respectively) and when assessed in the afternoon in comparison with the evening at far distance ( P = .02). The magnitude of accommodative response was higher in the morning, and it decreased throughout the day at 500 ( P < .001), 40 ( P = .05), and 20 cm ( P < .001). No statistically significant differences were obtained for any other variable. This study shows small diurnal variations in some accommodative and binocular vergence parameters, but no effects were observed for the pupil response. These outcomes are of special relevance for eye care specialists when performing repeated accommodative or binocular vergence measures. However, the diurnal variations were modest and may not influence a routine orthoptic examination.

Changes in Accommodation and Vergence Measurements After Smartphone Use in Healthy Young Adults

Background The primary objective of this study was to explore the impacts of extended smartphone usage on accommodation and vergence measurements among healthy young adults. Specifically it seeks to identify any changes that may occur in these ocular functions as a result of extended use of smartphones.Objectives To determine pre and post accommodation and vergence components.Methods A cross-sectional research project was conducted at Mangala College of Allied Health Sciences in Mangalore. The study involved 32 young and healthy individuals with normal vision emmetropia aged between 18 to 25 years. After initial visual screening the participants were evaluated for their accommodation and vergence abilities. Specifically they were asked to read N8 text on a smartphone device placed at a working distance of 40 cm for a duration of 30 minutes. Measurements were taken before and after this task and tabulated for analysis.Results In this study a total of 32 participants were included comprising of 12 37 males and 20 63 females with an average age of 19.00plusmn1.21 years. The results obtained from the assessment of accommodation and vergence measurements before and after 30 minutes of reading on a smartphone device indicate statistically significant changes.Conclusion The findings of this research indicate that prolonged reading on a smartphone device for 30 minutes can have a significant impact on the accommodation vergence and unit of vision for the individual.

Accommodation and vergence function in children using atropine combined with orthokeratology

PurposeThis study aimed to evaluate binocular vision in terms of vergence and accommodative measurements in children treated with 0.01% atropine combined with orthokeratology (OK). MethodsThis was a prospective and randomized controlled clinical trial involving participants aged 8 to 12 years, with a spherical equivalent (SE) ranging from − 1.00 to − 6.00D. Participants were randomly divided into four groups: 1) a combination group using 0.01% atropine solution and OK lens; 2) an OK group using placebo solution and OK lens; 3) an atropine group using 0.01% atropine solution and wearing spectacles; and 4) a control group using placebo solution and wearing spectacles. Binocular vision was determined at baseline and at 3-month visits, with evaluations including horizontal phoria, fusional vergence, the accommodative convergence/accommodation (AC/A) ratio, accommodative lag, and accommodative amplitude (AA). The Wilcoxon signed-rank test was used to compare the changes in binocular vision in each group, and the Kruskal–Wallis test was used for comparisons of four groups. ResultsSixty-two participants completed the study. There was no significant difference in baseline refraction, accommodation or vergence measurements among the groups (all P > 0.05). Three months later, the accommodative lag significantly decreased in the OK group (P = 0.002) but remained unchanged in the other three groups (all P > 0.05). In addition, binocular accommodative facilities and positive relative accommodations increased in the combination and OK groups (both P < 0.05) but remained unchanged in the atropine and control groups (both P > 0.05). Only the participants with esophoria in the OK group had a significant decrease in esophoria (P = 0.008). Moreover, the changes in fusional vergence and AC/A did not significantly differ between the four groups (all P > 0.05). ConclusionAccommodative measurements changed similarly in the groups treated with OK. Changes in vergence measurements after treatment with 0.01% atropine were not significant.

Reliability of step vergence method for assessing fusional vergence in intermittent exotropia.

To evaluate the reliability of the step vergence method in measuring fusional vergence in subjects with intermittent exotropia. Thirty-two Chinese participants aged 7-20years with intermittent exotropia (excluding the convergence insufficiency type) were enrolled in this prospective study. At the eligibility screening, visual acuity, cover test and the Office Control Score were performed. For eligible participants at study visit 1, negative and positive fusional vergence at distance and near, eye dominance and the fusion maintenance test were performed. All eligible participants returned for study visit 2 on the same day (2-4h later), and the testing was repeated. The primary outcome measures were the intra-class correlation coefficient, coefficient of repeatability and smallest detectable change in the break and recovery points of negative and positive fusional vergence between the two study visits. The intra-class correlation coefficient for different vergence parameters ranged from 0.64 to 0.87. The coefficient of repeatability and the smallest detectable change for the distance positive fusional vergence break point were ±20.5 and 13.1 ∆, respectively. There was no significant difference in any vergence parameter between the first and second visits. The coefficient of repeatability and the smallest detectable change in all distance vergence parameters were high when compared to the mean value. The association between distance vergence parameters and the Office Control Score was significant only when including subjects who failed to fuse at the beginning of the test. The data demonstrate that measurement of fusional vergence with a prism bar has low repeatability in subjects with intermittent exotropia. In these individuals, convergence ability at distance is compromised, whereas other vergence parameters are not adversely affected. While the step vergence method is a valuable test in daily practice, caution is warranted when using it in clinical research.

Effects of Virtual Reality Head-mounted Displays on Oculomotor Functions

Purpose: Three-dimensional (3D) video games played using virtual reality head-mounted displays (VR-HMDs) are becoming increasingly popular. However, the use of this technology may lead to visual symptoms and discomfort by disrupting the normal linkage between the accommodation and vergence systems. This study aimed to investigate the effect of playing 3D video games using VR-HMDs on different oculomotor functions (i.e., accommodation and/or vergence system parameters) and to quantify symptoms associated with playing games using VR-HMD technology. Methods: Twenty –six male and female young adults (age range 19–27 years) with normal binocular vision completed this study. Different clinical accommodative and vergence measurements were collected before and after playing 3D video games using a VR-HMD system for 45 minutes. In addition, visual- and non–visual-related symptoms were measured before and after the video game sessions using the standardized Simulator Sickness Questionnaire. Results: The majority of accommodative parameters—including negative relative accommodation, accommodative accuracy, and monocular and binocular accommodative facilities—were significantly affected after playing 3D video games. With respect to vergence system measurements, the horizontal negative fusional vergence range at near and vergence facility test outcomes were affected significantly after the 3D video game sessions. Significant increments in different types of symptoms (i.e., visual and nonvisual) were also observed after playing 3D video games using the VR-HMD system. Conclusions: Playing 3D video games using VR-HMD systems can lead to a deterioration of certain oculomotor functions (i.e., accommodative and vergence systems). Players can be expected to experience eyestrain and discomfort after just 45 minutes of playing.

Correlations between clinical measures and symptoms: Report 2: Accommodative and vergence measures with symptoms

AimThe aim of this study was to explore associations among clinical measures of accommodation and vergences with symptoms, which could facilitate the validation of the Convergence Insufficiency Symptoms Survey to screen for deficient clinical measures. MethodsUsing a multi-stage random cluster sampling, 1211 high school students (481 males and 730 females) between 13 and 18 years of age were selected and examined. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated. The validity of the Convergence Insufficiency Symptoms Survey to distinguish between children with and those without anomalies in the clinical measures were characterized using the Receiver Operation Curve, sensitivity and specificity of the tests. ResultsThe overall mean and standard deviation for symptoms score was 27.38 ± 11.04. Deficient accommodative measures revealed worse symptoms scores than did deficient vergence measures and children with deficient clinical measures had significantly higher mean symptoms scores. (p = 0.001) However, the correlations between defective clinical measures and symptoms were significant but relatively weak. The Receiver Operation Curve showed that the clinical measures with the highest sensitivities using the CISS (≥16) were: reduced amplitude of accommodation 0.63, 95% Confidence interval, 0.59−0.68%) accommodative facility 0.62 (95% Confidence interval, 0.58−0.67) and near point of convergence 0.60 (95% Confidence interval, 0.53−0.67). ConclusionDeficient clinical measures and symptoms of asthenopia are prevalent and correlated in the sample of school children studied. Overall, findings suggest that high school children with deficient clinical measures may be symptomatic when they perform intense near task compared to those without deficiencies. In addition, although validated for convergence insufficiency, the Convergence Insufficiency Symptoms Survey could barely distinguish between children with and without defective clinical measures. Findings highlight the need for and provide baseline data towards possible validation of a fast and reliable screening tool for vision anomalies. Further studies on similar populations are needed to confirm these findings and add to knowledge base.

A Normative Study of Objective Measures of Disparity Vergence and Saccades in Children 9 to 17 Years Old

This study establishes normative data for objective outcome measures of vergence and saccade eye movements for the pediatric population. These data should facilitate future clinical trial design. This study was designed to establish normative data for objective measures of disparity vergence and saccades in children between the ages 9 and 17 years using an objective binocular eye movement tracking system. Participants (aged 9 to 17 years) had a vision examination including refraction, accommodative, and binocular vision testing. Eligibility criteria included 20/25 visual acuity with best correction, normal accommodation, and binocular vision. The ISCAN RK-826PCI binocular tracking system (ISCAN, Woburn, MA) was used to objectively record horizontal, symmetrical disparity vergence, and saccadic eye movements. Parameters assessed included peak velocity, time to peak velocity, latency, and response amplitude for both disparity vergence and saccades. One hundred eighteen participants were recruited (54.94% female; mean age, 13.5 years), and 77.1% (91/118) of the participants completed the assessment with usable data. A sample of the normative data included peak velocity (°/s), which had a mean ± standard deviation of 25.4 ± 2.9, 22.0 ± 3.0, 225 ± 16.7, and 332.5 ± 20.5 for 4° convergence, 4° divergence, 5° saccades, and 10° saccades, respectively. The mean ± standard deviation for the latency (seconds) measures were 0.28 ± 0.1, 0.28 ± 0.16, 0.23 ± 0.05, and 0.23 ± 0.05 for 4° convergence, 4° divergence, 5° saccades, and 10° saccades, respectively. Normative data enable researchers to have benchmark results for comparison with patient populations with binocular dysfunction. These objective disparity vergence measures can serve as outcome measures in future clinical trials to assess the effectiveness of therapeutic interventions by determining whether post-treatment results are similar to normal data.

Correlations between clinical measures and symptoms: Report 1: Stereoacuity with accommodative, vergence measures, and symptoms

AimThe aim of this study was to explore associations between reduced stereoacuity and clinical measures of accommodation, vergences, and symptoms which could facilitate the development of quick and reliable screening tools. MethodsUsing a multi-stage random cluster sampling, 1211 high school students (481 males and 730 females) between 13 and 18 years of age, were selected and examined. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated. Correlations among variables and the validity of Randot stereoacuity to distinguish between children with and without defective clinical measures as well as symptomatic versus asymptomatic children were characterized by the sensitivity and specificity of the tests. ResultsThe overall mean stereoacuity was 43.9 ± 25.23 s arc, and 18.9% [95% Confidence Interval, 16.6−21.4%)] of the participants had reduced stereoacuity (defined as ≥60). Stereoacuity values and symptoms scores were worse in children with defective clinical measures. The Receiver Operation Curve showed that maximum sensitivity and specificity was obtained with near point of convergence break (≥10 cm) of (0.70 95% confidence interval: 0.63–0.77) with Randot stereoacuity test (defined as ≥60 s arc). The correlations between reduced stereoacuity and symptoms scores was moderately strong and statistically significant (Pearson’s, r = 0.507, p = 0.01). The Receiver Operation Curve showed that maximum sensitivity and specificity obtained with the Convergence Insufficiency Symptoms Survey was 0.57 (95% Confidence interval = 0.53–0.62, p = 0.001), sensitivity of 90.26%, and specificity 15.26% with the Randot stereoacuity test. ConclusionReduced stereoacuity, defective clinical measures and symptoms of asthenopia were prevalent among sample of school children studied. Randot stereoacuity test could fairly distinguish between defective and normal clinical measures; though the accuracy to differentiate between symptomatic and asymptomatic school children is poor. These findings highlight the need for validation of a simple and fast screening tool in school settings. Further studies to confirm above findings will be needed.

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.

Normative values for clinical measures used to classify accommodative and vergence anomalies in a sample of high school children in South Africa

AimTo determine normative values for stereoacuity, accommodative and vergence measures for high school populations. MethodsUsing a multi-stage random cluster sampling, 1211 children (481 males and 730 females) between 13 and 18 years of age, with a median age of 16 years, were selected. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated. ResultsMost data did not have a normal distribution. The range of normality for the vergence measures were: near point of convergence break, 5–10cm, recovery, 6–13cm, near lateral phoria, 2.5–6 prism dioptre (pd) (nasal), near vertical, orthophoria to 0.50pd, negative fusional vergence break, 12–23pd, recovery, 8–17pd, positive fusional vergence break, 16–35 and recovery 11–24pd. For accommodative measures, the range of normality for accommodative measures was: amplitude of accommodation, 12–18pd, accommodative response, plano to +0.75D, binocular accommodative facility, 5–12 cycles per minute (cpm), negative relative accommodation, 1.75–2.50DS, positive relative accommodation, −2.0 to −3.0DS and 17–69s arc for stereoacuity. ConclusionThis study provides norms for clinical measures which could be used to classify accommodative and vergence parameters for children aged 13–18 years in this population or beyond. Findings should be applied in the context of the measurement techniques and the associated limitations outlined in this report.

Near Point of Convergence and Gait Deficits in Adolescents After Sport-Related Concussion.

To prospectively examine gait characteristics of participants acutely after concussion with and without receded near point of convergence (NPC), compared with healthy controls. Cross-sectional study. Sports-medicine clinic. Patients examined after concussion (n = 33; mean ± SD = 7.2 ± 3.1 days) and a group of uninjured athletes (n = 31) completed a Postconcussion Symptom Scale, underwent NPC testing, and single/dual-task gait assessments. Near point of convergence was defined as the patient-reported diplopia distance when a fixation target moved toward the nose. Receded NPC was defined as a distance >5 cm from the tip of the nose. Spatiotemporal gait characteristics in single-task and dual-task conditions were evaluated with analysis of variance; correlations were calculated between NPC and gait measures. Eighteen of 33 (55%) patients with concussion presented with receded NPC. Those with receded NPC exhibited slower gait speed (single-task = 1.06 ± 0.14 m/s vs 1.19 ± 0.15 m/s; dual-task = 0.80 ± 0.13 m/s vs 0.94 ± 0.13 m/s; P = 0.003) and shorter stride lengths (single-task = 1.11 ± 0.10 m vs 1.24 ± 0.11 m; dual-task = 0.97 ± 0.11 m vs 1.09 ± 0.11 m; P = 0.001) than healthy controls. Near point of convergence was moderately correlated with dual-task average walking speed for the normal NPC group (ρ = -0.56; P = 0.05). Postconcussion Symptom Scale scores did not significantly differ between groups (27 ± 18 vs 28 ± 16). After concussion, adolescents with receded NPC exhibited significant gait-related deficits compared with healthy controls, whereas those with normal NPC did not. Vergence and gross motor system dysfunction may be associated after concussion. Gait and vergence measures may contribute useful information to postconcussion evaluations.

Measurement of vergence and eye movement during eyes closed by EOG for human interface

The eye sensing technology using EOG is thought to be useful as a simple human interface that does not use fingers. However, only the planar viewpoint movement and blinking are used in the human interface by EOG. In this study, we aimed to measure and use the vergence movement and eye movement during eyes closed. In this research, we made a measuring equipment and actually measured the vergence and the eye movement during eyes closed. In addition, experiments using eye movements during eyes closed were performed and showed that it can be used as a human interface.

Neurobiological marker for child and adult ADHD diagnoses

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorder. It is a chronic disease where 50–60% of ADHD cases persist into adult life. ADHD is associated with a range of clinical and psychosocial impairments. In children hyperactivity, impulsivity and inattention are the core symptoms of ADHD. In adults these core symptom are also present but inattention is more prominent. Correct diagnosis of ADHD remains challenging, especially as several other psychiatric and medical disorders show the similar symptomology.ObjectivesThe diagnosis of ADHD is clinical based upon a cluster of symptoms and criteria established by guidelines such as the DSM-5. Yet, objective markers are needed to support the clinical ADHD diagnosis in children and adults. Studies suggest that a neurobiological marker (eye vergence i.e. where the eyes move in opposite directions) can detect ADHD in children and adults. The eyes converge during orienting attention, as evidenced by visual event related potentials at parietal locations. This attention related vergence is impaired in ADHD patients.MethodsWe review the neurobiology and findings of eye vergence and the relevance of its measurement for the clinical diagnosis of ADHD.ResultsNeural circuits underlying eye vergence and attention largely overlap. Using machine learning, eye vergence measurements can classify ADHD in children and adults with high (&gt; 90%) accuracy.ConclusionsEye vergence is a promising candidate for an objective clinical diagnosis of ADHD.Disclosure of interestPart of this research was paid by Braingaze. HS is co-founder and shareholder of Braingaze.

Hacia un diagnóstico más objetivo del TDAH: el papel de la Vergencia Ocular

El Trastorno por Déficit de Atención con Hiperactividad (TDAH) es uno de los trastornos más comunes del neurodesarrollo. El diagnóstico actual se fundamenta en la presencia de síntomas de inatención, hiperactividad o impulsividad detectados a través de la anamnesis, la exploración, las entrevistas con padres y profesores y las escalas de evaluación de conducta observada. Además deben realizarse exploraciones médicas y psicopatológicas para excluir otras causas de los síntomas. El proceso es complejo y laborioso. Dada la importancia de una identificación adecuada de los casos para intervenir precozmente se sugiere la necesidad de mejorar los métodos de diagnóstico añadiendo pruebas objetivas o marcadores que permitan un mayor precisión. Se revisan distintas estrategias utilizadas hasta el momento concluyendo que por ahora, ningún método ha demostrado una sensibilidad y especificidad suficiente. Recientemente encontramos una relación entre la vergencia ocular y el nivel de atención en adultos y niños. Mostramos que durante la fijación de la mirada los estímulos visuales modulan el ángulo de vergencia debido a su capacidad para capturar la atención. En un primer estudio piloto la prueba de vergencia ocular permitió discriminar entre niños sanos y niños con TDAH con un elevado grado de precisión. Se presentan los resultados iniciales de un estudio de validación donde se compara los resultados de vergencia ocular efectuados de forma ciega a un grupo de niños sanos con un grupo de niños con TDAH y un grupo de niños con otros trastornos de atención o aprendizaje y mediante algoritmos basados en “machine learning” se obtiene un grado de discriminación del 96% entre sanos y TDAH y entre estos y el grupo de niños con otros problemas de atención o aprendizaje es de 85%. En conclusión, la evaluación de la Vergencia Ocular puede constituir una herramienta válida y objetiva de ayuda al diagnóstico clínco del TDAH.

Oculomotor-Based Vision Assessment in Mild Traumatic Brain Injury: A Systematic Review.

The purpose of this article is to synthesize and appraise the evidence regarding the use of oculomotor-based vision assessment to identify and monitor recovery from mild traumatic brain injury (mTBI). Specific objectives are to (1) identify changes in oculomotor-based vision following mTBI; (2) distinguish methods of assessment; (3) appraise the level and quality of evidence; and, if warranted, (4) determine clinical recommendations for assessment. A systematic review was undertaken to identify and appraise relevant literature. A search was conducted of 7 databases of peer-reviewed literature from January 1990 to January 2015. Articles were included if study populations were clearly identified as having mTBI and used an assessment of oculomotor-based vision. Articles with pooled data (eg, mTBI and stroke), addressing afferent visual function (eg, visual field deficits) or using single case designs, were excluded. Twenty articles were selected for inclusion. Exploratory findings suggest that measurements of saccades, smooth pursuit, and vergence are useful in detecting changes associated with mTBI. Assessment methods included eye tracker protocols, optometric assessment, and the King-Devick test. The strength of this evidence is not yet sufficient to warrant clinical recommendations. Research using rigorous methods is required to develop reliable, valid, and clinically useful assessment protocols.

Variability of Fusion Vergence Measurements in Heterophoria

ABSTRACTPurpose: The aims of this study were to compare fusional vergence measurements between orthophoria, esophoria, and exophoria, and to determine the strength of correlations between fusional convergence and divergence and angle of deviation.Methods and materials: A cross-sectional study was performed in children with best-corrected visual acuity of 0.0 LogMAR in either eye, compensated heterophoria within 10 prism diopters (PD), full ocular rotations, presence of fusional vergence, and stereopsis (60 seconds of arc or better). Fusional amplitudes were compared between orthophoric and heterophoric children. The fusion reserve ratio was determined as compensating vergence divided by alternating cover test.Results: Five hundred and thirty children (7.66±1.20 years) were recruited to this study. The most common heterophoria was exophoria (n=181, 34.2% for near; n=20, 3.8% for distance). Exophoric children had significant lower mean positive fusional vergences (exophoria-orthophoria: P=0.003; exophoria-esophoria: P=0.035) for near (19.54±5.23 base-out) compared with children with orthophoria (20.48±4.83 base-out) and esophoria (22.27±5.60 base-out). Smaller convergence fusion amplitudes were associated with larger angles of deviation at near (rs=-0.115; P=0.008) and lower fusion reserve ratios were associated with larger angles of deviation at distance (rs=-0.848; P<0.001) and at near (rs=-0.770; P<0.001).Conclusions: Exophoric children have reduced convergence break points when compared with orthophoric and esophoric children. Vergence measurements, taking into consideration the baseline heterophoria, give important information about the ability of the patient to increase their vergence demand and maintain ocular alignment.

Fusional Vergence Measures and Their Significance in Clinical Assessment

Purpose: The aims of this study have been to evaluate differences between ranges in eso or exo deviances and with varying target size.Methods: Evaluation of sensory status in compensated deviations included measures of fusional vergence (blur, break and recovery values) with randomization of target size and order of prism base. Angle of deviation measures were assessed for each case.Results: Twenty-two subjects, 7 esophoric and 15 exophoric, were recruited. Median prism fusional vergence range at near fixation was 25BO to 10BI (central target); 35BO to 12BI (peripheral target). At distance fixation median range was 16BO to 6BI (central); 25BO to 6BI (peripheral). Esophorics had a range shift towards the base out range. Exophorics had a shift towards the base in range.Conclusions: Smaller positive fusional vergence values were obtained with small compared with large target sizes. Additionally, esophoric subjects had a trend towards larger base out ranges while exophoric subjects had a trend towards larger base in ranges.

Objective vs subjective measurements of dark vergence

Dark vergence is a resting position of vergence (tonic vergence), measured in a dark visual field to eliminate fusional, accommodative, and proximal stimuli. The vergence resting position is relevant for measures of phoria and fixation disparity. Dark vergence differs reliably among subjects: the average subject converges at a viewing distance of about 1 m, while the inter-individual range is from infinity to about 40 cm. In previous research, dark vergence was measured subjectively, i.e. observers adjusted the horizontal offset of dichoptically presented nonius targets to perceived alignment. Results of such subjective vergence tests do not necessarily agree with those of the objective measurements of eye position with eye trackers. Therefore, we made simultaneous subjective and objective measurements of dark vergence and found similar results with both methods in repeated tests in two sessions. Thus, the nonius test is sufficient for a subjective estimation of dark vergence.

Application of video-based technology for the simultaneous measurement of accommodation and vergence

Accommodation and vergence are two ocular motor systems that interact during binocular vision. Independent measurement of the response dynamics of each system has been achieved by the application of optometers and eye trackers. However, relatively few devices, typically earlier model optometers, allow the simultaneous assessment of accommodation and vergence. In this study we describe the development and application of a custom designed high-speed digital photorefractor that allows for rapid measures of accommodation (up to 75 Hz). In addition the photorefractor was also synchronized with a video-based stereo eye tracker to allow a simultaneous measurement of accommodation and vergence. Analysis of accommodation and vergence could then be conducted offline. The new instrumentation is suitable for investigation of young children and could be potentially used for clinical populations.

Vergence Dynamics and Variability of Fixation Disparity in Children and Adults

With dichoptic nonius lines presented repetitively on a computer monitor for only short moments in time (e.g., 80 ms), temporal aspects of vergence can be assessed: the variability of fixation disparity with a stationary central fusion stimulus and the velocity of convergence or divergence changes. Results and test-retest correlations of these psychophysical vergence measures are shown for children and adults. In most children older than about 7 years, the estimation of vergence velocity turned out as well as in adults in terms of amount and reliability.