Repeatability and agreement in the measurement of horizontal fusional vergences

Innovative Binocular Vision Testing for Phoria and Vergence Ranges Using Automatic Dual Rotational Risley Prisms

This study evaluated binocular visual function using automatic dual rotational Risley prisms (ADRRPs) to measure phoria and vergence ranges. Thirty-nine (mean age: 21.82 ± 1.10 years; age range: 20-24 years) healthy adults with normal binocular vision participated. Each underwent baseline refraction exams followed by phoria and vergence tests conducted using both a phoropter with Maddox rods and the ADRRPs. The results revealed a strong positive correlation between the two instruments for distance phoria (r = 0.959, p < 0.001) and near-phoria measurements (r = 0.968, p < 0.001). For vergence testing, positive fusional vergence (PFV) at distance showed a moderate-to-strong correlation for break points (r = 0.758, p < 0.001) and a moderate correlation for recovery points (r = 0.452, p < 0.001). Negative fusional vergence (NFV) at distance demonstrated a strong correlation for break points (r = 0.863, p < 0.001) and a moderate correlation for recovery points (r = 0.458, p < 0.01). Near-vergence testing showed moderate-to-strong correlations for break points (r = 0.777, p < 0.001) and recovery points (r = 0.623, p < 0.001). The inclusion of Bland-Altman analysis provides a more comprehensive evaluation of agreement between ADRRPs and the phoropter. While strong correlations were observed, systematic bias and LoA indicate that these methods are not perfectly interchangeable. The ADRRPs demonstrated potential for binocular vision assessment but require further validation for clinical application.

Minimum perceptual time (MPT). Repeatability and reproducibility of variables applied to "sports vision"

PURPOSE

"Minimum Perceptual Time" (MPT) is the ability to take the most visual information in the least time. The purpose of the study was to assess intraobserver and interobserver repeatability of a MPT measurement method by using COI-SV® software and to analyze the possible influence of age and sex.

METHODS

MPT was measured in 79 participants by using COI-SV® software. Visual acuity was 20/80 (2.50 m) and numbers were gradually increasing in quantity and decreasing in exposure time. The most quantity of numbers and the least time was written down. To assess intraobserver and interobserver repeatability, a protocol based on repeating the test 4 times (2 intrasession and 2 intersessions with 2 examinators) was established. Comparison of means and Spearman correlation were performed to evaluate the influence of sex and age. It was investigated inter and intraexaminer variability using repeatability indices, as well as Bland-Altman analysis to define limits of agreement.

RESULTS

A total of 79 participants were included (mean age 32.8 ± 11.95 years, range 19-64 years). Regarding sex, there were no significant differences between men and women (p = 0.080), whereas age and MPT had an inverse correlation (p = 0.01). Interexaminer and intraexaminer repeatability proved to be moderate to good in all methods. Bland-Altman showed difference between sessions was 0.259 ± 2.189 (-4.030 and + 4.549) and difference between examiners was - 0.519 ± 2.104 (-4.642 and + 3.604).

CONCLUSION

MPT measurements with COI-SV® software evidenced moderate to good repeatability and observers` independent result, so it could be included in optometric examinations.

KEY MESSAGES

WHAT IS KNOWN : Sports optometry is a relatively new field, so research is scarce and of poor quality. The scarcity of literature is practically limited to studies in the field of psychology, although they do not provide us with much information since they have not been studied for the mentioned field. The in-depth study of new standardized measurement methods would be of great help for optometrists in their clinical practice.

WHAT IS NEW

This study is the first to determine intraobserver and interobserver repeatability and reproducibility for Minimum Perceptual Time (MPT) measurements acquired by the COI-SV® software, exhibiting ICC > 0.7 and establishing limits of agreement by using Bland-Altman analysis. In a significant way, MPT and age would have an inverse correlation, whereas MPT results would be better in men than women. Our results add evidence towards validating the test included in COI-SV® software so that the optometrist can include it in their clinical protocols in order to obtain more complete information on visual examinations.

Does the subjective response during the measurement of fusional reserves affect the clinical diagnosis?

INTRODUCTION

Fusional reserves differ with the method of measurement. The goal of this study was to compare the subjective and objective responses during the measurement of positive and negative fusional reserves using both step and ramp methods.

METHODS

A haploscopic system was used to measure fusional reserves. Eye movements were recorded using an EyeLink 1000 Plus eye tracker (SR Research). The stimulus disparity was changed to either mimic a prism bar (steps) or a Risley prism (ramp). Subjective responses were obtained by pressing a key on the keyboard, whereas objective break and recovery points were determined offline using a custom algorithm coded in Matlab.

RESULTS

Thirty-three adults participated in this study. For the ramp method, the subjective and objective responses were similar for the negative (break and recovery points (t(32) = -0.82, p = 0.42) and (t(32) = 0.42, p = 0.67), respectively) and positive fusional reserves (break and recovery points (U = -1.34, p = 0.18) and t(19) = -0.25, p = 0.81), respectively). For the step method, no significant differences in positive fusional reserves were observed when measured subjectively and objectively for the break (t(32) = 1.27, p = 0.21) or the recovery point (U = -2.02, Bonferroni-adjusted p = 0.04). For the negative fusional reserve, differences were not significant for either the break or recovery points (U = -0.10, p = 0.92 and t(19) = 1.17, p = 0.26, respectively).

CONCLUSION

Subjective and objective responses exhibited good agreement when measured with the ramp and step methods.

No agreement between expected phoropter Risley prism and prism bar fusional vergences in a prospective cross-sectional study of African school children

Purpose: To determine the agreement between phoropter Risley prism and prism bar fusional vergence amplitudes in a normative group of school-aged children, aged 8 to 17 years. Method: This prospective cross-sectional study utilized multistage sampling to recruit participants with normal binocular vision. Horizontal fusional vergence amplitudes were measured at distance and near using the phoropter with Risley prisms and the prism bar. Result: The study included 422 normal participants (48.1% male, 51.9% female) with a mean age of 12.39 ± 1.94 years. There were significant differences in the base-in break, base-in recovery, base-out blur, base-out break, and base-out recovery at distance and near between phoropter Risley prism and prism bar fusional vergences (p < 0.05); amplitudes for phoropter Risley prism were higher than that for prism bar. Their mean differences were clinically meaningful except for base-in recovery at distance; however, there was no level of agreement on Bland Altman analysis. Conclusion: Fusional vergence amplitudes measured with the phoropter Risley prism and prism bar should not be considered interchangeable in African schoolchildren.

The Interaction between Vergence and Accommodation Cues in the Assessment of Fusional Vergence Range

Fusional vergence range tests are commonly used in optometric practice. The aim of this study was to investigate the possible contribution of CA/C, AC/A, and proximal cues (PCT) to the magnitude and presence of blur and recovery during the measurement of fusional vergence ranges and to determine whether the occurrence of blur is influenced by these vergence and accommodation cues. A total of 27 participants with normal binocular vision were included and AC/A, CA/C, and PCT ratios were evaluated. Blur, break, and recovery values in convergence and divergence were assessed with base-out and base-in prisms, respectively. No statistical correlations were found between AC/A, CA/C, and PCT ratios and the magnitude of blur, break, and recovery values in neither far, near, convergence, nor divergence testing conditions. However, better near point of convergence values were related to higher break values in convergence at far distances, but not at near distances. In addition, for convergence and far distance, a statistical difference was found between groups reporting and not reporting blur in AC/A stimulus and PCT ratios. The present results cannot confirm whether vergence and accommodation cues, such as AC/A, CA/C, and PCT ratios, may play an active role during the assessment of fusional vergence range.

Binocular vision measurements with a new online digital platform: comparison with conventional clinical measures

CLINICAL RELEVANCE

New digital systems are being developed for evaluating different aspects of the visual function, such as binocularity, and it is important to know their real performance in clinical practice in order to use them appropriately.

BACKGROUND

The aim was to compare binocular vision measures obtained with an online digital platform with conventional measures using prisms and printed tests.

METHODS

Prospective study enrolling 49 healthy patients (mean age: 35.5 ± 13.6 years). A complete visual examination was performed including measurement of near phoria (cover test), negative fusional vergence (NFV) and positive fusional vergence (PFV) ranges (prism bar), and stereopsis (24 patients Randot Stereo Test and 25 patients TNO Random Dot Test 19th edition). These same parameters were also measured with the Bynocs system (Kanohi Eye Pvt Ltd). Bland - Altman plots were used to analyse the agreement between methods.

RESULTS

Digital measurement of near phoria was significantly lower than that obtained with the cover test, with a median difference (MD) of 4.71 (-0.07-20.07) prism dioptres (pd) (p < 0.001). No significant differences were found between Bynocs and prism bar methods in NFV break (MD 2.00, range -21-26 pd, p = 0.584) and recovery points (MD 0.00, range -16-24 pd, p = .571). Near PFV were significantly lower with Bynocs (break: MD -9.00, range -38-12 pd; recovery: MD -14.00, range -43-20 pd; p < 0.001). Bynocs stereoacuity threshold was significantly lower than that obtained with TNO (p = 0.004), but significantly higher compared to Randot (p < 0.001). Large and clinically relevant confidence intervals for the comparison between digital and conventional measures were detected in Passing-Bablok analysis.

CONCLUSIONS

Digital measures of near phoria, NFV, PFV, and stereopsis with the Bynocs platform cannot be used interchangeably with conventional measures. The normal ranges of normality for this new tool are defined.

Binocular vision parameters and visual performance in bilateral keratoconus corrected with spectacles versus rigid gas-permeable contact lenses

PURPOSE

To analyze binocular vision of individuals aged 18 to 35 years diagnosed with keratoconus, utilizing spectacles and rigid gas-permeable (RGP) contact lenses. Research was led by the Universidad Autónoma de Aguascalientes, México and Fundación Universitaria del Área Andina Pereira, Colombia.

METHODS

A single center, prospective non-randomized, comparative, interventional, open-label study, in which the differences in binocular vision performance with both spectacles and RGP contact lenses was carried out from December 2018 to December 2019. Sampling was performed according to consecutive cases with keratoconus that met the inclusion criteria until the proposed sample size was reached.

RESULTS

Rigid gas-permeable (RGP) contact lenses notably enhanced distance and near visual acuity in keratoconus patients compared to spectacles. Visual alignment analysis shows exophoria at both distances and is slightly higher with RGP contact lenses. The difference was statistically significant (p<0.05), with 82.5 % presenting compensated phoria with spectacles and pnly 42.50% with RGP contact lenses. Stereoscopic vision improved while wearing RGP contact lenses (42.59 %), although accommodation and accommodative flexibility remained within normal ranges.

CONCLUSIONS

Patients with keratoconus fitted with RGP contact lenses have improved binocular vision skills such as visual acuity, stereopsis, and accommodative flexibility. However, even when the vergence and motor system is decompensated with respect to normal ranges, the range between break and recovery points for both fusional reserves and the near point of convergence (NPC) improves with the use of RGP contact lenses, giving indications of an adaptive condition of the motor system from the medium to the long term.

Are Horizontal Fusional Vergences Comparable When Measured Using a Prism Bar and Synoptophore?

Aim

To determine whether horizontal fusional vergences are comparable when measured using a prism bar and synoptophore.

Methods

Thirty two participants (18-23 years) had their blur, break, and recovery points measured for convergence and divergence amplitudes using a prism bar (6 m) and synoptophore. All participants had VA of 0.1 LogMAR or better in either eye, were heterophoric or orthophoric and had binocular single vision. The prism bar target was a 0.2 LogMAR letter. The synoptophore target was the foveal 'rabbit' fusion slides. The prism bar was placed over the dominant eye and the testing speed was two seconds per two prism dioptres (Δ), increasing to five seconds per 5Δ when the increments began to increase in 5Δ. Synoptophore testing speed was two seconds per degree.

Results

The synoptophore measured significantly higher convergence break points than the prism bar (Z = 3.37, p = 0.001). No significant differences were found between both tests for divergence break points (Z = 0.99, p = 0.32). However, both tests displayed wide limits of agreement (LoA) when measuring convergence (-24Δ to + 49.59Δ) and divergence break points (-7.70Δ to + 10.19Δ). Differences when measuring convergence and divergence blur and recovery points were not statistically significant.

Conclusion

There was a statistically and clinically significant difference when measuring convergence break points using the prism bar and synoptophore but no significant difference when measuring divergence break points. However, both tests displayed wide LoA when measuring convergence and divergence break points, indicating they should not be used interchangeably in clinic to measure horizontal fusional vergences.

Assessment of distance-near control disparity in basic and divergence excess paediatric intermittent exotropia

CLINICAL RELEVANCE

In intermittent exotropia (IXT), deviation is better controlled at near fixation. Understanding of the mechanism responsible for this common observation may improve clinical management of IXT.

BACKGROUND

The physiological basis for the distance-near difference in control of deviation in IXT is vastly undetermined. A new parameter, 'control score disparity (CSD)', defined as the difference between distance and near control scores, is introduced. Association of CSD with positive fusional amplitude (PFA), accommodative convergence to accommodation (AC/A) ratio and distance angle of deviation was investigated to further understand the mechanisms.

METHOD

Patients aged between four and fifteen years with basic and divergence excess IXT were included. Subjects with previous strabismus surgery, amblyopia and inability to perform clinical tests were excluded. A standardized office-based scoring system was used to assess IXT controls. Subjects were sub-divided into group 1 (CSD <2) and group 2 (CSD ≥2). Pearson's univariate and regression analysis were used to determine relationships between CSD and other independent variables.

RESULTS

Mean age of the total 141 subjects (57.6% female) was 6.8 ± 2.5 years. Basic IXT was more common (60%) and 60% had CSD ≥2. The mean±SD distance angle of deviation, AC/A ratio, PFA and CSD were 22.1 ± 6.6 prism dioptres, 5.0 ± 1.0, 28.6 ± 6.3 prism dioptre and 2.0 ± 0.5, respectively. CSD was significantly correlated to PFA (r = 0.64, p < 0.001) and AC/A ratio (r = 0.27, p < 0.001) in overall samples and Group 2 subjects (r = 0.41, p = 0.001).

CONCLUSIONS

PFA is a major factor associated with the distance/near difference of IXT control. Individuals with a higher PFA demonstrated greater CSD. While AC/A ratio was associated in better control at near in divergence excess IXT, magnitude of angle appears irrelevant.

Objective estimation of fusional reserves using infrared eye tracking: the digital fusion-range test

CLINICAL RELEVANCE

Horizontal fusional reserves are used in the diagnosis and monitoring of common vergence disorders, such as convergence insufficiency, which can cause asthenopia and impact near work. Infrared eyetracking technology shows promise for obtaining automated and objective measurements of fusional reserves, expanding options for screening, clinical testing, and at-home monitoring/vision training.

BACKGROUND

Current clinical tests for fusional reserves rely on subjective judgements made by patients (for diplopia) and clinicians (for eye movements). This paper describes an objective and automated "digital fusion-range test" pilot-tested in adults without current eye disease or binocular vision anomalies. This test combines a consumer-grade infrared eyetracker, a dichoptic display, and custom analyses programs to measure convergence and divergence reserves.

METHODS

Twenty-nine adult participants completed the study. Horizontal fusional reserves at 55 cm were measured using prism bars and with our computer-based digital fusion-range test. For the digital test, observers viewed dichoptic targets whose binocular disparity modulated over time (at speeds of 0.5, 1.0, or 2.0 Δ/s) while their eye movements were continuously recorded. Subjective reports of break and recovery (by keyboard button press) were compared to objective estimates extracted from eyetracking recordings (via automated analyses).

RESULTS

Objective and subjective measures of break and recovery agreed closely. Clinically small (0.3-2Δ) but statistically significant (p < 0.012) differences were found between measurement types for divergence breaks/recoveries and convergence recoveries. No significant differences were found for convergence breaks (p = 0.11). Such differences are consistent with an average 0.91 (SD 1.66) seconds delay between objective break/recovery and subjective responses. The digital test produced comparable results to the standard clinical prism bar method.

CONCLUSION

The digital fusion-range test supports an automated, reliable assessment of horizontal fusional reserves, which do not depend on subjective responses. This technology may prove useful in a variety of clinical and community-based settings.

Divergence excess and basic exotropia types of intermittent exotropia: a major review. Part 1: prevalence, classification, risk factors, natural history and clinical characteristics

INTRODUCTION

Intermittent exotropia (IXT) is a common form of strabismus. It is an outward deviation of one eye typically when viewing at distance. Symptoms include, but are not limited to double vision, eyes feeling tired, excessive blinking, and reduced quality of life. Its clinical characteristics are distinctive from other types of strabismus. This paper provides a comprehensive review of prevalence, classification, risk factors, natural history and clinical characteristics of the divergence excess and basic exotropia types of IXT.

METHODS

Search strategies involving combination of keywords including intermittent exotropia, exotropia, divergences excess, basic exotropia, prevalence, incidence, classification, terminology, risk factor, natural history, observation, angle of deviation, control, control score, symptom, quality of life, suppression, anomalous retinal correspondence, AC/A, accommodative convergence/accommodation, accommodative convergence, convergence, accommodation, vergence, incomitance and vertical were used in Medline. All English articles from 1900/01/01 to 2020/09/01 were reviewed. The reference list of the identified article was also checked for additional relevant article. Studies focused on animal model or strabismus associated with neurologic disorder or injury were excluded.

RESULTS

The estimated prevalence of IXT in children ranges from 0.1% to 3.7%. Hypoxia at birth and being female are potential risk factors of IXT. Using validated measures of control, multicenter prospective studies showed that the rate of conversion from IXT to constant exotropia is low. The angle of deviation is the most reported outcome measure in studies of IXT. It is often used to represent the severity of the condition and has been suggested as one of the four core outcomes for studies of the surgical management of IXT. Control of exodeviation is one of the four suggested core outcomes for study of surgery of IXT and is considered the main parameter of disease severity. Several validated tools for quality of life score are available to evaluate the subjective severity of IXT.

DISCUSSION

We reviewed the prevalence, classification, risk factors, natural history and clinical characteristics of the divergence excess and basic exotropia types of IXT. Further research into these areas, especially its clinical characteristics (e.g. suppression, dual retinal correspondence), will increase our understanding of this condition and potentially lead to better management of this common form of strabismus.

The effect of concentric and aspheric multifocal soft contact lenses on binocular vision in young adult myopes

PURPOSE

Multifocal soft contact lenses (MFCLs) are prescribed to inhibit myopia progression; these include aspheric and concentric designs. The effects of MFCLs on visual quality, accommodation and vergence in young-adult myopes were evaluated.

METHODS

Participants were twenty-six myopes (19-25 years, spherical equivalent -0.50 to -5.75D), with normal binocular vision and no past myopia control. Pupil sizes were 4.4 ± 0.9 mm during distance viewing and 3.7 ± 0.8 mm at near. In random order, participants wore four MFCLs: Proclear single vision distance, MiSight concentric dual focus (+2.00D), distance center aspheric (Biofinity, +2.50D) (CooperVision lenses), and NaturalVue aspheric (Visioneering Technologies). Testing included visual acuity, contrast sensitivity (Pelli-Robson), stereoacuity, accommodation response, negative and positive relative accommodation, horizontal phorias, horizontal fusional vergence and AC/A ratio, and a visual quality questionnaire.

RESULTS

The four lenses differed in distance (p = 0.001) and near visual acuity (p = 0.011), and contrast sensitivity (p = 0.001). Compared with the single vision lens, the Biofinity aspheric had the greatest visual impact: 0.19 ± 0.14 logMAR distance acuity reduction, 0.22 ± 0.15 log contrast sensitivity reduction. Near acuity was affected less than distance acuity; the reduction was greatest with the NaturalVue (0.05 ± 0.07 logMAR reduction). The MFCLs altered the autorefraction measure at distance and near (p = 0.001); the accommodation response was less with aspheric lenses. Negative relative accommodation reduced with the aspheric lenses (p = 0.001): by 0.9 ± 0.5D with Biofinity and 0.5 ± 0.7D with NaturalVue. Exophoric shifts were greater with aspheric lenses (1.8 ± 2.4Δ Biofinity, 1.7 ± 1.7Δ NaturalVue) than with the concentric MiSight (0.5 ± 1.3Δ).

CONCLUSIONS

MFCLs alter visual performance, refraction and vergence; two aspheric lenses had greater effect than a concentric lens.

Feasibility of measuring fusional vergence amplitudes objectively

Two tests to measure fusional vergence amplitudes objectively were developed and validated against the two conventional clinical tests. Forty-nine adults participated in the study. Participants' negative (BI, base in) and positive (BO, base out) fusional vergence amplitudes at near were measured objectively in an haploscopic set-up by recording eye movements with an EyeLink 1000 Plus (SR Research). Stimulus disparity changed in steps or smoothly mimicking a prim bar and a Risley prism, respectively. Break and recovery points were determined offline using a custom Matlab algorithm for the analysis of eye movements. Fusional vergence amplitudes were also measured with two clinical tests using a Risley prism and a prism bar. A better agreement between tests was found for the measurement of BI than for BO fusional vergence amplitudes. The means ± SD of the differences between the BI break and recovery points measured with the two objective tests were -1.74 ± 3.35 PD and -1.97 ± 2.60 PD, respectively, which were comparable to those obtained for the subjective tests. For the BO break and recovery points, although the means of the differences between the two objective tests were small, high variability between subjects was found (0.31 ± 6.44 PD and -2.84 ± 7.01 PD, respectively). This study showed the feasibility to measure fusional vergence amplitudes objectively and overcome limitations of the conventional subjective tests. However, these tests cannot be used interchangeably due to their poor agreement.

Comparison of Measured Fusional Vergence Amplitudes using Prism Bar and Synoptophore in Sudanese Patients with Near Exophoria

Background:

Assessment of the fusional vergence amplitudes constitutes one of the most important diagnostic tools to obtain information about the ability to maintain binocular vision. Several techniques can be used to assess this function. However, those methods are not interchangeable, and the measurement repeatability has been questioned.

Objective:

This study aimed to compare fusional vergence range measurements using prism bars and synoptophore in Sudanese patients with near exophoria

Methods:

The study was a comparative cross-sectional hospital-based, performed in the binocular vision clinic at the Al-Neelain Eye Hospital. Fusional vergence amplitudes (positive and negative) were measured on 122 patients (67 females and 55 males), and the mean age and standard deviation were 16.79 ± 5.22 years old using prism bar and synoptophore methods.

Results:

The findings showed that the higher positive fusional vergence was obtained using the synoptophore method (24.7 ± 7.2 Δ base-out), whereas the prism bar method provided the lower finding (22.6± 7.6 Δ base-out). Conversely, the prism bar method revealed a higher measurement for negative fusional vergence (13.9± 3.9 Δ base-in) than the synoptophore method (12.7± 3.7 Δ base-in). Using the t-test, significant differences were found between all measurements with the two techniques, P<0.05. Measurements of positive and negative fusional vergence amplitudes by the two methods showed no relationship between age and fusional vergence, P>0.05.

Conclusion:

Given the significant difference in the results obtained between the two methods for measuring the positive and negative fusional vergence amplitudes, caution should be taken when making decisions regarding fusional vergence assessment in patients with latent and manifest strabismus.

Accommodation Response Variations in University Students under High Demand for Near-Vision Activity

The objective of this study was to investigate accommodation changes and visual discomfort in a university student population after a period of high demand for near-vision activity. A total of 50 university students aged between 20 and 22 years were recruited. The tests performed involved positive relative accommodation (PRA), negative relative accommodation (NRA), accommodation amplitude (AA), and monocular and binocular accommodative facility (MAF and BAF). Visual discomfort was measured on a scale involving a visual discomfort questionnaire (VDQ). All accommodative variables underwent changes during the exam period; specifically, regarding NRA and PRA, 30.4% and 15.1% of the studied population, respectively, appeared to be below average. Moreover, 42.3% of the population exhibited values below average in the second measure of AA. On the other hand, a small percentage of the population was below average in MAF and BAF measurements: 3% in the monocular right eye test, 6% in the left eye test, and 9.1% in the binocular facility test. Finally, the VDQ score did not reveal a statistically significant difference between the two measurements. Prolonged near-distance work, such as a university exams period, changed all accommodation systems (amplitude of accommodation, relative accommodation, and accommodation facility). These changes influence an accommodation excess that results in blurred vision, headache, and problems with focusing.

Convergence insufficiency: Review of clinical diagnostic signs

Convergence insufficiency (CI) is a common binocular vision (BV) disorder characterized by difficulty in maintaining motor fusion at near, which affects approximately 7.5 percent of the population. Diagnostic criteria for the disorder are inconsistent, ranging from one to many clinical signs. Methodology for clinical tests is inconsistent in measurement technique, visual targets, required repetitions, and normative values. This manuscript demonstrates the inconsistencies amongst published studies, and highlights the importance of consistent clinical diagnostic signs, measurement techniques, visual targets, and cut-off criteria. For each clinical sign, the recommended methodology for the procedure is described. Several studies do not take age into account when diagnosing CI in their cohorts. As such, the review emphasizes changes in diagnostic signs with age. This manuscript highlights the need for consistent and clear procedures and diagnostic criteria amongst clinicians and provides the basis for future studies in terms of diagnostic testing required for CI of varying age groups.

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

PURPOSE

To evaluate the reliability of the step vergence method in measuring fusional vergence in subjects with intermittent exotropia.

METHODS

Thirty-two Chinese participants aged 7-20 years 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 (2-4 h 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.

RESULTS

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.

CONCLUSION

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.

Effect of Vergence Facility Testing on Horizontal Fusional Reserves

SIGNIFICANCE

The effect of vergence adaptation on test sequences should be considered in clinical practice.

PURPOSE

This study aimed to compare the effect of vergence adaptation after different vergence facility (VF) testing methods on following horizontal fusional reserve measurement at near.

METHODS

This cross-sectional study was performed on 50 healthy subjects with a mean ± standard deviation age of 21.18 ± 1.41 years. The baseline horizontal fusional reserves were measured using base-in (BI) and base-out (BO) prisms (∆) at near. Then, VF was measured using 3∆BI/12∆BI flip prism at near, and then the measurement of fusional reserves was repeated. In the next step, fusional reserves were measured after VF testing using 8∆BI/8∆BO flip prism. The values of fusional reserves were compared with their baseline findings.

RESULTS

The results of negative fusional reserves after VF measurement using the 3∆BI/12∆BO prisms were significantly lower than the baseline values (blur [P = .03], break [P = .03], and recovery [P = .03]). There were no significant differences between the values of fusional reserves before and after VF testing using the 8∆BI/8∆BO prisms (P > .05). No correlation was observed between fusional reserves and VF responses (P > .05); however, the results revealed a positive correlation between the values of fusional reserves before and after VF testing using both methods (all P < .05). There was no significant difference in VF findings between the methods (P = .23).

CONCLUSIONS

The measurements of horizontal fusional reserves followed by VF testing were not affected except for the responses of negative fusional reserves, which decreased after VF determination using the 3∆BI/12∆BO method. Although the vergence adaptation does not seem clinically significant, it is recommended to evaluate horizontal fusional reserves before VF measurement or long-enough time after VF testing for the vergence system to return to its nonadapted state.

Image Size and the Range of Clear and Single Binocular Vision in 3D Displays

SIGNIFICANCE

The range of clear and single binocular vision differs between 3D displays and clinical prism vergences, but this difference is unexplained. This difference prevents clinicians from predicting the range of clear and single binocular vision in 3D-viewing patients. In this study, we tested a hypothesis for this difference.

PURPOSE

The purpose of this study was to determine whether changing fixation target size in 3D viewing significantly affects the vergence ranges and, if so, then to determine whether the target size effect is driven by fusional vergence gain changes, threshold of blur changes, or both.

METHODS

Twenty-one visually normal adults aged 18 to 28 years viewed 3D images at 40 cm in an electronic stereoscopic. The fixation target, a Maltese cross, moved in depth at 2∆/s by way of changing crossed or uncrossed disparity until blur and diplopia ensued. We used four target sizes: (1) small (width × height, 0.21° × 0.63°), (2) medium (1.43° × 4.3°), (3) large (3.6° × 10.8°), and (4) 3D (size changing congruently with disparity). The effect of target size on responses was tested by mixed ANOVAs.

RESULT

Mean convergence blurs and breaks increased with target size by 40% (P < .001) and 71% (P < .001), respectively, and in divergence by 33% (P = .03) and 30% (P = .04), respectively. The increases in break magnitude with target size implicate fusional vergence gain change in the size effect. Increasing target size raised the threshold of blur from 1.06 to 1.82 D in convergence and from 0.97 to 1.48 D in divergence (P = .008).

CONCLUSIONS

Growing fixation target size in 3D viewing increases fusional vergence gain and blur thresholds, which together increase the limits of clear and single binocular vision. Therefore, the clarity of a 3D image depends not only on its disparity but also on the size of the viewed image.

Deterioration of binocular vision after alcohol intake influences driving performance

In this study, we assessed the influence of moderate alcohol intake on binocular vision, vergence system and simulated driving performance by analyzing the interactions between visual deterioration and driving variables. Thirty young healthy subjects were recruited. For the analysis, we measured: visual function (visual acuity and stereoacuity), phorias and fusional reserves. Also, we checked Sheard's and Percival's criteria at near and far. The accommodative convergence/accommodation (AC/A) ratio was calculated and vergence facility was also obtained at near. A driving simulator was used to assess driving performance under natural conditions and after alcohol consumption with a breath alcohol content of 0.40 mg/l. Alcohol intake significantly reduced binocular visual performance and vergence function, except for vertical phorias, horizontal phoria at near and Sheard's and Percival's criteria at near. Driving performance parameters also presented a statistically significant deterioration after alcohol consumption. A statistically significant correlation was found between the deterioration in overall visual function and overall driving performance, highlighting the influence of the visual deterioration on the driving performance. Moderate alcohol consumption impairs binocular visual and simulated driving performances, implying a greater safety hazard. In addition, deteriorations in binocular visual function and vergence correlated with simulated driving impairment, which indicates that the deterioration of binocular vision due to alcohol consumption affects driving, thus reducing road safety.

How to assess visual function in acquired brain injury-Asking is not enough

BACKGROUND

Acquired brain injury affects many brain areas and causes a range of dysfunctions including vision-related issues. These issues can have negative impacts on rehabilitation progress and activities of daily life but may easily be overlooked. There is no common recommendation about how to assess visual impairments after ABI. The purpose of this study was to estimate the frequency of objectively measures oculomotor dysfunctions, and also how these findings are related to two inventories intended to support detection of visual impairment.

METHODS

The study was cross-sectional and included 73 outpatients. In addition to the standard evaluation program, the patients went through a comprehensive optometric examination. The inventories used were the Vision Interview (VI) and the Convergence Insufficiency Symptom Survey (CISS).

RESULTS

All three types of examinations showed a high proportion vision-related symptoms. Fusion vergence was the most common objectively measured finding, 83%. There were seven statistically significant associations between five VI items and five visual deficits. The strength of associations was moderate (Phi 0.261-0.487, p < .05). The sensitivity and specificity of the CISS were moderate.

CONCLUSION

We found high percentages of the patients with visual symptoms and dysfunctions. Due to the complexity of visual symptoms and functional deficits in ABI, we find it necessary to combine both symptom assessment and vision examination in order to capture visual function issues.

Zone of Clear Single Binocular Vision in Myopic Orthokeratology

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

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.

Vision therapy as part of neurorehabilitation after acquired brain injury - a clinical study in an outpatient setting

Introduction: Oculomotor (OM) functions may be affected by acquired brain injury (ABI). The ability to benefit from rehabilitation or to perform daily activities may be affected by OM dysfunctions and associated symptoms. The purpose of this study was to investigate the effects of vision therapy (VT) as part of neurorehabilitation after ABI.Materials and Methods: The study included two groups of outpatients (median 49.5-52.0 years, range 27-67) admitted to neurorehabilitation due to moderate to severe ABI. One group received VT while the other group served as controls to monitor the course of OM dysfunctions without VT.Results: The intervention group showed significant improvements in convergence (Z = 2.26, p = .02), vergence facility (Z = -2.16, p = .03) and vergence reserves (Z = -2.44, p < .01 and t = -4.47, DF = 15, p < .01) along with a significant reduction in vision-related symptoms (Z = 2.97, p < .01).Discussion: We conclude that OM issues were frequent and that targeted VT, as part of neurorehabilitation, can be an efficient treatment resulting in improved functions and reduced symptoms. Further study will be required to understand how improved functions link to performance and satisfaction with everyday activities.

The Effect of Age on Binocular Vision Normative Values

PURPOSE

To establish a relationship between age and horizontal heterophoria, horizontal fusional vergence amplitudes, and vergence facility testing.

METHODS

The sample consisted of 112 patients with a mean age of 39.8 ± 14.97 years (range: 18 to 65 years) and was composed of 61 women (54.5%) and 51 men (45.5%). The non-presbyopic group included patients 18 to 39 years old (n = 49) and the presbyopic group included patients 41 to 65 years old (n = 63). Binocular vision was studied by heterophoria horizontal magnitude (prism diopters [PD]), horizontal fusional vergences amplitudes (PD), and vergence facility testing (cycles per minute [cpm]) and quantified with a combination of 3 PD base-in and 12 PD base-out prisms.

RESULTS

Significant differences were obtained in near heterophoria with compensation (exophoria increased by 3.74 PD, t = 2.12, P < .05), distance positive fusional vergence (PFV) recovery (decreased by 2.86 PD, t = 3.03, P < .01), near PFV blur (decreased by 3.13 PD, t = 1.98, P = .05), near PFV break (decreased by 4.45 PD, t = 2.75, P < .01), near PFV recovery (decreased by 4.69 PD, t = 3.30, P < .01), and vergence facility testing (decreased by 2.63 PD, t = 2.77, P < .01).

CONCLUSIONS

The results indicated an increase of exophoria, a decrease in near positive horizontal fusional vergences, and vergence facility was dependent on age; thus, the authors suggest that changes in the normal values should be considered for each age range. [J Pediatr Ophthalmol Strabismus. 2020;57(6):363-371.].

Visual Binocular Disorders and Their Relationship with Baropodometric Parameters: A Cross-Association Study

The aim of this study was to establish a relationship between nonstrabismic binocular dysfunction and baropodometric parameters. A total of 106 participants underwent binocular vision assessment by evaluating horizontal heterophoria, horizontal and vertical fusional vergence ranges, and vergence facility. Posturography was measured using the FreeMED baropodometric platform. Among the variables that the software calculates are foot surface, foot load, and foot pressure. Our results showed that in the participants with positive fusional vergence (PFV) (near) blur and recovery values outside the norm, there are statistically significant differences between the total foot area (p < 0.05), forefoot area (p < 0.05), forefoot load (p < 0.05), and rearfoot load (p < 0.05), in all of the cases of left foot vs. right foot. In the group of subjects who did not meet Sheard's criterion (distance), that is, those with unstable binocular vision, there was a statistically significant difference (p < 0.01) between maximum left and right foot pressure. In conclusion, our results establish a relationship between nonstrabismic binocular dysfunctions and some baropodometric parameters.

Clear and Single Binocular Vision in Near 3D Displays

SIGNIFICANCE

Accommodation/convergence mismatch induced by 3D displays can cause discomfort symptoms such as those induced by accommodation/convergence mismatch in clinical vergence testing. We found that the limits of clear and single vision during vergence tests are very different between 3D and clinical tests. Clinical vergences should not be used as substitutes for measures of vergences in 3D displays.

PURPOSE

The purposes of this study were to determine whether the limits of clear and single binocular vision derived from phoropter prism vergence tests match the limits measured in a 3D display and to determine whether vergence mode, smooth versus jump, affected those limits in the 3D display.

METHODS

We tested the phoropter prism vergence limits of clear and single vision at 40 cm in 47 binocular young adults. In separate sessions, we tested, in a 3D display, the analogous 40-cm vergence limits for smooth vergence and jump vergence. The 3D fixation target was a Maltese cross whose visual angle changed congruently with target disparity.

RESULTS

Our mean phoropter vergence blur and break values were similar to those reported in previous studies. The mean smooth divergence limit was less in the 3D display (9.8Δ) than in the phoropter (12.8Δ). Most smooth convergence limits were much larger in the 3D display than in the phoropter, reaching the 35Δ limit of the 3D display without blur or diplopia in 24 subjects. Mean jump vergence limits were significantly smaller than smooth vergence limits in the 3D display.

CONCLUSIONS

The limits of clear and single binocular vision derived from phoropter vergence tests were not a good approximation of the analogous limits in our 3D display.

One-year test-retest reliability of ten vision tests in Canadian athletes

Background: Vision tests are used in concussion management and baseline testing. Concussions, however, often occur months after baseline testing and reliability studies generally examine intervals limited to days or one week. Our objective was to determine the one-year test-retest reliability of these tests.

Methods: We assessed one-year test-retest reliability of ten vision tests in elite Canadian athletes followed by the Institut National du Sport du Quebec. We included athletes who completed two baseline (preseason) annual evaluations by one clinician within 365±30 days. We excluded athletes with any concussion or vision training in between the annual evaluations or presented with any factor that is believed to affect the tests (e.g. migraines). Data were collected from clinical charts. We evaluated test-retest reliability using Intraclass Correlation Coefficient (ICC) and 95% limits of agreement (LoA).

Results: We examined nine female and seven male athletes with a mean age of 22.7 (SD 4.5) years. Among the vision tests, we observed excellent test-retest reliability in Positive Fusional Vergence at 30cm (ICC=0.93) but this dropped to 0.53 when an outlier was excluded in a sensitivity analysis. There was good to moderate reliability in Negative Fusional Vergence at 30cm (ICC=0.78), Phoria at 30cm (ICC=0.68), Near Point of Convergence break (ICC=0.65) and Saccades (ICC=0.61). The ICC for Positive Fusional Vergence at 3m (ICC=0.56) also decreased to 0.45 after removing two outliers. We found poor reliability in Near Point of Convergence (ICC=0.47), Gross Stereoscopic Acuity (ICC=0.03) and Negative Fusional Vergence at 3m (ICC=0.0). ICC for Phoria at 3m was not appropriate because scores were identical in 14/16 athletes. 95% LoA of the majority of tests were ±40% to ±90%.

Conclusions: Five tests had good to moderate one-year test-retest reliability. The remaining tests had poor reliability. The tests would therefore be useful only if concussion has a moderate-large effect on scores.

Measurement of fusional vergence: a systematic review

Background: Fusional amplitudes are important for clinical practice in diagnosing and managing binocular vision anomalies. Several measurement methods can be used to assess fusional amplitudes. However, those methods are not interchangeable, and measurement repeatability has been questioned. Objectives: To compare the normative values of tests for the measurement of fusional vergence and to investigate sources of heterogeneity of diagnostic accuracy including: age, variation in method of assessment, study design and size, type (convergent, divergent, vertical, cyclo) and severity of strabismus (constant/intermittent/latent). Data sources: Bibliographic databases were searched up to March 2018, including Cochrane registers, PubMed, Web of Science^TM, Google Scholar and Science Citation Index. Trial registers and conference proceedings were hand searched. Review methods: The review observed and reported according to the PRISMA guidelines and was registered with PROSPERO. The I² was used to show the percentage of observed total variation across studies that is due to real heterogeneity rather than chance. The results of the different studies and the overall effect (meta-analysis under the random effects model) are shown. Results: Eighty-one studies were included in the review. Heterogenous information about break vergence amplitudes is reported for the step vergence method (I² > 50%; p < 0.05) in children. Four parameters were reported consistently to affect measurements; age, method of assessment, order of testing and target size. For the smooth vergence technique break vergence values heterogeneity was not present in children and adults (I² = 0%; p > 0.05). Limitations: The results are based on cross-sectional studies that were performed independently of each other, with different examiners, methods of examination and different populations. Conclusions: The source of heterogeneity between studies for vergence break points measured with the step vergence method seems to be linked with age. Normal vergences reported in children had considerable heterogeneity compared with adults. In clinical practice, the population-based vergence ranges measured with the step vergence method in children should not be used as one single criterion. For the smooth vergence technique, normative population data can be used.

Nonstrabismic binocular dysfunctions and cervical complaints: The possibility of a cross-dysfunction

The aim of this study is to establish a relationship between non-strabismic binocular dysfunction and neck pain. One hundred twelve participants underwent binocular vision assessment by evaluating horizontal heterophoria, horizontal and vertical fusional vergence ranges and vergence facility. The subjects were classified into two groups: binocular anomalies and normal binocular function. Neck complaints were measured with the Neck Disability Index, visual analogue scale, cervical range of motion, deep-flexor muscle activation score (AS) and performance index (PI). Our results showed that participants with low AS had significantly altered values of lateral phoria (near) (mean = -6.99 SD ± 6.96 PD) and PFV (near) blur (mean = 9.49 SD ± 5.45 PD) against those who presented normal AS (lateral phoria (near) mean = -3.64 SD ± 6.37 PD; PFV (near) blur mean = 12.84 SD ± 6.20 PD). In addition, participants with NFV (near) recovery outside the norm had a significantly lower right side-bending (mean = 35.63 SD ± 8.35 PD) than those within the standard (mean = 39.64 SD ± 9 PD). The subjects with binocular vision impairment showed a diminished response to the deep cervical musculature, with low AS and PI, as well as a tendency to suffer from cervicalgia of more than three months’ evolution and a lower range of motion.

Functional Magnetic Resonance Imaging and Oculomotor Dysfunction in Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is a significant cause of disability, especially when symptoms become chronic. This chronicity is often linked to oculomotor dysfunction (OMD). To our knowledge, this is the first prospective study to localize aberrations in brain function between mTBI cohorts, by comparing patients with mTBI with OMD with an mTBI control group without OMD, using task and resting-state functional magnetic resonance imaging (fMRI). Ten subjects with mTBI who had OMD (OMD group) were compared with nine subjects with mTBI who had no findings of OMD (control group). These groups were determined by a developmental optometrist using objective testing for OMD. The (convergence) task fMRI data demonstrated significantly decreased brain activity, measured as decreases in the blood oxygen level dependent (BOLD) signal, in the OMD group compared with the control group in three brain regions: the left posterior lingual gyrus, the bilateral anterior lingual gyrus and cuneus, and the parahippocampal gyrus. When doing a seed-based resting state fMRI analysis in the lingual/parahippocampal region, a large cluster covering the left middle frontal gyrus and the dorsolateral pre-frontal cortex (Brodmann areas 9 and 10), with decreased functional correlation in the OMD group, was identified. Together these observations provide evidence for neural networks of interactions involving the control of eye movement for visual processing, reading comprehension, spatial localization and navigation, and spatial working memory that appear to be decreased in mTBI patients with OMD compared with mTBI patients without OMD. The clinical symptomatology associated with post-traumatic OMD correlates well with these MRI findings.

Stereopsis: are we assessing it in enough depth?

The assessment of stereoacuity is an integral part of the ophthalmic assessment, with the responses used to inform clinical management decisions. Stereoacuity impacts on many aspects of life, but there are discrepancies reported where people without measurable stereoacuity report appreciating 3-D vision. This could be due, in part, to the presentation of the stimuli. A literature review was undertaken to evaluate current assessment techniques, how they relate to patient outcomes, identify the limitations of current tests and discuss how they could be improved. Recent evidence has been collated on currently available tests, used commonly within vision clinics, with normative data provided allowing responses to the tests to be interpreted. The relevance of the results is evaluated in relation to a range of outcomes, where a reduced level of stereopsis has a negative impact on the ability of an individual to perform many tasks, and can lead to an increase in difficulty interacting in the world. Current tests are limited in the aspects of stereoacuity they assess and their ability to precisely measure stereopsis. The world is not static, yet clinical tests are limited to measuring static stereoacuity, even though higher grades of depth perception can be identified in the presence of changing depth. Presentation methods of stereoacuity tests have remained similar over time, with a limited number of disparity levels assessed. New assessment methods are becoming available that include automated staircase testing to present multiple levels of disparity using digital technology. Current clinical tests are limited in their presentation, and are poor at detecting/measuring stereoacuity in those with limited stereopsis. Given the relevance of the stereoacuity measurement to management choices and functional outcomes, new testing methods would be beneficial to fully assess stereoacuity, both static and dynamic.

Is it possible to relate accommodative visual dysfunctions to neck pain?

The aim of this study was to establish whether there is a relationship between conditions of accommodative visual dysfunctions and cervical complaints. Fifty-two participants were included. Variables were accommodative amplitude, positive and negative relative accommodation (NRA), accommodative response, and accommodative facility. Subjects were classified as accommodative insufficiency, accommodative excess, or normal. Neck complaints were measured with the Neck Disability Index, the Visual Analogue Scale, and by cervical range of motion, deep flexor muscle activation score, and performance index. We found the following significant relationships: between NRA and both performance index and left-side bending; accommodative amplitude right-eye with right-side bending and with left-side bending; accommodative amplitude left-eye with right-side bending; and accommodative facility left-eye with both performance index and left-side bending. In accommodative amplitude right-eye, aIl participants showed significant values and greater than those with accommodative excess. In both groups, performance index values were decreased. Greater pain and lower right-rotation were found in participants with accommodative excess than in those with accommodative insufficiency. We conclude that accommodative dysfunctions are related to low performance index, decreased range of motion, as well as greater neck pain.

Effect of Induced Vertical Disparity on Horizontal Fusional Reserves

PURPOSE

The aim of this study was to investigate the effects of induced vertical disparity on horizontal fusional reserves at near.

MATERIALS AND METHODS

In 170 healthy subjects wearing best corrective refraction, the negative and positive horizontal fusional reserves were measured with base-in (BI) and base-out (BO) prisms, respectively, in the presence of 0.5 prism diopters (^∆) and 1^∆ vertical prisms placed in trial frames in front of the right eye. The prism power was slowly increased step by step until the subject reported sustained blur, break, and recovery. These were compared to horizontal fusional reserves in the same subjects without a vertical prism. Data were analyzed in SPSS.17 software using a repeated measures ANOVA.

RESULTS

Induced vertical disparity decreased negative fusional reserves (NFR) horizontally and was more significant with 1^∆ vertical disparity (P<0.001). There were significant differences between the blur (P<0.001), break (P<0.001), and recovery (P<0.001) for NFR before and after induced vertical disparity and no significant difference between blur (P=0.173) and recovery points (P=0.261) with a marginal difference for break points (P=0.045) for the positive fusional reserves (PFR).

CONCLUSION

Inducing vertical disparity even with small magnitudes affects all 3 aspects (blur, break, and recovery) of horizontal negative fusional reserves while only break is affected in positive fusional reserves. These changes are statistically significant but do not seem to be clinically significant except for cases accompanied by symptoms.

The minimum test battery to screen for binocular vision anomalies: report 3 of the BAND study

PURPOSE

This study aims to report the minimum test battery needed to screen non-strabismic binocular vision anomalies (NSBVAs) in a community set-up. When large numbers are to be screened we aim to identify the most useful test battery when there is no opportunity for a more comprehensive and time-consuming clinical examination.

METHODS

The prevalence estimates and normative data for binocular vision parameters were estimated from the Binocular Vision Anomalies and Normative Data (BAND) study, following which cut-off estimates and receiver operating characteristic curves to identify the minimum test battery have been plotted. In the receiver operating characteristic phase of the study, children between nine and 17 years of age were screened in two schools in the rural arm using the minimum test battery, and the prevalence estimates with the minimum test battery were found.

RESULTS

Receiver operating characteristic analyses revealed that near point of convergence with penlight and red filter (> 7.5 cm), monocular accommodative facility (< 10 cycles per minute), and the difference between near and distance phoria (> 1.25 prism dioptres) were significant factors with cut-off values for best sensitivity and specificity. This minimum test battery was applied to a cohort of 305 children. The mean (standard deviation) age of the subjects was 12.7 (two) years with 121 males and 184 females. Using the minimum battery of tests obtained through the receiver operating characteristic analyses, the prevalence of NSBVAs was found to be 26 per cent. Near point of convergence with penlight and red filter > 10 cm was found to have the highest sensitivity (80 per cent) and specificity (73 per cent) for the diagnosis of convergence insufficiency. For the diagnosis of accommodative infacility, monocular accommodative facility with a cut-off of less than seven cycles per minute was the best predictor for screening (92 per cent sensitivity and 90 per cent specificity).

CONCLUSION

The minimum test battery of near point of convergence with penlight and red filter, difference between distance and near phoria, and monocular accommodative facility yield good sensitivity and specificity for diagnosis of NSBVAs in a community set-up.

Fusional Amplitudes: Developing Testing Standards

PURPOSE

The stability of binocular vision depends upon good fusional amplitudes, but the clinical assessment of fusional amplitudes varies around the world. The purpose of this study was to determine whether or not there is variation in the assessment of fusional amplitudes in normal subjects. The author looked at the testing distance, the order of testing, the role of examiner encouragement, and the subject's level of alertness.

METHODS

In a prospective study using a modified crossover design, the author assessed fusional amplitudes in 99 subjects with normal eye exams. The measurements were done in two separate sessions on different days with each subject being randomized as to the order of fusional vergence testing. All subjects were assessed without and with encouragement in the first session. In the second session, all were assessed at different testing distances.

RESULTS

The author previously presented data on 50 subjects. In this expanded cohort, statistical significance was reached confirming the previous findings that convergence is significantly affected by encouragement, divergence is significantly reduced if assessed after convergence, and near amplitudes are significantly higher than distance amplitudes. Finally, there is a negative correlation between age and convergence break point.

CONCLUSIONS

The results of this study demonstrate that divergence is significantly reduced if assessed after convergence in the subject with normal binocular function. Next, convergence is significantly affected by the use of encouragement. Measurements at near produced significantly higher results for all of the convergence and divergence tests. Finally, there is a significant negative correlation between age and convergence break point. We need to develop a standard of testing fusional amplitudes so there is consistency in the clinical assessment.

Objective Measurement of Fusional Vergence Ranges and Heterophoria in Infants and Preschool Children

Purpose

Binocular alignment typically includes motor fusion compensating for heterophoria. This study evaluated heterophoria and then accommodation and vergence responses during measurement of fusional ranges in infants and preschoolers.

Methods

Purkinje image eye tracking and eccentric photorefraction (MCS PowerRefractor) were used to record the eye alignment and accommodation of uncorrected infants (n = 17; 3–5 months old), preschoolers (n = 19; 2.5–5 years), and naïve functionally emmetropic adults (n = 14; 20–32 years; spherical equivalent [SE], +1 to −1 diopters [D]). Heterophoria was derived from the difference between monocular and binocular alignments while participants viewed naturalistic images at 80 cm. The presence or absence of fusion was then assessed after base-in (BI) and base-out (BO) prisms (2–40 prism diopters [pd]) were introduced.

Results

Mean (±SD) SE refractions were hyperopic in infants (+2.4 ± 1.2 D) and preschoolers (+1.1 ± 0.6 D). The average exophoria was similar (P = 0.11) across groups (Infants, −0.79 ± 2.5 pd; Preschool, −2.43 ± 2.0 pd; Adults, −1.0 ± 2.7 pd). Mean fusional vergence range also was similar (P = 0.1) for BI (Infants, 11.2 ± 2.5 pd; Preschool, 8.8 ± 2.8 pd; Adults, 11.8 ± 5.2 pd) and BO (Infants, 14 ± 6.6 pd; Preschool, 15.3 ± 8.3 pd; Adults, 20 ± 9.2 pd). Maximum change in accommodation to the highest fusible prism was positive (increased accommodation) for BO (Infants, 1.69 ± 1.4 D; Preschool, 1.35 ± 1.6 D; Adults, 1.22 ± 1.0 D) and negative for BI (Infants, −0.96 ± 1.0 D; Preschool, −0.78 ± 0.6 D; Adults, −0.62 ± 0.3 D), with a similar magnitude across groups (BO, P = 0.6; BI, P = 0.4).

Conclusions

Despite typical uncorrected hyperopia, infants and preschoolers exhibited small exophorias at 80 cm, similar to adults. All participants demonstrated substantial fusional ranges, providing evidence that even 3- to 5-month-old infants can respond to a large range of image disparities.

Near binocular visual function in young adult orthokeratology versus soft contact lens wearers

PURPOSE

To compare near point binocular vision function of young adult myopes wearing orthokeratology (OK) lenses to matched single vision soft disposable contact lens (SCL) wearers.

METHODS

A retrospective clinical record analysis of all OK wearers (18-30 years) presenting over an 18 month period was undertaken. Data was extracted for 17 OK wearers, with 17 SCL wearers matched for age, refractive error and duration of contact lens wear. Binocular vision data included horizontal phoria (phoria), horizontal base-in (BIFR) and base-out fusional reserves (BOFR) and accommodation accuracy (AA).

RESULTS

The OK group was 25.8±3.2years, with a duration of wear of 45.7±25months and refractive error of R -2.09±1.23D, L -2.00±1.35D. Compared to matched SCL wearers the OK group were significantly more exophoric (OK -2.05±2.38Δ; SCL 0.00±1.46Δ, p=0.005) and had better accommodation accuracy (OK 0.97±0.33D; SCL 1.28±0.32D, p=0.009). BIFR and BOFR were not different in the two groups. Frequency histograms showed that more SCL wearers had high lags of accommodation (AA≥1.50D: 8 SCL,2 OK) and esophoria (≥1Δ: 5 SCL,1 OK) than OK wearers. A positive correlation was found between refraction and phoria in the SCL group (r=0.521, p=0.032).

CONCLUSION

Young adult myopes wearing OK lenses display more exophoria and lower accommodative lags at near compared to matched single vision SCL wearers. Young adult myopes with specific binocular vision disorders may benefit from OK wear in comparison to single vision SCL wear. This has relevance to both the visual acceptance of OK lenses and in managing risk factors for myopia progression.

Binocular vision anomalies and normative data (BAND) in Tamil Nadu: report 1

BACKGROUND

This population-based, cross-sectional study was designed to determine normative data for binocular vision and accommodative testing in rural and urban populations of Tamil Nadu.

METHODS

A sample of 936 was determined, based on a previous pilot study. The epidemiological field work included a comprehensive eye examination and a binocular vision and accommodative assessment carried out in a total of four public schools, two each in the rural and urban arms of Chennai. An overall sample of 3,024 children between seven and 17 years of age was screened in the four schools and 920 children were included in the study.

RESULTS

We found significant differences in expected values from the current clinical criteria for near point of convergence (NPC) with penlight, distance and near horizontal phorias, vergence facility, accommodation convergence/accommodation (AC/A) ratio, accommodative amplitudes, monocular and binocular accommodative facility (t-test: p < 0.001). The mean and standard deviation break/recovery values for NPC (in centimetres) with an accommodative target and penlight with red filter was 3 ± 3/4 ± 4 and 7 ± 5/10 ± 7, respectively. The mean accommodative amplitudes for the population could be estimated from the linear regression equation 16 - 0.3 × (age). The vergence facility was 12 ± 4 cycles/minute and 14 ± 4 cycles/minute in the seven to 10 and 11 to 17 age groups, respectively. Monocular accommodative facility was 11 ± 4 cycles/minute and 14 ± 5 cycles/minute and binocular accommodative facility was 10 ± 4 cycles/minute and 14 ± 5 cycles/minute in the seven to 12 and 13 to 17 age groups, respectively. The mean calculated AC/A ratio was 5.4 ± 0.6/1.

CONCLUSION

The normative data for vergence and accommodative parameters for the Indian children between seven and 17 years of age are reported. The developmental trend of accommodation and vergence differences and significant differences in cut-off between the current data and available literature are reported. These differences have clinical implications for the interpretation, diagnosis and management of anomalies of binocular vision.

Binocular vision and abnormal head posture in children when watching television

AIM

To determine the association between the binocular vision and an abnormal head posture (AHP) when watching television (TV) in children 7-14y of age.

METHODS

Fifty normal children in the normal group and 52 children with an AHP when watching TV in the AHP group were tested for spherical equivalents, far and near fusional convergence (FC) and fusional divergence (FD) amplitudes, near point of convergence, far and near heterophoria, accommodative convergence/ accommodation ratio and stereoacuity. The values of these tests were compared between the two groups. The independent t test was applied at a confidence level of 95%.

RESULTS

The far and near FC amplitudes and far FD amplitudes were lower in the AHP group (the far FC amplitudes: break point 13.6±5.4(Δ), recovery point 8.7±5.4(Δ). The near FC amplitudes: break point 14.5±7.3(Δ), recovery point 10.3±5.1(Δ). The far FD amplitudes: break point 3.9±2.7(Δ), recovery point 2.6±2.3(Δ)) compared with those in the normal group (the far FC amplitudes: break point 19.1±6.2(Δ), recovery point 12.4±4.5(Δ). The near FC amplitudes: break point 22.3±8.0(Δ), recovery point 16.1±5.7(Δ). The far FD amplitudes: break point 7.0±2.1(Δ), recovery point 4.6±1.9(Δ)). Other tests presented no statistically significant differences.

CONCLUSION

An association between the reduced FC and FD amplitudes and the AHP in children when watching TV is proposed in the study. This kind of AHP is considered to be an anomalous manifestation which appears in a part of puerile patients of fusional vergence dysfunction.

[Assessment of a 3D digital orthoptic test platform]

PURPOSE

To compare standard orthoptic tests with a novel digital 3D orthoptic platform, 3DeltaEasy(©) from Orthoptica(®).

MATERIALS AND METHODS

This study tests the 3D digital orthoptics platform, 3DeltaEasy(©) from Orthoptica(®) and compares it to the corresponding standard orthoptic tests. This platform consists of a computer equipped with dedicated software, a video projector and 3D liquid crystal glasses. Three tests were compared: Wirt test, measurement of horizontal and vertical phorias, and the horizontal fusional amplitude in convergence and divergence. A total of 102 subjects, 53 males (52 %) and 49 females (48 %), aged between 9 years and 72 years (mean age 33±16.4 years) were examined at the ophthalmologic department of the Brest Hospital (France) and included in this observational cross-sectional study. Subjects recruited in this study were patients requiring orthoptic screening or therapy. Patients without their optimal visual corrections were excluded. All patients underwent both ophthalmological and orthoptic examination including Wirt fly stereotest with polarizing spectacles, cover tests to evaluate and measure the horizontal and vertical deviation of the lines of sight, horizontal vergence ranges using prism bar and their equivalent tests implemented in the digital 3D orthoptic tests 3DeltaEasy(©) from Orthoptica(®).

RESULTS

All data were processed using MedCalc Statistical Software version 14.12.0 (MedCalc Software bvba, Ostend, Belgium). The main result of this study is that 3DeltaEasy(©) and the classical Wirt test are correlated (Spearman's coefficient of rank correlation: ρ=0.74; P<0.0001), cover tests are equivalent for intermediate and far vision (paired t-test; P=0.46 and P=0.51), and horizontal and vertical vergence range are comparable for distance vision (paired t-test; P=0.34 and P=0.94).

CONCLUSION

New digital 3D tools could easily substitute for some orthoptic tests with better ergonomics. Eventually, by increasing the number of tests performed, it could substitute for nearly all tests.

Fusional vergence detected by prism bar and synoptophore in chinese childhood intermittent exotropia

Purpose. To measure the changes in fusional vergence in Chinese children with intermittent exotropia (IXT) and the association with the control of IXT. Methods. Ninety-two patients with IXT (8–15 years old) were compared with 86 controls. Exodeviation control was evaluated using the Revised Newcastle Control Score. Angle of deviation was measured using prism and alternate cover testing at distance and near. Fusional vergence was measured using prism bar and synoptophore. This study was registered with ChiCTR-RCC-13003920. Results. Using prism bar, convergence break points were lower whereas divergence break points were higher in children with IXT at distance (P < 0.001) and near (P < 0.001) compared with controls. There was no significant difference in mean divergence amplitudes between the two groups when testing using a synoptophore (P = 0.53). In children with IXT, the distance between recovery point and break point in both convergence (distance: P = 0.02; near: P = 0.02) and divergence (distance: P < 0.001; near: P < 0.001) was larger than controls when detected by prism bar and synoptophore (convergence: P = 0.005; divergence: P = 0.006). Conclusions. Children with IXT have reduced convergence amplitudes as detected by both prism bar and synoptophore.

Fusional amplitudes: exploring where fusion falters

BACKGROUND AND PURPOSE

The stability of binocular vision depends on good fusional amplitudes, but the assessment of fusional amplitudes varies around the world. The author reviewed the literature on fusional amplitudes and surveyed international orthoptists on their assessment of fusional amplitudes. The purpose of the study was to determine whether or not there is variation in fusional amplitudes in normal subjects when looking at the role of examiner encouragement; the order of testing; the method of testing; and the subject's level of alertness. The preliminary results from this ongoing, prospective study are presented.

PATIENTS AND METHODS

Using a modified crossover design study, the author prospectively assessed fusional amplitudes in fifty participants with normal eye exams who met inclusion criteria. The measurements were done in two separate sessions with each participant being randomized as to the order of fusional vergence testing. All participants were assessed without and with encouragement in the first session. In the second session, all were assessed at different testing distances.

RESULTS

Convergence is significantly affected by encouragement and divergence is significantly reduced if assessed after convergence. Numbers were too small to get meaningful data on the effect of fatigue on final outcome measures.

CONCLUSIONS

We need to develop consistency in assessing fusional amplitudes and agree upon a standard of testing. Variables such as the order of testing, whether or not encouragement is given, and a person's level of alertness can affect the final outcome. Encouragement should be done especially when assessing convergence fusional amplitudes and divergence should be assessed prior to convergence. Finally, it is important to note a patient's level of alertness during vergence testing, especially if they are feeling foggy on one visit and are alert on the next. By implementing these strategies into your assessment of fusional amplitudes, the examiner will know if a change in amplitudes is due to treatment effect or just testing method.

Diagnostic validity of clinical signs associated with a large exophoria at near

Purpose. To analyze the diagnostic validity of accommodative and binocular tests in a sample of patients with a large near exophoria with moderate to severe symptoms. Methods. Two groups of patients between 19 and 35 years were recruited from a university clinic: 33 subjects with large exophoria at near vision and moderate or high visual discomfort and 33 patients with normal heterophoria and low visual discomfort. Visual discomfort was defined using the Conlon survey. A refractive exam and an exhaustive evaluation of accommodation and vergence were assessed. Diagnostic validity by means of receiver operator characteristic (ROC) curves, sensitivity (S), specificity (Sp), and positive and negative likelihood ratios (LR+, LR-) were assessed. This analysis was also carried out considering multiple tests as serial testing strategy. Results. ROC analysis showed the best diagnostic accuracy for receded near point of convergence (NPC) recovery (area = 0.929) and binocular accommodative facility (BAF) (area = 0.886). Using the cut-offs obtained with ROC analysis, the best diagnostic validity was obtained for the combination of NPC recovery and BAF (S  =  0.77, Sp = 1, LR+ = value tending to infinity, LR- = 0.23) and the combination of NPC break and recovery with BAF (S  =  0.73, Sp = 1, LR+ = tending to infinity, LR- = 0.27). Conclusions. NPC and BAF tests were the tests with the best diagnostic accuracy for subjects with large near exophoria and moderate to severe symptoms.

Bagolini glasses: do they affect the horizontal prism fusion amplitude?

PURPOSE

Bagolini striated glasses (BSG) can be used while performing the prism fusion amplitude to verify the maintenance of binocularity. The aim of this clinical study was to evaluate whether these glasses affect the prism fusion amplitude.

METHODS

Fifty-six subjects were examined at the Eye Care Clinic at the University of Applied Sciences Utrecht. The positive and negative prism fusion amplitudes were measured, incorporating the BSG at random, for both near and distance, with right and left eye fixating.

RESULTS

Fifty-two normal subjects with a mean age of 21 years (range 17-28) were recruited. The median prism fusion amplitude at near was 10 BI to 33 BO with the BSG and 13 BI to 38 BO without (p < 0.001). At distance the median amplitude was 8 BI to 33 BO both with and without these glasses (p = 0.104).

CONCLUSION

Although BSG are useful to verify whether binocularity is maintained, significantly smaller fusional ranges were obtained during measurements at near. In clinical terms, fusional ranges can vary significantly when using the BSG.

Is the aligning prism measured with the Mallett unit correlated with fusional vergence reserves?

Background

The Mallett Unit is a clinical test designed to detect the fixation disparity that is most likely to occur in the presence of a decompensated heterophoria. It measures the associated phoria, which is the “aligning prism” needed to nullify the subjective disparity. The technique has gained widespread acceptance within professions such as optometry, for investigating suspected cases of decompensating heterophoria; it is, however, rarely used by orthoptists and ophthalmologists. The aim of this study was to investigate whether fusional vergence reserves, measured routinely by both orthoptists and ophthalmologists to detect heterophoria decompensation, were correlated with aligning prism (associated phoria) in a normal clinical population.

Methodology/Principal Findings

Aligning prism (using the Mallett Unit) and fusional vergence reserves (using a prism bar) were measured in 500 participants (mean 41.63 years; standard deviation 11.86 years) at 40 cm and 6 m. At 40 cm a strong correlation (p<0.001) between base in aligning prism (Exo FD) and positive fusional reserves was found. Of the participants with zero aligning prism 30% had reduced fusional reserves. At 6 m a weak correlation between base out aligning prism (Eso FD) and negative fusional reserves was found to break (p = 0.01) and to recovery (p = 0.048). Of the participants with zero aligning prism 12% reported reduced fusional reserves.

Conclusions/Significance

For near vision testing, the strong inverse correlation between base in aligning prism (Exo FD) and fusional vergence reserves supports the notion that both measures are indicators of decompensation of heterophoria. For distance vision testing and for those patients reporting zero aligning prism further research is required to determine why the relationship appears to be weak/non-existent?

Relationship between binocular vision, visual acuity, and fine motor skills

PURPOSE

The aims of this study were to analyze the relationship between the performance on fine motor skills tasks and peripheral and bifoveal sensory fusion, phasic and tonic motor fusion, the level of visual acuity (VA) in the poorer seeing eye, and the interocular VA difference.

METHODS

Subjects aged 12 to 28 years with a range of levels of binocular vision and VA performed three tasks: Purdue pegboard (number of pegs placed in 30 s), bead threading task (with two sizes of bead to increase the difficulty, time taken to thread a fixed number of beads), and a water pouring task (accuracy and time to pour a fixed quantity into five glass cylinders). Ophthalmic measures included peripheral (Worth 4 dot) and bifoveal (4 prism diopter) sensory fusion, phasic (prism bar) and tonic (Risley rotary prism) motor fusion ranges, and monocular VA.

RESULTS

One hundred twenty-one subjects with a mean age of 18.8 years were tested; 18.2% had a manifest strabismus. Performance on fine motor skills tasks was significantly better in subjects with sensory and motor fusion compared with those without for most tasks, with significant differences between those with and without all measures of fusion on the pegboard and bead task. Both the acuity in the poorer seeing eye (highest r value of all motor tasks = 0.43) and the interocular acuity difference were statistically significantly related to performance on the motor skill tasks.

CONCLUSIONS

Both sensory and motor fusion and good VA in both eyes are of benefit in the performance of fine motor skills tasks, with the presence of some binocular vision being beneficial compared with no fusion on certain sensorimotor tasks. This evidence supports the need to maximize fusion and VA outcomes.