Associations between Binocular Vision Disorders and Contact Lens Dissatisfaction.

SIGNIFICANCE: These data demonstrate that binocular vision disorders (BVDs) contribute to contact lens (CL) dissatisfaction independently of CL discomfort (CLD) in myopic, pre-presbyopic, adult, single-vision CL wearers. PURPOSE: This study aimed to determine whether BVDs contribute to CL dissatisfaction and whether this contribution is independent of CLD. METHODS: Participants attended one clinical visit while wearing their habitual CLs. Symptoms from CLD and BVDs were measured with the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8) and Convergence Insufficiency Syndrome Survey (CISS), respectively. A comprehensive binocular vision (BV) assessment was performed. The Ocular Surface Disease Index (OSDI) was used to measure CL dissatisfaction from CLD and BVDs based on reported correlations between the CLDEQ-8 and the CISS with the OSDI. Participants were categorized according to their CL comfort status (CLD [≥12 on CLDEQ-8] or non-CLD [<12 on CLDEQ-8]) and BV status (BVD or non-BVD). RESULTS: Seventy-six participants completed the trial, and 19 (25%) were diagnosed with BVD. Those diagnosed with BVD scored higher than did those diagnosed with non-BVD for the OSDI (25.1 ± 12.7 vs. 10.7 ± 7.3, P < .001) and CISS (18.7 ± 7.7 vs. 11.9 ± 5.9, P = .001), but not the CLDEQ-8 (P = .25). Those categorized as having CLD scored higher than did those categorized as having non-CLD for the OSDI (19.0 ± 12.3 vs. 9.3 ± 5.9, P = .003) and CISS (16.1 ± 6.8 vs. 11.0 ± 6.2, P = .001). There were no significant interactions between BV status and CL comfort status for any questionnaire (P > .08). CONCLUSIONS: Higher scores for OSDI in those with CLD or BVD indicate that both conditions contribute to CL dissatisfaction. Higher scores for the CISS in those with CLD suggest a degree of overlap for some BVD symptoms. Nonsignificant differences between BVD and non-BVD for the CLDEQ-8 suggest that BVDs contribute to CL dissatisfaction independently of CLD.

Treatment and compliance with virtual reality and anaglyph-based training programs for convergence insufficiency.

BACKGROUND: Convergence insufficiency may be treated by visual exercises designed to increase convergence while maintaining single, clear, binocular vision. However, compliance with treatment is problematic, as patients often cease treatment when symptoms start to improve and before treatment is complete. The purpose of the present study was to assess the feasibility of using gamification of vision training to: (a) treat convergence insufficiency; and (b) improve compliance to treatment in comparison to a conventional treatment over a six-week treatment period. METHODS: Two interventions, anaglyphs and a virtual reality game of Snakes, were evaluated for their effectiveness in treating adults with convergence insufficiency. The prescribed training regimen was 20 minutes, three times per week for six weeks. Vision was assessed before and after the treatment period. Participants also filled in the Core Elements of the Gaming Experience Questionnaire to gauge impact of game design on compliance. RESULTS: Eighteen participants (mean age 20.8 ± 1.8 years) met the inclusion criteria for convergence insufficiency and nine participants were randomly assigned to each intervention. Repeated measures analysis of variance showed a significant effect of visit for near point of convergence (F1,16 = 38.32, p < 0.0001), near positive fusional reserves break (F1,16 = 21.94, p < 0.0001) and recovery (F1,16 = 26.87, p < 0.0001), but not of intervention type. Total time played was significantly longer for the virtual reality Snake Game than the anaglyph intervention (p < 0.0001), which translated to mean compliance of 82 per cent and 51 per cent respectively. CONCLUSION: Gamification of vision training in a virtual reality environment is feasible and associated with increased compliance, hence may be a useful strategy to treat convergence insufficiency.

A psychophysical study of human binocular interactions in normal and amblyopic visual systems.

During infancy and childhood, spatial contrast sensitivity and alignment sensitivity undergo maturation, and during this period the visual system has considerable plasticity. The purpose of this study was to compare the nature of interocular interactions of these spatial functions in normally sighted children and adults, and to study the extent to which interocular interactions are impaired in anisometropic amblyopia. Spatial functions were measured under three viewing conditions: monocular (fellow eye occluded), dichoptic (uniform stimulus presented to the fellow eye but with a peripheral fusion lock), and binocular. Measurements were made in each eye during monocular and dichoptic viewing. In the contrast sensitivity task, Gabor stimuli were presented in one of two temporal intervals. For the alignment task, a three-element Gabor stimulus was used. The task of the subject was to indicate the direction of displacement of the middle patch with respect to the outer patches. The findings indicate that in children, binocular contrast sensitivity was better than monocular (binocular summation) but so too was dichoptic sensitivity (dichoptic summation). The magnitude of binocular/dichoptic summation was significantly greater in children than in normally sighted adults for contrast sensitivity, but not for alignment sensitivity. In anisometropic amblyopes, however, we find that for the group as a whole the amblyopic eye does not benefit when the fellow eye views a dichoptic stimulus, compared to dark occlusion of that eye. In addition, we found considerable inter-individual variation within the amblyopic group. Implications of these findings for techniques used in vision therapy are discussed.

Interocular interactions during acuity measurement in children and adults, and in adults with amblyopia.

The binocular interactions that occur during dichoptic and binocular viewing were investigated using a letter acuity task in normally sighted children (age range 6-14 years) and adults, and in adults with anisometropic amblyopia. Our aims were to investigate the nature of binocular interactions that occur in each group, and the extent to which the characteristics of binocular interactions differ across the groups. The non-tested eye was occluded during monocular (baseline) viewing, and was allowed to view a uniform stimulus with fusion lock in dichoptic viewing. In adults and children with normal vision, acuity under dichoptic viewing was unchanged relative to monocular baseline in the dominant eyes, while acuity of the non-dominant eye improved under dichoptic viewing relative to baseline. The magnitude of dichoptic change in the non-dominant eyes was similar in the two normally sighted groups, but the dichoptic advantage was found to decrease with increasing age within the children tested. Binocular acuity was better than monocular acuity in normal subjects, and a decrease in binocular summation with age was noted within the age range of the children tested. In contrast, the amblyopic observers showed no change in acuity with viewing conditions. The results demonstrate development of interocular interactions during childhood, and wide inter-individual variation in pattern of interocular interactions among anisometropic amblyopic adults.

Negligible impact on posture from 5-diopter vertical yoked prisms.

PURPOSE: Yoked prisms are used by some optometrists to adjust posture, but evidence to support this practice is sparse and low level. The aim of this research was to investigate whether vertical yoked prisms have an impact on posture in healthy adults. METHODS: Posture was assessed objectively in 20 healthy adults, by recording a range of joint angles or body segment locations at the ankle, hip, torso, neck, and head during participant observation of a straight-ahead target, and subsequently with eyes closed. Recording occurred before, during, and after wearing goggles with control plano lenses, and 5-diopter (D) base-up and 5-D base-down yoked prisms. In each viewing condition, the goggles were worn for 30 minutes. Interaction effects of lens/prism condition by time on joint angles and body orientation were determined. RESULTS: In the eyes-open and eyes-closed conditions, no significant lens/prism × time interaction effects were found at the torso, neck, hip, or ankle (P > 0.1). However, in both eyes-open and eyes-closed conditions a significant lens/prism × time interaction was found at the head (P = 0.031 and 0.006, respectively), with head extended (tilted backward) by up to 2.5 degrees more while viewing with base-down prisms than with plano lenses. CONCLUSIONS: In healthy adults, 5-D base-down yoked prisms were not associated with a change in body posture. A small effect on head orientation and not at other locations suggests a minimal effect on posture. Research in a larger sample and in individuals with abnormal posture is needed to verify this.

The effects of vertical yoked prisms on gait.

PURPOSE: To investigate the influence of base down (BD) and base up (BU) yoked prism wear on gait. METHODS: Gait was assessed in 31 young healthy adults (mean age, 24.0 ± 5.1 years) during and after wearing 5 prism diopter ((Δ)) BU yoked prisms, 5(Δ) BD yoked prisms, and plano (PL) (zero power; control condition) lenses, worn in a pseudorandom order. Velocity; cadence; step length; double support phase; step width; and variability in step time, step width, step length, and swing time were measured as participants walked at a freely chosen walking speed along a 5.3-m electronic mat placed in the center of a 7.5-m walkway. Gait parameters were analyzed for each viewing condition before, during, and after prism wear. RESULTS: BD yoked prisms, when compared with PL, led to slower velocity, lower cadence, decreased step length, and increased step time variability (P ≤ 0.001) These gait parameters did not significantly differ between BU yoked prisms and PL lenses (P > 0.05). Measurements taken immediately on removal did not differ from those taken after a time delay of 5 minutes. CONCLUSIONS: BD yoked prisms affected gait in young healthy adults walking across an unobstructed path at their freely chosen walking speed, in that participants adopted a slower, apparently more cautious gait pattern; BU yoked prisms did not significantly affect gait. The effect of BD prism on gait may be due in part to a perception of increased height.

Context and crowding in perceptual learning on a peripheral contrast discrimination task: context-specificity in contrast learning.

Perceptual learning is an improvement in sensitivity due to practice on a sensory task and is generally specific to the trained stimuli and/or tasks. The present study investigated the effect of stimulus configuration and crowding on perceptual learning in contrast discrimination in peripheral vision, and the effect of perceptual training on crowding in this task. 29 normally-sighted observers were trained to discriminate Gabor stimuli presented at 9° eccentricity with either identical or orthogonally oriented flankers with respect to the target (ISO and CROSS, respectively), or on an isolated target (CONTROL). Contrast discrimination thresholds were measured at various eccentricities and target-flanker separations before and after training in order to determine any learning transfer to untrained stimulus parameters. Perceptual learning was observed in all three training stimuli; however, greater improvement was obtained with training on ISO-oriented stimuli compared to CROSS-oriented and unflanked stimuli. This learning did not transfer to untrained stimulus configurations, eccentricities or target-flanker separations. A characteristic crowding effect was observed increasing with viewing eccentricity and decreasing with target-flanker separation before and after training in both configurations. The magnitude of crowding was reduced only at the trained eccentricity and target-flanker separation; therefore, learning for contrast discrimination and for crowding in the present study was configuration and location specific. Our findings suggest that stimulus configuration plays an important role in the magnitude of perceptual learning in contrast discrimination and suggest context-specificity in learning.

Configuration specificity of crowding in peripheral vision.

Peripheral vision is characterized in part by poor spatial resolution and impaired visual performance, particularly when the object is surrounded by flanking elements, a phenomenon popularly known as "crowding". Crowding scales with eccentricity irrespective of the target size, both in terms of magnitude and spatial extent, which is determined by varying the target-flanker separation. However, the extent to which crowding depends upon the flanking stimuli parameters alone without separating target and flankers is poorly understood. In the present study, we investigated the effect of flanking stimulus parameters on crowding in orientation and contrast discrimination tasks using closely located "chain" lateral Gabor stimuli in order to enhance our understanding of the underlying mechanisms of crowding in peripheral vision. We found a strong configural effect on crowding in both orientation and contrast discrimination tasks, with reduced crowding when the flanker parameters enhanced the target salience and increased crowding when the flankers were perceptually grouped with the target. While in orientation discrimination crowding was dependent on eccentricity, and in contrast discrimination it was dependent on flanker contrast and eccentricity, crowding showed little dependence on the number of flankers in either task. We conclude that crowding in peripheral orientation and contrast discrimination is configuration specific, which can be reduced without alterations to the target-flanker separation and that crowding is a combination of low-level as well as high-level cortical processing.