James Kundart

Patching vs atropine to treat amblyopia in children aged 7 to 12 years: A randomized trial

OBJECTIVE To compare patching with atropine eyedrops in the treatment of moderate amblyopia (visual acuity, 20/40-20/100) in children aged 7 to 12 years. METHODS In a randomized, multicenter clinical trial, 193 children with amblyopia were assigned to receive weekend atropine or patching of the sound eye 2 hours per day. Main Outcome Measure Masked assessment of visual acuity in the amblyopic eye using the electronic Early Treatment Diabetic Retinopathy Study testing protocol at 17 weeks. RESULTS At 17 weeks, visual acuity had improved from baseline by an average of 7.6 letters in the atropine group and 8.6 letters in the patching group. The mean difference between groups (patching - atropine) adjusted for baseline acuity was 1.2 letters (ends of complementary 1-sided 95% confidence intervals for noninferiority, -0.7, 3.1 letters). This difference met the prespecified definition for equivalence (confidence interval <5 letters). Visual acuity in the amblyopic eye was 20/25 or better in 15 participants in the atropine group (17%) and 20 in the patching group (24%; difference, 7%; 95% confidence interval, -3% to 17%). CONCLUSIONS Treatment with atropine or patching led to similar degrees of improvement among 7- to 12-year-olds with moderate amblyopia. About 1 in 5 achieved visual acuity of 20/25 or better in the amblyopic eye. CLINICAL RELEVANCE Atropine and patching achieve similar results among older children with unilateral amblyopia. TRIAL REGISTRATION (clinicaltrials.gov) Identifier: NCT00315328.

Comparing measurement techniques of accommodative amplitudes

Aim and Background: This study was designed to compare four standard procedures, for determining the monocular accommodative amplitudes. Materials and Methods: Fifty-two students participated in this analytical-descriptive study. Accommodative amplitudes were measured using four common clinical techniques, namely: Push-up, push-down, minus lens, and modified push-up. Results: The highest amplitude was obtained using the push-up method (11.21 ± 1.85 D), while the minus lens technique gave the lowest finding (9.31 ± 1.61 D). A repeated-measures Analysis of Variance (ANOVA) showed a significant difference between these methods (P < 0.05), further analysis showed that this difference was only between the minus lens and other the three methods (the push-up (P < 0.001), the push-down (P < 0.001) and the modified push-up (P < 0.001)). The highest and the lowest mean difference was related to the push-up with the minus lens, and the push-down with the modified push-up, while the highest and the lowest 95% limits of agreement were related to the push-up with the modified push-up and the push-up with the push-down methods. There was almost a perfect agreement between the push-up and the push-down method, whereas, a poor agreement was present between the modified push-up and the minus lens technique, and a fair agreement existed between the other pairs. Conclusions: The quick and easy assessment of the amplitude using the push-up and the push-down methods compared to other methods, and the obtained perfect agreement between these two methods can further emphasize their use as a routine procedure in the clinic, especially if a combination of the two techniques is used to offset their slight over- and underestimation.

The effectiveness of home-based pencil push-up therapy versus office-based therapy for the treatment of symptomatic convergence insufficiency in young adults

Purpose: To compare the effectiveness of pencil push-up therapy (PPT) versus office-based vision therapy in patients with convergence insufficiency. Materials and Methods: In this study, 60 students from Zahedan University of Medical Sciences with convergence insufficiency were selected. After determining their refractive error (with a retinoscope), near point of convergence (by millimeter ruler), near heterophoria (by alternate prism cover test), and positive fusional vergence at near (by prism bar), subjects were divided into two groups to receive PPT (at least three times a day for 5 minutes each time) or office-based therapy (two times each week for 60 minutes each visit) without home reinforcement. Subjects were re-examined 4 and 8 weeks after initiation of treatment. Statistical analysis was performed with the independent samples t-test and the analysis of variance (ANOVA). Statistical significance was indicated by P < 0.05. Results: The near point of convergence, phoria, and positive fusional vergence were not statistically different between the two groups before treatment (P > 0.05). After 4 and 8 weeks of therapy, only the positive fusional vergence was statistically significantly different between groups (P = 0.001). Results from ANOVA indicated a considerable difference between the two groups in general but the observed difference was related only to positive fusional vergence. Conclusion: PPT and office-based vision therapy are comparable for treatment of convergence insufficiency. While we do not deny the more efficacious nature of office-based therapy, it is not always practical, may be too expensive, and may not be locally available. A home-based therapy offers a cost-effective reasonable alternative.

Induced vertical disparity effects on local and global stereopsis

Abstract Purpose: Although significant amounts of vertical misalignment could have a noticeable effect on visual performance, there is no conclusive evidence about the effect of very small amount of vertical disparity on stereopsis and binocular vision. Hence, the aim of this study was to investigate the effects of induced vertical disparity on local and global stereopsis at near. Materials and Methods: Ninety participants wearing best-corrected refraction had local and global stereopsis tested with 0.5 and 1.0 prism diopter (Δ) vertical prism in front of their dominant and non-dominant eye in turn. This was compared to local and global stereopsis in the same subjects without vertical prism. Data were analyzed in SPSS.17 software using the independent samples T and the repeated measures ANOVA tests. Results: Induced vertical disparity decreases local and global stereopsis. This reduction is greater when vertical disparity is induced in front of the non-dominant eye and affects global more than local stereopsis. Repeated measures ANOVA showed differences in the mean stereopsis between the different measured states for local and global values. Local stereopsis thresholds were reduced by 10 s of arc or less on average with 1.0Δ of induced vertical prism in front of either eye. However, global stereopsis thresholds were reduced by over 100 s of arc by the same 1.0Δ of induced vertical prism. Conclusion: Induced vertical disparity affects global stereopsis thresholds by an order of magnitude (or a factor of 10) more than local stereopsis. Hence, using a test that measures global stereopsis such as the TNO is more sensitive to vertical misalignment than a test such as the Stereofly that measures local stereopsis.

Stereoacuity as an indicator of prism adaptation

Abstract Purpose: The purpose of this study was to determine whether stereoacuity can be used as an indicator of prism adaptation. In particular, we wanted to know whether the time required for stereoacuity to return to the initial level after viewing through a prism can be used to determine the degree of adaptation. Materials and Methods: Eighteen subjects participated in this study. Stereoacuity and dissociated phoria were determined using the TNO stereotest and the Maddox rod, respectively. Prism vergences were measured using a prism bar. For each participant, prism power equivalent to the blur point of base-in (BI) and base-out (BO) fusional vergence at 40 cm was divided and placed in front of both eyes. At 0, 3, 6, 9 and 12 min after prism introduction, the stereoacuity was measured, and at 0 and 12 min, the heterophoria was measured. Results: The repeated measures ANOVA showed a significant difference between the mean stereoacuity for BI and BO prisms at the different measurement times (p < 0.05). For BO prism, the initial value was different between 0 and 3 min after the prism introduction, whereas for BI prism, a difference in stereoacuity was found between the pre-prism value and the value at 0, 3 and 6 min. The size of the heterophoria with BO and BI prisms was different from 0 to 12 min (p < 0.05). Conclusion: The time required for stereoacuity to return to baseline level was more than 3 min for BO, and more than 6 min for BI prism. In addition, the time required to return to baseline values was not similar for the stereoacuity and heterophoria. The recovery of stereoacuity is slower when adapting to divergence, as when looking from near to far. This implies that stereopsis responds faster to near targets than to distant one, and may precede complete phoria adaptation.

Effect of Induced Vertical Disparity on Horizontal Fusional Reserves

ABSTRACT 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.

Evaluation of Fixation Disparity Curve with the Modified Near Mallett Unit and the Wesson Fixation Disparity Card in Symptomatic and Asymptomatic Subjects

Purpose: The purpose of this study is the evaluation of fixation disparity curve (FDC) parameters with an instrument that includes a central fusion lock (the modified near Mallett unit) and another without one (the Wesson fixation disparity card) to determine which is useful for diagnosis of symptomatic from asymptomatic subjects. Materials and Methods: In this analytical-descriptive study, 100 students were selected randomly and divided into symptomatic and asymptomatic groups. FDC parameters were determined with the Wesson card and the modified near Mallett unit for each subject and compared in symptomatic and asymptomatic groups. Data were analyzed by Wilcoxon, Mann-Whitney U, Spearman correlation coefficient and Chi-square tests. Results: The mean slope, y-intercept, and x-intercept with the Mallett unit and the Wesson card were significantly different in the symptomatic and asymptomatic groups (p < 0.001). Significant correlations were obtained between the Mallett unit and the Wesson card in y-intercept, x-intercept and slope (p < 0.001). There was a significant difference in the distributions of fixation disparity curve types in the two symptom groups with the Mallett unit (p = 0.01) and the Wesson card (p = 0.002) by Chi-square test. Conclusions: Among symptomatic participants in this study, both Type I and Type III FD are more common than previously thought, but depend upon the method used to measure it. The x-intercepts were on average displaced in the base-in direction, y-intercepts were shifted in the exo direction, and the slopes were steeper with the Wesson FD card compared with the modified near Mallett unit. This may be related to the design of two devices. These differences were more significant in the symptomatic group.