Deficient Binocular Combination of Second-Order Stimuli in Amblyopia

Abstract

Citation: Zhou J, Liu R, Feng L, Zhou Y, Hess RF. Deficient binocular combination of second-order stimuli in amblyopia. Invest Ophthalmol Vis Sci. 2016;57:163557: -164257: . DOI:10.1167 PURPOSE. Sensory imbalances in humans with amblyopia have been well documented using luminance-modulated (first-order) stimuli. However, little is known regarding whether there is a deficient binocular combination in amblyopes for stimuli defined by modulations in contrast (second-order stimuli). To address this, we asked two questions: Does a sensory imbalance also exist in the binocular combination of second-order stimuli, and if so, is it more severe than that expected on the basis of the imbalance for first-order stimuli?METHODS. The sensory imbalances of 14 adult amblyopes (mean age: 30.5 6 11.5 years; 5 with strabismus and 9 without) were measured using a dichoptic phase combination task. Three types of second-order dichoptic stimulus pairs were used in the study, where the carriers in the two eyes were either correlated, anticorrelated, or uncorrelated. Results were compared with those obtained using first-order stimuli in all observers. RESULTS.We found that second-order binocular combination in amblyopes was not affected by the interocular carrier correlations. The amblyopic eye's contribution to the binocularly fused percept was much less than that of the nonamblyopic eye. The resulting sensory imbalance in binocular combination for second-order images was comparable to that for first-order images in 8 of the observers but was more severe in the other 6 amblyopes.CONCLUSIONS. These results indicate that amblyopia does not disrupt the normal architecture of binocular combination for second-order signals; however, there is an additional deficit in binocular combination of second-order image in some amblyopes that cannot be fully accounted for by the known first-order sensory imbalance.Keywords: amblyopia, suppression, second-order, contrast-gain control, sensory imbalance A mblyopia is a common disorder caused by abnormal visual development during childhood. [1][2][3] This makes amblyopia a unique model for investigating what factors are critical in early development. Normally, people with amblyopia have reduced visual function when viewing stimuli with their amblyopic eye, even when the appropriate optical correction is used. These deficits can include reduced visual acuity, reduced contrast sensitivity function, and spatiotemporal distortions. 3-8 Recently, imbalances in binocular function have been put forward as a possible primary factor in the disorder. [9][10][11] This has led to new binocular training therapies. 12-16 Such a sensory imbalance has been demonstrated in several paradigms, for example, local phase combination, 9,17 global motion coherence, 18 and global orientation coherence. 19 Even at low spatial frequencies where the two eyes have equivalent monocular visual thresholds, the amblyopic eye still makes less of a contribution to the binocularly fused percept than the nonamblyopic eye. 9,11,[17][18][19]...

Abnormal Monocular and Dichoptic Temporal Synchrony in Adults with Amblyopia

“…A mblyopia affects 0.5% to 3.6% of the population 1,2 and is one of the most common causes of vision deficit in children. 3 Extensive evidence has demonstrated that amblyopes have poor spatial vision, including visual acuity, vernier acuity, grating acuity, contrast sensitivity, 4 binocular combination, 5 stereoacuity, 6 second-order motion perception, 7 and global form integration 8 in the amblyopic eye. Apart from the spatial visual deficits, amblyopes also experience temporal visual deficit.…”

“…The binocular visual deficit in amblyopia has been receiving more recognition, 5,[20][21][22][23][24][25][26] namely, the role of interocular suppression from the fellow eye to the amblyopic eye. 5,20,22,23,27,28 The importance of interocular suppression has been well documented in various binocular spatial visual processes, including binocular phase combination, 5,7 binocular contrast combination, 23 binocular global form integration, 29 and binocular rivalry. 30 These binocular visual deficits have been studied using suprathreshold visual stimuli.…”

Effect of Illumination on Ocular Status Modifications Induced by Short-Term 3D TV Viewing

“…We did not examine the mechanism in this study, but we demonstrated that front illumination is an appropriate illumination mode for watching 3D displays. There is much evidence suggesting that illumination of the environment is a modifying factor forocular status [2, 3, 6], visual asthenopia [25, 28], and the contrast modulation of visual cortical cells [29, 30]. Low luminance levels, as in Mode A (complete darkness), would create inadequate viewing conditions and notable variations in the eyes when moving the gaze intermittently between the bright display and darker surroundings and would potentially cause eye strain.…”

Concerning Manuscript “Deficient Binocular Combination of Second-Order Stimuli in Amblyopia”

“…And for patients A1 through A3 and patients A5 through A7, the balance point of the secondorder perceived phase versus interocular modulation depth ratio (PvR) was less than that of the first-order PvR. 2 Here we want to point out that the diagnosis of anisometropic amblyopia for subject A9 may need to be reconsidered. There are not unified anisometropic diopters for the definition of anisometropic amblyopia.…”

“…We read with great interest the article by Jiawei Zhou et al on second-order deficits in amblyopia. 2 We appreciate the authors' rigorous experimental methods and deliberate mathematical analysis, and we have some of our own thoughts about the authors' work.…”