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Wuli Jia, WUXIAO ZHAO, Chang-Bing Huang, Zhong-Lin Lu; Ocular Imbalance in Clinically Treated Amblyopia. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2201.
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© ARVO (1962-2015); The Authors (2016-present)
The current gold standard of a successful amblyopia treatment is the full recovery of visual acuity in the amblyopic eye. Although anecdotal evidence suggests that other visual functions such as contrast sensitivity might still be deficient after full acuity recovery, there has been no systematic study on how the previously amblyopic eye (pAE) will behave in binocular vision. In this study, we aimed to quantify sensory dominance of the pAE in a group of treated amblyopia.
Eight treated amblyopes with very similar acuity in the two eyes (logMAR: .03 vs .00) participated in this study. Stereoacuity, monocular and binocular contrast sensitivity functions (CSF) with the quick CSF method (Lesmes et al., 2010), perceived phase of binocularly combined sinewave grating as a function of interocular contrast ratio (Huang et al., 2009), and pAE dominance in viewing dichoptically presented incompatible images of equal contrasts were measured. To quantify sensory eye dominance, we derived three different indices: (1) binocular contrast summation ratio: the ratio of the areas under binocular and previously fellow eye (pFE) CSFs, (2) balance point in binocular combination: the interocular contrast ratio at which the two eyes contribute equally to binocular phase combination, and (3) percentage of pAE dominance. The lower the binocular summation ratio and balance point, the weaker the pAE relative to the pFE is; a less than 0.5 eye dominance percentage indicates weaker pAE than pFE.
Near stereo acuity (31.38”±6.93”) and pAE dominance percentage (.5 at 1 c/d and .43 at 8 c/d) of the treated amblyopes were largely comparable to those of normal subjects. Contrast sensitivity remained deficient in high spatial frequencies, consistent with Huang et al. (2007), although their binocular contrast summation ratio (1.26±0.16) is only slightly less than that of normal subjects (Baker et al. 2007). However, the average balance point in binocular combination was only 0.41---the effective contrast of images in the pAE is equal to about 41% of the same contrast presented to the pFE in binocular phase combination.
Although near stereoacuity, binocular contrast summation ratio, and eye dominance in treated amblyopia were normal or nearly normal, the pAE remained “lazy” in binocular phase combination. Our results suggest that structured monocular and binocular training are necessary to fully recover deficient functions in amblyopia.
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