Jiawei Zhou1, Alexandre Reynaud2, Zhimo Yao1, Rong Liu3, Lixia Feng4, Yifeng Zhou3, Robert F Hess2. 1. School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, People's Republic of China. 2. McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada. 3. Chinese Academy of Sciences Key Laboratory of Brain Function and Disease, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China. 4. Department of Ophthalmology, First Affiliated Hospital, Anhui Medical University, Hefei, Anhui, People's Republic of China.
Abstract
Purpose: To test the amblyopic suppression at mid to low spatial frequencies when compensating for signal attenuation. Methods: Eight amblyopes with (n = 5) or without (n = 3) strabismus and 10 normal controls with normal or corrected to normal visual acuity (≥20/20) and normal stereopsis (≤40 arcseconds) participated. Using a quick contrast sensitivity function approach, we measured individuals' monocular contrast sensitivity functions when the untested eye saw a mean luminance background and when the untested eye saw a bandpass filtered noise whose peak spatial frequency was matched to that of the test grating. Interocular suppression was quantified by the difference in thresholds occurring between these two conditions for each eye. The contrast of the noise mask was set at five times the threshold of the untested eye. Results: Selected spatial frequencies (0.67-1.31 cyc/deg) were identified where neither ceiling (five times the mask contrast threshold in the amblyopic eye <100%) nor floor (threshold of the amblyopic eye when there was a noise mask in the fellow eye <100%) effects occurred for all observers. Within this frequency range, we found no interocular suppressive imbalance in normal observers. However, in amblyopes, the amblyopic eye exerted significantly less suppression than the fellow eye, while the suppression from the fellow eye to the amblyopic eye was similar to that found in the normal controls. Conclusions: We conclude that the reduced dichoptic masking by the amblyopic eye, within the context of normally balanced interocular inhibition, produces the amblyopic suppression at mid to low frequencies.
Purpose: To test the amblyopic suppression at mid to low spatial frequencies when compensating for signal attenuation. Methods: Eight amblyopes with (n = 5) or without (n = 3) strabismus and 10 normal controls with normal or corrected to normal visual acuity (≥20/20) and normal stereopsis (≤40 arcseconds) participated. Using a quick contrast sensitivity function approach, we measured individuals' monocular contrast sensitivity functions when the untested eye saw a mean luminance background and when the untested eye saw a bandpass filtered noise whose peak spatial frequency was matched to that of the test grating. Interocular suppression was quantified by the difference in thresholds occurring between these two conditions for each eye. The contrast of the noise mask was set at five times the threshold of the untested eye. Results: Selected spatial frequencies (0.67-1.31 cyc/deg) were identified where neither ceiling (five times the mask contrast threshold in the amblyopic eye <100%) nor floor (threshold of the amblyopic eye when there was a noise mask in the fellow eye <100%) effects occurred for all observers. Within this frequency range, we found no interocular suppressive imbalance in normal observers. However, in amblyopes, the amblyopic eye exerted significantly less suppression than the fellow eye, while the suppression from the fellow eye to the amblyopic eye was similar to that found in the normal controls. Conclusions: We conclude that the reduced dichoptic masking by the amblyopic eye, within the context of normally balanced interocular inhibition, produces the amblyopic suppression at mid to low frequencies.