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Xin Jie Lai, Suzanne McKee; Dichoptic and Monocular Masking in Strabismic Amblyopia. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3996.
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The lack of functional stereopsis and fusional ability in amblyopes may result from the prolonged exposure to binocularly uncorrelated signals and inhibition of the amblyopic eye. This study compared dichoptic and monocular masking to investigate suppression in strabismic amblyopia.
Vernier acuity was measured in both eyes of 4 strabismic amblyopic adults and in the non-dominant eye of 4 normally sighted adults in dichoptic and monocular masking conditions and in a control condition. A Vernier target composed of two dark squares at 15% contrast, each subtending 23 by 23 minutes with a 1.4 minutes gap, were oriented horizontally (vertical offsets) and were presented at 100ms. In the masking condition, we used a variety of masks: 3-degree dark and bright squares at 60% contrast; 60% contrast vertical Gabors at 0.5, 4 and 10cpd; 60% contrast 10cpd Gabors oriented at 0, 15, 60, 90, 120 and 165-degree; vertical 4cpd Gabors at 10, 20, 40, 50 and 60% contrast. In the control condition, the non-tested eye viewed a mean luminance background with no mask or target. The masking effect was calculated using the acuity measured in the masking condition divided by the acuity measured in the control condition.
Masking was stronger dichoptically than monocularly in all subjects. With the masks used here, dichoptic masking of amblyopic eyes was found to be stronger than that of fellow eyes and the non-dominant eyes of normal observers.
For strabismic amblyopes, all types of dichoptic masking tested here produced strong suppression of Vernier acuity in the amblyopic eye.
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