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Luminita Tarita-Nistor, Michael H. Brent, Martin J. Steinbach, Esther G. Gonzalez; Binocular Coordination During Fixation in Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5714.
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Binocular ocular motor control in patients with age-related macular degeneration (AMD) is poorly understood. This is mainly because the location of the new reference position of the ocular motor system is not predictable and, with present technology, it is difficult to identify during binocular viewing. The goal of this study was to explore binocular coordination during fixation in people with AMD and to investigate the causes of shifts in eye position when viewing condition changes from binocular to monocular.
Sixteen people with normal vision (mean age 28.25 ± 10.13 years) and 12 patients with AMD (mean age 79.25 ± 7.31 years) were asked to look at a 3-deg fixation target with both eyes, and with each eye individually while the fellow eye was covered by an infra-red filter which blocked visible light. Fixational eye movements were recorded for both eyes with the EyeLink eye-tracker in all conditions. The shift in eye position at the end of every fixation period was calculated for each eye.
All people with normal vision as well as the majority of patients had very good binocular coordination during fixation in the binocular viewing condition. For one patient with a relatively healthy eye and the other eye severely affected by disease, the worse eye showed a large horizontal deviation (4.4 deg) during binocular viewing. When the viewing condition changed from binocular to monocular, patients had atypical shifts in their gaze position which were not observed in people with normal vision. The shift was related to 1) the loss of fixational control when the better eye was covered and the worse eye viewed the target, or 2) slow drift of the viewing eye that was associated with extreme phoria in the covered eye.
A change in viewing condition from binocular to monocular can lead to disturbances in ocular motor control in patients with AMD, especially when the worse eye takes up fixation.
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