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Sean A. kennedy, Ewa Niechwiej-Szwedo, Manokaraananthan Chandrakumar, Herbert C. Goltz, Agnes M. Wong; Effects of Induced Monocular Blur versus Anisometropic Amblyopia on Saccadic Eye Movements. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4861.
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Anisometropic amblyopia is a visual impairment of one eye due to a significant difference in refractive error between the eyes. Patients with anisometropic amblyopia have prolonged and more variable saccade latency. We investigated whether the prolonged saccade latency is due to a loss of visual acuity alone, or due to a unique effect of amblyopia as a result of abnormal visual development during early childhood.
Twelve patients with anisometropic amblyopia and 12 visually-normal participants were tested. Participants executed saccades to targets presented randomly at ±5 degrees and ±10 degrees on a computer screen during binocular and monocular viewing (fellow eye / amblyopic eye for patients, right / left eye for control subjects). Control subjects were tested before, immediately after, and 5 hours after artificially-induced monocular blur (to 20/50) using a plus contact lens. Latency, amplitude, and peak velocity of primary saccades were analyzed.
Patients with amblyopia had significantly longer (p=0.006) and more variable (p=0.037) saccade latency during amblyopic eye viewing (221±67 ms), compared to fellow eye (185±29 ms) or binocular viewing (189±52 ms). In contrast, induced monocular blur did not affect saccade latency or variability: normal vision (binocular: 169±29 ms; monocular left: 186±30 ms; monocular right: 193±32 ms), immediately after induced blur (binocular: 172±31 ms; normal acuity eye: 183±29 ms; blurred eye: 189±31 ms) and 5 hours after induced blur (binocular: 177±32 ms; normal acuity eye: 193±35 ms; blurred eye: 191±33 ms).
Patients with amblyopia demonstrated significantly longer and more variable saccade latency during amblyopic eye viewing. This observation was not reproduced after artificially-induced monocular blur in visually normal subjects, suggesting that a loss of visual acuity alone could not explain the saccadic deficits seen in amblyopia.
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