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A.K. Bittner, F. Eshraghi, G. Dagnelie; Validated Psychophysical Measurements in Severe Vision Loss . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1801.
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Purpose: To establish vision measures allowing objective visual function monitoring in patients with severe vision loss during Phase I experimental trials. Methods: Legally blind volunteers and normally sighted control subjects were enrolled in a repeated-measures study to determine the reproducibility of psychophysical visual function measures. Tests included ETDRS LogMar visual acuity (VA) under normal, dim, and glare illumination, Pelli-Robson contrast sensitivity (CS) under the same three conditions, fixation controlled AVIAS perimetry, dark adaptation curve measurement, dark adapted full field flash testing, and dark adapted macular field test using Humphrey perimeter with 500 and 650 nm targets. Visually impaired subjects were legally blind from retinitis pigmentosa (23), macular disease (9), optic nerve disease (3), and other retinal degenerations (2). Four subjects were normally-sighted. All visually impaired subjects were legally blind, due to either visual acuity <20/200 or visual field diameter <20°. RP and AMD subjects were divided into four and two groups, resp., on the basis of their remaining vision level. Two to four repetitions of each test were performed at monthly intervals. Results: With the exception of VA and CS tests in subjects with advanced RP, meaningful test results on all tests were obtained from all subjects. Some RP subjects were unable to perform glare and low illumination tests, and a few had no measurable VA or CS. 95% confidence intervals (CI.95, in dB) within subject groups were computed for each measure. In all groups, VA measures had CI.95 <= 2 dB, CS measures <=4 dB; most measures were half of these values. These values are similar to those reported for normally-sighted individuals. Conclusions: Data collection in these severely visually impaired subjects is slow and painstaking, If done carefully, however, psychophysical measures of VA and CS can be similarly reliable in these patients as in normally-sighted observers. Results for remaining psychophysical tests will be presented.
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