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L. Liu, T.K. Kuyk, P.W. Fuhr; How Fast Could An AMD Patient Identify An Eccentric Target? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3691.
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© ARVO (1962-2015); The Authors (2016-present)
To detect and identify an eccentric visual target is an important visual skill. The impact of advanced Age–Related Macular Degeneration (AMD) on this skill was investigated.
Thirty–four patients with advanced AMD (mean age 76.18 years, mean LogMAR 0.845) and 25 normal controls (NC, mean age 67.24 years, mean LogMAR 0.016) were studied. The target was either a 2x2 deg square or a 2x2 deg triangle. It randomly appeared at one of the 16 positions organized on two virtual concentric circles (eccentricities). Each circle had 8 evenly distributed target positions located at 0, 45, 90, 135, ... , 315 deg from horizontal. The circle radii for tests 1, 2, and 3 were 5 & 10 deg, 7.5 & 15 deg and 10 & 20 deg, respectively. The patient was instructed to look at a fixation target at the center of the virtual circles, and to start a display of the target at one of the 16 positions. The patient’s task was to find the target as fast as he/she could, and to report whether it was a square or a triangle. Both response accuracy and reaction time of each trial were recorded. The patient practiced one set of the tests per day for 4 days, and test results of the 5th day were analyzed.
Response accuracies of both AMD and NC groups were high (>96%), and the differences between the two groups were not significant. The AMD group took significantly longer time than the NC group to detect and identify the target in all three tests (1143, 1213 and 1271 msec for the AMD group and 932, 871 and 885 msec for the NC group). The reaction time differences between the two groups were significant at all target eccentricities. The reaction time of the AMD group showed a significant dependence on target eccentricity, rose from 1100 msec at 5 deg eccentricity to 1320 msec at 20 deg eccentricity. The reaction time of the NC group did not change significantly with target eccentricity. Practice on the task improved performance in both groups, with most significant improvements at smaller target eccentricities.
Although AMD affects mainly the macula, the patient’s ability to detect and identify eccentric visual stimuli is impaired. The impairment increases with increasing eccentricity, and may be alleviated by practicing.
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