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H. E. Bedell, S. Y. Woo, J. Tong, J. R. House, T. Nguyen, T. C. Lien; Agreement Between Psychophysical Orientation Discrimination and Observable Macular Changes That Precede Amd. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2252.
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The retinal distribution of errors in a psychophysical orientation-discrimination task was compared to the observed location of subtle macular changes that precede early AMD.
By comparing digital fundus photographs to Nidek-MP1 fundus images, a masked examiner specified the meridian of macular drusen and/or early RPE changes with respect to the retinal fixation locus in 26 eyes of 16 patients, aged 52 - 82. Visual acuities ranged from 20/15 to 20/30, with a median value of 20/20. To assess orientation discrimination, two 1-deg patches of 0.4-deg lines were presented for 200 ms on opposite sides of a central fixation spot. In one patch, all of the lines were parallel. In the other, each line varied from the mean orientation by a pre-determined angular standard deviation. After each presentation, the patient indicated which patch contained the more parallel lines. The orientation-discrimination threshold and the meridional distribution of errors were determined from the responses to 80 trials. Automated 10-2 perimetry, retinal micro-perimetry, and Amsler grid testing were performed also for each eye.
The average orientation-discrimination threshold in the eyes with subtle macular changes was 10.0 deg, similar to previous results. Meridians with ≥ 25% errors agreed with the meridian of one or more observable macular abnormalities in 62% of the eyes. In contrast, defects in the central 2 deg determined with automated perimetry (P < 0.05) and Nidek retinal micro-perimetry (sensitivity < 20 dB) agreed with the meridian of macular abnormalities (within +45 deg) in only 42% and 50% of eyes. Amsler grid responses were abnormal in just 2 eyes.
The distribution of errors on a psychophysical test of orientation discrimination agrees better with the observed location of subtle macular abnormalities than do perimetry results.
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