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Janet S Sunness, Carol A Applegate; Following Disease Progression Using Visual Function Changes at 1 and 2 Years In Patients With Bilateral Geographic Atrophy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1239.
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For clinical trials for advanced dry AMD, visual function outcome measures may be affected by the patient’s adaptation to eccentric fixation. Prior work has shown that for the worse-seeing eyes of patients with bilateral GA, there may be spontaneous improvement in visual acuity, and this may confound the use of visual acuity as an outcome measure in GA. This study looks at contrast sensitivity and reading speed as other possible outcome measures.
In our prospective natural history study of GA, 53 patients with bilateral GA had both 1 and 2 year follow-up visits. Best-corrected VA, Pelli-Robson contrast sensitivity, and maximum reading rate were assessed at each visit. The results are broken down by visual acuity categories: group 1=VA 20/50 or better; group 2=VA from 20/51 to 20/199; group 3=VA 20/200 or worse
For contrast sensitivity, findings were similar in better and worse seeing eyes. The mean baseline log contrast sensitivity was reduced by 0.48 log units (10 letters) relative to normal for groups 1 and 2. For groups 1 and 2, 10% had a 0.3 further worsening in contrast sensitivity at 1 year, and 16% at 2 years relative to baseline. 5% of groups 1 and 2 improved by 0.3 at 1 year and at 2 years relative to baseline. For reading rate, findings were similar in better and worse seeing eyes for group 1, but different for group 2. For group 2, better-seeing eye baseline reading rate was 60 wpm, and there was a mean decline of 10 letters at one year and 13 at 2 years. Worse-seeing eye baseline reading rate was 36 wpm, and mean decline was 6 letters at 1 year and 1.5 letters at 2 years. At both 1 and 2 years, reading rate improved by >=10 wpm in 25% of worse-seeing eyes.
Contrast sensitivity does not change greatly over 2 years, and reading rate may improve from better eccentric fixation despite worsening of GA. Visual function measures are difficult to use as main outcome measures for GA.
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