To investigate the relationship between clinical impairment measures and reading performance in a large population with age-related macular degeneration.
The following clinical measures were evaluated on 243 patients with age-related macular degeneration: better eye distance visual acuity (ETDRS chart); threshold near word reading acuity (Bailey-Lovie Word Reading chart); maximum reading speed and critical print size (MNREAD chart); letter contrast sensitivity (Pelli-Robson); and kinetic perimetry (Bjerrum screen) to determine the nearest non-scotomatous point to fovea (NNPF; in degrees) and the central scotoma area (mm2).
Distance acuity correlated well to threshold near word acuity (r = 0.71), but word acuity was usually poorer. Critical print size was strongly related (p < 0.001) to near visual acuity (r2 = 0.31 and β = 0.47) and was poorer than threshold near word visual acuity by a mean difference of −0.41 (range, −1.10 to 0.34), which represents a mean acuity reserve of 2.5:1. On single regression, distance (p < 0.0001, r2 = 0.35, and β = −102.37) and near acuities (p < 0.0001, r2 = 0.52, β = −126.53), critical print size (p = 0.0001, r2 = 19, and β = 0.002), contrast sensitivity (p < 0.0001, r2 = 19, and β = 79.47), scotoma size (p = 0.006, r2 = 12, and β = −0.04), and NNPF (p = 0.001, r2 = 12, and β = −4.39) were all highly significantly related to reading speed although these predicted only a low percentage of variance. Best prediction of reading speed was obtained on multiple regression, where NNPF and near word acuity explained 60% of the variance (p < 0.0001).
Optimal prediction of reading speed with clinical parameters appears to be based on the combination of near word acuity and scotoma area, explaining 60% of the variance. Other factors not measured in this study are likely to account for the rest of the prediction.