Purpose. To investigate the relationship between clinical impairment measures and reading performance in a large population with age-related macular degeneration.
Methods. 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).
Results. 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).
Conclusions. 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.
‡DPhil, MCOptom, DipGlauc
Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.
This research was supported by funding from The Health Foundation.
Received April 30, 2009; accepted December 21, 2009.
Reprint requests: Christine M. Dickinson, Faculty of Life Sciences, The University of Manchester, Moffat Building, PO Box 88, Manchester, M60 1QD; e-mail: firstname.lastname@example.org.