Reading and eye movements in age-related maculopathy

Reading characteristics were studied in age-related maculopathy (ARM) by monitoring eye movement patterns as subjects read word charts and text charts that contain a wide range of print sizes. Eye movements were monitored with an infrared scleral reflection device and subjects were tested over a wide range of chart luminances. In normal subjects, as print size approaches threshold, reading speed slows mainly because of a decrease in fixation rate, whereas regressive saccades remain infrequent. There is little change in the ratio of number of letters read per forward saccade. With decreased luminance, there is a decreased reading acuity but the relation between reading speed and the size of print relative to the threshold size remains relatively constant. Subjects with ARM show similar fixation rates to normals, but they average fewer letters per forward saccade and make more frequent regressions. ARM subjects are more likely to have reading performance strongly affected by luminance. The number of letters per forward saccade can show a strong dependence on luminance, whereas fixation rates remain relatively unchanged. It is proposed that reduced reading performance in ARM is predominantly the result of a reduced perceptual span, with poor oculomotor control playing a secondary role. Optimal print size may be best predicted from letter chart acuity (r = 0.70) or word reading acuity (r = 0.69). Word reading acuity is the best predictor of peak reading speed (r = -0.74), whereas peak reading speed is poorly correlated with contrast sensitivity (r = 0.26) and scotoma area (r = -0.42).