Abstract
Eye movements during reading are consisted of repetitions of saccade and fixation and function effectively. Meanwhile, it shows that reading speed decreases even in the healthy elderly due to some effects such as presbyopia. We examined a relationship between decrease of reading speed and eye movements with aging. Subjects comprised 15 adults from 21 to 60 years old with no ophthalmic diseases. Experiment1: The subjects were asked to read the clinical-used vertical text, MNREAD-J, 10 letters ×3 lines (30 letters), appeared on PC, and showed 30 times each letter size of logMAR 10 and 0.5 with keeping 30 cm distances from the text. We measured fixation time, fixation frequency, eye-movement tracking, and pupil size using Eyemark Recorder (Nac). Experiment2: The elderly tend to have low near visual acuity because of accommodation degeneration. We compared eye movements of young adult with of the elderly under a certain condition which young adult asked to reduce vision with convex lenses. The mean logMAR among the elderly was 0.13±0.11 and near visual acuity of young adult was reduced under the average. Text was reformed MNREAD-J, 20 vertical letters with logMAR 1.0 and 0.5 size, and measured in the same way as Experience 1. Reading speed decreased with aging. Fixation frequency of 50s increased compared with 20s although there was no difference in fixation time with age, which showed saccade length decreased significantly (p<0.05) and suggested that this was a main reason of decrease of reading speed in the elderly. Saccade length of young adult was significantly long compared with the elderly with the usage of convex lenses (p<0.05). Also the elderly made regressions back frequently. Decrease of reading speed with aging is attributed to reduction of saccade length not to the delay of fixation time and has something to do with factors other than degeneration of near visual acuity.
