Abstract
Purpose: :
Eye movements during reading consist of repetitions of saccade and fixation, and function effectively. It is known that reading speed decreases in healthy elderly due to effects such as presbyopia. We investigated the relationship between decrease of reading speed and eye movements with aging.
Methods: :
Subjects comprised 15 adults aged 21 to 60 (20s N=5, 30s N= 2, 40s N= 3, 50s N=5) years old with no ophthalmic diseases. Experiment1: Subjects read aloud letters, (MNREAD-J, 10 letters x3lines = 30 letters size logMAR 1.0 and 0.5 at distance of 30 cm) presented on a PC screen thirty times while measures of fixation time, fixation frequency, eye-movement tracking and pupil size using eye tracking system (Eyemark Recorder, Nac) were taken. Experiment2: To control for lower near visual acuity in the elderly, young adults wore convex lens. Mean logMAR among the elderly was 0.13±0.11 and near visual acuity of young adults was reduced to below this. Text was presented (MNREAD-J, 20 letters size logMAR 1.0 and 0.5) and measurements were similarly taken.
Results: :
Reading speed decreased with aging. Fixation frequency of those aged 50s increased compared with those aged 20s with no difference in fixation time, showing that saccade length decreased significantly (p<0.05) suggesting this to be the reason for decreased reading speed in the elderly. Saccade length of young adults wearing convex lens was significantly longer than that of the elderly (p<0.05). Also the elderly frequently made regressions back to previous letters.
Conclusions: :
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.
Keywords: eye movements • aging • reading