N Nagai¹, T Kakizawa¹, H Nakata¹, H Kato²
¹University of Tsukuba, Institute of Disability Sciences, Tsukuba, Japan; ²Tsukuba College of Technology, Division for Visually Impaired, Tsukuba, Japan
PURPOSE: The purpose of this experiment was to investigate effects of character size enlargement on reading eye movements of individuals with low vision.
METHOD: Subjects were three low vision females. We used three character sizes (large, middle, small). In each subject, the small character size was 0.05 log larger than the estimated critical character size and each character size was changed in 0.1 log unit steps. The Japanese text of three lines, where single line consists of ten characters was displayed on the CRT display. Subjects read it silently. Eye movements were recorded by means of a pupil-corneal reflection principle eye tracking system.
RESULT: From recordings of horizontal eye movements, we measured the fixation duration, the saccade length and the reading time. In all subjects, the average fixation duration and the average reading time were reduced as the character size increased. The average saccade length (in visual angle) increased as the character size increased. On the other hand, the average saccade length (in character spaces) remained almost constant in all character sizes. It was the same tendency observed in normal subjects (Morrison and Rayner, 1981).
CONCLUSION: The main effect of character size enlargement was the reduction of the average reading time resulting primarily from the reduction in the average fixation duration.
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