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K Ma, HJ Wyatt, D Yager; Reading Characteristics of Subjects with Simulated Retinitis Pigmentosa . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3800.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Many patients with retinitis pigmentosa (RP) retain relatively good visual acuity, but they have severe peripheral visual field defects. In this experiment, we have simulated this situation, to study the reading characteristics of subjects with peripheral loss. Method: We measured reading speed and simultaneously recorded eye movements in 8 normally-sighted subjects using three presentation methods: (1) "Circular Window" (simulated RP). An entire sentence was presented on a single line on the screen. At any moment, subjects could see only the characters (approximate10) within a circular window, which was stabilized on the subject's retina (The circular window was centered on the fovea). (2) "Line". The entire sentence remained visible throughout the presentation. (3) "Line + Ring" (A control condition for the effect of the edge of the circular window). The entire sentence remained visible throughout the presentation. A thin white circle, with diameter approximate 10 characters, moved as for the "Circular Window" condition. Results: All subjects read more slowly in the "Circular Window" condition (351wpm), than in the "Line" condition (751wpm). The subjects' eye movements in the " Circular Window" conditions showed longer fixation durations, more saccades, and smaller saccade amplitudes than eye movements in the "Line" condition. There was no significant difference of reading speed or of subjects' eye movements between the "Line" condition and the "Line + Ring" condition. Conclusion: The findings of this study suggest that peripheral visual field defects could cause reading difficulty for patients with RP. A simple hypothesis would be that the "tunnel vision" of RP may reduce the information which is obtained during each fixation. By making it harder to plan the next saccade, this could result in increased saccade latency and decreased saccade amplitude.
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