Abstract
Abstract: :
Purpose: Previous results (Ma et at, ARVO 2002) suggested that peripheral visual field defects could cause reading difficulty for patients with Retinitis Pigmentosa (RP) because the tunnel vision associated with RP reduces information during fixation, and also suggested that RSVP (rapid serial visual presentation) can facilitate reading in such conditions. In the present study, we used different sizes of restricted visual fields in order to study the reading characteristics of subjects with different degrees of simulated peripheral visual field loss. Methods: We measured reading speed and simultaneously recorded eye movements in 10 normally–sighted subjects using seven presentation methods: (1) "Circular Window 5" (the most severe visual field loss, approx 5 characters visible at the same time.) (2) "Circular Window 10" (approx10 characters visible). (3) "Circular Window 20" (approx 20 characters visible). (4) "Circular Window 30" (approx 30 characters visible). (5) "Line" (normal reading). (6) RSVP –– one word at a time displayed. (7) RSVP5 –– 5 characters at a time displayed, with word hyphenation as necessary. Results: The smaller the circular window, the more slowly all subjects read. There was no significant difference between the "Circular Window 30" condition (413 wpm) and the "Line" condition (421 wpm). With smaller circular windows, subjects’ eye movements showed longer fixation durations, more saccades, and smaller saccade amplitudes. In addition, subjects made more regression eye movements in the "Circular Window 5" condition than in any other condition. All subjects read much more rapidly in the RSVP and the RSVP5 conditions than in the corresponding circular window conditions. Conclusions: Tunnel vision associated with RP may reduce reading speed. During a fixation, by reducing the information available for planning the next saccade (reduced "perceptual span"), it could increase saccade latency and decrease saccade amplitude. By reducing the available lexical information (reduced "visual span"), it could affect saccade planning and also increase the number of regressions. RSVP was found to offer some benefits to subjects with tunnel vision; the more severe the peripheral visual field loss, the greater the benefits potentially offered by RSVP presentation techniques.
Keywords: eye movements • reading • low vision