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A. Scherlen, V. Gautier; Improvement of reading performance with a visual scotoma by synchronizing eye movements to visual information availability . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5439.
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Purpose: To improve reading rates for patients with central scotoma, we are investigating the coordination of patients’ visual and cognitive performances with respect to their visual deficit. Instead of focusing on retraining fixation, we ask whether letting the patient continue to use central fixation while dynamically displacing information relative to words from the fovea to intact retinal areas (or unmasking the information in the scotoma) could improve reading performance. This condition would avoid the need to search for words in the periphery. We tested the efficacy of unmasking of visual information present under the scotoma continuously and in real time. Methods: Six healthy subjects were tested on a reading task. A central scotoma of various sizes (expressed in number of letters) was simulated. Letter size was 1 deg. We compared reading speed and several parameters related to reading (fixation time, saccade size, number of fixations per word) for three conditions: without scotoma, with letters hidden under the scotoma (pathological condition) and during the unmasking in real time of information to the right of the scotoma. Results: Our results show that reading speed improved when unmasking the information for scotoma widths greater than six letters. We attribute this to that unmasking resulted in fewer fixations per word than the masked condition. When less than six letters were masked by the scotoma, reading was less disrupted and the unmasking was less effective. Interestingly, reading performance was independent of the size of the scotoma when information was unmasked. Conclusions: We can improve reading performance by unmasking the visual information continuously and in real time. These initial experiments lead us to believe that the total linguistic availability is a more crucial criterion for reading performance, than reduction of the visual acuity in the peripheral retina.
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