| Summary: | Cerebral damage to the optic radiations or striate cortex causes ‘homonymous hemianopia’, blindness in the contralateral half of the visual field in each eye. In cultures that read left to right, a right hemianopia has a severe effect on reading efficiency, particularly when the central 5° are lost, because most of the information acquired during reading lies in the right parafoveal field. We explored the importance of right hemifield loss in diagnosing pure alexia (Experiments 1, 2). Later, we assessed the feasibility of an online training program for the rehabilitation of hemianopic dyslexia, and the eye-movement changes that might accompany learning (Experiment 3). In the first two experiments, human subjects performed several visual processing tasks, using a simulated hemianopia gaze-contingent display. We found that hemianopia alone can account for some previously reported impairments in pure alexia. Subsequently, we provide diagnostic criterion for using the word-length effect to discriminate between hemainopic dyslexia and pure alexia for various types of central involvement by right hemifield loss. In the final experiment, a pilot rehabilitation study, two patients with hemianopic dyslexia performed a 10-week on-line perceptual learning task to increase reading span, and improve reading efficiency. Following training, benefits were limited to an increase in the size of forward saccades in one patient (patient JW). We conclude that this training approach is feasible, though further studies are needed to establish efficacy. === Medicine, Faculty of === Graduate
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