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BA Sabel, S Kenkel, A Schreiber, U Schiefer, J Reinhard, S Trauzettel-Klosinski, C Connert, E Kasten; Visual Restitution Training (VRT) in Patients With Homonymous Field Defects: Improvements of Subjective Vision and Their Relation to Reaction Time, Visual Field Enlargements and Eye Movements . Invest. Ophthalmol. Vis. Sci. 2002;43(13):229.
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Purpose: Visual field defects (VFD) after brain damage have been considered to be non-treatable, but training residual vision using visual restitution training (VRT, Kasten et al., Nature med. 4, 1998, p. 1083) reportedly enlarge the visual field. We now studied whether VRT has benefits in every day life as subjectively reported by patients. Methods: 17 patients with homonymeous VFD were included in an open pilot trial. VFD were caused by cerebral ischemia or haemorrhage (lesion age ≷1 yr.). To assess subjective vision before and after a 6- months VRT-training (daily for 1 hr.), patients were asked to fill out a standardized questionnaire, and semi-structured interviews were conducted by two independent observers. These results were correlated with perimetric/campimetric procedures (see Kasten, Schreiber and Reinhard abstracts, ARVO 2002). Results: In 14 patients questionnaires revealed subjective improvements due to VRT. In the interviews, 13 patients reported highly specific improvements of activities of daily life such as reading, watching TV, driving a car, shopping in supermarkets etc. Subjective improvements did not correlate with performance gains in campimetry, (r= 0.43, trend at p=0.12) nor with fixation accuracy as assessed by detection of minor color changes of the fixation point (r= -0.176, p=0.5). The latter finding is at variance with the proposal that eye movements alone cause apparent visual field enlargements. Reaction significantly improved due to VRT from 435 ms to 409 ms, which correlated significantly with subjective improvements (r=0.55, p<0.03). Conclusion: Patients benefit subjectively from visual restitution training in every day life. Because these improvements correlate only slightly with increased detection ability in campimetry but more with improved reaction times, we now propose that the primary effect of VRT is to improve temporal processing of residual vision. This may explain why patients without visual field enlargements sometimes still experience subjective improvements of vision. Thus, restoration of vision is primarly mediated by plasticity of neuronal processing in time.
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