Abstract
Abstract: :
Purpose: To investigate whether perceptual filling–in is modified by the presence of toxoplasmosis retinal lesions. Patients with such lesions perceive the visual field as uninterrupted, suggesting completion of the damaged regions by perceptual filling–in process. We asked whether the preserved retina just outside the edge of the lesions suffers any reorganization of change in sensibility that could influence the filling–in process. Methods:We selected 2 patients and 4 controls. The first patient had acute lesion on inferior left retina; the second had chronic lesion on superior right retina. The exact localization and the edge of the lesions were determined by perimetry. Artificial scotomas were projected just outside the edge of retinal lesion and on two another equidistant points in the visual field of the same eye. The target and surround stimulus were gray; the surround area with a luminance of 28 cd/m², target with 33 cd/m². The target was a 1° square patch, with an eccentricity of 13° from central fixation point. Each position was tested 24 times. Control patients had no retinal lesions and were tested just outside the edge of natural blind spot and two another equidistant points. All subjects gave their informed consent and the Brasília University's Human Research Ethics Committee has approved this protocol. Results: Control patients and patient with chronic lesion presented no significant difference in the filling–in latencies between edge of blind spot/scotoma and the other two points tested (p>0.01). The patient with acute lesion took more time for completion just outside the edge of retinal lesion than at the other points tested (p<0.01). Conclusions: Chronic retinal lesions might have a very similar filling–in process as compared to natural blind spot. Acute lesions might enhance temporally neighboring retina sensibility and provoke longer filling–in latencies at this region.
Keywords: toxoplasmosis • retinochoroiditis • perimetry