Contrast grating sensitivity and visual evoked potentials in parkinsonian patients

Contrast grating sensitivity to horizontal and vertical sinegratings was measured in parkinsonian patients and compared with matched healthy controls. The patients did not detect the bars with a high spatial frequency (31 cpd) and showed a very high contrast threshold for all the spatial frequencies tested. Visual evoked potentials to horizontal sinegratings (3, 6 and 16 cpd) with different contrasts (subliminal and above the contrast threshold) and to high contrast checkerboard were also measured and showed significant prolongation of the P-100 latencies in the parkinsonian patients. Our study emphasizes the subclinical visual system abnormalities in this condition.