Visual Impairment in Parkinson??s Disease: Deficits in Orientation and Motion Discrimination

Abstract

Purpose. In order to obtain a better understanding of the pathophysiology of visual impairment in Parkinson's disease (PD), orientation and motion discrimination were investigated in PD patients. Methods. Orientation and motion discrimination thresholds were assessed psychophysically in PD patients with normal cognition (N=11) and compared to results for agematched controls (N=22). Results. PD patients exhibited a significant deficit in orientation discrimination for horizontal but not for vertical gratings. Also, motion discrimination thresholds were elevated significantly in PD patients. No significant correlations were found between motion and orientation discrimination thresholds. Conclusions. Our results indicate that PD patients exhibit significant visual dysfunction in the absence of cognitive impairment supporting the contention that neural dysfunction in PD is more generalized than previously realized. The results provide further evidence of an orientation selective visual deficit in PD and show that the ability to discriminate global motion is also attenuated in PD.