Retinal Visual Dysfunction, in Parkinson’s Disease, is Enhanced by Low Contrast Stimuli
Electrophysiological studies, performed in the past several years, (Bodis-Wollner and Yahr 1978) have demonstrated visual alterations in Parkinson’s disease (PD) patients. Further studies confirmed the delay of the pattern reversal Visual Evoked Potential’s (VEP) (Sollazzo 1984; Tartaglione et al. 1984; Bodis-Wollner et al. 1986) major positive wave (P100). Research has proved that the cause of this delay also dependens on several parameters of the visual stimulus: the type of visual pattern (Tartaglione et al. 1984), the spatial (Onofrj et al. 1986) and temporal frequency (Marx et al. 1987), and the contrast level (Gottlob et al. 1987) (for a review see Bodis-Wollner et al. 1988). Namely, an enhanced P100 delay has been observed in PD patients, when sinusoidal grating stimuli at high spatial frequency (2–4cpd) and at low contrast levels (less then 50%) are utilized (Bodis-Wollner 1988). The physiopathologic relationship with the dopaminergic deficit of PD has been proved by several studies emphasizing the recovery of this delay during L-DOPA therapy (Bodis-Wllner and Yahr 1978; Sollazzo 1984; Bodis-Wollner et al. 1988).
Key WordsPERG Parkinson’s disease contrast sensitivity
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