Progressive worsening of spatial and chromatic processing deficits in Parkinson disease

Impairments of color discrimination (CD) and contrast sensitivity are established signs of Parkinson disease (PD), but their temporal evolution has not been studied.

To determine whether there is progressive, longitudinal deterioration of color discrimination (CD) and contrast sensitivity (CS) in PD.

A prospective study.

Tertiary care center-based sample of PD patients without dementia with normal visual acuity (Snellen fraction >0.6 in the best eye).

With a mean +/- SD interval of 19.8 +/- 2.8 months, the following tests were applied twice in 28 patients: the Lanthony D15 test and the Farnsworth Munsell 100 Hue test as tests of CD and the monocular and binocular Pelli-Robson test and the binocular Vistech tables as tests of CS.

There was deterioration of both CD (Farnsworth Munsell 100 hue test: P =.002) and CS (binocular Vistech test at a spatial frequency of 6 cycles per degree, P<.001). Both deficits correlated with age, and the chromatic deficit additionally correlated with higher impairment of motor function (Unified Parkinson's Disease Rating Scale motor section, P =.04) and activities of daily life (Unified Parkinson's Disease Rating Scale activities of daily living section, P =.006). Patients with the highest pathologic psychiatric rating score (Brief Psychiatric Rating Scale) performed worse on both CS (P =.02) and CD (P =.01) at the second examination.

Impairments of CD and CS in PD are progressive over time. Visual deficits may influence overall motor function and lead to enhanced motor impairment.