Contrast Sensitivity Visual Acuity Defects in the Earliest Stages of Parkinsonism

To demonstrate that contrast sensitivity defects are present in patients with Parkinsonism in its earliest stages. Testing for such deficiencies may prove a sensitive screening tool for this disease. Diminished contrast sensitivity visual acuity is recognized in patients with Parkinson's disease (PD), presumably due to loss of retinal dopamine. However, to date no study has detailed the presence or degree of loss correlated with the stages of Parkinsonism, particularly the earliest stages.