The purpose of this study is to assess whether tear secretion in patients with Parkinson's disease will be altered to exhibit a characteristic or diagnostic biomarker profile, that will be reflected in changes in the protein composition of tear fluid, which can be measured relatively easily, cost-effectively, and non-invasively. Tear fluid samples will be collected from Parkinson's patients, and through biochemical assays, the profile of proteins in tears will be characterized and compared to that from control subjects. The profiles will be analyzed with respect to any differences between Parkinson's patients and control subjects. If differences appear, the levels of these potential biomarkers in Parkinson's patients will be compared to the severity of their disease.

Inclusion Criteria:

• established Parkinson's Disease for at least 6 months
• Healthy controls without neurological illness

Exclusion Criteria:

• currently taking anti-cholinergic medication
• dementia
• have an exposure to neuroleptic medications other than Quetiapine or Clozapine in the 6 months prior to screening
• have an active eye infection or have had eye surgery within 3 months prior to screening
• control subjects will be excluded if they have a history of neurological disease
• PD subjects will be excluded if they have an atypical Parkinsonian syndrome

The investigators will recruit participants with Parkinson's disease and controls from the Parkinson's Disease and Movement Disorder Center at the University of Southern California (USC) and from the surrounding community.