To determine if there is any difference in the presence of retinal deterioration in PD patients treated with pramipexole IR versus ropinirole as monitored by comprehensive ophthalmologic assessments from baseline to the end of study at two years.

• Drug: pramipexole IR
• Drug: ropinirole

Inclusion Criteria:

Diagnosis and main criteria for inclusion. Patients must meet all of the following inclusion criteria to be eligible for enrollment into the study:

1. Patients with idiopathic Parkinson's disease of less than 7 years characterized as Stage I-III by the Modified Hoehn and Yahr Scale and with a maximum of 6 months cumulative lifetime exposure to levodopa and/or dopamine agonist. Patients on current dopamine agonist therapy would require 14-day washout.
2. Age at least 30 years.
3. Women of childbearing potential must have a negative serum beta-HCG pregnancy test at the Screen (Baseline) visit and the patient must use adequate contraceptive methods.
4. Evidence of a personally signed and dated informed consent document indicating that the patient (or a legally acceptable representative) has been informed of all pertinent aspects of the study.
5. Patients who are willing and able to comply with scheduled visits, treatment plan, and other study procedures.

Exclusion Criteria:

Main criteria for exclusion. The presence of any of the following would make a patient ineligible for enrollment into the study:

1. Previous history of allergic response or complications with any dopaminergic agonist drug
2. Atypical PD syndromes
3. History of stereotactic brain surgery
4. Positive hepatitis B (surface antigen) or hepatitis C (antibody)
5. Surgery within 180 days of randomization which would negatively impact participation
6. Folstein's Mini Mental State Examination (MMSE) score of 24 or less
7. History of active epilepsy (seizure) in the past 1 year
8. Third degree AV block or sick sinus syndrome
9. Congestive heart failure, Class III or IV
10. Unstable heart disease such as unstable angina, dysrhythmia, or myocardial infarction in prior 6 months
11. Symptomatic orthostatic hypotension
12. Clinically significant liver disease or renal disease
13. Malignant melanoma or history of previously treated malignant melanoma.
14. Prohibited medications taken (including any drug known to have potential retino-toxic effects taken in the prior 12 months; neuroleptics taken within prior 6 months, MAO inhibitors except rasagiline or selegiline taken within prior 3 months, beta-blockers taken to treat Parkinson's disease in the prior 30 days, and Coenzyme Q10 taken within 14 days)
15. Albinism/Albinoidism of any degree, type or syndrome
16. History of glaucoma with or without treatment
17. Inherited or acquired retinopathy such as age-related macular degeneration with visual loss
18. Sarcoidosis
19. Diabetes mellitus of any degree even if diet or insulin controlled
20. Best corrected visual acuity (BCVA) of less than 20/40 by ETDRS
21. Refractive error of greater than minus-6 diopters
22. Abnormal electroretinogram (ERG)
23. Unable to dilate pupils
24. History of severe eye trauma that might affect the outcome of the study
25. History of psychosis
26. Participation in other investigational drug studies or use of investigational drugs within prior 30 days