The Effect of Dopamine on Diabetic Retinopathy

The purpose of this study is to evaluate the use of electroretinogram (ERG) using a novel
handheld system, RETeval, and evaluate contrast sensitivity testing in detecting pre-clinical
retinopathy on a tablet device.

Investigators also seek to assess if a medication called Sinemet™ CR can improve the
electrical functions of the eye in participants with diabetes mellitus. This study will
include a total of 45 participants; 30 with diabetes mellitus and 15 age-matched non-diabetic
controls. Participants with diabetes mellitus and electroretinogram (ERG) delays will be
randomized to a low or high dose Sinemet™ CT group.

Age-matched controls will not receive Sinemet Ct drug treatment.

The study involves four visits over the course of 4 weeks, each visit consisting of 2-3
hours. Visual testing will be performed at 1 day and 2 weeks following treatment. The drug
treatment will be halted and testing repeated again after a 2 week wash-out period.

Inclusion Criteria

Participants with Diabetes Mellitus:

- Diagnosis of diabetes mellitus type-2

- HbA1c between 8 and 12%

Age-Matched Controls:

- Non-diabetic

Exclusion Criteria

Participants with Diabetes Mellitus:

- Currently taking dopamine-enhancing drugs (L-DOPA, bromocriptine)

- Currently taking nonselective monoamine oxidase (MAO) inhibitors

- Diagnosis of psychosis, Parkinson's disease, restless leg syndrome, major depression,
confounding ocular disease (eg. visually significant cataract, glaucoma, macular
degeneration, or retinitis pigmentosa)

- Pregnancy

Age-Matched Controls:

- Diabetes diagnosis

- Currently taking dopamine-enhancing drugs (L-DOPA, bromocriptine)

- Currently taking nonselective monoamine oxidase (MAO) inhibitors

- Diagnosis of psychosis, Parkinson's disease, restless leg syndrome, major depression,
confounding ocular disease (eg. visually significant cataract, glaucoma, macular
degeneration, or retinitis pigmentosa)

- Pregnancy