Diabetic retinopathy (DR) is caused by changes in the blood vessels of the retina associated with long-term Type 1 or Type 2 diabetes mellitus. DR is a leading cause of blindness in the United States. Standard optical coherence tomography (OCT) cannot directly detect vascular changes, which may occur early affecting the passage of blood through the tiny capillaries (reduced capillary flow) or cause the greatest damage through formation of abnormal blood vessel growth (neovascularization). Currently, fluorescein angiography (FA) is the gold standard for detecting these changes, but FA requires an injection of a dye into the vein of the arm of the patient. This dye can cause undesirable side effects. Recently, OCT has been used to make functional measurements (such as total retinal blood flow among others) and to perform angiography. Thus, functional OCT may provide a useful, alternate way to evaluate diabetic retinopathy.

Inclusion Criteria for participants with diabetes:

• Male or female participants 18-79 years old
• With Type 1 diabetes for over 5 years or Type 2 diabetes of any duration

Exclusion Criteria for participants with diabetes:

• Vision worse than 20/200
• Inability to maintain fixation for OCT imaging
• Significant kidney disease, kidney failure or kidney transplant
• Unstable medical status, including blood pressure greater than 180/110 or unstable heart disease
• Pregnant or nursing an infant
• Presence of an eye disease (other than diabetic retinopathy) that can affect retinal blood flow, retinal permeability or retinal anatomy
• Significant cataract, corneal scar, vitreous bleed or other media opacity
• History of major eye surgery within 4 months prior to enrollment in this study

Inclusion Criteria for participants without diabetes (controls):

• Male or female participants 18-79 years old

Exclusion Criteria for participants without diabetes (controls):

• Vision worse than 20/200
• Inability to maintain fixation for OCT imaging
• Significant kidney disease, kidney failure or kidney transplant
• Unstable medical status, including blood pressure greater than 180/110 or unstable heart disease
• Pregnant or nursing an infant
• Presence of any eye disease that can affect retinal blood flow, retinal permeability or retinal anatomy
• Significant cataract, corneal scar, vitreous bleed or other media opacity
• History of major eye surgery within 4 months prior to enrollment in this study

Participants with Type 1 diabetes of greater than 5 years duration OR Type 2 diabetes of any duration. Healthy controls are also being enrolled in this study.