Inclusion Criteria: To be eligible, the following inclusion (1-4) and exclusion criteria (5-8) must be met:

1. Age >= 18 years

   • Patients <18 years old are not being included because there would be an insufficient number of patients <18 years old who would meet eligibility criteria for the study in order to be able to generalize the results to patients <18 years old or to provide informative data as to the effects of treatment in this age group.

2. Diagnosis of diabetes mellitus (type 1 or type 2)

   • Any one of the following will be considered to be sufficient evidence that diabetes is present:

   1. Current regular use of insulin for the treatment of diabetes
   2. Current regular use of oral anti-hyperglycemia agents for the treatment of diabetes
   3. Documented diabetes by ADA and/or WHO criteria
3. At least one eye meets the study eye criteria listed in section 2.2.2.

4. Able and willing to provide informed consent.

   Exclusion Criteria: A patient is not eligible if any of the following exclusion criteria (5-8) are present:

5. History of chronic renal failure requiring dialysis or kidney transplant.
6. History of pancreatic transplant.

7. A condition that, in the opinion of the investigator, would preclude participation in the study (e.g., unstable medical status including blood pressure and glycemic control).

   • Patients in poor glycemic control who, within the last 4 months, initiated intensive insulin treatment (a pump or multiple daily injections) or plan to do so in the next 4 months should not be enrolled.

8. Patient is expecting to move out of the area of the clinical center to an area not covered by another clinical center during the next 8 months.

The patient must have at least one eye meeting all of the inclusion criteria (a-d) and none of the exclusion criteria (e-k) listed below.

A patient can have only one study eye. If both eyes are eligible, the investigator at his/her discretion will select one to be the study eye.

The eligibility criteria for a study eye are as follows:

Inclusion

1. Presence of early proliferative or severe nonproliferative diabetic retinopathy for which investigator intends to perform full scatter photocoagulation in either one sitting or four sittings.
2. Central subfield thickness on OCT ≤ 299 microns. Note: Clinically significant macular edema is not an exclusion provided the central subfield is ≤299 microns.
3. Visual acuity 73 letters or greater (20/32 or better).

4. Media clarity, pupillary dilation, and patient cooperation sufficient to administer full scatter photocoagulation and obtain adequate fundus photographs and OCT.

   Exclusion

5. Prior scatter photocoagulation.
6. High risk (severe proliferative) retinopathy.
7. Presence of an ocular condition (other than diabetes) that, in the opinion of the investigator, might produce macular edema or alter visual acuity during the course of the study (e.g., vein occlusion, uveitis or other ocular inflammatory disease, neovascular glaucoma, Irvine-Gass Syndrome, significant vitreomacular interface disease, etc.).
8. Treatment for diabetic macular edema is planned.
9. History of any treatment for DME within prior 6 months, including focal/grid macular photocoagulation and corticosteroids by any route.
10. History of major ocular surgery (including cataract extraction, vitrectomy, scleral buckle, any intraocular surgery, etc.) within prior 6 months or anticipated within the next 8 months following enrollment.
11. History of YAG capsulotomy performed within 2 months prior to enrollment.