General Inclusion Criteria

To be eligible, the following inclusion criteria must be met:

• Age >= 18 years
• Diagnosis of diabetes mellitus (type 1 or type 2.
• At least one eye meets the study eye criteria.
• Able and willing to provide informed consent.
• General Exclusion Criteria

A subject is not eligible if any of the following exclusion criteria are present:

• Significant renal disease, defined as a history of chronic renal failure requiring dialysis or kidney transplant.
• A condition that, in the opinion of the investigator, would preclude participation in the study (e.g., unstable medical status including blood pressure, cardiovascular disease, and glycemic control).
• Blood pressure > 180/110 (systolic above 180 OR diastolic above 110).
• Participation in an investigational trial within 30 days of enrollment that involved treatment with any drug that has not received regulatory approval at the time of study entry.
• Subject is expecting to move out of the area of the clinical center to an area not covered by another clinical center during the next 6 months.

Study Eye Inclusion Criteria

The subject must have one eye meeting all of the inclusion criteria and none of the exclusion criteria listed below. If both eyes are eligible, the study eye is selected by the investigator and subject.

• Best corrected E-ETDRS visual acuity letter score >= 24 (i.e., 20/320 or better) within 8 days of enrollment.
• On clinical exam, definite retinal thickening due to diabetic macular edema involving the center of the macula.
• OCT central subfield >=250 microns within 8 days of enrollment.
• Media clarity, pupillary dilation, and subject cooperation sufficient for adequate OCT.
• Investigator believes that focal photocoagulation is the most appropriate treatment for the DME.
• Study Eye Exclusion Criteria

The following exclusions apply to the study eye only (i.e., they may be present for the nonstudy eye):

• Macular edema is considered to be due to a cause other than diabetic macular edema.
• An ocular condition is present such that, in the opinion of the investigator, visual acuity loss would not improve from resolution of macular edema (e.g., foveal atrophy, pigment abnormalities, dense subfoveal hard exudates, significant macular ischemia, nonretinal condition).
• An ocular condition is present (other than diabetes) that, in the opinion of the investigator, might affect macular edema or alter visual acuity during the course of the study (e.g., vein occlusion, uveitis or other ocular inflammatory disease, neovascular glaucoma, etc.).
• Substantial cataract that, in the opinion of the investigator, is likely to be decreasing visual acuity by 3 lines or more (i.e., cataract would be reducing acuity to 20/40 or worse if eye was otherwise normal).
• History of treatment for DME at any time in the past 4 months (such as focal/grid macular photocoagulation, intravitreal or peribulbar corticosteroids, anti-VEGF drugs, or any other treatment).
• History of panretinal (scatter) photocoagulation (PRP) within 4 months prior to enrollment or anticipated to be performed within next 6 months.
• History of major ocular surgery (including vitrectomy, cataract extraction, scleral buckle, any intraocular surgery, etc.) within prior 4 months or anticipated within the next 6 months.
• History of YAG capsulotomy performed within 2 months prior to enrollment.