A total of 30 diabetic patients with treatment-refractory clinically significant diabetic macular edema will be included in this study and randomized into two equal groups. One eye per participant will be included to avoid exposure of both eyes to the study intervention. If both eyes are eligible, the eye with worse visual acuity will become the study eye. One group will be treated with standard-of-care (intravitreal anti-VEGF agent) injections. The PBM intervention group will be treated with the standard-of-care intravitreal anti-VEGF injections and 670 nm PBM in one eye. Baseline functional and anatomic assessments will be made and anti-VEGF therapy will be administered as determined by the treating Ophthalmologist.

Subjects in the PBM intervention arm will be treated (in addition to standard care) with 670nm light (WARP10, Quantum, Devices, Inc, Barneveld, WI). The portable, battery-operated 670 nm LED array specifically designed not to generate heat will be hand held 1 inch from the closed treatment eye. An 80-sec light treatment will be delivered. After 80 sec a timer turns off the light. The dose of light delivered at the surface of the cornea is calculated to be 4.0 J/cm2 (80 sec x 0.05 W/cm2 = 4.0 J/cm2). PBM treatment will be applied for 80 sec once per day, three consecutive days per week for 8 weeks. Previous clinical studies, have shown this treatment regimen and dose to be safe and effective in the treatment of dry AMD and non-center involving DME.

ASSESSMENTS: Subjects will undergo a detailed functional and structural evaluation at baseline and at 8 and 24 weeks. Seven-field color fundus photographs will be obtained for ETDRS retinopathy grading at baseline 8 and 24 weeks. Best corrected visual acuity (BCVA) Early Treatment Diabetic Retinopathy Study (ETDRS) will be obtained at every visit. Fundus fluorescein angiography and Spectralis OCT scans will be obtained according to predefined protocols. Blood pressure and glycosylated hemoglobin level will be recorded at baseline and 8 and 24 weeks to identify any changes in systemic status that could affect retinopathy grade and macular edema. Cataract status will be recorded at baseline and 8 and 24 weeks as a safety measure and as a possible confounding factor for visual acuity assessment.

OUTCOME MEASURES: Functional measure will be change in ETDRS BCVA from baseline. Structural outcome measures will include changes in qualitative and quantitative OCT parameters, including macular thickness and volume in 9 ETDRS subfields, obtained from automated measures in the Heidelberg Eye Explorer software (Heidelberg Engineering GmbH, Heidelberg, Germany) without formally correcting for boundary detection error; these measures are highly reproducible. Changes in intraretinal and subretinal fluid on OCT will be evaluated. The change in ETDRS severity grade of diabetic retinopathy will be reported from 7-field color fundus photographs. Safety parameters will include the reporting of ocular and nonocular adverse events. Changes to the greatest linear dimension and area of the foveal avascular zone on fluorescein angiography, together with the degree of perifoveal capillary loss, will be reported. The grading of photographs both for retinopathy grade and foveal avascular zone measurements will be carried out by a trained and certified senior diabetic retinopathy grader at the Medical College of Wisconsin. The number of anti-VEGF treatments in the two arms will be compared as a secondary measure of effect of PBM.