Evaluation of Doxycycline Verses Placebo for the Treatment of Severe Nonproliferative or Mild or Moderate Proliferative Diabetic Retinopathy

Inclusion Criteria: * age ≥ 18 years old * diagnosis of type 1 or type 2 diabetes mellitus * have a hemoglobin A1c less than 11% at pre-qualification visit * able and willing to give informed consent * best-corrected ETDRS visual acuity in study eye ≥ 49 letters (20/100) * severe non-proliferative diabetic retinopathy (ETDRS level 53E) or retinal and/or optic disk neovascularization less than the "high-risk" characteristics defined by the Diabetic Retinopathy Study (ETDRS level61- 65), and in whom panretinal photocoagulation is not imminently required in the ophthalmologist's judgment * able to perform reliable visual field and dark adaptation testing * central subfield thickness on OCT of ≤ 275microns * foveal fixation present in each eye (assessed by fundus photography using an internal fixation pointer or assessed by the investigator) * media clarity and pupil dilation sufficient for high-quality fundus photographs and fluorescein angiograms Exclusion Criteria: * high-risk neovascularization in study eye * prior panretinal photocoagulation in the study eye * focal/grid laser photocoagulation in the macula within the past 15 weeks in the study eye * intraocular pressure \> 22mmHg by Goldmann Tonometry in the study eye * history of pars plana vitrectomy in the study eye * vitreous or pre-retinal hemorrhage in the study eye * systemic or intravitreal anti-VEGF agent to the study eye or the fellow eye within the past 3 months * peribulbar steroid injection to the study eye …