This study is investigating if the oral beta antagonist propranolol can induce regression of retinal neovascularization associated with proliferative diabetic retinopathy.

Oral propranolol 120mg daily will be given to 10 patients with proliferative diabetic retinopathy over a 12 week period to evaluate the effect on retinal neovascularization.

Inclusion Criteria:

• Age >=18 years
• Eyes with proliferative diabetic retinopathy and neovascularization
• Eyes with a history of panretinal photocoagulation treatment and persistent neovascularization deemed by the investigator to be a potential threat to visual acuity either by causing a vitreous hemorrhage or tractional retinal detachment. (Group 1 - maximum 5 eyes enrolled with these characteristics)
• Eyes without a history of panretinal photocoagulation treatment, but that do not have high-risk proliferative diabetic retinopathy characteristics (i.e. these are eyes that have early proliferative diabetic retinopathy that are not yet at a high-risk for vitreous hemorrhage and tractional retinal detachment such that panretinal photocoagulation laser may be deferred). (Group 2 - maximum 5 eyes enrolled with these characteristics)

Exclusion Criteria:

• Either panretinal photocoagulation laser or focal/grid laser into study eye within 3 months of study enrollment
• Anti-Vascular endothelial growth factor injection into study eye within 3 months of study enrollment
• Contraindications to beta-blockers such as: allergy, previous intolerance, abnormally slow heart rates, asthma or chronic obstructive pulmonary disease, use of medications that have an effect on certain drug metabolic pathways that may cause interactions.
• Known coronary arterial disease or left ventricular dysfunction, or known peripheral vascular disease
• Resting heart rate <60 or systolic blood pressure <90 and/or diastolic blood pressure <50
• Pregnancy
• All patients will either be post-menopausal, have adequate birth control and, if of childbearing age, will have a urinary pregnancy test performed
• Allergy to fluorescein dye
• Media opacity obscuring adequate determination of neovascularization including dense cataract or dense vitreous hemorrhage
• Patient is already taking an oral beta-blocker
• Vulnerable populations such as prisoners and minors will also be excluded