Handwritten Video Lecture on the pathophsyiology, symptoms and treatment of Diabetic Retinopathy for USMLE Step 1 and USMLE Step 2

PATHOPHYSIOLOGY OF DIABETIC RETINOPATHY
Hyperglycemia increases blood flow to the retina which damages blood vessels and become leaky causing macular edema.

Also production of Sorbitol from glucose by aldose reductase enzyme. This consumes NADPH, which increases oxidative stress. Glucose is osmotically active causing further edema.

Advanced Glycated Enzymes causes crosslinks in collagen and increase vessel permeability leading to cataracts. RAGE causes proinflammatory state in patients with diabetic retinopathy.

Neovascularization in the eye of diabetic retinopathy leads to hypoxia and thrombi. Tissue release VEGF and causes new vessel formation. New vessels are leaky and contribute to edema

In the non-proliferative Diabetic Retinopathy (NPDR) is the early stage of diabetic retinopathy. MIcrovascular disfunction leads to loss of pericytes and damaged endothelium leading to microaneurysms. Also basement membrane dysfunction leads to leakage of lipids and proteins leading to hard exudates. Intraretineal hemorrhages which shows as generalized hemorrhage. Nerve fiber infarcts in patients with diabetic retinopathy also occurs.

Proliferative Diabetic Retinopathy (PDR). Ischemia of the retinal tissue releases VEGF and causes neovascularization. Once ruptures it shows as flame shaped hemorrhages or blot hemorrhages. Vitreous hemorrhage may also occur in patients with diabetic retinopathy.

Fibrosis of diabetic retinopathy causes tractional retinal detachment which may lead to permanent vision loss.

Macular Edema can occur at any stage and is a common cause of vision loss in diabetic retinopathy.

FUNDOSCOPIC EXAM OF DIABETIC RETINOPATHY
Hemorrhage isolated around the vessels. Microaneurysms seen as dilation. Hard exudates seen as yellow. Cotton wool spots due to low blood flow. Tortous vessel show neovascularization in patients with Diabetic Retinopathy.

SYMPTOMS OF DIABETIC RETINOPATHY
Generally asymptomatic and symptoms depends on undelrying cause. Therefore screening for diabetic retinopathy is important.

Diabetes Mellitus type 1 screening begins 5 years after diagnosis then ever 2 years.

Diabetic Mellitus Type 2 screening begins at diagnosis and then continues every 2 years.

MANAGEMENT FOR DIABETIC RETINOPATHY
Glycemic control
Nonproliferative Diabetic Retinopathy does not require treatment.
Proliferative Diabetic Retinopathy - anti-VEGF and Photocoagulation.

If there is vitreous hemorrhage then perform vitrectomy.
Macular Edema requires treatment even if occurs in nonproliferative Diabetic Retinopathy.