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Diabetic Retinopathy
Definition
Diabetic retinopathy is a microvascular complication of diabetes affecting the retinal blood vessels.
Risk Factors
Diabetic retinopathy is pre…
Diabetic retinopathy develops after years of hyperglycemia and worsens with hypertension, dyslipidemia, smoking, pregnancy, and puberty.
The disease progresses in two stages: nonproliferative and proliferative.
In the nonproliferative stage, the loss of pericytes weakens retinal capillaries, producing microaneurysms that appear as tiny red dots on fundoscopy.
Increased vascular permeability allows lipids to leak, forming yellow, hard exudates. Macular edema may develop at any stage of the disease and is the leading cause of blindness in diabetics.
Additionally, this stage involves worsening ischemia. Occluded capillaries and arterioles create areas of poor perfusion, producing cotton wool spots, intraretinal hemorrhages, venous beading, and intraretinal microvascular abnormalities.
In the proliferative stage, ischemia increases vascular endothelial growth factor levels, driving abnormal neovascularization.
These fragile capillaries may rupture, causing vitreous hemorrhage, or exert traction that detaches the retina, both of which can lead to vision loss.
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Q1: What causes microaneurysms to form in diabetic retinopathy?
Microaneurysms develop due to pericyte loss caused by sorbitol accumulation, reactive oxygen species, and advanced glycation end products, which trigger pericyte apoptosis. This weakens retinal capillaries, allowing them to bulge outward and appear as tiny red dots on fundoscopy during the nonproliferative stage.
Q2: How does macular edema develop in diabetic retinopathy?
Macular edema occurs when increased vascular permeability allows fluid and lipids to leak from damaged retinal capillaries into the macula. This can develop at any stage of diabetic retinopathy and is the leading cause of vision loss in patients with diabetes, making early detection critical.
Q3: What role does ischemia play in advancing diabetic retinopathy?
Persistent ischemia from occluded capillaries and arterioles creates areas of poor perfusion, producing cotton wool spots, intraretinal hemorrhages, and venous beading. As ischemia worsens, it triggers hypoxia-inducible factor upregulation, which stimulates vascular endothelial growth factor expression and drives progression to the proliferative stage.
Q4: Why are fragile new blood vessels dangerous in proliferative diabetic retinopathy?
Abnormal neovascularization produces fragile capillaries that lack structural integrity. These vessels may rupture, causing vitreous hemorrhage and vision loss, or exert tractional forces that detach the retina, a significant cause of blindness especially in type 1 diabetes.
Q5: What risk factors accelerate the progression of diabetic retinopathy?
Poor glycemic control, hypertension, dyslipidemia, smoking, pregnancy, and puberty all accelerate diabetic retinopathy progression. Diabetic retinopathy is present in almost all individuals with type 1 diabetes and more than 60% of those with type 2 diabetes after two decades of disease.
Q6: What is the difference between nonproliferative and proliferative diabetic retinopathy?
Nonproliferative retinopathy features microaneurysms, hard exudates, and hemorrhages from capillary damage and ischemia. Proliferative retinopathy involves abnormal new blood vessel growth driven by vascular endothelial growth factor, creating fragile vessels prone to rupture and retinal detachment.
Q7: How does chronic hyperglycemia damage retinal blood vessels?
Chronic hyperglycemia causes retinal hypoxemia, endothelial injury, and red blood cell aggregation. These mechanisms converge to damage retinal vessels, increasing abnormal permeability and triggering ischemia. Sorbitol accumulation and advanced glycation end products also induce pericyte apoptosis, weakening capillary structure.