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Retinopatia diabetica
Definizione
La retinopatia diabetica è una complicanza microvascolare del diabete che interessa i vasi retinici.
Fattori di rischio
La retinopatia dia…
La retinopatia diabetica si sviluppa dopo anni di iperglicemia e peggiora con ipertensione, dislipidemia, fumo, gravidanza e pubertà.
La malattia progredisce in due fasi: non proliferativa e proliferativa.
Nella fase non proliferativa, la perdita di periciti indebolisce i capillari retinici, produendo microaneurismi che appaiono come minuscoli puntini rossi durante la fundoscopia.
L'aumento della permeabilità vascolare permette ai lipidi di fuoriuscire, formando essudati gialli e duri. L'edema maculare può svilupparsi in qualsiasi stadio della malattia ed è la principale causa di cecità nei diabetici.
Inoltre, questa fase comporta un peggioramento dell'ischemia. Capillari e arteriole occlusi creano aree di scarsa perfusione, producendo macchie di cotone, emorragie intraretiniche, perlatura venosa e anomalie microvascolari intraretiniche.
Nella fase proliferativa, l'ischemia aumenta i livelli di fattori di crescita endoteliale vascolare, portando a una neovascolarizzazione anomala.
Questi capillari fragili possono rompersi, causando emorragie vitreee, oppure esercitare trazione che stacca la retina, entrambi i quali possono causare perdita della vista.
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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.