pathogenesis of diabetic retinopathy
Last edited 05/2023
- Genetic studies, suggest that diabetic retinopathy is an interaction between
- environmental factors, especially hyperglycaemia (1,2), and
- several genetic factors
- associated genes under study are aldose receptor, advanced glycation end products receptor, vascular endothelial growth factor, intercellular adhesion molecule 1, beta3-adrenergic receptor gene, hemochromatosis, and alpha2beta1 integrin (1).
- The retinopathy in diabetes result from five fundamental processes (2):
- retinal capillary microaneurysms
- excessive vascular permeability
- vascular occlusion
- proliferation of new blood vessels and accompanying fibrous tissue
- contraction of fibrovascular proliferations and vitreous.
- Duration of diabetes and severity of hyperglycemia are the major risk factors for developing retinopathy (2).
- Severity of hyperglycemia is the key alterable risk factor.
- Increased retinal blood flow results in microaneurysm formation in capillaries, precapillary arterioles and venules, leading to occlusion and transudation of fluid and lipid.
- Hyperglycaemia is the cause of high retinal blood flow.
- Other factors include pregnancy and high blood pressure.
- Occlusion of capillaries results in retinal ischaemia with compensatory neovascularisation on the retina, iris, and optic disc (proliferative retinopathy).
- Ischaemic retina may express an unknown vasoproliferative substance leading to new vessel formation.
- Vitreous haemorrhage may occur as a result of bleeding from new vessels.
- Fibrous tissue is carried along with the new vessels; there is an increased risk of retinal detachment as a result of retraction of this tissue.
- Cotton wool spots occur secondary to occlusion and represent retinal microinfarcts.
- Retinal thickening, oedema and hard exudates occur as a result of leakage from capillaries; hard exudates are composed of lipoprotein and lipid filled macrophages.
- Flame-shaped haemorrhages occur when rupture of microaneurysms occurs at nerve level.
- Blot haemorrhages occur if rupture of microaneurysms occur deep in the retina.