All of the following are implicated in the pathogenesis of macular oedema in diabetic retinopathy, EXCEPT:

Diabetic macular edema (DME) / Can develop at any stage of retinopathy. Now the leading cause of vision loss in persons with diabetes. Increased vascular permeability causes plasma leaks from the macular vessels, leading to swelling and formation of hard exudates at the central retina. Incidence over 10 years (1) 20% in persons with type 1 DM (2) 25% in persons with type 2 DM who require insulin (3) 14% in persons with type 2 DM who do not require insulin Very Impoant VEGF (vascular endothelial growth factor) is one of the many cytokines that plays an impoant role in diabetic retinopathy. VEGF is a marker for oxidative stress and induces hyperpermeability of macular capillaries, contributing to macular oedema. The molecular mechanisms involved in endothelial damage and macular ischemia are complex and involves sorbitol pathway, AGE formation (advanced glycation end products), protein kinase C, renin-angiotensin system, inflammation, oxidation and alterations in gene expression. Ref: Diabetic Retinopathy, By David J. Browning, Page 205, Springer, 2010.