The role of vitamin D in the onset and progression of diabetic retinopathy.

Having a classical role in the regulation of calcium homeostasis in skeletal system, vitamin D has also been recognized as being involved in the activity of the immune system, as well as in the pathology of the visual analyzer. Thus, regarding the function of vitamin D in the eye, this is supported by the identification of vitamin D receptors (VDR) in several structures of the eyeball, such as corneal epithelial and endothelial cells, ciliary body and retinal cells. One of the ophthalmological pathologies in which vitamin D plays an important role is diabetic retinopathy, both through its effects on the immune system (reduction of the pro-inflammatory cytokines - IL-1, IL-6, IL-012, TNF alpha, and stimulation of anti-inflammatory cytokines IL-10), as well as by reducing the level of vascular endothelial growth factor (VEGF) and thus inhibiting retinal neovascularization. Vitamin D demonstrates a protective role on the development and progression of diabetic retinopathy by reducing blood sugar, hypertension and atherosclerosis, but randomized studies are still needed to establish the direct causal relationship between the development of diabetic retinopathy and vitamin D levels.