Retinal Neurodegeneration In Patients With Type 2 Diabetes Mellitus Without Diabetic Retinopathy or With Mild Non Proliferative Diabetic Retinopathy Detected by Optical Coherence Tomography

Retinal complications in diabetes mellitus (DM) patients were typically considered part of a vascular process. However, recent studies suggest that ocular degeneration in DM might be caused by 2 different conditions: vasculopathy and neuropathy . For some authors, neuropathy observed in the retina of DM patients might be a part of an underlying polyneuropathy ; for others, however, neuropathic changes might precede microvascular alterations .

Axons of retinal ganglion cells compose the retinal nerve fiber layer (RNFL) in the retina and then form the optic nerve connecting the eyeball and brain. Retinal nerve fiber layer (RNFL) loss is recognized as an important neurodegenerative sign in glaucoma. Thinning of the RNFL has also been found in multiple sclerosis, Parkinson's disease and Alzheimer's disease, indicating neurodegeneration of the retina. If RNFL thinning is significant in diabetic patients with preclinical diabetic retinopathy, evaluation of peripapillary RNFL thickness would be very important, because early detection and treatment of diabetic retinopathy is critical to reduce the risk of blindness Optical coherence tomography (OCT) has been introduced into clinical practice as the most noninvasive and objective method to visualize the retina, showing an amount of detail that resembles histological specimens. Initially, OCT was applied to detect complications of DR (edema macular or epiretinal membrane). Later on, it allowed quantitative and qualitative measurements of retinal thickness and segmentation of all intraretinal layers. OCT might detect early retinal neurodegenerative changes, and thus help define which diabetic patients may be at risk to develop DR.