Type-2 diabetes mellitus affects almost all the systems of the body and is associated with high mortality and morbidity if not managed properly. Involvement of the peripheral nervous system in diabetes is documented and there is growing evidence of central nervous system involvement too. This central nervous system dysfunction involving the visual pathways can be assessed by electrophysiological techniques like visual evoked potential testing. This book is about the role of pattern reversal visual evoked potentials (PVEP) in patients with type-2 diabetes mellitus to detect visual changes even before the appearance of symptoms.