Diabetes mellitus: a brief history, epidemiology, definition and classification

Diabetes mellitus is a systemic disease of great significance to optometrists. This review includes a brief history of the key discoveries in the understanding of diabetes from ancient times and a summary of the present knowledge of diabetes with respect to prevalence, epidemiology and major complications. The currently accepted classification of diabetes mellitus includes the major categories of type 1 and type 2 diabetes, specific diabetes types and gestational diabetes. The definition of diabetes has also been revised recently. The new diagnostic criterion for diabetes mellitus is a confirmed fasting plasma glucose equal to or greater than 7.0 mmol/L, with a reduced reliance on the role of oral glucose tolerance testing.