Retinal Vascular Changes in Pre-Diabetes and Prehypertension

The retinal vasculature can be viewed directly and noninvasively, offering a unique and easily accessible “window” to study the health and disease of the human microcirculation in vivo. In the last decade, advances in digital retinal photography and imaging techniques have allowed precise characterization of subtle retinal vascular changes in large populations. These retinal changes can be broadly divided into four groups: 1 ) classic retinal vascular changes in diabetes and hypertension (i.e., diabetic and hypertensive retinopathy), 2 ) isolated retinopathy signs in individuals with diabetes or hypertension (e.g., microaneurysm, retinal hemorrhage, or cotton wool spot), 3 ) changes in retinal vascular caliber, and 4 ) changes in retinal vascular architecture (e.g., retinal tortuosity). New studies in large populations now show that retinal vascular changes are common in the general population and may precede the subsequent development of overt diabetes and hypertension. A consistent pattern of associations is also emerging, showing that specific retinal vascular changes may be related differently to hyperglycemia and blood pressure. In this review, we summarize recent studies on the retinal vascular changes seen in diabetes and hypertension and speculate on potential research and clinical implications. ### Diabetic retinopathy In individuals with diabetes, the classic primary retinal vascular complication—diabetic retinopathy—is well described (1). Diabetic retinopathy signs are broadly divided into nonproliferative and proliferative retinopathy. The prevalence of diabetic retinopathy increases with duration of diabetes. The Australian Diabetes, Obesity and Lifestyle Study (AusDiab) showed that the prevalence of diabetic retinopathy is less than 10% in those with diabetes duration of less than 5 years but more than 50% in those with 20 years or longer diabetes (2). The two major risk factors of diabetic retinopathy are hyperglycemia and hypertension, with hyperlipidemia as a possible third major risk factor. The importance of hyperglycemia has been confirmed in epidemiological studies (3), as well as two pivotal …