Wall-to-lumen ratio of retinal arterioles as a tool to assess vascular changes.

The retina offers a beautiful and unique opportunity to visualize and examine the body’s microvasculature safely, repeatedly, quickly, and noninvasively in vivo. Retinal arterioles appear to undergo similar changes as cerebral and peripheral arterioles in hypertension, indicating that retinal arteriolar abnormalities mirror structural and functional microvascular changes elsewhere in end-organ tissues.1–4 Since the pioneering work by Keith et al5 in 1939, several studies have confirmed the prognostic significance of retinal vascular abnormalities on mortality attributed to a cardiovascular cause.5–7 However, although there is solid evidence for the prognostic significance of advanced retinopathy, the evidence of a prognostic impact of early retinal vascular abnormalities on cardiovascular risk stratification is less well established.1,8 It was suggested that methodological issues might be the cause for the lack of a solid evidence that early retinal vascular abnormalities are closely linked to cardiovascular risk.1,9 Therefore, much research effort over the last decade has focused on the development of new methodological approaches to enable more precise and reliable detection and evaluation of early retinal vascular abnormalities in hypertensive patients. A new approach focuses on retinal arteriolar structural parameters by using scanning laser Doppler flowmetry (SLDF) with automatic full-field perfusion imaging analyses (AFFPIAs).2,10 This approach allows the assessment of both the outer diameter (OD) and inner diameter (ID) of retinal arterioles in vivo and, thus, analyzes vascular remodeling of retinal arterioles by calculating wall:lumen ratio, wall thickness, and wall cross-sectional area (volume of wall per unit of length) of retinal arterioles. These methods do not need to determine diameter of retinal venules, which are also subject to changes in cardiovascular disease. This review introduces and describes this new methodology, explains the improved power of measuring retinal vascular changes, and discusses our recent findings using this tool.