Retinal Vessel Analysis for the Morphological and Functional Examination of a Central Microcirculation Area – A New Clinical Method

Purpose: Changes of retinal blood vessels have been known in a number of vascular systemic diseases for a long time. The examination by a ophthalmoscope performed usually in hypertensive patients gives hitherto a subjective assessment of the morphological condition according to a qualitative scale. Method: The retinal vessel analysis is based on measured vessel diameters and their local and temporal changes. The static vessel analysis (SVA) examines quantitative vessel parameters in one single image of the fundus, i.e., the arterio-venous ratio. Signs of retinopathy were evaluated additionally in the image. The dynamic vessel analysis (DVA) observes automatically and online changes of the vessel diameters in a sequences of images (25/s). By means of standardized external influences (i.e., flicker light), the regulatory function of the arteries and veins can be measured. Results: The correlation of parameters of the SVA and vascular risks (i.e., stroke) was proved in epidemiological studies [1]. SVA using new automated routines possibly enables a more precise monitoring of individual vessel changes. In DVA retinal arteries and veins showed different responses to flicker light. A reduced arterial response to flicker light was shown by DVA in hypertensive patients [2]. The flicker reaction of neighbouring arterial segments of 20µm vessel length can be different. Conclusions: DVA is a functional non-invasive examination technique for arteries and veins of a central microcirculation area. The combination with morphologic-descriptive and well evaluated parameters of SVA seems to be useful. The significance of the results for the prognosis of vascular risks (i.e., stroke) and for the control of the time course of hypertensive organ damage should be evaluated in controlled studies.

References: [1] Wong TY, Klein R, Couper DJ et al. Retinal microvascular abnormalities and incident stroke: the Atherosclerosis Risk in Communities Study. Lancet 2001; 358:1134–1140. [2] Nagel E, Vilser W, Lanzl I. Age, blood pressure and vessel diameter as factors influencing the arterial retinal flicker response. Invest Ophthalmol Vis Sci. 2004 45: 1486–1492.