Objective: Microvascular rarefaction influences peripheral vascular resistance, perfusion and metabolism by affecting blood pressure and flow pattern. In hypertension microvascular rarefaction has been described in experimental animal studies as well as in capillaroscopy of skin and biopsies of muscle tissue in patients. Retinal circulation mirrors cerebral microcirculation and allows non-invasive investigations. The aim of this study is to compare capillary rarefaction of retinal vessels in hypertensive versus normotensive subjects. Methods: This is a comparative study consisting of 134 patients with hypertension stage 1 or 2 and 55 healthy control subjects, who participated in clinical trials in our Clinical Research Center (www.clinicaltrials.gov: NCT01318395, NCT00627952, NCT00152698, NCT01319344). Retinal vascular parameters were measured in perfusion image, non-invasively and in vivo by scanning laser Doppler flowmetry (Heidelberg Engineering, Germany). Capillary rarefaction was assessed by capillary area (CapA) (in pixel-number) and intercapillary distance (ICD) (in µm). Additionally retinal capillary flow (RCF) was measured. Results: ICD was greater in the hypertensive group (23.2 ± 5.8 µm vs 20.2 ± 4.2 µm, p = 0.001). Hypertensive patients showed less CapA compared to healthy people (1556 ± 649 vs 1821 ± 652, p = 0.013). Accordingly, RCF was significantly lower in the hypertensive group compared to the healthy control group (291 ± 71 AU vs 314 ± 61 AU, p = 0.018). Our data indicate a lower level of retinal capillary density in hypertensive patients. Conclusion: Patients with hypertension stage 1 or 2 showed retinal capillary rarefaction in comparison to healthy normotensive subjects.
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