Relationship Between Renal Resistance Index and Retinal Vascular Density in Individuals with Hypertension

Background/Objectives: Considering the physiological analogies between the eye and the kidney, this study aimed to investigate the potential relationship between retinal vascular density, assessed using Optical Coherence Tomography Angiography (OCT-A), and the renal resistive index (RRI) in patients with arterial hypertension. Methods: A total of 82 hypertensive patients were enrolled in the study. Participants underwent routine biochemical evaluations, 24-hour ambulatory blood pressure monitoring, OCT-A imaging, and renal Doppler ultrasound examinations. Results: The mean RRI in the study population was 0.616 ± 0.06. Participants were divided into two groups based on the 75th percentile threshold of RRI distribution. The group with RRI > 75th percentile exhibited Significantly higher mean triglyceride levels and urinary albumin excretion (UAE) a significantly reduced estimated glomerular filtration rate (eGFR) and a higher prevalence of smokers, approaching statistical significance. Among the hemodynamic parameters analysed, 24-hour pulse pressure (PP), daytime and nighttime PP, and nighttime systolic blood pressure (SBP) were significantly higher in the group with RRI > 75th percentile. Regarding retinal vascular density indices, the only significant difference was observed in the deep foveal vascular plexus, which displayed a reduced density in the group with RRI > 75th percentile. Logistic regression analysis revealed that RRI > 75th percentile was independently associated with increased nighttime mean pulse pressure (OR = 1.13, 95% CI: 1.049–1.221, p = 0.0014) and reduced deep foveal vascular density (OR = -0.5026, 95% CI: 1.0493–1.2211, p = 0.0044). Conclusions: Our findings demonstrate that ocular microvascular alterations are associated with RRI, a marker with a well-established prognostic value for renal disease progression and systemic macrovascular dysfunction. These results further substantiate the close relationship between renal and ocular microcirculation.