Investigating Retinal Microvascular Changes Using OCT-Angiography: The Role of Oxidative Stress and Endothelial Dysfunction in Hypertensive Nephropathy

Background and Objectives: Arterial hypertension is a major cause of systemic microvascular damage involving target organs such as the kidneys and retina. Because the retinal and renal microcirculations share common pathogenic mechanisms, retinal imaging may provide non-invasive biomarkers of hypertensive microvascular injury. This study investigated the association between the renal resistive index (RRI), systemic oxidative stress biomarkers, and retinal abnormalities in patients with essential hypertension. Retinal structural and microvascular parameters were evaluated using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). Materials and Methods: In this cross-sectional exploratory study, 32 patients with essential hypertension (64 eyes) underwent comprehensive ophthalmic examination, OCT/OCTA imaging, renal Doppler ultrasonography for RRI assessment, and evaluation of systemic oxidative stress biomarkers. Associations between renal, ocular, and biochemical parameters were analyzed. Results: No significant differences were observed in most global OCT/OCTA parameters. However, higher RRI values were associated with localized macular thinning and reduced optic nerve head perfusion metrics. Patients with RRI values ≥ the 75th percentile showed significantly increased hydrogen peroxide levels (p = 0.004) and reduced nitric oxide bioavailability (p = 0.033), together with thinning of selected inner macular sectors. A trend toward reduced optic nerve head flow index was also observed, suggesting early microvascular impairment that may not be detected by conventional global OCT measurements. Conclusions: These exploratory findings suggest a possible association among increased renal vascular resistance, oxidative stress, and localized retinal structural alterations in patients with essential hypertension. The coexistence of systemic redox imbalance and sectorial retinal changes supports the hypothesis of an eye–kidney–redox interplay and indicates that advanced retinal imaging, particularly detailed sectorial OCT analysis, may represent a complementary non-invasive tool for the early detection of subclinical microvascular damage. Larger prospective studies are warranted to validate these findings.