Retina as a window to systemic hypertension: From hypertensive retinopathy to artificial intelligence-driven microvascular biomarkers

Abstract

The retinal microvasculature is the only vascular bed in the human body that can be visualised directly, non-invasively and repeatedly in vivo.Because retinal arterioles share embryological origin, calibre and autoregulatory physiology with the cerebral and coronary microcirculation, hypertension-induced retinal changes offer a unique window onto systemic small-vessel disease.For this narrative minireview, PubMed/MEDLINE, EMBASE, Scopus, Web of Science and IEEE Xplore were searched from database inception to April 30, 2026 for peer-reviewed English-language human studies of hypertensive retinopathy, quantitative retinal vascular biomarkers, multimodal retinal imaging and artificial intelligence (AI) applied to fundus images; population-based cohorts, individual-participant meta-analyses and AI studies reporting external validation were prioritised, and evidence was synthesised thematically and tabulated for cross-study comparison.Classical hypertensive retinopathy, graded for over eight decades by the Keith-Wagener-Barker and Scheie systems, has been supplemented by quantitative measurement of retinal vessel calibre and by geometric parameters such as fractal dimension and tortuosity.Large population cohorts have established that these parameters predict incident hypertension, stroke, coronary heart disease and mortality independently of conventional risk factors.Optical coherence tomography (OCT), OCT angiography and adaptive optics have extended assessment to the capillary and cellular level, while deep learning has enabled automated retinopathy grading and direct inference of blood pressure and cardiovascular risk from fundus photographs.Critically, the high accuracies reported on small private datasets are not reproduced on the first public benchmark, where the best algorithms achieved only fair agreement, and no randomised evidence yet shows that acting on a retina-derived biomarker improves outcomes.Clinical translation therefore depends on measurement standardisation, prospective multicentre and multi-ethnic external validation, explainable models, 4 / 43 defined referral pathways from an abnormal retinal screen to blood pressure confirmation and cardiovascular risk management, and clarity on the regulatory status of software that infers systemic disease from ocular images.