The use of static objective retinal vessel analysis in optometric practice

Abstract

At present optometric examination of the retinal microcirculation consists of a subjective assessment of artery size when compared to a neighbouring vein; the arterio-venous ratio (AVR). Despite it’s documented limitations, the AVR still features in UK optometric clinical guidance. An objective method of recording the central retinal artery and vein equivalent sizes (CRAE and CRVE) has been used for research purposes for two decades but has yet to be validated in a clinical setting. A review of the present literature identified correlations between CRAE and CRVE and three key cardiovascular pathologies; hypertension, diabetes mellitus and stroke. A methodological study was undertaken to establish whether retinal photographs acquired in clinical practice yielded results with reproducibility comparable with those in the literature. It was shown that calibre measurements do not fluctuate significantly with the use of mydriatics, or subject to minor temporal fluctuations. When the technique was applied in clinical practice, a cross-sectional cohort (n = 271) revealed vessel correlations with systemic biomarkers in agreement with those identified in the literature review. CRAE was seen to be reduced in those with raised blood pressure, and objective AVR was reduced in those with increased cardiovascular risk (QRISK). There did not appear to be significant fluctuations in vessel measurements when the cohort was observed longitudinally across a period of 12 – 24 months, suggesting changes either too slow or too small to be detected at present; supporting theories of gradual morphological changes. When considered as part of scope of primary care, improved cardiovascular assessment through retinal vessel analysis (especially when supplemented with blood pressure and cardiovascular risk calculations) relieves pressure on GPs and identifies a significant number of previously undiagnosed and unmanaged cases of cardiovascular disease. The results build a strong case for the incorporation of objective retinal vessel analysis into routine optometric clinical guidelines.