Retinal arteriovenous oxygen saturation difference is inversely associated with cardiac output measured by echocardiography: a non-invasive pilot study

Cardiac output is a key determinant of systemic perfusion and is commonly assessed using invasive or echocardiographic methods. Retinal oximetry provides a non-invasive estimate of retinal arteriovenous oxygen saturation difference and may reflect systemic haemodynamics. In this single-centre prospective observational pilot study, healthy volunteers and clinically stable cardiac patients underwent dual-wavelength retinal oximetry in both eyes and transthoracic echocardiography on the same day. Fourteen participants were included in the final analysis. Cardiac output showed an inverse association with the mean retinal arteriovenous oxygen saturation difference across both eyes (Pearson r = - 0.73, 95% CI - 0.91 to - 0.33, p = 0.003; Spearman ρ = -0.77, p = 0.001). These findings support the concept of systemic-ocular haemodynamic coupling. As this was a small exploratory study in a physiologically selected cohort, larger prospective studies are needed to assess reproducibility, external validity and potential clinical relevance.