Keer KV, et al. - Authors gauged the association between retinal vessel oxygen saturation and mixed venous oxygen saturation (SvO_2-mixed) and cardiac output (CO). They measured the retinal arterial (SaO_2-retinal-retinal) and venous (SvO_2-retinal-retinal) oxygen saturation non-invasively with dual-wavelength retinal oximetry in patients receiving invasive measurements of SvO_2-mixed and CO via right heart catheterization. Evidence supporting the use of retinal oximetry as a non-invasive tool to evaluate systemic cardiovascular function was seen in the findings. They noted a significant association of retinal arteriovenous oxygen saturation difference with the inverse of CO. SvO_2-retinal showed a positive correlation with SvO_2-mixed when adjusted for age.