The effect of pars plan vitrectomy on oxygen saturation in retinal vessels - a pilot study

Purpose: To determine the effect of pars plana vitrectomy (PPV) on oxygen saturation in retinal vessels. Methods: We performed a prospective consecutive interventional case series of 20 eyes of 20 patients with macular hole or epiretinal membrane. We performed automatic retinal oximetry (Oxymap Inc., Reykjavik, Iceland) in each patient 24hr prior to and 45days (range 42-49) after PPV (classic 20G or sutureless 23G). We analysed oxygen saturations in retinal arteries and veins. Vessel segments of first or second degree were selected. The same segment was analysed before and after PPV. Oximetry data were compared by paired two-tailed t-test. Results: Pars plana vitrectomy did not alter arterial haemoglobin saturation with oxygen (982% prior to the surgery and 98 +/- 3% after the procedure, p=0.549). The mean venous haemoglobin saturation with oxygen increased after vitrectomy from 63 +/- 10% to 66 +/- 8% (p=0.012). Conclusions: Oxygen saturation is higher in retinal veins after pars plana vitrectomy. Further studies are needed to unveil the mechanism of how vitrectomy affects oxygen metabolism in the retina.