Impact of patient face mask use on endophthalmitis after intravitreal anti-VEGF injections.

Abstract Objective To compare the incidence of endophthalmitis after intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections with and without patient face masking. Design Two-centre retrospective cohort study Participants Patients receiving a total of 28 501 injections (period 1 before masking: n = 13 863; period 2 after masking: n = 14 638) Methods Periods before and after implementation of patient masking were compared: period 1 (July–December 2019) and period 2 (July–December 2020). All patients requiring treatment for endophthalmitis following intravitreal anti-VEGF injections were reviewed. Endophthalmitis risks were compared. Statistical simulations were run to determine the number of injections or endophthalmitis cases required to detect a statistically significant difference between both periods. Results Five patients (0.036%) had endophthalmitis in period 1 compared with 7 patients (0.048%) in period 2. Odds ratio, 95% confidence interval, for risk of patient masking was 1.326, 0.421–4.179 (p = 0.63). Three patients (0.022%) in period 1 had culture-positive endophthalmitis compared with 2 patients (0.014%) in period 2. Risk of patient masking for culture-positive endophthalmitis was 0.631, 0.105–3.779 (p = 0.61). Assuming similar rates of endophthalmitis, 476,806 injections in both groups would be required to detect a significant difference. Alternatively, assuming that masking would increase endophthalmitis risk in period 2, a significant difference would require twice as many cases (n = 15, 0.102%) for a risk of 2.843, 1.033–7.825 (p = 0.043). Conclusions The implementation of patient masking in clinical practice did not significantly alter the rate of endophthalmitis following intravitreal anti-VEGF injections.