Background/aims To determine the incidence and causative pathogens of endophthalmitis after vitrectomy during strict face mask wearing in the COVID-19 period.

Methods This was a retrospective multicentre study including 31 ophthalmological institutions of the Japanese Retina and Vitreous Society or Japan-Clinical Retina Study group. Patients who had undergone vitrectomy during 2019, the pre-COVID-19 period, and from July 2020 to June 2021, the COVID-mask period, were studied. The results of cataract surgery were used as a control. The total number of vitrectomies and the total number of postoperative endophthalmitis were determined. Then, the differences in the incidence of postoperative endophthalmitis between the pre-COVID-19 period and the COVID-mask period, and the type of pathogens causing the endophthalmitis were studied.

Results The incidence of postvitrectomy endophthalmitis was significantly lower in the pre-COVID-19 period with 16 568 surgeries and 18 endophthalmitis cases (0.11%) than in the COVID-mask period of 14 929 surgeries and 31 endophthalmitis cases (0.21%; p=0.031, OR=1.913, 95% CI 1.078 to 3.394). In the pre-COVID-19 period, 4 of the 18 eyes were culture positive, and all were of the Staphylococcus family. In the COVID-mask period, 9 of the 31 eyes were culture positive, and 4 cases were related to oral commensals including Streptococcus spp, which are reportedly very rare in endophthalmitis after vitrectomy.

Conclusions It is necessary for physicians to be aware of the higher incidence of postvitrectomy endophthalmitis during the COVID-mask period, and to treat their patients appropriately.