Endophthalmitis after intravitreal injection: The importance of viridans streptococci

Purpose: To determine the rate of postinjection endophthalmitis and compare microbial etiology and outcomes in office-based injection-related endophthalmitis versus those acquired after operating room procedures. Methods: Retrospective, observational case series. Consecutive cases of endophthalmitis seen at Retina Consultants of Houston between July 2000 and July 2010 were classified as postsurgical or post-intravitreal injection. Cases secondary to glaucoma surgery, trauma, and endogenous sources were excluded. Main study measures were incidence of endophthalmitis, microbiology results, and visual outcomes. Results: In all, 109 cases of endophthalmitis were identified: 88 postsurgical and 21 post-intravitreal injection (3 from clinical trials and 5 from outside ophthalmologists). A total of 33,580 intravitreal injections were performed at Retina Consultants of Houston (endophthalmitis rate = 0.04%, 13 of 33,580; 95% confidence interval, 0.02-0.07%). The most common organisms isolated overall were coagulase-negative staphylococci, while viridans streptococci, a component of human oral flora, was identified over three times more often in the postinjection group compared with the postsurgical group. Compared with all other culture-positive cases related to intravitreal injection, postinjection endophthalmitis secondary to viridans streptococci presented much more rapidly (P < 0.001) and final visual outcomes were much worse (P = 0.004) Conclusion: Although the overall risk of postinjection endophthalmitis is low, viridans streptococci were identified over three times more frequently in postinjection cases compared with postsurgical cases and these cases had much worse clinical outcomes. The office-based setting for intravitreal injections may lead to a higher risk for infection from oral pathogens.