# Comparison of Endophthalmitis Rates Between Prefilled Syringes and Standard Vials in Aflibercept Intravitreal Injections: A Retrospective Study in Japan

## TL;DR

This study compared bacterial endophthalmitis rates after using prefilled syringes versus standard vials for aflibercept eye injections in Japan, finding no significant difference in infection rates.

## Contribution

The study is one of the largest to compare endophthalmitis rates between prefilled syringes and vials in real-world clinical settings.

## Key findings

- Endophthalmitis rates were 0.0046% with prefilled syringes and 0.0092% with vials, but the difference was not statistically significant.
- Poor visual outcomes were linked to specific bacteria like Enterococcus faecalis and Streptococcus spp., as well as diabetes.

## Abstract

Background: Bacterial endophthalmitis is a rare but serious complication of intravitreal injections (IVIs). Prefilled syringes have been introduced to reduce contamination risk during drug preparation. However, whether they lower the incidence of bacterial endophthalmitis compared to vials remains unclear. Methods: This retrospective cohort study analyzed aflibercept IVIs performed at 17 clinical centers in Japan between 2015 and 2022. Patients aged ≥20 years who received aflibercept IVIs (vial or prefilled syringe) for age-related macular degeneration, diabetic macular edema, retinal vein occlusion, or myopic choroidal neovascularization were included. Bacterial endophthalmitis was diagnosed based on clinical signs (e.g., rapid vision loss, pain, hypopyon, vitreous opacity). Incidence rates were compared using Fisher’s exact test. Results: Among 152,039 injections (43,684 prefilled syringes; 108,355 vials), 12 cases of bacterial endophthalmitis were identified (0.0046% vs. 0.0092%, p = 0.53). Poor visual outcomes were associated with Enterococcus faecalis, Streptococcus spp., and diabetes. Conclusions: Although incidence was lower in the prefilled syringe group, the difference was not statistically significant. Detecting a significant difference requires a larger sample. Further studies are needed to confirm the potential benefits of prefilled syringes in reducing endophthalmitis risk.