The Effect of Syringe-Filling Technique on the Risk for Endophthalmitis after Intravitreal Injection of Anti-VEGF Agents

Purpose: This study aimed to compare the risk for post-injection endophthalmitis between different anti-vascular endothelial growth factor (VEGF) agents and syringe preparation techniques. Methods: A retrospective study of anti-VEGF injections performed in 3 large ophthalmology departments between 2013 and 2019 was conducted. Injections were categorized according to the drug and the syringe-filling technique - prefilling by a hospital pharmacy, prefilling by a good manufacturing practice (GMP) pharmacy, self-drawing from the vial by the injecting physician, and use of a prefilled syringe. Cases of endophthalmitis were identified, and their rates were analyzed. Results: A total of 197,402 injections were included, and 53 cases of endophthalmitis were identified (0.027% risk). The risk of endophthalmitis following injections with syringes that were prefilled by GMP pharmacies or the manufacturers was significantly lower than that following injections which were self-drawn by the physician (0.019% vs. 0.055%, p < 0.0001). For ranibizumab, risk of endophthalmitis decreased since it became available in a prefilled syringe (0.054% vs. 0.014%, p = 0.066), bordering on statistical significance. Conclusions: The syringe-filling technique is an important factor determining risk of post-injection endophthalmitis. Use of GMP-grade prefilling by professional pharmacies or the manufacturers significantly reduces this risk and should be the technique of choice for all drugs administered by intravitreal injection.