Effect of Syringe Design on the Accuracy and Precision of Intravitreal Injections of Anti-VEGF Agents

Purpose: To evaluate the accuracy and precision of different syringe designs for intravitreal injection of anti-VEGF agents. Methods: Volume output was measured from three syringe designs—1) 1.0 mL tuberculin syringe, 2) 1.0 mL syringe with low dead space plunger, and 3) 0.5 mL low-volume syringe—to deliver 50 µL of bevacizumab, ranibizumab, or aflibercept, each repeated four times by three different physicians for 108 total simulated injections. Volume output was calculated from difference in syringe weight before and after expelling the drug. Accuracy was determined by mean absolute percentage error (MAPE), and precision was measured by coefficient of variation (CV). Results: Volume output from all three syringes was significantly different from 50 µL, with mean volumes of 58.0 ± 5.7 µL for the tuberculin syringe, 58.0 ± 4.0 µL for the low dead space syringe, and 55.5 ± 5.1 µL for the low-volume syringe (p < 0.00001 for all). The low-volume syringe was the most accurate (MAPE = 12.8 ± 7.8% vs. 17.3 ± 9.3% or 15.9 ± 8.1%), and the low dead space syringe was the most reproducible (CV = 0.068 vs. 0.091 or 0.097). There was no significant difference in volume output between different anti-VEGF agents. Conclusions: Intravitreal injections of anti-VEGF agents using a 1.0 mL tuberculin syringe demonstrate poor accuracy and precision. A lower capacity syringe may improve accuracy, while a low dead space plunger may improve precision.