To evaluate the accuracy and precision of anti–vascular endothelial growth factor volume delivery by intravitreal injections in the clinical setup.Methods:
Volume output was measured in 669 intravitreal injections administered to patients, calculated from the difference in syringe weight before and after expelling the drug. Three groups were included: prefilled bevacizumab 1.0 mL syringe (Group 1, n = 432), pre-filled ranibizumab in a small-volume syringe with low dead-space plunger design (Group 2, n = 125), and aflibercept drawn and injected using a 1.0-mL syringe (Group 3, n = 112). Accuracy was analyzed by mean absolute percentage error, and precision by coefficient of variation.Results:
Volume outputs in all 3 groups were significantly different from the target of 50 μL (P < 0.0001 for all), and mean absolute percentage error values were 12.25% ± 5.92% in Group 1, 13.60% ± 8.75% in Group 2, and 24.69% ± 14.84% in Group 3. No difference was found between groups 1 and 2, but both were significantly more accurate than Group 3 (P < 0.0001 for both).Conclusion:
The current practices used for intravitreal injections are highly variable, with overdelivery of the anti–vascular endothelial growth factor drugs measured in most cases, but underdelivery in 16.3% of injections. Use of a prefilled syringe was associated with improved accuracy, and low dead-space plunger design may improve precision.