SYRINGE DESIGN AND FILLING TECHNIQUE AFFECT ACCURACY OF ANTI–VASCULAR ENDOTHELIAL GROWTH FACTOR INTRAVITREAL INJECTIONS

Abstract

Purpose: To evaluate the effect of syringe design and filling technique on the accuracy of anti–vascular endothelial growth factor delivery. Methods: Volume output was measured with three syringe designs: a 1.0-mL slip-tip syringe, a 1.0-mL Luer-lock syringe, and a ranibizumab prefilled syringe—using two filling techniques (“upward” and “downward”) and two fluids (water and bevacizumab). A total of 300 simulated injections were performed. Accuracy was determined by difference from the intended volume of 50 µL and by mean absolute percentage error. Results: Volume outputs were significantly different between syringe designs, with mean values of 61.99 ± 4.18 µL with the 1-mL slip-tip syringe, 57.43 ± 4.95 µL with the Luer-lock 1-mL syringe, and 51.06 ± 4.74 µL with the ranibizumab syringe, making the latter the most accurate syringe. There were 37 cases (12.3%) of underdosing below 50 µL, the majority of which occurred with the ranibizumab syringe. The “downward” technique reduced the occurrence of air bubbles. Conclusion: Intravitreal injections using 1.0-mL syringes are less accurate than using the ranibizumab prefilled syringe, which has a low-volume and low dead-space plunger design. The variability in volume output may result in less predictable treatment response, especially in cases of underdosing, which were more common with the ranibizumab syringe.