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

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.