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Abstract

We appreciate the letter from Dr Raevis and would like to thank him for his response to our recent work.1Lee D.J. Scruggs B.A. Sánchez E. et al.Transient vision loss associated with pre-filled aflibercept syringes: a case series and analysis of injection force.Ophthalmol Sci. 2022; 2: 100115Abstract Full Text Full Text PDF PubMed Google Scholar Here we highlight valid points and provide certain clarifications. We agree with Dr Raevis’ comments regarding other factors related to syringe design that may have contributed to the episodes of severe transient vision loss seen in our case series. In our article, we discussed that factors such as siliconization and fluid viscosity may contribute to variability in injection force. Dr Raevis insightfully hypothesized that plunger shape and deformability may also play a role. The increased injection force generated from aflibercept prefilled syringes (PFS) may lead to increased plunger deformability, which may potentially allow additional volume to be expressed at the end of an injection by minimizing syringe dead space. Our team recently conducted a survey of ophthalmologists who regularly use aflibercept PFS,2Lee D.J. Scruggs B.A. Faridi A. et al.Survey of intravitreal injection outcomes amongst ophthalmologists using pre-filled aflibercept syringes [letter].Clin Exp Ophthalmol. 2022; 50: 803-805Crossref PubMed Scopus (0) Google Scholar and many respondents believed that syringe design plays a contributing factor to the spikes in intraocular pressure observed after aflibercept PFS use. Many of these physicians also reported that they have little tactile feedback when pushing down on the PFS plunger or when the plunger comes to a soft stop. This further corroborates Dr Raevis’ point. It would be interesting to study this theory in the future and to quantify the volume delivered beyond the target of 0.05 ml when applying this increased force at the end of an injection. We want to clarify that our study demonstrated that injection force was proportional to injection speed in all syringe types. Additionally, we showed that the aflibercept PFS required more force compared with other syringe types across all predetermined injection speeds while keeping the volume constant as measured by a lens optical system. The barrel inner diameter of the aflibercept PFS was 35% wider than that of the ranibizumab PFS. This finding explains the increased force generated and may also explain why more volume is delivered per second with the aflibercept PFS despite both syringe types having hollow tapered plunger tips. Overall, our original study findings and Dr Raevis’ additional insights into the matter highlight that plunger misalignment owing to user error may not sufficiently explain our clinical outcomes, and modifications to syringe design may be warranted. Taken together, our team suggests that syringe manufacturers improve syringe components so that physicians can (1) avoid misalignment of the plunger, (2) decrease the injection speed, and (3) avoid deformation of the stopper. Additionally, standardizing injection force across syringe designs by manufacturers may be useful in the future. Re: Lee et al.: Transient vision loss associated with prefilled aflibercept syringes (Ophthalmol Sci. 2022;2:100115)Ophthalmology ScienceVol. 2Issue 4PreviewLee et al1 evaluated multiple cases of severe transient vision loss after receiving an intravitreal injection of aflibercept from a prefilled syringe (PFS). They demonstrated that injection speed and syringe design both influence the injection force required to depress the syringe. Their data show that injection speed is directly proportional to injection force and recommend that physicians perform intravitreal injections at a slower rate. Full-Text PDF Open Access