New prefilled syringe aflibercept design. A cause of symptomatic IOP spike after aflibercept PFS?

Objective: To describe ocular hypertension cases after using a new aflibercept prefilled syringe and to assess the main characteristics of these eyes and their possible association with intraocular pressure (IOP) changes.

Methods: Case series. We reported all the cases of ocular hypertension following aflibercept prefilled syringes (PFS) treatment in our department between April 2021 and December 2023.

Results: A total of 4183 eyes were treated with aflibercept PSF. Thirteen transitory IOP elevations were observed immediately after injection (0.3%). Two eyes had an IOP between 30-35 mmHg, five eyes had an IOP between 36-55 mmHg and three eyes had an IOP > 56 mmHg. The mean IOP was 45.5 mmHg±11.33. Only six eyes needed anterior chamber paracentesis (37.5%). The other patients were treated conservatively (ocular massage and/or IOP-lowering drops). The mean IOP after treatment was 15.71 mmHg±7.20. Visual acuity improved after treatment in all the patients.

Discussion: Compared with other injectors, reports have indicated a higher incidence of moderate and severe IOP spikes with aflibercept PSF. The European Medicine Agency (EMA) has associated this significant increase with incorrect syringe handling, leading to higher injection volumes. Although plunger misalignment seems to play a role in the IOP spikes, some other characteristics of this new injector could play a role. Factors such as syringe diameter, plunger alignment, and injection force may contribute to this issue. The reason some authors found no significant differences in IOP elevation after IVI, with aflibercept PFS, could be due to variations in patient characteristics, which may also play an important role in post-IVI pressure changes.

Conclusions: Intraocular pressure spikes after aflibercept PFS can be explained by injector characteristics. The PFS of aflibercept has a domed plunger. Incorrect alignment between the base of the plunger and the black dosing line could cause an increase in the injected volume. Furthermore, the wider syringe diameter of aflibercept PFS could imply a larger injection force, increasing the risk of IOP elevation. Patient characteristics, such as previous VPP, axial length, or glaucoma history, may also play a role. Further studies are required to develop an ideal intravitreal syringe.