Abstract
Purpose :
Intravitreous injections (IVI) with prefilled syringes (PFS) are supposed to reduce procedure time and the risk of endophthalmitis. Postoperative rise in intraocular pressure (IOP) is suspected to lead to glaucomatous changes and there are informal reports that IOP can increase greatly following injections by the aflibercept PFS. Therefore, our aim was to analyze the emptying volumes (EV) of the aflibercept PFS depending on the injection technique.
Methods :
The amount of the EV was assessed using 40 aflibercept PFS. We measured the EV in four different groups with 10 injections in each group: In the first two groups, the cone was set precisely at the indication line (Normal Volume, NV) and the fluid was ejected without (nP) or with forced pressure (wP) at the end of emptying the syringe (NVnP and NVwP groups). In two further groups, the plunger was set right below the line (High Volume, HV) and was ejected without or with forced pressure (HVnP and HVwP groups). A laboratory weighing scale (AX105 DeltaRange®, Mettler Toledo, Ohio) was used for the measurements of EV calculated with a density of 1.034 mg/ml.
The EV data of the four groups were compared by one-way ANOVA test followed by post hoc Tukey HSD test.
Results :
The EV values in the NVnP, NVwP, HVnP and HVwP groups were 56.06 ± 10.32, 70.69 ± 4.56, 74.22 ± 7.41 and 81.63 ± 3.67 µl, respectively. The EV was significantly different in the four groups (ANOVA p<0.001, F=23.56), the NVnP group was statistically significantly lower compared to all other groups (p<0.001 in all comparisons). The EV in three cases (30%) was below 50 µl in the NVnP group (40.62, 42.35 and 45.64 µl) while in the NVwP group all values were above 64 µl, with 7 values (70%) exceeding 70 µl. In the HVwP group 8 measurements (80%) exceeded an EV of 80 µl.
Conclusions :
Our results point toward the importance of the right injection technique with the aflibercept PFS to ensure the correct amount of drug intravitreally. With the right injection technique the drug can be underdosed in one third of the cases. 60% (30 µl) excess volume can be achieved by using suboptimal settings and injection technique. One explanation could be the design including the relatively high syringe diameter of the aflibercept PFS. This should be taken into consideration when applying them in the daily routine and might be addressed in future development of further PFS.
This is a 2021 ARVO Annual Meeting abstract.