In-vitro assessment of release of silicone oil droplets with the use of variety of syringes and needles used in intravitreal injections

Purpose: To assess the variability of silicone oil (SO) particles released across syringes from the same lot and the role of different needle gauges. Materials and methods: Four syringe models and six needle models were assessed for SO release. About 50 microliters of a buffer solution were loaded into the syringe, needle or syringe/needle setup. The data were analyzed by imaging flow cytometry with fluorescently labeling for SO. Results: All syringe models had a high coefficient of variation in SO release across syringes from the same lot. The amount of SO was significantly greater in the syringe when the needle was attached. SO particles with the BD 30G needle attached to the syringe were statistically greater than the 27G counterpart ( p = 0.005). None of the other comparisons was statistically different. Finally, the number of SO particles was higher in the syringe/needle setup than in needles only ( p = 0.0024). Conclusion: We found a high variability in SO content across syringes from the same lot. Additionally, there was no clear association between needle gauge and the number of SO particles, as well as their coefficient of variation. Finally, the needles accounted for a small number of SO particles in comparison to the combined syringe-needle setup.