Release of silicone oil and the off-label use of syringes in ophthalmology

Background/aims: To assess silicone oil (SO) release by different brands of syringes used for intravitreal injection under different handling conditions.

Methods: Eight syringes were analysed: from the USA, Terumo 0.5 mL, Becton-Dickinson (BD) Tuberculin 1 mL, BD Luer-lok 1 mL, BD Ultra-Fine 0.3 mL and Exel Insulin 0.3 mL; from Germany, Braun Omnifx-F 1 mL and Braun Injekt-F 1 mL and from Spain, BD Plastipak 1 mL.
Theimpact of air, priming the plunger, agitation by flicking and fluid temperature on SO release were assessed by light microscopy. Fourier transform infrared spectroscopy (FTIR) was performed to identify the molecular compound in each syringe.

Results: Five hundred and sixty syringes were analysed.
Terumo 0.5 mL and BD Ultra-Fine 0.3 mL released more SO than all others. BD Luer-lok 1 mL, BD Plastipak and Braun Omnifx-F 1 mL released little SO; BD Tuberculin 1 mL, Exel 0.3 mL and Braun Injekt-F 1 mL released the least SO. Priming the syringe and different temperatures did not signifcantly affect SO release. Agitation by flicking caused a signifcantly higher proportion of samples to have SO droplets and an increased number of oil droplets. Air had an additive effect on the release of oil in the agitation groups. FTIR identifed polysiloxane in all syringes but Injekt-F.

Conclusion: Syringes commonly used for intravitreal injections frequently release SO droplets, especially when agitated by flicking. To avoid unnecessary ocular risks, syringes should not be agitated before intravitreal injection. It is desirable that syringes be manufactured specifcally for ophthalmic use.