Silicone Oil Droplets are More Common in Fluid From BD Insulin Syringes as Compared to Other Syringes

Purpose: During 2016 and 2017, numerous retina specialists reported silicone oil droplets after intravitreal injection, primarily associated with insulin syringes with a fixed needle. By contrast, adverse events were relatively rare for tuberculin syringes. We hypothesized that fixed-needle syringe injections have more silicone droplets due to the lack of dead space at the syringe–needle junction. Methods: Fluid from Becton Dickenson (BD) insulin syringes, BD tuberculin syringes, Henke Sass Wolf (HSW) insulin syringes, and HSW silicone-free syringes was examined microscopically for silicone oil droplets. Fluid was sampled at the beginning, middle, and end of injection; and droplets were photographed and quantified. Results: Silicone oil droplets were identified in 30% of the BD insulin syringes, measuring 0.9 ± 0.2 mm3; no oil droplets were found in BD tuberculin syringes or HSW silicone-free syringes (analysis of variance, P < .05). All 6 samples with silicone oil droplets were from the end of injection (full depression of the plunger), while samples from the beginning and middle of injections did not have droplets. Challenging syringes with extra silicone oil resulted in increased droplets for fixed-needle syringes (but not for syringes with detachable needles). Conclusion: Significant silicone oil droplets were present in BD insulin syringes and were expressed at the end of injection (with plunger depressed maximally), supporting the hypothesis that insulin syringe injections have more droplets due to the lack of dead space where the plunger meets the hub of the needle. However, there are additional factors such as the amount or type of silicone lubricant in a syringe.