Prevalence of silicone oil droplets in eyes treated with intravitreal injection

OBJECTIVE: To assess the number of eyes with silicone oil in the vitreous after intravitreal injection. METHODS: This cross-sectional, comparative study was divided into 2 groups: (1) treatment—eyes subjected to antiangiogenic therapy; (2) control—no history of intravitreal injection. Subjects were assessed regarding age, gender, clinical diagnosis, lens status, visual acuity and number of previous intravitreal injections. All eyes underwent a meticulous slit-lamp and ultrasound examination for the identification of silicone oil. ImageJ software was used to quantify the index of silicone oil (IOS) by ultrasonography. RESULTS: Sixty-seven eyes (30 controls, 37 treated) were included. Slit-lamp examination found silicone oil droplets in 25 out of 37 (67.57%) treated eyes and in none of the control group. Ultrasonography identified silicone oil in 28 out of 37 (75.68%) treated eyes and in 1 out of 30 (3.33%) controls. An observed agreement of 85.07% and a Cohen’s Kappa coefficient of 69.10% (p < 0.0001) between ultrasonography and biomicroscopy were found. Wilcoxon test showed a statistically significant difference (p = 0.0006) in IOS between controls (0.41 ± 0.43%) and treated eyes (2.69 ± 2.55%). Spearman’s correlation test (0.61; p < 0.0001) showed that the greater the number of injections, the higher the IOS. CONCLUSIONS: Silicone oil droplets were found in the majority of the eyes previously treated with antiangiogenic intravitreal injection. The greater the number of injections, the higher the likelihood of finding silicone oil. An improvement in the technique of injection and better-quality syringes post-injection silicone oil droplets.