AIM: The complications of intraocular silicone oil include emulsification, which may lead to vision-threatening disorders such as keratopathy, secondary glaucoma and retinopathy. The authors study the effect of mechanical energy from surgical instruments on the emulsification of silicone oil. METHODS: Three different handpieces (phacofragmentation, phacoemulsification, high-speed vitrectomy) were placed at the interface of balanced salt solution and silicone oil (1000 and 5000 cst, 200 fluid; Dow Corning). The phacofragmentation handpiece was evaluated over different ultrasound powers and duration. Emulsification was quantified with phase-contrast microscopy and manual counting of digital photographs by a masked examiner. In addition, phacoemulsification was performed in the anterior chamber of a human ex vivo eye with full-fill silicone oil. RESULTS: Emulsification increases with higher phacofragmentation power and duration and is greater for 1000 cst silicone oil. Emulsification of silicone oil occurs with phacoemulsification and high-speed vitrectomy handpieces. CONCLUSIONS: The energy from surgical handpieces is sufficient to result in silicone oil emulsification.