ObjectiveTo explore the presence of residual emulsified silicone oil (SO) droplets in patients with rhegmatogenous retinal detachment (RRD) and their possible risk factors.MethodsPatients who underwent primary pars plana vitrectomy with SO injection for RRD and SO removal at the same eye centre were included. Approximately 10 weeks after SO removal, B-scan ultrasonography was performed, and using ImageJ, the silicone oil index (SOI) was measured, and its possible correlations with other clinical factors were explored.ResultsA total of 101 eyes were included. Residual SO particles were found in all the patients (100%), and the mean SOI was 4.04% ± 5.16% (range 0.06%–19.88%). Multiple linear regression revealed that, among all the clinical factors, axial length (AL) and ocular hypertension (intraocular pressure (IOP) > 21 mmHg or the use of antiglaucoma medications) before SO removal were positively and significantly associated with the SOI (allP< 0.05).Patients with ocular hypertension after SO removal had a higher SOI, a longer SO duration, a higher IOP before SO removal and a longer AL than those without (allP< 0.05).ConclusionsPatients with a larger AL and higher IOP before SO removal were more prone to have more residual SO droplets, which might in turn lead to an elevated IOP. In these eyes, thorough irrigation or repeated fluid-air exchange might be necessary.