Objective To observe the emulsification of silicone oil in eyes with rhegmatogenous retinal detachment (RRD) after silicone oil filling surgery, and to preliminarily analyze the possible clinical factors related to it. MethodsA cross-sectional clinical study. From January 2019 to April 2022, 50 eyes of 50 patients with RRD who underwent pans plana vitrectomy (PPV) combined with silicone oil filling surgery in Eye and ENT Hospital of Fudan University were included in the study. Among them, there were 25 males with 25 eyes and 25 females with 25 eyes; the age was 54.86±11.79 years old. The retina was in place 3 months after surgery. Before silicone oil removal surgery, intraocular pressure ＞21 mm Hg (1 mm Hg=0.133 kPa) or treated with≥1 anti-glaucoma drug (high intraocular pressure) in 20 eyes; intraocular pressure ≤21 mm Hg and no anti-glaucoma drug treatment in 30 eyes (normal intraocular pressure). During follow-up after surgery, silicone oil emulsification was found and those who met the indications for silicone oil removal were subjected to silicone oil removal surgery. The first 2 ml of lavage fluid was collected immediately after removal of the silicone oil, and the particle diameter and number of emulsified silicone oil were measured using a Multisizer® 3 particle/cell counter and particle size analyzer. The measuring range was 0.4-12.0 μm, and the diameter is accordingly divided into 0.4-＜1.0, 1.0-＜3.0, 3.0-＜5.0, 5.0-＜7.0, 7.0-12.0 μm. Each sample was measured 3 times and the average value was taken. Spearman correlation analysis and multiple linear regression analysis were used to analyze the correlation between the number of emulsified silicone oil particles and clinical factors. ResultsThe number of emulsified silicone oil particles was (1.74±2.94)×107/ml (0.96×107-14.11×107/ml), of which the diameter of 0.4-＜1.0 μm emulsified silicone oil particle was (1.25±2.41)×107/ml, accounted for (64.26±12.70)% [(1.25±2.41)×107/(1.74±2.94)×107]. The results of correlation analysis showed that there was no correlation between the total particle number of emulsified silicone oil and various clinical factors (P＞0.05). The number of emulsified silicone oil particles with a diameter of 7.0-12.0 μm was negatively correlated with age (r=－0.298, P=0.036), and positively correlated with axial length (r=0.325, P=0.021). There was no correlation between the previous ocular trauma, choroidal detachment and different lens states and the number of emulsified silicone oil particles (P＞0.05). Multiple linear regression analysis showed that eye axis (β=1 570.868, P=0.023) and age (β=－316.128, P=0.039) were the risk predictors of silicone oil emulsification into large diameter particles (7-＜12 μm). The number of emulsified silicone oil particles with a diameter of 7-12 μmin the patients with high intraocular pressure was significantly higher than that in the patients with normal intraocular pressure, and the difference was statistically significant (U=195.00, P=0.037). ConclusionsMost of the emulsified silicone oil particles in the eyes of RRD patients after silicone oil filling surgery are small-diameter particles; the silicone oil emulsification is more serious in young patients and patients with long ocular axis, and young patients are more prone to high intraocular pressure.