To evaluate the incidence and risk factors of late-onset intraocular pressure (IOP) elevation in patients who underwent pars plana vitrectomy with silicone oil (SO) injection for the management of various vitreoretinal pathologies.

A retrospective observational study.

A single-center study involving 135 eyes of 129 patients who underwent vitrectomy with SO injections between January 2018 and May 2023 and maintained SO tamponade for ≥1 month. Eyes with prior glaucoma surgery; a history of SO injection; SO removal or exchange within a month; a follow-up period of <1 month; or those who showed IOP elevation on postoperative day 1 were excluded from the analysis. Late-onset IOP elevation was defined as IOP ≥ 21 mm Hg after postoperative day 7.

Late-onset IOP elevation developed in 22.2% (30/135 eyes) and the mean onset was 38.0±53.4 days (7–251 days) after surgery. In the multivariate logistic regression analysis, late-onset IOP elevation was associated with pre-existing glaucoma (odds ratio [OR], 7.16; P=0.041), longer axial length (OR, 1.40, P=0.037), and higher preoperative IOP (OR, 1.12; P=0.037). Among the patients with late-onset IOP elevation, 50% (15/30) required oral acetazolamide despite the administration of IOP-lowering eye drops. Among them, surgical intervention was required in 8 cases (53.3%).

Late-onset IOP elevation is a common complication associated with SO tamponade. Risk factors for late-onset IOP elevation are pre-existing glaucoma, longer axial length, and preoperative higher IOP. Since a substantial proportion of eyes require surgical intervention, proactive measures should be considered for effective IOP control.