The effect of Pars Plana Vitrectomy and Silicone Oil Injection on Pre-Existing Filtering Blebs

Purpose: To determine the effect of pars plana vitrectomy (PPV) and silicone oil injection on the intraocular pressure (IOP) in eyes with previous glaucoma filtering surgery (GFS). Methods: Patients with previous GFS who underwent PPV and silicone oil injection were prospectively evaluated. The time since GFS, the indication of GFS, the pre-operative IOP, and anti-glaucoma medications used were recorded. Placement of pars plana sclerotomies in the immediate vicinity of the bleb was avoided. Post-operative IOP and need for glaucoma medications were recorded. Results: Five patients were evaluated. The median age was 62 years (range: 19-65 years). Two patients were males. The median time since GFS was 2 years (range: 2 months to 15 years). The indication of GFS was congenital glaucoma (n=2), chronic angle closure glaucoma (n=l), primary openangle glaucoma (n=l), and neovascular glaucoma (n=l). The median pre-operative IOP was 15 mmHg (range: 13-20). Only one patient was using two glaucoma medications. The indica- tion for PPV was vitreous hemorrhage (n=2), and rhegmatog- enous retinal detachment (n=3). Median follow-up was 6 months (range: 3-11 months). During follow-up, two patients underwent silicone oil removal. At last follow-up, the median IOP was 15 mmHg (range: 13-50). To maintain adequate IOP, one patient needed revision of the filtering bleb at the time of silicone oil removal, one patient needed combined dorzola- mide/timolol, and one patient (with neovascular glaucoma) required a cyclodestructuve procedure. Conclusion: With caution during surgery and adequate follow-up, most patients with previous GFS may maintain normal IOP after PPV and silicone oil injection.