The Effect of Trabeculectomy on Intraocular Pressure of the Untreated Fellow Eye in the Collaborative Initial Glaucoma Treatment Study

Purpose: To describe the intraocular pressure (IOP) of the untreated fellow eye after unilateral trabeculectomy in the Collaborative Initial Glaucoma Treatment Study (CIGTS). Design: Data collected from a prospective, multicenter, randomized clinical trial. Participants: Three hundred patients with newly diagnosed open-angle glaucoma enrolled at 14 centers in the United States who were randomized to initial trabeculectomy. Methods: After baseline evaluation and randomization to initial trabeculectomy in the study eye, patients were evaluated at 3 and 6 months and at 6-month intervals thereafter. The IOP was measured by Goldmann applanation tonometry. All eyes included in the analysis were untreated fellow eyes, and the data were censored for potential IOP-lowering events in the fellow eye, including trabeculectomy, argon laser trabeculoplasty, or cataract extraction. Predictive factors for IOP response in the fellow eye to initial trabeculectomy in the study eye were analyzed using a linear mixed model. Main Outcome Measures: Intraocular pressure in the untreated fellow eye during follow-up. Results: Although the IOP in the fellow eye was lower than baseline at 3, 6, 12, 18, and 24 months after trabeculectomy in the study eye, this decrease was statistically significant only at month 12 (mean decrease from baseline, 0.73 +/- 3.37 mmHg; P = 0.0134). Predictive associations with higher IOP in the fellow eye during follow-up included higher baseline IOP (P < 0.0001), lower level of education (P = 0.0129), time (P = 0.0005), and the presence of other vascular disease (P = 0.0069). Patients who ultimately required fellow eye trabeculectomy (P < 0.0001) or argon laser trabeculoplasty (P < 0.0001), but not cataract extraction (P = 0.4597) in the fellow eye, had lower IOPs during follow-up after these procedures. Conclusions: There was no evidence of a substantial effect of trabeculectomy on the IOP of the untreated fellow eye during follow-up. Trabeculectomy does not seem to decrease the mean IOP of the fellow eye, as suggested by some previous studies. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references. Ophthalmology 2010; 117: 2055-2060 (C) 2010 by the American Academy of Ophthalmology.