Participants were patients who underwent trabeculectomy with mitomycin C at the Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, an academic tertiary care center, between January 1999 and September 2003. The Institutional Review Board at the University of Southern California, Los Angeles, approved the study protocol, and all study procedures conformed to tenets of the Health Insurance Portability and Accountability Act and the Declaration of Helsinki for research involving human participants. All participants had provided written consent before trabeculectomy. Inclusion criteria were a minimum 6-month follow-up period and diagnosis of primary open-angle glaucoma, low-tension glaucoma, exfoliation glaucoma, pigmentary glaucoma, or chronic angle-closure glaucoma. Exclusion criteria were aphakia, prior intraoperative complications, other concurrent surgical procedure, or a diagnosis of neovascular glaucoma, pediatric glaucoma, or uveitic glaucoma. Preoperative characteristics were determined, including age, sex, race/ethnicity, diagnosis, lens status, prior filtration surgery, IOP, Snellen visual acuity (VA), cup-disc ratio, Humphrey VF (HVF) mean deviation, presence of split fixation based on HVF measurements, and number of quadrants with split fixation. Split fixation was defined as a sensitivity of less than 10 dB in any of the cardinal quadrants (supratemporal, infratemporal, supranasal, and infranasal) on HVF examination. Also obtained at intervals of 1 day, 1 week, and 1, 3, 6, 12, and 24 months were postoperative data, including VA, IOP, complications, choroidal effusions, flat or shallow anterior chamber, hypotonia (IOP ≤5 mm Hg), and postoperative procedures.