Clinical risk factors for failure in glaucoma tube surgery. A comparison of three tube designs.

We studied a cohort of 165 eyes that had undergone tube implant surgery for glaucoma, with a minimum follow-up of 12 months (range, 12 to 72 months). Of the 57 cases (34.5%) in which surgery failed to control intraocular pressure (less than 22 mm Hg), 15 (26%) occurred by 3 months, 36 (63%) by 12 months, and 46 (80%) by 24 months. Cox regression modeling was used to evaluate independent risk factors in the absence of additional therapy. The use of a two-piece (anterior chamber-to-encircling band) tube system was associated with a 2.4 times higher risk of failure (P less than .001) compared with a one-piece system. Neovascular glaucoma was associated with a 2.1 times higher risk of failure (P less than .037) than other types of glaucoma. Late failure of tube implant surgery is common and there is a steady attrition rate over a 2-year follow-up period.