Vol 34 No 1 Original Article PDF

Predictors for failure of primary trabeculectomy

Franz Marie O. Cruz, MD, Patricia M. Khu, MD MS

This study determined the success and failure rates of primary trabeculectomy in a university hospital and identified the factors predictive of failure. A retrospective, nested case-control study was conducted involving primary trabeculectomies done in a university hospital from January 2005 to December 2007 with at least one year of follow-up. Depending on the outcomes, patients were classified as cases or controls. Cases were those with failed trabeculectomies defined as intraocular pressure (IOP) >21 mm Hg in all patients and >15 mm Hg in advanced glaucoma at 1 year follow-up. Eyes requiring further glaucoma surgery were also considered failure. Controls were those with successful trabeculectomies defined as IOP <21 mm Hg in all patients and <16 mm Hg in advanced glaucoma, and at least 20% reduction from the presenting IOP and on no more than 2 antiglaucoma medications at one-year follow-up. Preoperative, intraoperative, and postoperative variables were collected and analyzed by bivariate analyses and multiple logistic regression.

At one-year follow-up, the success rate was 79.8%. Age at the time of surgery, gender, eye laterality, presence of diabetes, history of intraocular surgery, previous laser treatment, maximum IOP, glaucoma diagnosis, and total number and duration of preoperative antiglaucoma medications were not shown to affect outcome of surgery. Variations in the intraoperative technique, including conjunctival flap approach, location and shape of the scleral flap, suturing technique, and surgeon’s competency were not associated with outcome. Postoperative IOP at 1 month, 3 months, and 6 months were predictors of successful outcome at 1 year. Postoperative subconjunctival 5FU injection, bleb manipulation, and laser suture lysis did not alter outcome.

Early postoperative IOP at 1 month is already predictive of the outcome of primary trabeculectomy at 1 year.

Keywords: Trabeculectomy, Predictors, Risk factors, Glaucoma, Surgery, Postoperativeintraocular pressure