Assessing risk factors for postoperative hypotony in Ahmed glaucoma valve implantation surgery.

PURPOSE To assess the risk factors associated with the development of hypotony after Ahmed glaucoma valve (AGV) implantation. METHODS One hundred and ninety-three eyes of 177 patients with various types of glaucoma that were treated with AGV implantation were retrospectively evaluated. Intraocular pressure lower than 6 mmHg related to the surgery is defined as postoperative hypotony. Patients' demographic characteristics, type of glaucoma, preoperative and postoperative visual acuity, necessity of antiglaucoma treatments, lens status, previous ocular surgeries, intraocular pressure (IOP) measurements before and after surgeries, the need for additional procedures and postoperative complications were recorded from the patients' charts. RESULTS Hypotony was seen in 68 of 193 eyes (35.2%) postoperatively. In 45 eyes (23.3%), it has occurred in first postoperative day and in 23 eyes (11.9%) after the first day within the first week. There was no difference in intraocular pressures between two groups in the first year follow-up. Pre- and postoperative best-corrected visual acuities, age and gender were not statistically different between hypotony and no hypotony groups (p > 0.05). Also, lens status, history of previous ocular surgery, type of glaucoma and number of preoperative glaucoma medication usage were not found to be different between groups (p > 0.05). CONCLUSIONS Potential risk factors such as age, sex, lens status, history of previous ocular surgeries, preoperative glaucoma medication usage or glaucoma type are not found to influence upon postoperative hypotony prevalence for AGV surgery. Surgery type and personal ocular factors, which could not be determined beforehand, could be more important than demographic features.