Effect of Phacoemulsification on Intraocular Pressure Control in Primary Open Angle Glaucoma Previously Treated by Trabeculectomy: A Case-Control Study

Purpose: To analyse the effect of phacoemulsification on the control of intraocular pressure in primary open angle glaucoma in patients having phacoemulsification after previous trabeculectomy and compare them with a control group who had trabeculectomy alone. Patients and Methods: Twenty one patients (one eye from each) who had phacoemulsification subsequent to trabeculectomy were identified, and compared with 41 controls. Intraocular pressure, bleb appearance, glaucoma medications, iris manipulation and complications were recorded. Each patient was followed for full 12 months. Failure of control was defined as follows: 1) intraocular pressure >21 mm Hg on medication, or 2) a greater number of glaucoma medications than before phacoemulsification. Results: The post operative change in intraocular pressure in the case group at 12 months was much less than that in the control (p = 0.001). The mean intraocular pressure had changed from 15.3 mm Hg to 14.7 mm Hg. The control group showed an average intraocular pressure reduction of 6 mm Hg at the last visit (p > 0.001). In phacoemulsification group, 19% required 1 or 2 glaucoma medications at one year follow-up vs 19.5% in the control group. In phacoemulsification group, 9.5% showed flattening of a previously formed bleb at the last visit (P < 0.001), compared with 9.7% of controls. Conclusions: The stability of glaucoma control in the first year after phacoemulsification in previously filtered eyes with primary open angle glaucoma is comparable to that of the natural course after trabeculectomy. The study is limited by the small number of cases available.