Medical versus surgical interventions for open angle glaucoma

Background Open angle glaucoma (OAG) is the commonest cause of irreversible blindness worldwide.

Objectives To study the relative effects of medical and surgical treatment of OAG.

Search strategy We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2005), MEDLINE ( 1966 to February 2005), EMBASE ( 1988 to February 2005), and reference lists of articles. We also contacted researchers in the field.

Selection criteria Randomised controlled trials comparing medications to surgery in adults.

Data collection and analysis Two authors independently assessed trial quality and extracted data. We contacted trial investigators for missing information.

Main results Four trials involving 888 participants with previously untreated OAG were included. Surgery was Scheie's procedure in one trial and trabeculectomy in three trials. In three trials, primary medication was usually pilocarpine, in one trial a beta-blocker.

In the most recent trial, participants with mild OAG, progressive visual field (VF) loss, after adjustment for cataract surgery, was not significantly different for medications compared to trabeculectomy ( Odds ratio ( OR) 0.74; 95% CI 0.54 to 1.01). Reduction of vision, with a higher risk of developing cataract ( OR 2.69, 95%% CI 1.64 to 4.42), and more patient discomfort was more likely with trabeculectomy than medication.

There is some evidence, from three trials, for people with moderately advanced glaucoma that medication is associated with more progressive VF loss and 6 to 8 mmHg less intraocular pressure (IOP) lowering than surgery, either by a Scheie's procedure or trabeculectomy. There was a trend towards an increased risk of failed IOP control over time for initial pilocarpine treatment compared to trabeculectomy. In the longer-term ( two trials) the risk of failure was significantly greater with medication than trabeculectomy ( OR 3.90, 95% CI 1.60 to 9.53; HR 7.27, 95% CI 2.23 to 25.71). Medicine and surgery have evolved since these trials were undertaken, and additionally the evidence is potentially subject to detection and attrition bias.

Authors' conclusions Evidence from one trial suggests, for mild OAG, that VF deterioration up to five-years is not significantly different whether treatment is initiated with medication or trabeculectomy. Reduced vision, cataract and eye discomfort are more likely with trabeculectomy. There is some evidence, for more severe OAG, that initial medication ( pilocarpine, now rarely used as first line medication) is associated with greater VF deterioration than surgery. In general, surgery lowers IOP more than medication.