Screening for primary angle closure in Mongolia: a randomised controlled trial to determine whether screening and prophylactic treatment will reduce the incidence of primary angle closure glaucoma in an east Asian population.

AIM To describe the methods used and initial results of a prospective study designed to determine whether screening and prophylactic treatment will reduce the incidence of primary angle closure glaucoma (PACG) in Mongolia. METHODS A total of 4725 individuals aged 50 years and above were recruited to the study and randomised to intervention or control groups. All subjects had non-mydriatic optic disc examination. The intervention arm had measurement of anterior chamber depth (ACD) by A-scan ultrasound and intraocular pressure (IOP) with Tonopen. Gonioscopy was performed on test positive cases (ACD <2.53 mm or IOP >or=24 mm Hg either eye). Those with occludable angles were offered laser iridotomy. Primary outcome will be incidence of PACG at 5 year follow up. RESULTS Glaucoma was diagnosed in 128 (2.7%) subjects. Of the remaining 4597, 2293 were randomised to intervention. Intervention as allocated was received by 2280 (99.4%) individuals. 160 (23.4%) of 685 test positive cases had occludable angles, of which 156 were treated with iridotomy. CONCLUSIONS This trial is a further step in determining whether screening and prophylactic treatment for primary angle closure in east Asian populations will reduce the incidence of glaucoma.