Aims To determine if screening with an ultrasound A-scan and prophylactic treatment of primary angle closure (PAC) with laser peripheral iridotomy (LPI) can reduce the incidence of primary angle closure glaucoma (PACG) in Mongolia.
Methods A single-masked randomised controlled trial was initiated in 1999. 4725 volunteer Mongolian participants ≥50 years old from the capital Ulaanbaatar or the rural province of Bayankhongor were recruited, of which 128 were excluded with glaucoma. 4597 were randomly allocated to the control, no-screening arm or screening with ultrasound central anterior chamber depth (cACD), with the cut-off set at <2.53 mm. 685 screen-positive participants were examined and angle closure was identified by gonioscopy in 160, of which 156 were treated with prophylactic LPI. Primary outcome of incident PACG was determined using both structural and functional evidence from objective grading of paired disc photographs from baseline and follow-up, objective grading of follow-up visual fields and clinical examination.
Results Six years later, 801 (17.42%) participants were known to have died, and a further 2047 (53.92%) were traced and underwent full ophthalmic examination. In an intention to treat analysis using available data, PACG was diagnosed in 33 participants (1.61%, 95% CI 1.11% to 2.25%), of which 19 were in the screened group and 14 in the non-screened group (OR 1.29, 95% CI 0.65 to 2.60, p=0.47), indicating no difference between groups.
Conclusions We were not able to identify a reduction in the 6 year incidence of PACG after screening with cACD <2.53 mm and prophylactic treatment of PAC.
- clinical trial
- optic nerve
- public health
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Funding The Wellcome Trust, British Council for Prevention of Blindness (London), Christian Blind Mission (CBM) (Bensheim), The National Lotteries Fund through Fight for Sight (London). The YAG laser used in this study was donated by the Velux Foundation, Copenhagen. The authors acknowledge a proportion of their financial support from the Department of Health through the award made by the National Institute for Health Research to Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology for a Specialist Biomedical Research Centre for Ophthalmology. The views expressed in this publication are those of the authors and not necessarily those of the Department of Health.
Competing interests None.
Ethics approval This study was conducted with the approval of the London School of Hygiene and Tropical Medicine, UK and Ministry of Health, Ulaanbaatar, Mongolia.
Provenance and peer review Not commissioned; externally peer reviewed.