Iridotomy to slow progression of visual field loss in angle closure glaucoma (Review).

Author: Rouse B, Le JT, Gazzard G.

Geographical coverage: Singapore and China

Sector: Biomedical

Sub-sector: Treatment

Equity focus: Not reported

Study population: Patients classified as primary angle‑closure suspects

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background

Primary angle‑closure glaucoma (PACG) is characterised by physical obstruction of the anterior chamber angle, which blocks aqueous‑humour drainage and raises intra‑ocular pressure (IOP). Laser peripheral iridotomy (LPI) is routinely performed to relieve pupillary block by creating an opening that allows aqueous humour to flow directly from the posterior to the anterior chamber. Nevertheless, its effectiveness in slowing visual‑field deterioration remains uncertain.

Objectives 

To assess the effects of iridotomy compared with no iridotomy for PACG, primary angle closure and primary angle‑closure suspects.

Main findings

No reliable conclusions can yet be drawn regarding whether iridotomy slows visual‑field loss at one year compared with no iridotomy, owing to a lack of outcome data from randomised controlled trials (RCTs).

The search retrieved 4 045 records; two studies (13 records) involving 1 251 participants (2 502 eyes) met the inclusion criteria. Both trials, conducted in Asia, enrolled participants with bilateral asymptomatic primary angle‑closure suspects and randomised one eye to iridotomy and the fellow eye to no iridotomy. Full trial reports were unavailable at the time of the review, so data on visual‑field change, IOP reduction, the need for additional surgery, use of IOP‑lowering medication, best‑corrected visual acuity and quality of life could not be analysed.

Preliminary data from one trial showed that iridotomy increased angle width at 18 months by 12.70° (95 % confidence interval [CI] 12.06° to 13.34°; 1 550 eyes; moderate‑certainty evidence) and may be associated with transient IOP spikes one hour post‑treatment (risk ratio 24.00, 95 % CI 7.60 to 75.83; 1 468 eyes; low‑certainty evidence). Overall risk of bias was judged unclear because the full reports had not been published.

Methodology 

Systematic searches were undertaken in PubMed, MEDLINE, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), LILACS, ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform (ICTRP) on 18 October 2017 without language or time restrictions. Reference lists of included studies were screened, and trial authors were contacted for additional information.

Two reviewers independently screened titles and abstracts, assessed full‑text eligibility and extracted data, resolving disagreements through discussion or, if necessary, consultation with a third reviewer. Risk of bias was appraised using guidance from Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions.

Where possible, findings were pooled using meta‑analysis. Fixed‑effect models were applied when fewer than three trials were available and heterogeneity was negligible; otherwise, random‑effects models were used. Subgroup and sensitivity analyses were prespecified. Statistical heterogeneity was quantified with the I² statistic, and potential publication bias was explored with funnel plots.

Applicability / external validity

Both included trials were conducted in Asian populations, where PACG is most prevalent, and focused on older adults with bilateral primary angle‑closure suspects. These factors, together with the absence of long‑term outcomes such as quality of life and disease progression, limit the generalisability of the findings to other settings and population groups.

Geographic focus 

Included studies were conducted in Singapore and China.

Summary of quality assessment 

Confidence in the review’s conclusions is high, but certainty about the effects of iridotomy remains low because outcome data were unavailable at the time of analysis.