Lens extraction versus laser peripheral iridotomy for acute primary angle closure

Author: Ong AY, McCann P, Perera SA, Lim F, Ng SM, Friedman DS, Chang D.

Geographical coverage: Hong Kong and Singapore

Sector: Glaucoma

Sub–sector: Treatment

Equity focus: Not explicitly stated

Study population: Adult patients with acute primary angle closure

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background

Acute primary angle closure (APAC) is an ocular emergency that can cause sudden, painful loss of vision. The underlying event is an abrupt rise in intraocular pressure (IOP) when the trabecular meshwork is blocked. Typical symptoms include ocular pain, redness, headache, nausea and blurred vision, and irreversible blindness can occur if treatment is delayed. East‑Asian populations experience APAC far more frequently than European or African populations. The standard first‑line intervention is laser peripheral iridotomy (LPI), whereby a laser creates a small opening in the iris to equalise anterior‑ and posterior‑chamber pressure. However, LPI does not always prevent progression to chronic primary angle closure glaucoma (PACG) or the need for long‑term medication. Early removal of the crystalline lens by clear‑lens phacoemulsification may deepen the anterior chamber, widen the iridocorneal angle and provide better long‑term IOP control.

Objectives

To compare the effectiveness and safety of early lens extraction with those of LPI in the treatment of APAC.

Main findings

The review included two randomised controlled trials with a total of 99 participants (one eye per participant). One trial took place in Hong Kong (62 participants) and the other in Singapore (37 participants); most participants were female and of Chinese ethnicity. Both compared phacoemulsification with LPI.

• IOP control at 18 – 24 months was more likely after lens extraction than after LPI (risk ratio, RR = 1.66; 95 % confidence interval, CI 1.28 to 2.15; two studies, n = 97).
• The need for additional IOP‑lowering surgery was lower in the lens‑extraction group (RR = 0.07; 95 % CI 0.01 to 0.51; two studies, n = 99).
• Evidence for a difference in recurrent APAC episodes was very uncertain (RR = 0.32; 95 % CI 0.01 to 7.30; one study, n = 37).
• Meta‑analysis detected no clear difference in best‑corrected visual acuity at six months, measured as the mean logMAR score (mean difference, MD = ‑0.09; 95 % CI ‑0.20 to 0.02; two studies, n = 94).
• Lens extraction was associated with a lower mean IOP at 12 months and a small reduction in the median number of IOP‑lowering medicines required at 18 months; however, the clinical importance of these changes is uncertain.
• Adverse events were more common after lens extraction (for example, intra‑operative corneal oedema and post‑operative anterior‑segment inflammation). Complications after LPI included iridotomy closure and the need for supplementary laser treatment.

Methodology

CENTRAL, MEDLINE (including “in‑process” and E‑pub ahead‑of‑print records), Embase, PubMed, LILACS, ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform were searched without date or language limits; the most recent search was on 10 January 2022. Two reviewers independently screened titles, abstracts and full‑text articles, resolved disagreements by consensus or third‑party arbitration, extracted data and assessed risk of bias with the Cochrane risk‑of‑bias 2 tool. Dichotomous outcomes were pooled as risk ratios and continuous outcomes as mean differences using a random‑effects model. Heterogeneity was quantified with the I² statistic; an I² value of 50 % or more was considered substantial. Because only two trials were available, publication bias, subgroup analyses and sensitivity analyses were not undertaken.

Applicability / external validity

Both trials were conducted in tertiary centres in Hong Kong and Singapore and included predominantly Chinese participants. Results therefore may not apply to other ethnicities or to clinical settings with less surgical expertise. The small sample sizes and follow‑up limited to two years restrict confidence in the long‑term benefits and harms of early lens extraction.

Geographic focus

The included studies were carried out in Hong Kong and Singapore.

Summary of quality assessment

Only two small trials of moderate methodological quality were available, and several outcomes were reported by a single study. The limited evidence base, coupled with uncertainty about long‑term safety and generalisability, means that the certainty of the evidence is low. Further large, well‑conducted randomised trials are required to confirm these findings.