Laser peripheral iridoplasty for chronic angle closure.

BACKGROUND

In at least a third of primary angle closure cases, appositional angle closure persists after laser peripheral iridotomy, and further intervention may be considered. Laser peripheral iridoplasty (LPIp) can be used in treating chronic angle closure when angle closure persists after laser peripheral iridotomy. Previous reviews have found insufficient data to determine its clinical effectiveness, compared to other interventions. This is an update of a Cochrane Review first published in 2008 and updated in 2012. It examines all studies to date to establish whether LPIp shows any effectiveness over other available treatment options.

OBJECTIVES

To assess the effectiveness of laser peripheral iridoplasty in the treatment of people with chronic angle closure, when compared to laser peripheral iridotomy, medical therapy or no further treatment.

SEARCH METHODS

We searched various electronic databases. The date of the search was 20 December 2020.

SELECTION CRITERIA

We included only randomised controlled trials (RCTs) assessing the use of LPIp in cases of suspected primary angle closure (PACS), confirmed primary angle closure (PAC), or primary chronic angle-closure glaucoma (PACG). We applied no restrictions with respect to gender, age or ethnicity of participants. Trials evaluating LPIp for acute attacks of angle closure were not eligible.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two authors independently assessed studies for risk of bias using Cochrane's 'risk of bias' tool. We collected adverse effects information from the trials.

MAIN RESULTS

We included four RCTs involving 252 participants (276 eyes). In total, three different methods of intervention were used and 15 outcomes reported, with different time points. We used narrative synthesis to describe the majority of the findings, as meta-analysis was only possible for a limited number of outcomes due to the variation in study design and outcomes assessed. Study Characteristics Participants were adults recruited from outpatient settings in the UK, Singapore, China and Korea with either PACS, PAC or PACG. All studies compared argon LPIp (as either a primary or secondary procedure) to an alternative intervention or no further treatment. Three studies were of parallel group design, and one within-person, randomised by eye. All studies showed elements of high risk of bias. Due to the nature of the intervention assessed, a lack of masking of both participants and assessors was noted in all trials. Findings Laser peripheral iridoplasty with iridotomy versus iridotomy alone as a primary procedure Two RCTs assessed the use of argon LPIp as a primary procedure with peripheral iridotomy, compared with peripheral iridotomy alone. However, neither study reported data for the primary outcome, disease progression. Argon LPIp showed no evidence of effect on: final mean intraocular pressure (IOP) at 3 months and 12 months (mean difference (MD) 0.39 mmHg, 95% confidence interval (CI) -1.07 to 1.85; I = 38%; 2 studies, 174 participants; low-certainty evidence); further surgical or laser intervention at 12 months (risk ratio (RR) 1.21, 95% CI 0.66 to 2.21; 1 study, 126 participants; low-certainty evidence); or mean number of additional medications required at 12 months (MD 0.10, 95% CI -0.34 to 0.54; 1 study, 126 participants; low-certainty evidence). Complications were assessed at 3 to 12 months (2 studies, 206 participants; low-certainty evidence) and found to be mild and uncommon, with comparable levels between groups. The only severe complication encountered was one case of malignant glaucoma in one study's argon LPIp group. Quality of life measures were not assessed. In the other study, investigators found that argon LPIp showed no evidence of effect on final mean anterior segment optical coherence tomography (AS-OCT) measurements, including anterior chamber depth (MD 0.00 mm, 95% CI -0.10 to 0.10; 24 participants, 48 eyes; very low-certainty evidence). Laser peripheral iridoplasty as a secondary procedure versus no treatment One RCT assessed the use of argon LPIp as a secondary procedure compared with no further treatment in 22 participants over three months. Disease progression, additional medications required, complications, further surgical or laser intervention, and quality of life outcomes were not assessed. There was only very low-certainty evidence regarding final maximum IOP value (MD -1.81 mmHg, 95% CI -3.11 to -0.51; very low-certainty evidence), with no evidence of effect on final minimum IOP values (MD -0.31 mmHg, 95% CI -1.93 to 1.31; very low-certainty evidence). The evidence is very uncertain about the effect of argon LPIp on AS-OCT parameters. The trial did not report AS-OCT measurements for the control group. Laser peripheral iridoplasty as a secondary procedure versus medication One RCT assessed the use of argon LPIp as a secondary procedure compared with travoprost 0.004% in 80 participants over 12 months. The primary outcome of disease progression was reported for this method: argon LPIp showed no evidence of effect on mean final cup/disk ratio (MD -0.03, 95% CI -0.11 to 0.05; low-certainty evidence). Argon LPIp showed no evidence of effect for: mean change in IOP (MD -1.20 mmHg, 95% CI -2.87 to 0.47; low-certainty evidence) or mean number of additional medications (MD 0.42, 95% CI 0.23 to 0.61; low-certainty evidence). Further surgical intervention was required by one participant in the intervention group alone, with none in the control group  (low-certainty evidence). No serious adverse events were reported, with mild complications consisting of two cases of 'post-laser IOP spike' in the argon LPIp group. Quality of life measures were not assessed. The evidence is very uncertain about the effect of argon LPIp on AS-OCT parameters. The trial did not report AS-OCT measurements for the control group. Adverse events Availability of data were limited for adverse effects. Similar rates were observed in control and intervention groups, where reported. Serious adverse events were rare.

AUTHORS' CONCLUSIONS: After reviewing the outcomes of four RCTs, argon LPIp as an intervention may be no more clinically effective than comparators in the management of people with chronic angle closure. Despite a potential positive impact on anterior chamber morphology, its use in clinical practice in treating people with chronic angle closure is not supported by the results of trials published to date. Given these results, further research into LPIp is unlikely to be worthwhile.