What are the benefits and risks of laser peripheral iridoplasty (a surgical procedure) for chronic primary angle closure (an eye condition)?

Why is this question important?
‘Primary angle closure’ (PAC) is a condition in which the eye does not drain properly because the iris (the coloured part of the eye) blocks the drainage channel. A blockage can happen suddenly (acute PAC) or slowly (chronic PAC). A blockage causes a build-up of fluid and raises pressure inside the eye, which damages the optic nerve and can lead to partial or complete vision loss.

The main treatment for PAC is a surgical procedure called laser peripheral iridotomy. Peripheral iridotomy involves using a laser to create an opening in the iris so that fluid can drain out. For more than one in three people, however, peripheral iridotomy does not improve drainage. An alternative to peripheral iridotomy is laser peripheral iridoplasty (LPIp), in which a laser is used to reshape the iris so that it does not block drainage.

To find out how well LPIp works for people with chronic PAC, we reviewed the research evidence.

How did we identify and evaluate the evidence?
First, we searched the medical literature for studies that compared the effects of LPIp to other treatments or no treatment. We then compared the results, and summarised the evidence from all the studies. Finally, we rated our confidence in the evidence, based on factors such as study methods and sizes, and the consistency of findings across studies.

What did we find?
We found four studies on a total of 252 people, mostly from Asia. The studies followed participants for between 3 and 12 months, and compared:

- LPIp plus peripheral iridotomy to peripheral iridotomy alone, as a primary treatment (that is, in people who had not received any other treatment for PAC before);

- LPIp to no treatment, as a secondary treatment (that is, in people who had previously been treated for PAC, but not with LPIp); and

- LPIp to eye drops (travoprost 0.004%), as a secondary treatment.

LPIp plus peripheral iridotomy compared to peripheral iridotomy alone, as a primary treatment

The evidence suggests that adding LPIp to peripheral iridotomy may make little or no difference to:

- eye pressure (2 studies, 174 people);

- the need for medicines after 12 months (1 study, 126 people);

- the need for further laser or surgical treatment (1 study, 126 people); and

- the shape of the front of the eye (1 study, 48 people).

Evidence provided by two studies suggests that:

- unwanted effects (such as bleeding inside the front of the eye) are uncommon; and

- adding LPIp to peripheral iridotomy may make little or no difference to the frequency of unwanted events.

We do not know if adding LPIp to peripheral iridotomy slows disease progression or improves quality of life because no study investigated this.

LPIp compared to no treatment, as a secondary treatment

We found one study on 22 people that compared the effects of LPIp to no treatment on:

- eye pressure; and

- the shape of the front of the eye.

This study was not robust enough for us to determine which treatment is better.

The study did not investigate whether LPIp is better than no treatment to:

- slow disease progression;

- limit the need for medications;

- avoid the need for more laser or surgical treatment; or

- improve quality of life.

The study did not investigate unwanted events.

LPIp compared to travoprost 0.004% eye drops, as a secondary treatment

The evidence from one study on 80 people suggests that there may be little to no difference between the effects of LPIp and travoprost 0.004% on:

- disease progression;

- eye pressure;

- the need for medicines after 12 months; and

- the need for further laser or surgical treatment.

The evidence further suggests that:

- unwanted effects are uncommon; and

- there may be little or no difference in the frequency of unwanted events between the two treatments.

The evidence was not robust enough for us to determine whether the treatments have different effects on the shape of the front of the eye.

We do not know which treatment works better to improve quality of life because no study investigated this.

What does this mean?
The evidence suggests that:

- LPIp may not be better than other treatments for chronic PAC; and

- unwanted events may be as common with LPIp as with other treatments for chronic PAC.

How up-to-date is this review?
The evidence in this Cochrane Review is current to December 2020.

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.

Read the full abstract...
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 strategy: 

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; I2 = 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.

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