Key messages
• Laser trabeculoplasty may work better than topical medication (eye drops) in slowing down the progression of open-angle glaucoma (rate of visual field loss i.e. vision loss at the edges of vision) and may be similar to modern eye drops in controlling eye pressure at a lower cost. It is not associated with any serious unwanted effects, particularly for the newer types of trabeculoplasty, such as selective laser trabeculoplasty.
• Laser trabeculoplasty appears to work less well than trabeculectomy (surgery for glaucoma).
What is open-angle glaucoma?
Glaucoma is an eye disease where the nerve that connects the eye to the brain (optic nerve) is damaged. Usually, this happens because the pressure inside the eye (intraocular pressure) is too high, probably because the drainage channels in the eye have become blocked.
How is open-angle glaucoma treated?
The aim of treatment for glaucoma is to reduce the pressure in the eye to protect the optic nerve from more damage. Reducing the pressure in the eye can be done by eye drops, laser treatment, or surgery. Laser trabeculoplasty involves opening up the blocked drainage channels in the eye.
What did we want to find out?
The aim of this Cochrane Review is to find out how well laser trabeculoplasty works as a treatment for open-angle glaucoma.
What did we do?
This review compared laser treatment (laser trabeculoplasty) with topical medication (eye drops) and surgery (trabeculectomy). Cochrane researchers collected and analysed all relevant studies to answer this question.
What did we find?
Cochrane researchers found 40 studies. These studies were mainly from Europe and the USA.
The results were as follows:
• Different studies found different effects on eye pressure when comparing laser trabeculoplasty with eye drops. Older studies were more likely to show a benefit of laser trabeculoplasty which may be because the eye drops in these older studies did not work as well as modern eye drops (low-certainty evidence). Three studies showed a benefit of trabeculoplasty over eye drops for avoiding visual field progression at 24 months (argon) and 48 months (selective) (moderate-certainty evidence, downgraded for risk bias).
• Harmful effects were more common in the laser trabeculoplasty group and included more cases where the iris was stuck to the edge of the drainage mechanism inside the eye (peripheral anterior synaechiae) but this was seen only with older types of laser (argon) trabeculoplasty (low-certainty evidence).
• People receiving laser trabeculoplasty may be more likely to have pressure in the eye that is too high compared with people who had surgery (trabeculectomy) (low-certainty evidence).
• Surgery (trabeculectomy) may increase the risk of cataract compared with laser (very low-certainty evidence).
• A number of studies compared different types of laser (argon, selective, diode, excimer, pattern scanning, titanium-sapphire, and micropulse) but with inconclusive results.
What are the limitations of the evidence?
Some of the studies were not masked and were not large enough to provide a reliable answer to the question. There have been changes over time in both laser and eye drops which meant that, for some outcomes, there were different effects in different studies.
How up-to-date is this evidence?
Cochrane Review authors searched for studies that had been published up to 28 October 2021.
Laser trabeculoplasty may work better than topical medication in slowing down the progression of open-angle glaucoma (rate of visual field loss) and may be similar to modern eye drops in controlling eye pressure at a lower cost. It is not associated with serious unwanted effects, particularly for the newer types of trabeculoplasty, such as selective laser trabeculoplasty.
Open-angle glaucoma (OAG) is an important cause of blindness worldwide. Laser trabeculoplasty, a treatment modality, still does not have a clear position in the treatment sequence.
To assess the effects of laser trabeculoplasty for treating OAG and ocular hypertension (OHT) when compared to medication, glaucoma surgery or no intervention. We also wished to compare the effectiveness of different laser trabeculoplasty technologies for treating OAG and OHT.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2021, Issue 10); Ovid MEDLINE; Ovid Embase; the ISRCTN registry; LILACS, ClinicalTrials.gov and the WHO ICTRP. The date of the search was 28 October 2021. We also contacted researchers in the field.
We included randomised controlled trials (RCTs) comparing laser trabeculoplasty with no intervention, with medical treatment, or with surgery in people with OAG or OHT. We also included trials comparing different types of laser trabeculoplasty technologies.
We used standard methods expected by Cochrane. Two authors screened search results and extracted data independently. We considered the following outcomes at 24 months: failure to control intraocular pressure (IOP), failure to stabilise visual field progression, failure to stabilise optic neuropathy progression, adverse effects, quality of life, and costs. We graded the 'certainty' of the evidence using GRADE.
We included 40 studies (5613 eyes of 4028 people) in this review. The majority of the studies were conducted in Europe and in the USA. Most of the studies were at risk of performance and/or detection bias as they were unmasked. None of the studies were judged as having low risk of bias for all domains. We did not identify any studies of laser trabeculoplasty alone versus no intervention.
Laser trabeculoplasty versus medication
Fourteen studies compared laser trabeculoplasty with medication in either people with primary OAG (7 studies) or primary or secondary OAG (7 studies); five of the 14 studies also included participants with OHT. Six studies used argon laser trabeculoplasty and eight studies used selective laser trabeculoplasty. There was considerable clinical and methodological diversity in these studies leading to statistical heterogeneity in results for the primary outcome "failure to control IOP" at 24 months. Risk ratios (RRs) ranged from 0.43 in favour of laser trabeculoplasty to 1.87 in favour of medication (5 studies, I2 = 89%). Studies of argon laser compared with medication were more likely to show a beneficial effect compared with studies of selective laser (test for interaction P = 0.0001) but the argon laser studies were older and the medication comparator group in those studies may have been less effective. We considered this to be low-certainty evidence because the trials were at risk of bias (they were not masked) and there was unexplained heterogeneity. There was evidence from two studies (624 eyes) that argon laser treatment was associated with less failure to stabilise visual field progression compared with medication (7% versus 11%, RR 0.70, 95% CI 0.42 to 1.16) at 24 months and one further large recent study of selective laser also reported a reduced risk of failure at 48 months (17% versus 26%) RR 0.65, 95% CI 0.52 to 0.81, 1178 eyes). We judged this outcome as moderate-certainty evidence, downgrading for risk of bias. There was only very low-certainty evidence on optic neuropathy progression. Adverse effects were more commonly seen in the laser trabeculoplasty group including peripheral anterior synechiae (PAS) associated with argon laser (32% versus 26%, RR 11.74, 95% CI 5.94 to 23.22; 624 eyes; 2 RCTs; low-certainty evidence); 5% of participants treated with laser in three studies of selective laser group had early IOP spikes (moderate-certainty evidence). One UK-based study provided moderate-certainty evidence that laser trabeculoplasty was more cost-effective.
Laser trabeculoplasty versus trabeculectomy
Three studies compared laser trabeculoplasty with trabeculectomy. All three studies enrolled participants with OAG (primary or secondary) and used argon laser. People receiving laser trabeculoplasty may have a higher risk of uncontrolled IOP at 24 months compared with people receiving trabeculectomy (16% versus 8%, RR 2.12, 95% CI 1.44 to 3.11; 901 eyes; 2 RCTs). We judged this to be low-certainty evidence because of risk of bias (trials were not masked) and there was inconsistency between the two trials (I2 = 68%). There was limited evidence on visual field progression suggesting a higher risk of failure with laser trabeculoplasty. There was no information on optic neuropathy progression, quality of life or costs. PAS formation and IOP spikes were not reported but in one study trabeculectomy was associated with an increased risk of cataract (RR 1.78, 95% CI 1.46 to 2.16) (very low-certainty evidence).