Laser trabeculoplasty. A prospective study of treatment variables

Laser trabeculoplasty for open-angle glaucoma and ocular hypertension

BACKGROUND

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.

OBJECTIVES

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.

SEARCH METHODS

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.

SELECTION CRITERIA

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.

DATA COLLECTION AND ANALYSIS

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.

MAIN RESULTS

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).

AUTHORS' CONCLUSIONS

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.

Evaluation of a modified protocol for selective laser trabeculoplasty

PURPOSE

To compare the intraocular pressure (IOP) response to a modified protocol for selective laser trabeculoplasty (SLT) to standard protocols for SLT and argon laser trabeculoplasty (ALT).

MATERIALS AND METHODS

A retrospective study of 318 eyes of 284 patients diagnosed with either primary open angle, pigmentary or pseudoexfoliation glaucoma who underwent laser trabeculoplasty from September 1997 to September 2005. One hundred and two patients, who underwent a modified SLT protocol with 100 overlapping laser spots over 180 degrees of trabecular meshwork were compared with 89 patients who received SLT with 100 nonoverlapping spots over 360 degrees and another 127 patients who received ALT with 50 spots over 180 degrees. IOPs were measured at baseline and postoperatively at 1 hour, 6 weeks, 4 months, and 14 months. Regression models, based on the observed data, were used to predict the fall in IOP in the 3 groups, controlling for differences in baseline pressure.

RESULTS

The IOP response to overlapping SLT was significantly worse than to nonoverlapping SLT or ALT, both of which had similar responses. Baseline IOP was the only preoperative factor that predicted response to ALT (P<0.0001) and nonoverlapping SLT (P=0.0019) at all follow-up times. There were no statistically significant predictive factors for IOP reduction in the overlapping SLT group.

CONCLUSIONS

Overlapping application of SLT results in a poorer IOP response compared with ALT and nonoverlapping SLT.

Laser trabeculoplasty for open angle glaucoma

BACKGROUND

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.

OBJECTIVES

The objective of this review was to study the effects of laser trabeculoplasty for OAG.

SEARCH STRATEGY

We identified trials from CENTRAL in The Cochrane Library, MEDLINE, EMBASE, LILACS and manual searching. We also contacted researchers in the field.

SELECTION CRITERIA

We included randomised controlled trials comparing laser trabeculoplasty with no intervention, with medical treatment, or with surgery. We also included trials comparing different technical modalities of laser trabeculoplasty.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted the data. We contacted trial investigators for missing information.

MAIN RESULTS

This review included 19 trials involving 2137 participants. Only five trials fulfilled the criteria of good methodological quality. One trial compared laser trabeculoplasty with topical beta-blocker to no intervention in early glaucoma. The risk of glaucoma progression was higher in the control group at six years of follow up (risk ratio (RR) 0.71 95% confidence interval (CI) 0.53 to 0.95). No difference in health-related quality of life was observed between the two groups. Three trials compared laser trabeculoplasty to medication (regimens used before the 1990s) in people with newly diagnosed OAG. The risk of uncontrolled intraocular pressure (IOP) was higher in the medication group compared to the trabeculoplasty group at six months and two years of follow up. Three trials compared laser trabeculoplasty with trabeculectomy. The risk of uncontrolled IOP was significantly higher in the trabeculoplasty group at six months but significant heterogeneity was observed at two years. Diode and selective laser are compared to argon laser trabeculoplasty in three trials and there is some evidence showing a comparable effect in controlling IOP at six months and one year of follow up.

AUTHORS' CONCLUSIONS

Evidence suggests that, in people with newly diagnosed OAG, the risk of uncontrolled IOP is higher in people treated with medication used before the 1990s when compared to laser trabeculoplasty at two years follow up. Trabeculoplasty is less effective than trabeculectomy in controlling IOP at six months and two years follow up. Different laser technology and protocol modalities were compared to the traditional laser trabeculoplasty and more evidence is necessary to determine if they are equivalent or not. There is no evidence to determine the effectiveness of laser trabeculoplasty compared to contemporary medication (prostaglandin analogues, topical anhydrase inhibitors and alpha2-agonists) and also with contemporary surgical techniques. Also there should be further investigation in to the effectiveness of laser trabeculoplasty in specific racial groups, specific diagnostic groups, such as pseudoexfoliation and pigmentary glaucoma and different stages of OAG. More research is also required determining cost-effectiveness of laser trabeculoplasty in the management of glaucoma.

High Failure Rate Associated With 180?? Selective Laser Trabeculoplasty

PURPOSE

To determine the efficacy of selective laser trabeculoplasty (SLT) in a tertiary care referral center.

PATIENTS AND METHODS

In this retrospective study of selective laser trabeculoplasty performed by five physicians, 94 eyes from 94 patients were included. A majority (83/92, 90%) underwent 180 degrees selective laser trabeculoplasty. Selective laser trabeculoplasty failure was defined in two ways: (1) IOP decrease <3 mm Hg (definition one), or (2) IOP decrease <20% (definition two), on two successive visits > or =4 weeks after SLT.

RESULTS

Overall failure rates were 68% (64/94) and 75% (70/94) (by definitions one and two, respectively). By survival/life-table analysis, mean time to failure was 6 months and 5.5 months, by definitions one and two, respectively. By the end of the study (14.5 months), the failure rates were 86% and 92% by definitions one and two, respectively. By each definition, in both univariable and multivariable analysis, only lower baseline IOP was a significant predictor of failure.

CONCLUSIONS

Selective laser trabeculoplasty had an overall low success rate in our tertiary clinic population, with overall failure rates of 68% to 74% in those who underwent 180 degrees selective laser trabeculoplasty.

The effect of argon laser trabeculoplasty on the blood-aqueous barrier and intraocular pressure in human glaucomatous eyes treated with diclofenac 0.1%

BACKGROUND

We studied the effect of argon laser trabeculoplasty (ALT) on the blood-aqueous barrier (BAB) in 41 eyes of 41 patients with primary open-angle glaucoma, pseudoexfoliation glaucoma, or pigment dispersion glaucoma using the Fluorotron Master II.

METHODS

Fluorophotometry was performed the day before ALT and on the 3rd day after surgery at 30 and 60 min after intravenous injection of 7 mg/kg body weight sodium fluorescein 10%. Intraocular pressure (IOP) was measured using Goldmann applanation tonometry on the day before surgery and at 3rd days and 1 year (mean) after ALT. Patients were treated with argon laser by one surgeon (180 degrees, 0.1 s, 50 microns 0.6-1.0 W, 56 laser burns). Eyes were randomly assigned to either diclofenac-sodium 0.1% eye drops or vehicle. Eye drops were applied six times 1 h before ALT into the operated eyes and five times daily for 3 days postoperatively.

RESULTS

On the 3rd day after ALT there was significant disruption of the BAB in the placebo-treated eyes compared to the diclofenac 0.1%-treated eyes. In the placebo-treated eyes as well as in diclofenac-sodium 0.1%-treated eyes there was a significant decrease of IOP postoperatively for up to 1 year. There was no significant difference concerning the IOP reduction after 1 year. Diclofenac-sodium 0.1% eye drops significantly stabilized the BAB on the 3rd day after ALT, compared to placebo, in this model.

CONCLUSION

Diclofenac-sodium 0.1% significantly stabilized the disruption of the blood-aqueous barrier on the 3rd day after ALT. Concerning the IOP-lowering effect of ALT, the postoperative application of steroids should be avoided.

Laser trabeculoplasty

Over a decade, laser trabeculoplasty has evolved from being a novel new treatment to one that is a commonly accepted intervention in the management of open-angle glaucoma. Despite its widespread use, however, there are still many unanswered questions about laser trabeculoplasty, including its mechanism of action and the ideal treatment parameters. In this review, we will discuss the history of the technique, the clinical experience, and some of the experimental studies that have been conducted to answer the questions regarding its mechanism of action.

Long-term efficacy of low power argon laser trabeculoplasty

We studied the long-term efficacy of argon laser trabeculoplasty, applying low-power (a mean of 450 mW), a duration of 0.1 second, and a small number of burns (a mean total energy of 1.85 J) over 90 to 120 degrees of the trabecular meshwork. Fifty-four eyes with poorly controlled open-angle glaucoma were treated. The mean follow-up was 46 months. The mean intraocular pressure decrease was 5.3 mmHg in 35 eyes at one year, 6.1 mmHg in 23 eyes at 3 years, 5.1 mmHg in 13 eyes at 5 years, and 5.4 mmHg in 5 eyes at 6 years. Life-table analysis showed that the probability of success was 58% at one year, 49% at 3 years, and 46% at 5 years. Both the incidence and magnitude of the intraocular pressure rise in the early post-laser period were minimal and no serious complications were observed.

The immediate pressure response to primary laser trabeculoplasty--a comparison of one- and two-stage treatment

The immediate pressure response to primary LTP was studied prospectively in 40 eyes randomised to one- and two-stage treatment in 360 degrees of the trabecular meshwork. There were 26 eyes with glaucoma capsulare and 14 with glaucoma simplex. Mean prelaser IOP was 32.8 mmHg in the former, and 35.5 mmHg in the latter group. The frequency and magnitude of postlaser pressure increase were the same in both groups when taking into consideration the pressure spikes in both 180 degrees sessions. The pressure increase was higher than in earlier reports on LTP in presurgical glaucoma patients on maximum medication. Almost all IOP elevations appeared during the first 2 h following laser treatment. The results were the same in both groups 6 months after LTP.

The effects of different energy levels in argon laser trabeculoplasty

In a retrospective survey of 143 eyes of 143 patients with chronic open-angle glaucoma, 0.2 second argon laser trabeculoplasty was found to produce a greater decrease in intra-ocular pressure, especially at higher initial values, and was associated with a reduction in the medications used. In addition, fewer patients required further intervention (repeat trabeculoplasty or drainage surgery) compared with those undergoing 0.1 second trabeculoplasty. This effect may have occurred because of the difference in the mean energy delivered between the two groups, which arose chiefly as a result of the duration employed.

Repeated 50 burn/180 degree argon laser trabeculoplasty

Thirty-five repeated 50-spot/180 degree argon laser trabeculoplasties (ALT) are prospectively compared to as many first ALT's. The distribution of the treatment variables possibly affecting the results was almost identical between the two groups. The postoperative intraocular pressure decrease was statistically significant in both groups but it was significantly smaller in the re-ALT group as compared with the pressure reduction taking place in the group receiving their first ALT.

Long-term results of low power, long duration laser trabeculoplasty

We performed argon laser trabeculoplasty using 0.2-second duration on 15 patients with primary open-angle glaucoma. We then retrospectively compared the results to a similar group of 14 patients on whom a duration of 0.1 second was used. Power was titrated to achieve blanching or small bubble formation. All the other treatment variables were kept constant. Before treatment, the two groups did not differ in mean age, visual acuity, intraocular pressure, or number of drugs. After treatment, there was a 7 to 8 mm Hg decrease in intraocular pressure for both groups over a two-year follow-up period. No statistically significant difference between the two groups was observed for intraocular pressure, visual acuity, or drug score at the various follow-up periods. No patient required subsequent filtering surgery.

Primary lasertrabeculoplasty a comparison of 50 spots in 180 degrees and 100 spots in 360 degrees of the trabecular meshwork

Primary LTP was performed in 20 eyes with 50 spots in 180 degrees and in 26 eyes with 100 spots in 360 degrees of the trabecular meshwork. These eyes had received no earlier glaucoma medication. They were followed prospectively for 12 months. Prelaser IOP was 36.3 +/- 8.0 mmHg in the 50 spot group and 35.9 +/- 6.6 mmHg in the 100 spot group. Treatment was considered successful if IOP was less than or equal to 22 mmHg with no medication and no further disk damage or loss of visual field. The success rate 12 months after LTP was 15% in the 50 spot group and 69% in the 100 spot group.

Low power argon laser trabeculoplasty

Sixty-seven consecutive argon laser trabeculoplasties to as many patients were retrospectively followed-up for 3 to 12 (mean 7) months. The laser power used was substantially lower than originally proposed by Wise & Witter (1979) ranging from 100 mW to 500 mW. Factors influencing the outcome of low power trabebuloplasty were evaluated. The statistical analysis of the data was performed using multiple regression analysis, analysis of variance, t-test and chi 2-test. The mean success rate remained relatively low (33%). In the high power capsular glaucoma group it was 50%.

Argon laser trabeculoplasty and the open-angle glaucomas

Argon laser trabeculoplasty (ALT) was used to treat 237 eyes of 156 presurgical patients with various open-angle glaucomas. Patients with primary open-angle glaucoma formed the largest group; intraocular pressure (IOP) control judged clinically to be adequate was achieved in 77.3% of eyes. Eyes with pseudoexfoliative glaucoma demonstrated the greatest IOP reduction achieving control in 90.7%. Eyes with combined-mechanism glaucoma underwent argon laser iridectomy prior to ALT. One month after ALT the IOP was considered adequate in 70% of eyes. ALT may benefit eyes with low-tension glaucoma, pigmentary glaucoma and aphakic open-angle glaucoma. Treatment failures were frequent in eyes with angle recession and uveitis. Complications included IOP elevation (7.8%) and mild iritis; technique modifications minimized their frequency and intensity. ALT demonstrated an excellent benefit-to-risk ratio. Its effect additive to medications, ALT often permitted a reduction in the medical regimen, but rarely cessation of drug therapy. ALT is recommended as an alternative to drainage surgery.

Laser therapy for glaucoma

Three laser techniques for the treatment of glaucoma are described. The short-burn technique of argon laser iridotomy permitted perforation of the peripheral iris in one session without serious complications, thereby alleviating pupillary block in angle-closure glaucoma. The rates of successful intraocular pressure (IOP) control and visual acuity loss due to cataract progression were similar in laser iridotomy and surgical iridectomy. The tonographic outflow facility remained unchanged after argon laser iridotomy. Techniques of argon laser trabeculoplasty (ALT) to the anterior and posterior aspects of the trabecular band were evaluated. The anterior ALT gave fewer complications, but a lower IOP control rate than the posterior ALT. Posterior ALT over 180 degrees with about 50 burns gave fewer complications than treatment over 360 degrees with about 100 burns, yet the final effects in IOP control were better after the 180 degrees than after the 360 degrees treatment. Nd-YAG laser irradiation can separate dysgenetic iris insertion from the trabecular band in developmental glaucoma without serious complications. This Nd-YAG laser goniotomy may be useful for the treatment of juvenile primary developmental glaucoma.

Two-stage argon laser trabeculoplasty in open-angle glaucoma

Forty-five adults with primary open-angle glaucoma received argon laser trabeculoplasty in two stages (180 degrees in each session) separated by one month. The indication for argon laser trabeculoplasty in each case was uncontrolled glaucoma consisting of progressive optic disk cupping and visual field loss despite maximally tolerable medication. A P value of .01 by Student's two-tailed paired t-test was used for statistical significance in the analysis of the intraocular pressure data. In most cases, the greatest reduction in intraocular pressure followed stage 1. Some patients received no additional benefit from stage 2; in other cases, the second stage was not only beneficial but provided most of the reduction in pressure. The pretreatment intraocular pressure level influenced the response to laser therapy. Patients with the highest pretreatment intraocular pressures received the most benefit. Both stages were complicated by a transient postoperative increase of 5 mm Hg or more in 12 patients (approximately 19%).