Original article
Effects of Argon Laser Trabeculoplasty in the Early Manifest Glaucoma Trial

https://doi.org/10.1016/j.ajo.2011.04.036Get rights and content

Purpose

To analyze reduction of intraocular pressure (IOP) by argon laser trabeculoplasty (ALT) in the Early Manifest Glaucoma Trial and factors influencing the effect of such treatment.

Design

Cohort study based on 127 patients from the treatment group of the Early Manifest Glaucoma Trial, a randomized clinical trial.

Methods

Patients randomized to the treatment arm of the Early Manifest Glaucoma Trial received a standard treatment protocol (topical betaxolol hydrochloride followed by 360-degree ALT) and then were followed up prospectively at 3-month intervals for up to 8 years. One eye per patient was included in the analyses. We investigated the relationship between IOP before ALT and subsequent IOP reduction and other factors that might have influenced the effect of ALT, including stage of the disease, trabecular pigmentation, presence of exfoliation syndrome, and treating surgeon.

Results

The mean ± standard deviation IOP before ALT and after betaxolol treatment was 18.1 ± 3.9 mm Hg, and the mean ± standard deviation short-term IOP reduction 3 months after ALT was 2.8 ± 3.9 mm Hg (12.6 ± 20.5%). The IOP before ALT strongly affected IOP reduction (P < .001); each 3-mm Hg higher IOP before ALT value was associated with an additional mean IOP reduction of approximately 2 mm Hg. The treating surgeons also had a significant impact on IOP reduction (P = 0.001), with mean values ranging from 5.8 to −1.3 mm Hg.

Conclusions

In this cohort, which included many patients with low IOP levels, IOP before ALT markedly influenced the IOP reduction induced by ALT, seen as a much larger decrease in eyes with higher IOP before ALT. The treating surgeon also had a significant impact on ALT outcome.

Section snippets

Methods

The EMGT study design has been described in detail previously.6 Briefly, this trial included patients with newly diagnosed and untreated primary open-angle glaucoma (POAG) or exfoliation glaucoma with early to moderate damage. Most patients were found in a large, population-based screening of 44 000 elderly citizens in the cities of Malmö and Helsingborg, Sweden. Eligible eyes had glaucoma with established visual field damage, repeatedly demonstrated by the Humphrey 30-2 full-threshold test and

Results

Follow-up time ranged from at least 3 months to a maximum of 8 years (mean, 57 months; median, 60 months). Among the 127 patients, 3 (2.4%) were lost to follow-up during the study period. Sixty-four (50.4%) patients progressed, and 14 (11%) died. For 9 (7.1%) patients who either discontinued betaxolol or had a change of therapy, we included IOP values only as long as treatment remained unchanged.

Discussion

The present results regarding EMGT patients show a mean IOP reduction of 2.8 mm Hg 3 months after ALT, and the IOP slopes suggest that the mean pressure-lowering effect decreased slightly over time. Higher IOP before ALT was associated with a considerably and significantly better pressure-reducing influence of ALT. Moreover, the treating surgeon (P = .001) was another important factor related to the effectiveness of ALT.

The current study had strengths and weaknesses. Among the former were the

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