As first-line treatment, lasers for glaucoma?

Issue: February 1996

BALTIMORE—The follow-up results of a 9-year study concluded that argon laser trabeculoplasty (ALT) is at least as effective as topical therapy for first-line treatment of primary open-angle glaucoma.

According to the authors of the Glaucoma Laser Trial Follow-up Study, the results showed that "initial treatment with argon laser trabeculoplasty was both safe and effective." The study is a follow-up of the Glaucoma Laser Trial (GLT), which was conducted from 1984 to 1987.

But not all primary care optometrists are ready to change their treatment regimen. Anthony B. Litwak, OD, a glaucoma practitioner here, said the results of the study may cause practitioners to consider ALT earlier in treatment, "but as far as initial treatment, in a patient who is compliant and doesn't have contraindications, I'm still going to use the topical medications as a first-line therapy."

Jimmy D. Bartlett, OD, of Birmingham, said that the study's implication on glaucoma care "is to just sit tight," because the generally accepted practice in this country is medical therapy first. He said that if one or two topical medications do not work, "Clearly laser is the next best alternative."

Lower IOP with ALT

--- Normal nerve fiber layer.
[photo] --- A focal wedge defect in a glaucoma patient.

The study, which appeared in December's American Journal of Ophthalmology and was supported by the National Eye Institute, showed that mean IOP was lower for eyes treated with ALT than in eyes treated with a topical medication, and analysis of visual field data showed that eyes treated with ALT had better visual fields than eyes treated with drugs. The eyes initially treated with drugs also showed slightly more deterioration in optic nerve head assessment.

The study evaluated 203 of the 271 patients who originally participated in the GLT. The patients had an IOP of at least 22 mm Hg, and met one of three criteria:

a glaucomatous visual field defect in at least one eye;
IOP of at least 27 mm Hg in one eye and 31 mm Hg in the other, and cup-to-disk ratio disparity of -0.3 or less or 0.3 or more; or
IOP of at least 31 mm Hg in both eyes and cup-to-disk ratio of at least 0.8 in at least one eye.

One eye was treated with ALT, and the other with 0.5% timolol (Timoptic, Merck) twice daily. Over nine years, both sets of eyes showed a reduction in IOP. The eyes originally treated with ALT had 1.2 mm Hg more reduction than the timolol eyes. The ALT eyes also had a 0.6 dB greater improvement in visual field.

Clinical significance?

--- Diffuse thinning of the nerve layer in a glaucoma patient.

Bartlett said the results leave unanswered questions. "Although the statistics show a statistical difference between the two groups," he said, "clinically you would have to say that there was probably no difference at all."

And Litwak said that the study ignored the contralateral IOP-lowering effect of topical beta-blockers.

Two years after initial treatment more than half of the eyes in both groups needed additional medication to control IOP. However, only 56% of the ALT eyes needed additional treatment at this stage compared to 70% of the beta-blocker eyes.

While both sets of eyes experienced side effects, the study said the effects from ALT "were temporary or made no difference in the long run." Also, the eyes treated initially with ALT needed less medication overall than the beta-blocker eyes.