To compare the safety and long-term efficacy of argon laser treatment of the trabecular meshwork with standard medical treatment for primary open-angle glaucoma.

During the last decade, argon laser trabeculoplasty (ALT) has often been used instead of surgery as the treatment of choice in cases of open-angle glaucoma that could not be controlled by drugs. ALT treatment consists of tiny laser burns evenly spaced around the trabecular meshwork. It sometimes has been found to be effective in controlling glaucoma, although many eyes still require some medical treatment.

The Glaucoma Laser Trial (GLT), a randomized, controlled clinical trial, was conducted to determine whether ALT is effective in patients with newly diagnosed, primary, open-angle glaucoma. Each of the 271 patients in the trial received argon laser treatment in one eye and standard topical medication in the other eye. The eye to be started on medicine and the eye that would get the laser treatment were randomly selected. The Glaucoma Laser Trial Followup Study was a followup study of 203 of the 271 patients who enrolled in the Glaucoma Laser Trial. By the close of the Glaucoma Laser Trial Followup Study, median duration of followup since diagnosis of primary, open-angle glaucoma was 7 years (maximum, 9 years).

The argon laser treatment was done in two sessions 1 month apart, with one-half of the trabecular meshwork treated with 45 to 55 laser burns in each session. Patients were seen for a followup visit 3 months after the first laser treatment and every 3 months thereafter for a period of at least 2 years. At each visit, examination of the eyes included a check of intraocular pressure and visual acuity. Visual field examinations were performed 3, 6, and 12 months after randomization and annually thereafter. Disc stereo photographs were taken 6 and 12 months after randomization and annually thereafter.

The results of these examinations determined whether treatment should be changed. If the pressure in either eye had not been reduced to the desired level, the physician changed the medication in the eye treated with drops or started the use of drops in the laser-treated eye according to a standardized procedure being used in the trial. If intraocular pressure was still not successfully reduced, surgery or further laser treatment may have been required.

At the time of recruitment, patients had to be at least 35 years old with an intraocular pressure of at least 22 mm Hg or greater in each eye and evidence of optic nerve damage in at least one eye.