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).