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.