Influence of treatment protocol on the long-term efficacy of argon laser trabeculoplasty

Forty-five phakic eyes of 36 patients with open-angle glaucoma and uncontrolled intraocular pressure despite maximally tolerated medication underwent initial argon laser trabeculoplasty (ALT) in 1981 and 1982 as part of a prospective, randomized study to evaluate the effectiveness of different treatment standards. Each eye had been randomly assigned to receive either 100 laser applications over 360 degrees of trabecular meshwork, 50 applications over 180 degrees , or 50 applications over 360 degrees in a single session. Further treatment in each group was based on clinical standards prevailing at the time. The long-term results were analyzed using Kaplan-Meier survival analyses. By 4 years after initial ALT, six of the 15 remaining eyes in group 1 (40%), one of 14 eyes in group 2 (7%), and two of 13 eyes in group 3 (15%) had undergone filtration surgery, and one eye in group 1 (7%), three eyes in group 2 (21%), and three eyes in group 3 (23%) had received further ALT. By 7 years after initial ALT, seven of the nine remaining eyes in group 1 (78%), one of 12 eyes in group 2 (8%), and four of 12 eyes in group 3 (33%) received filtration surgery, and two eyes in group 1 (22%), three eyes in group 2 (25%), and four eyes in group 3 (33%) had received further ALT. Kaplan-Meier survival curves predict the following probabilities of avoiding either repeat ALT or filtration surgery at 4 years after an initial ALT: group 1, 54 +/- 12%; group 2, 76 +/- 12%; and group 3, 62 +/- 11%. Our results suggest that performing 50 rather than 100 burns at initial ALT may significantly delay the need for additional surgical or repeat laser intervention.