In advanced glaucoma, medication alone no longer reduces intraocular pressure adequately, and the eye has field defects. Before 1980, some type of filtering surgery, such as trabeculectomy, was the usual method of intervention. Since then, laser trabeculoplasty has become a popular alternative. Sometimes the first intervention chosen succeeds in controlling pressure for many years; at other times, the success lasts only a few weeks or months. Because success is limited, some patients, over time, need to undergo a sequence of surgical interventions. Little is known about which sequence gives the best long-range outcome.

The Advanced Glaucoma Intervention Study (AGIS) is designed to provide a comprehensive assessment of the long-range outcomes of medical and surgical management in advanced glaucoma. The study uses visual function status to compare two intervention sequences in managing the disease.

Eligible eyes are randomly assigned to one of two intervention sequences: (1) trabeculectomy, followed by argon laser trabeculoplasty (ALT) should trabeculectomy fail, followed by a second trabeculectomy should ALT fail; or (2) ALT, followed by trabeculectomy should ALT fail, followed by another trabeculectomy should the first trabeculectomy fail. Antifibrotic agents may be used as an adjunct to trabeculectomy, but only in eyes with a previous history of invasive surgery. Eyes that fail the entire assigned sequence of interventions are managed at the discretion of the AGIS physician in collaboration with the patient.

Interventions are supplemented with medical treatment as needed. A total of 789 eyes with advanced glaucoma have been enrolled. All patients are being followed under a standardized protocol for a minimum of 5 years to determine degree of visual function loss, failure rates of interventions, rates of complications, and need for supplemental therapy.

After the initial intervention, followup examinations are scheduled at 1 week, 4 weeks, 3 months, 6 months, and every 6 months thereafter. After second and third interventions, followup examinations are scheduled at 1 and 4 weeks. Additional visits are scheduled as necessary for the management of the disease.

The primary outcome variable in AGIS is average percent of eyes with decrease of vision, where decrease of vision is a substantial decline of either visual field or visual acuity attributable to the effect of glaucoma. Secondary outcome variables include sustained decrease of vision, failure of interventions, number of prescribed glaucoma medications, and level of intraocular pressure. An ancillary study is assessing filtering bleb encapsulation.