We currently understand the pathophysiology of glaucoma to be a progressive loss of ganglion cells resulting in visual field damage that is related to intraocular pressure (IOP). The goal of treatment is to delay or halt the ganglion cell loss and prevent symptomatic visual loss while attempting not to cause untoward side effects. Although many clinicians now feel that there are several factors involved in the pathogenesis of glaucoma, the only rigorously proven method of treatment is the lowering of IOP.

Glaucoma was first thought of as a surgical disease. The first filtration procedure (not iridectomy) was suggested by Louis de Wecker (1832 to 1906) in 1869. Although the miotic effects of eserine and pilocarpine had been reported in the early 1860s, they were not used for treatment until later. Adolf Weber (1829 to 1915) first introduced these agents as medical treatments of glaucoma in 1876. The first study comparing the two available forms of glaucoma treatment, eserine and iridectomy, was performed at Wills Eye Hospital in 1895 by Zentmayer et al. This study showed that both treatments were equivalent and that a patient’s visual status could be maintained for periods ranging from 5 to 15 years on chronic medical treatment.

The debate over the best initial therapy continues today. Most clinicians use medications as the initial treatment for glaucoma. In the United States, two large studies were performed to compare medical treatment with laser trabeculoplasty (Glaucoma Laser Trial [GLT] and the Selective Laser Trabeculoplasty [SLT] Med Study) and medical treatment with trabeculectomy (Collaborative Initial Glaucoma Treatment Study [CIGTS]). At 2-year follow-up in the GLT, eyes that received argon laser trabeculoplasty (ALT) showed a lower mean IOP (between 1 and 2 mm Hg) than eyes started on timolol but showed no difference in visual field
or acuity. At 7 years, eyes that received ALT had a greater reduction in IOP (1.2 mm Hg) and a greater sensitivity in the visual field (0.6 dB). Prospective randomized controlled trials (e.g., SLT/MED study and Nagar et al.) showed equivalence between SLT and prostaglandin analogues at 1-year follow-up. These results seem to indicate that laser trabeculoplasty is at least as good as contemporary medical treatment for glaucoma.

Results from the CIGTS study show no difference in visual field outcomes despite a lower IOP in the surgical group. One exception noted in CIGTS was that initial surgery led to less visual field progression than initial medicine in patients with advanced field loss at enrollment. Patients with diabetes had more visual field loss over time if treated initially with surgery. Smoking was also found to influence final pressure-lowering responses. We do not understand why these differences exist in different subgroups. Overall, visual acuity and local eye symptoms seem to be worse in the surgical group. However, the CIGTS results do not unequivocally support changing the current paradigm of medical treatment as initial treatment.

In recent years, there has been an explosion of innovation for the surgical treatment of glaucoma. New minimally invasive techniques have emerged. Long-term prospective randomized trials comparing these techniques to trabeculectomy are yet to occur, but case-controlled trials, cohort studies, and trials comparing to phacoemulsification cataract surgery seem to show great safety results. Newer generation devices and techniques attempt to build upon the high degree of safety and improve IOP reduction. The placement of these minimally invasive procedures/implants is yet to be resolved, but their safety profile would argue for involvement earlier than trabeculectomy.