Landmark Glaucoma Clinical Trials

OHTS: Ocular Hypertension Treatment Study

OHTS randomized patients with elevated IOP but no field or disc damage to observation versus topical treatment. Over 5 years, the untreated group converted to POAG at 9.5%; the treated group converted at 4.4%. That gap is the actual evidence base for treating ocular hypertension before any nerve damage has occurred, not just after. A second finding from the same cohort turned out to matter just as much: thin central corneal thickness independently predicted conversion, and it did so even after the investigators corrected for its known effect on tonometry (see IOP physiology and risk factors).

CNTGS & the Low-Pressure Glaucoma Treatment Study

The Collaborative Normal-Tension Glaucoma Study (CNTGS) randomized patients with normal-tension glaucoma to treatment or observation. A 30% IOP reduction significantly slowed visual field progression in the treated arm. Pressure still mattered, even in eyes where it was never technically high. The Low-Pressure Glaucoma Treatment Study picked up where CNTGS left off and added a systemic angle: patients with systemic arterial hypotension progressed faster. Ocular perfusion pressure, not IOP in isolation, drives outcomes in this subgroup. See normal-tension glaucoma for the full clinical picture.

LoGTS also ran a separate drug comparison. Patients were randomized to brimonidine or timolol, and the two produced similar average IOP reduction. Visual field progression occurred in only 9.1% of the brimonidine group compared with 39.2% of the timolol group. Because pressure control was nearly identical between arms, the gap pointed toward a protective effect from brimonidine that isn't fully explained by IOP alone.

The Tajimi Study

This Japanese population-based survey found that normal-tension glaucoma, not high-pressure POAG, accounted for the majority of open-angle glaucoma cases identified. That proportion runs well above what Western cohorts typically report. The finding is a reminder that glaucoma epidemiology varies by population, and that pressure-based screening alone will miss a large share of disease in some groups.

LiGHT: Laser in Glaucoma and ocular Hypertension Trial

LiGHT tested selective laser trabeculoplasty (SLT) as first-line therapy against topical medication as first-line therapy. SLT won on three counts: better disease control, fewer subsequent incisional surgeries, and lower overall cost. That result is why SLT is now offered as a legitimate starting point rather than a fallback for patients who fail or can't tolerate drops. See laser trabeculoplasty for the mechanism this trial is validating.