Ocular hypertension study extended to 20 years follow-up

The landmark Ocular Hypertension Study (OHTS) has been funded for a third phase that extends the follow up period to 20 years, Michael A Kass MD told Glaucoma 2015 at the American Academy of Ophthalmology Subspecialty Day in Las Vegas, USA. The information gained will help patients and clinicians make better informed, evidence-based decisions about managing ocular hypertension and early primary open-angle glaucoma (POAG), said Dr Kass in the American Glaucoma Society Lecture.

Launched in 1994, OHTS is a large prospective randomized trial examining the long-term impact of controlling intraocular pressure (IOP) in ocular hypertension (OHT) patients on POAG risk, and associated visual and functional disability. In its first phase, a group of OHT patients receiving IOP-reducing topical drugs progressed to POAG at only 40 per cent of the rate of an un-medicated observation group over five years. This demonstrated that lowering IOP does reduce POAG incidence, said Dr Kass, of Washington University, St Louis, USA.

In its second phase, both OHTS groups received topical IOP-lowering drugs and experienced similar POAG progression rates through 13 years. This showed that early IOP-lowering intervention reduces the cumulative burden of disease, Dr Kass said. The absolute effect was greatest in patients with the highest risk as determined by a prediction model that was developed and validated using OHTS data. It incorporates age, IOP, central corneal thickness, cup–to-disc ratio and field pattern standard deviation as significant risk factors.

The third phase will re-examine all living participants in the original OHTS cohort. The overall goal is to better understand how treating ocular hypertension and early POAG affect the risk of later loss of vision and quality of life – and what can be done to reduce the long-term risks, Dr Kass said.

Specific aims include determining the 20-year incidence of POAG in the OHTS cohort, and developing 20-year models for stratifying the risk of developing POAG, and predicting the rate of visual field loss. Frequency and severity of self-reported limitations associated with POAG will also be determined and correlated with clinical findings, which will help clarify the causal relationship of POAG to disability.

“The true goal of managing patients with ocular hypertension is to prevent the development of functional limitations from POAG,” Dr Kass said. A 20-year model will be particularly helpful because it approaches the life expectancy of patients diagnosed in their 60s and 70s, and half the life expectancy of those diagnosed in their 40s and 50s, he added.