High 20-year incidence of primary open-angle glaucoma in OHT
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The cumulative incidence of primary open-angle glaucoma after 20 years was almost 50% in patients with ocular hypertension, and the cumulative incidence of visual field loss was 25%, according to a study published in JAMA Ophthalmology.
“Ocular hypertension (OHT), a common condition, is a leading risk factor for the development of primary open-angle glaucoma (POAG),” Michael A. Kass, MD, Bernard Becker Professor of Ophthalmology and Vsual Sciences at Washington University School of Medicine in St. Louis, and colleagues wrote. “The Ocular Hypertension Treatment Study (OHTS) was designed to address the debate regarding the management of patients with OHT.”
Kass and colleagues enrolled 1,636 individuals (mean age, 55.4 years) in the OHTS to determine the cumulative incidence and severity of POAG after 20 years of follow-up or within 2 years of death.
The study was conducted in three phases: In phase 1, from February 1994 to June 2002, participants were randomized to either the topical ocular hypotensive medication or close observation groups; in phase 2, from June 2002 to December 2008, both randomized groups received medication, and beginning in 2009, treatment was no longer dictated by study protocol; in phase 3, from January 2016 to April 2019, study participants underwent ophthalmic examinations and visual function assessments. Researchers performed analyses from July 2019 to December 2020.
After adjusting for exposure time, the 20-year cumulative incidence of POAG in one or both eyes was 45.6% (95% CI, 42.3-48.8) among all study participants, including 49.3% (95% CI, 44.5-53.8) of participants in the observation group and 41.9% (95% CI, 37.2-46.3) of participants in the medication group. The 20-year cumulative incidence for visual field loss was 25.2% (95% CI, 22.5-27.8).
Researchers further categorized patients into low-, medium- and high-risk groups using a five-factor baseline model. The cumulative incidence of POAG among participants in each tertile was 31.7% (95% CI, 26.4-36.6), 47.6% (95% CI, 41.6-53.0) and 59.8% (95% CI, 53.1-65.5), respectively.
The cumulative incidence of POAG also was found to be highest among Black/African American participants (55.2%; 95% CI, 47.9-61.5) compared with participants of other races (42.7%; 95% CI, 38.9-46.3).
“These findings, combined with the use of a prediction model, may help to inform clinicians and patients about the prognosis of OHT and facilitate patient-specific management that takes into consideration age, health status, life expectancy and personal preference,” Kass and colleagues concluded.
Perspective
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What’s the difference between the OHTS and the Jelly of the Month Club? The OHTS is the gift that keeps on giving for decades, not just the whole year.
This landmark study has now informed the management of patients with OHT for 20 years. Arguably its most important contribution has been clarifying that not all individuals with elevated IOP should be treated identically.
While reducing IOP by just shy of 23% halved the 5-year incidence of OAG (from 9.5% to 4.4%) across the entire cohort, a number of risk factors (including age, IOP, vertical cup-to-disc ratio, visual field pattern standard deviation and, perhaps most famously, central corneal thickness) were identified, allowing stratification of both risk and treatment.
After 20 years, the incidence of OAG across the remaining cohort was nearly 50% (slightly higher in Black people, and lower in patients initially randomized to treatment), although manifest visual field loss was present in only 25%. However, persons in the highest risk tertile had nearly double the incidence of glaucoma than those in the lowest, reinforcing the importance of formally gauging risk prior to initiating treatment, being more aggressive when indicated and less so when not.
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