Glaucoma: To Screen or Not to Screen

A nationwide glaucoma screening program for African Americans, who are at particularly high risk for the condition, could be clinically effective.

Few countries have established national screening programs for primary open-angle glaucoma (POAG), the most common form of glaucoma. Barriers to effective screening include the disease’s considerable physiologic variation and the challenge of differentiating between people who have normal optic nerves and those who have early disease. Further, up to 40% of optic fibers can be damaged before vision loss occurs. The criteria for population-based screening generally has several drivers:

• A simple, safe, cost-effective test that is precise and validated should be available
• The distribution of test values in the population should be known, and experts should choose an appropriate cut-off point for referral
• The population that is screened should accept the test
• Experts should agree on further treatment steps when patients meet the definition for disease

No single test for glaucoma exists. Clinicians can use visual field testing, ophthalmoscopic observation of the optic nerve head, and/or tonometric intraocular pressure (IOP) measurement. Widespread screening for IOP will not catch all cases of glaucoma, however, since some patients have normotensive varieties of the condition.

Primary care providers should urge patients who are at high risk for glaucoma—those who have family histories, have elevated IOPs, are African American, are older than 40 years, or have myopia—to be screened annually. However, no data exists indicating how many people are screened, and studies are needed to demonstrate the effectiveness, acceptability, and costs of screening programs in various populations.

Researchers from Beth Israel Deaconess Medical Center and Harvard Medical School published one such study in the March 2012 issue of Archives of Ophthalmology. Using data from the Eye Diseases Prevalence Research Group and the Baltimore Eye Study, they used a computer-based mathematical model to determine if screening in 1 high-risk group—African Americans—could be cost effective.

They found that a national glaucoma screening policy for African American individuals between the ages of 50 and 59 years without known glaucoma would:

• Reduce the lifetime prevalence of undiagnosed glaucoma from 50% to 27%
• Reduce the prevalence of glaucoma-related visual impairment from 4.6% to 4.4%
• Reduce the prevalence of glaucoma-related blindness from 6.1% to 5.6%
• Diagnose 1 person with glaucoma for each 58 people screened
• Prevent 1 person from developing visual impairment for each 875 people screened

The researchers projected that the screening program would cost $80 per screened individual and determined that it could be clinically effective, although its impact on visual impairment and blindness levels might be modest.

Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.