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New glaucoma risk assessment tool helps identify patients in need of treatment

Issue: December 2005

ByDavid W. Mullin

ByLauren Wolkoff

ByTim Donald, ELS

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CHICAGO – A handheld calculator designed to predict the risk of glaucoma progression in patients with ocular hypertension could change the standard of care for glaucoma specialists, according to one of its developers.

Robert N. Weinreb, MD, described the risk calculator at a press briefing sponsored by Pfizer Ophthalmics during the American Academy of Ophthalmology’s annual meeting.

He said the aim of the device is to determine which patients are at high, moderate and low risk for progressing to glaucoma from ocular hypertension and, of those who will go on to develop glaucoma, which ones are likely to sustain functional impairment.

“Our challenge is to identify patients at moderate to high risk for conversion from ocular hypertension to glaucoma and to direct therapy to those patients at high risk,” Dr. Weinreb said. “It is really about a better allocation of our resources.”

In its current form, the device calculates risk based on a simplified version of a formula derived from findings in two independent study populations: the Ocular Hypertension Treatment Study and a subset of patients in the Diagnostic Innovations in Glaucoma Study at the Hamilton Glaucoma Center in San Diego, where Dr. Weinreb is director.

The clinician assesses six factors for each hypertensive patient: age, baseline IOP, central corneal thickness, pattern standard deviation on perimetry, vertical cup-to-disc ratio and whether diabetes is present. These data are configured on the calculator using sliding tabs, and the combined result shows the calculated risk of glaucoma development in 5 years for that particular patient.

Because every specialist’s threshold of treatment is different, the risk calculator specifies that patients shown to have a progression risk of less than 5% should be monitored, those with a risk of 5% to 15% should be considered for treatment, and those with a risk greater than 15% should be recommended for treatment.

Those with moderate risk fall into a “gray zone,” Dr. Weinreb said, and the decision to treat them or not depends on many factors, including overall health status, life expectancy, commitment to treatment, and the adverse events and costs associated with treatment. “This calculator should be an adjunct to, and not a substitute for, the expertise and judgment of the physician,” he said.

Dr. Weinreb noted that this slide-rule-like version of the risk calculator will at some point likely be replaced by a computerized version, but he said this version was intended to be as simple as possible to facilitate widespread acceptance.

Recent trials indicate that lowering IOP in patients with ocular hypertension can delay their conversion to glaucoma. But, with this information in hand, should the clinician treat most of these patients with IOP-lowering medications or treat only those at high risk of progressing to glaucoma?

This issue was debated by two glaucoma experts at Glaucoma Subspecialty Day.

David L. Epstein, MD, argued that “we need to treat more patients rather than less.” Paul R. Lichter, MD, took the view that “we need to decide where to draw the line” and treat only those ocular hypertensive patients with known risk factors for glaucoma, such as ethnicity or family history.

Dr. Epstein, arguing for treating most ocular hypertensive patients, said that he tries to practice by the Golden Rule: “Treat others as you would treat your own eye.” “IOP is not a risk factor for glaucomatous damage, it is a causative factor,” he said.

Making an analogy with the treatment of systemic hypertension, Dr. Epstein noted that five patients with borderline blood pressure elevation are treated in order to protect one patient, because that one patient cannot be identified prospectively. Similarly, he said, “We may need to treat five to save one” from conversion to glaucoma.

Taking the view that only patients with ocular hypertension with known risk factors for glaucoma should be treated, Dr. Lichter noted that the Ocular Hypertension Treatment Study suggested that 20 patients must be treated to prevent one conversion to glaucoma. He said that using Dr. Epstein’s strategy, the negative effects of medication, such as expense, inconvenience and side effects, would be experienced needlessly by 95% of the treated patients.

Responding to Dr. Epstein’s remark about the Golden Rule, Dr. Lichter said, “If it were my eye, I would not want you to treat me, unless I were at high risk.”

“We use a decision tree to decide who to treat,” Dr. Lichter said, including consideration of such risk factors as age, baseline IOP, ethnicity and family history.

“There is no evidence that treating most ocular hypertensive people will help them,” Dr. Lichter said.

This article also appears in Ocular Surgery News, a SLACK publication.