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New glaucoma risk assessment tool helps identify patients in need of treatment
Clinicians discussed how to lower IOP most effectively, how to identify and treat those at risk for developing glaucoma.
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Robert N. Weinreb |
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.
“This is what we’ve all been waiting for – the ability to calculate the risk [of glaucoma progression] in individual patients,” Dr. Weinreb said.
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.”
The risk calculator, which resembles a slide rule, was made available by Pfizer to attendees of the AAO and will be distributed to specialists worldwide by company representatives in the future. The research by Dr. Weinreb and colleagues that led to the development of the calculator was supported by Pfizer, according to the company.
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 physician 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. “It is a tool, and not meant to replace judgment.”
Dr. Weinreb added that the risk assessment tool presents an opportunity to track patients over time to see if the predictions are accurate and to “get a better assessment of the benefit of lowering IOP.”
“This is not an initiative to go out and put everyone on treatment,” he said. “It’s an initiative to more responsibly treat those who are most in need.”
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.
Other glaucoma news from the AAO meeting and from the Glaucoma Subspecialty Day that preceded the meeting is recapped below. These items originally appeared as daily coverage from the meeting on the OSN Web site, OSNSuperSite.com.
Treating ocular hypertensive patients
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.
Miniature glaucoma shunt
A miniature glaucoma shunt implanted under a scleral flap was equally successful in lowering IOP as trabeculectomy but had a lower hypotony risk, according to a poster presentation.
Peter J.G. Maris, MD, and Peter Andreas Netland, MD, PhD, reported the results of a comparative case-control series of 100 eyes, half of which were treated with the ExPress miniature glaucoma shunt and the other half with trabeculectomy.
IOP dropped 53.7% in eyes in which the ExPress shunt was implanted under a scleral flap, compared with 53.6% in eyes that underwent trabeculectomy. Hypotony occurred in 6% of the eyes with the implant, compared with 34% of the eyes with trabeculectomy.
“The ExPress implant under a scleral flap had similar IOP-lowering efficacy, with a lower rate of hypotony, compared with trabeculectomy,” the study authors concluded.
The ExPress miniature glaucoma shunt is manufactured by Optonol Ltd.
Corneal hysteresis a factor in IOP measurement
Direct measurement of the mechanical properties of the cornea offers the possibility of more accurate IOP measurement, according to David F. Garway-Heath, MD, MBBS.
Applying a “correction factor” to IOP to compensate for the error induced by central corneal thickness is “inadvisable,” Dr. Garway-Heath said. Corneal biomechanical factors may have a greater impact on measured IOP than corneal thickness, he said, and corneal hysteresis is one way of measuring these factors.
Dr. Garway-Heath spoke about two new devices for measuring IOP that either try to take mechanical properties into account or to eliminate their influence on IOP.
He said the Pascal Dynamic Contour Tonometer, from Ziemer Ophthalmic Systems, attempts to eliminate corneal biomechanical properties during IOP measurement. The device provides direct transcorneal measurement of IOP using the principle of contour matching instead of applanation, according to the manufacturer.
Dr. Garway-Heath’s presentation focused on another new instrument, the Ocular Response Analyzer from Reichert Ophthalmics. The device measures the cornea’s response to indentation twice: first as the cornea flattens, and again as it returns to its normal shape. The difference between the first and second measurements, called corneal hysteresis, is an indication of the dampening effect of the cornea.
“Hysteresis is a direct measurement that may relate to IOP more directly than central corneal thickness,” Dr. Garway-Heath said.
Early studies indicate that hysteresis is related to central corneal thickness and weakly associated with age, he said. IOP measurements with the Ocular Response Analyzer that take account of hysteresis are independent of corneal thickness, he said.
Patients with low vision require new skills, strategies
Glaucoma specialists must develop better skills for dealing with patients with functional vision impairment, according to Lylas G. Mogk, MD. Dr. Mogk spoke about strategies for making an ophthalmic office more friendly for patients with poor functional vision due to glaucoma.
Dr. Mogk said not only visual field loss, but also loss of contrast sensitivity and poor dark adaptation, are visual effects of glaucoma that can affect patients’ quality of life and lead to loss of confidence and mobility.
She made five suggestions — three things to avoid and two things to do — to adapt one’s practice for dealing with patients with function vision loss.
“We must avoid drawing conclusions about function from tests that measure disease,” Dr. Mogk said. While a patient’s visual field test may objectively appear good, other factors such as difficulty with glare or the non-ophthalmic effects of aging may be hindering that patient’s mobility or driving, she said.
Second, the physician should not underestimate the impact of contrast sensitivity and visual field loss on the patient’s quality of life. Third, the physician should not underestimate the benefits of training for dealing with functional loss. Devices and strategies to aid reading, resources for transportation and other services can give a tremendous boost to a patient’s quality of life, Dr. Mogk said.
“Our role includes helping these patients to cope with their functional loss,” she said.
Finally, she said, “Give your patients the information they need.”
Information on this AAO initiative can be found at www.aao.org/patient_ed/smartsight.cfm.
Device reminds patients to apply drops
A new device from Allergan, the Lumigan Compliance Aid, was released here to assist glaucoma and ocular hypertension patients in taking their daily dose of the bimatoprost ophthalmic solution. The device, which was designed to fit all Lumigan bottle sizes, contains a light timed to flash and an optional sound alarm if the bottle has not been removed for dosing in 24 hours. After a patient removes the bottle and replaces it, the device resets and will begin flashing 24 hours later if the bottle has not been removed again.
Joseph Schultz, senior vice president of U.S. Eye Care, said at an Allergan press conference that the device is a first-generation product and will improve. He said it should encourage patient participation, a key part of glaucoma and ocular hypertension treatment.
“Compliance is important to outcomes,” Mr. Schultz said.