Risk assessment will assist in predicting chance of glaucoma

But one clinician notes that a risk calculator cannot predict the future for an individual patient; it can only make generalizations.

Issue: December 1, 2005

ByErin L. Boyle

The introduction of risk assessment into the field of glaucoma promises to help physicians care for their patients with glaucoma more effectively and efficiently, glaucoma experts say. But clinicians must remember that new glaucoma risk assessment tools are based on studies in specific populations and cannot predict the future for an individual patient, one researcher cautioned.

Robert N. Weinreb

Risk assessment has been used in cardiovascular medicine for half a century with good results. Recently, ophthalmic researchers have applied the principles of risk assessment to glaucoma, resulting in the new risk calculator introduced by Pfizer Ophthalmics at the American Academy of Ophthalmology meeting.

That risk calculator, based on a study by Felipe A. Medeiros, MD, Robert N. Weinreb, MD, and colleagues, is designed to assist in determining a patient’s risk for progressing from ocular hypertension to glaucoma based on six risk factors.

Dr. Weinreb spoke about the risk calculator at a press briefing at the AAO meeting. He said the calculator may be a useful tool for clinicians who are managing ocular hypertensive patients.

“It provides the ability to estimate the risk of glaucoma progression in individual patients,” he said.

Dr. Weinreb said the device seeks to determine which patients are at high, moderate and low risk for progressing to glaucoma from ocular hypertension.

“By identifying patients who are at highest risk for conversion from ocular hypertension to glaucoma, diagnostic and treatment resources can be more effectively allocated,” he said.

Word of caution

During a spotlight session on glaucoma at the AAO meeting, Anne L. Coleman, MD, PhD, spoke about “risk assessment and predicting the future” for glaucoma patients. In her presentation, she recommended that physicians exercise judgment when using a risk calculator because the information used to design the tool was generalized from a large study population.

Dr. Coleman said, however, that a risk calculator can provide medical professionals with useful information for designing management strategies for patients at risk of developing glaucoma. She recommended that physicians assess patients’ risk on a case-by-case basis.

“The risk calculators and point systems will not precisely predict the future for individual patients, but it is going to give the clinician an idea about that patient’s risk for glaucoma based on a group of similar patients,” Dr. Coleman said. “You have to remember that patient preferences, the impact of glaucoma in the patient’s life and also life expectancy are not part of these risk calculators and really need to be considered when you trying to decide whether to start treatment on an ocular hypertensive patient.”

Possibility of glaucoma

Through a grant to the University of California, San Diego, the risk calculator, which resembles a slide rule, was made available by Pfizer to attendees of AAO. Pfizer supported in part the research by Dr. Weinreb and colleagues that led to the development of the calculator.

The device calculates risk based on a formula derived from published findings of the Ocular Hypertension Treatment Study (OHTS) and validated against 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 result shows the calculated risk of glaucoma development in 5 years for that patient.

Dr. Weinreb said a group of glaucoma experts had reached consensus previously that patients whose risk is 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. However, he said, each clinician can use his or her own risk threshold to guide treatment.

Risk assessment studies

Drs. Medeiros, Weinreb and colleagues conducted one of the two studies used to create the risk calculator. Their study, published in October in the Archives of Ophthalmology, sought to validate on an independent population a predictive model developed from the results of OHTS.

The independent population used in their study included 126 ocular hypertensive patients participating in the Diagnostic Innovations in Glaucoma Study.

“Our results suggest that an OHTS-derived predictive model can be useful to assess the risk of glaucoma development in untreated patients with ocular hypertension,” Dr. Medeiros and colleagues said in their report in the Archives. “Incorporation of such a risk model into clinical practice could provide a better assessment of the global risk for disease development in a particular patient and help in clinical decision making regarding treatment.”

Study population

According to Dr. Coleman, the OHTS study population had excellent representation of Caucasian and African Americans; however, it lacked Asian representation.

That is an important consideration in the overall results and validity of the risk calculator, she said.

“When you are using risk calculators and these point systems that have been developed from the OHTS data, it’s important to remember that you must assume that your patient is exchangeable with those enrolled in OHTS, which means your patient could have been enrolled in that study,” Dr. Coleman said.

“You need to remember that the risk factors being used with the point system and calculators are translating the baseline predictive factors, and they’re turning them into multipliers for the baseline risk. There is an assumption that this method is correct,” she said. “You need to realize that what is defined as ‘glaucoma’ in the Ocular Hypertension Treatment Study is also what’s used When you’re calculating the risk of glaucoma with the risk calculators or the point systems.”

For Your Information:

Anne L. Coleman, MD, PhD, can be reached at the Jules Stein Eye Institute, UCLA, 100 Stein Plaza 2-118, Los Angeles, CA 90095-7004; 310-825-5298; fax: 310-206-7773; e-mail: colemana@ucla.edu. Dr. Coleman has received research support from Eyetech/Pfizer. She has no direct financial interest in the products mentioned in this article.

Robert N. Weinreb, MD, director of the Hamilton Glaucoma Center at the University of California, San Diego, can be reached at 9500 Gilman Drive, La Jolla, CA 92093-0946; 858-534-8824; fax: 858-534-1625; e-mail: weinreb@eyecenter.ucsd.edu.

Felipe A. Medeiros, MD, can be reached at the Hamilton Glaucoma Center of the University of California, San Diego, 9415 Campus Point Drive, 0946, La Jolia, CA, 92093-0946; 858-534-8824; fax: 858-534-1625; e-mail: fmedeiros@eyecenter.ucsd.edu.

Reference:
Medeiros F, Weinreb R, et al. Validation of a predictive model to estimate the risk of conversion from ocular hypertension to glaucoma. Arch Ophthalmol. 2005; 123(10):1351-1360.

Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.