A new calculator model can help eye doctors estimate a patients risk of converting from ocular hypertension to glaucoma, and determine whether to initiate therapy.

The glaucoma risk calculator model uses key patient risk factors, which were identified in the Ocular Hypertension Treatment Study, to assess a patients risk of converting from ocular hypertension to glaucoma within the next five years. These risk factors include age, IOP, central corneal thickness, vertical cup-to-disc ratio, visual field pattern standard deviation values and diabetic status.

The calculator model and Scoring Tool for Assessing Risk were developed by Robert Weinreb, M.D., and researched by Felipe A. Medeiros, M.D., and colleagues, from the Hamilton Glaucoma Center at the University of California San Diego.

Practitioners position their clinical exam findings of the risk factors at various points on the Scoring Tool for Assessing Risk to determine a patients glaucoma risk value. If the risk of converting from ocular hypertension to glaucoma is 5% or less, no treatment recommendation is indicated, says optometrist Leo Semes, of Birmingham, Ala., who uses the calculator on ocular hypertensives. If the risk is 5% to 10%, practitioners should consider other factors that could tip the scale in favor of a treatment recommendation, and if the risk is 15% or greater, treatment should be strongly considered, he adds.

Clinicians should note that diabetes is protective against conversion from ocular hypertension to glaucoma, say Dr. Semes and his colleague, Paul Schacknow, M.D., Ph.D., from Lake Worth, Fla. If patients are diabetics, their glaucoma risk goes down.

This may be misleading because it contradicts other studies, and therefore may limit the interpretation of the results of the calculator, Dr. Schacknow says.

What I have found useful about the calculator is that I can present the results to patients to show them why I recommend that they be observed or treated, Dr. Semes says. Also, I can look at the data and say, What will happen to the risk value if I wait for a parameter to reach a certain level? This consideration also can help clinicians determine whether to watch the patient or to start treatment.