Adapted from Washington University School of Medicine in St. Louis
Investigators at Washington University School of Medicine in St. Louis have developed a model to identify patients at high risk of developing glaucoma. Their research was presented at the annual meeting of the American Academy of Ophthalmology in Las Vegas.
"The Ocular Hypertension Treatment Study (OHTS) was really designed to answer two questions," says Michael A. Kass, M.D., national chair of the 22-center study and head of the Department of Ophthalmology and Visual Sciences at Washington University School of Medicine. "We wanted to learn whether preventive treatment could reduce the incidence of glaucoma, and we also wanted to learn whether we could determine what risk factors might help us predict which patients will go on to develop glaucoma."
The first question was answered more than four years ago when the results of the OHTS study were announced. That study had looked at patients at risk for glaucoma because of high pressure in the eyes. Kass and colleagues concluded at that time that treating those people with pressure-lowering eye drops could delay, or possibly even prevent, glaucoma.
Now, using five important risk factors that emerged from closely analyzing data from the OHTS study, the researchers have found that it's possible to predict which patients will benefit most from pressure-lowering treatment and which ones don't have much to gain from the eye drops. The five factors researchers plug into the risk assessment model are age, intraocular pressure, cup/disc ratio (a measure of the appearance of the optic nerve head), thickness of the cornea and pattern standard deviation (a measurement derived from computerized visual field tests).
"When you enter these five factors—and our model is based on the average of these factors between the two eyes—you can determine an individual's risk of developing glaucoma during the next five years," says Mae O. Gordon, Ph.D., professor in the Department of Ophthalmology and Visual Sciences and the Division of Biostatistics at Washington University School of Medicine and first author of the study validating the risk assessment model that was presented at the Academy meeting.
"We have found that you can assess risk two ways," she says. "We can enter the raw data, and our model will calculate the risk. We've also put together a simplified points system that assigns a certain number of points to the various risk factors. Adding up those points then provides doctors with an estimate of a patient's risk of progressing from elevated intraocular pressure to glaucoma."
Kass believes the new risk assessment model not only will help physicians decide which patients to treat aggressively but will arm patients with information to help them decide whether to go through with treatment. For example, an 80-year-old patient with a 50 percent risk of developing glaucoma in the next five years might be inclined to go in a different direction than a 45-year-old patient with the same level of risk.
Because some eye drops cause harmful side effects and daily treatment can be inconvenient and expensive, Kass believes some patients at low risk may opt for close observation rather than treatment. He recommends doctors use the risk assessment model as only one of several factors to consider when designing a treatment strategy for an individual patient.
"We hope this information will be used to help doctors and patients make good decisions about testing, examination and the possibility of preventive treatment," he says.
Kass views this model as "version 1.1," and he expects it will be improved as more is learned about genetic risks and other factors related to glaucoma. He says scientists should view the risk assessment model as a "work in progress" and the best that science can do right now. But just as models of cardiovascular disease risk have improved over the last few decades, he expects this glaucoma risk model will improve and become even more useful in future years.