Risk factors guide early treatment of ocular hypertension

Fort Lauderdale, FL-Early treatment of ocular hypertension can decrease the incidence of primary open-angle glaucoma. Risk factors can be assessed relatively simply in the office to identify patients at high and low risk of developing glaucoma, Michael Kass, MD, said.

These statements are based on the results of data amassed in the Ocular Hypertension Treatment Study (OHTS), the focus of which is treatment of individuals with ocular hypertension who are at risk of developing glaucoma.

The goals of the study are to determine if early treatment is safe and effective for preventing the development of open-angle glaucoma and to identify baseline demographic and clinical factors that can predict which individuals are likely to develop glaucoma. The study participants had IOPs of 24 to 32 mm Hg in one eye and 21 to 34 mm Hg in the second eye, Dr. Kass said at the annual meeting of the Association for Research in Vision and Ophthalmology.

Results from study

The OHTS results indicated that treatment prevented ocular hypertension from developing into glaucoma in African Americans and other (mostly Caucasian) participants, said Dr. Kass, chairman, department of ophthalmology and visual sciences, Washington University School of Medicine, St. Louis. Analysis also indicated that African Americans have a worse prognosis whether the disease is observed or treated compared with the other patients in those groups; the prognosis was worse despite similar baseline and follow-up IOPs and similar treatments, he added.

Univariate analysis pinpointed age, African-American origin, male gender, heart disease, IOP, central corneal thickness (thinner corneas are associated with a greater risk), pattern standard deviation (PSD) based on average of two or three visual field measurements per eye, and cup-to-disc ratio as predictive factors; multivariate analysis identified age, IOP, central corneal thickness, PSD, and cup-to-disc ratio. Male gender, heart disease, and myopia are borderline risk factors that need further study, according to Dr. Kass.

Dividing the participants by corneal thickness (thin, medium, and thick) and IOP (low, medium, and high) allowed the identification of participants at low and high risk of developing open-angle glaucoma.

"What was evident was a remarkable dose-response curve. This analysis showed that there are groups at very low risk and at very high risk of developing glaucoma over a 5-year period," Dr. Kass emphasized. Many studies indicate that only 1% of these patients will develop glaucoma in a year. The OHTS data are useful because they demonstrate that within the group with ocular hypertension, there are people who are at much higher risk-up to 7% a year. This provides a way to distinguish these patients and allow physicians intelligent choices about treatment.

An interesting finding was that in the multivariate model, race dropped out as a predictive factor when corneal thickness and cup-to-disc ratio were included in the model. African Americans tend to have thinner central corneas and larger cup-to-disc ratios, and perhaps larger discs.

A shortcoming of the OHTS is that potentially important predictive factors such as the diurnal IOP, pseudoexfoliation syndrome, pigment dispersion, decreased outflow facility, and nerve fiber layer appearance were not evaluated, according to Dr. Kass.

"With time, our predictive models should improve with more understanding of genetic factors, quantitative measurement of the disc or the nerve fiber layer, and improvements in various psychophysical tests," he said. "Early treatment can decrease the incidence of primary open-angle glaucoma. Risk factors can be assessed relatively simply in the office to identify patients at high and low risk of developing glaucoma.

"However, just because treatment does work, this does not mean that all patients with elevated IOP should be treated. Perhaps only a minority of patients should be treated. The clinician has the option to offer treatment to those individuals with ocular hypertension who are at moderate to high risk for developing glaucoma. A number of factors should be taken into consideration, such as patient age, medical status, life expectancy, and patient preference for managing the condition," Dr. Kass concluded.