Most people at risk for developing glaucoma due to high eye pressure do not need treatment, according to a large, multicenter study in which the UC Davis Health System’s Eye Center played a central role.

The results of the 15-year Ocular Hypertension Treatment Study, or OHTS, were presented at the annual meeting of the American Glaucoma Society in Florida last weekend and published in Archives of Ophthalmology this week.

Out of 1,636 people in the study, the UC Davis Eye Center evaluated and treated 117 — representing the largest patient base of the 22 regional centers participating in the OHTS.

The UC Davis Department of Ophthalmology and Vision Science served as a center for the reading and analysis of thousands of visual field tests for the study.

“These results are just the beginning,” said James Brandt, professor of ophthalmology and vision science and the lead investigator of the OHTS at UC Davis. “Although the results show that many patients can simply be monitored without treatment, the OHTS also gives us the tools to identify who is at most risk and who should be treated.

“The OHTS participants are among the most carefully studied eye patients in history. Samples of their DNA are now being analyzed and further research is likely to result in new genetic tests and a better understanding of glaucoma.”

The OHTS ran from 1994 to 2009. All of the participants, ages 40 to 80, had elevated eye pressure but no evidence of glaucoma. For the first seven years, half of the subjects received eye drops. The other half were closely monitored but received no medication. That first phase of the study determined that drops could reduce the development of the potentially blinding disease by more than 50 percent.

After the first phase of the study, OHTS researchers put everyone on eye drops, and determined that in patients at lower risk, there was not much difference between those who started using eye drops in 1994 and the original control group, who did not get drops until more than seven years later.

Among those at low risk, 7 percent in the early treatment group developed glaucoma. Only 8 percent of the low-risk patients in the delayed treatment group went on to develop the disease. By contrast, 28 percent of high-risk patients in the original treatment group went on to develop glaucoma, compared with 40 percent of the high-risk patients in the delayed treatment group. Fortunately, most people with modest elevations in eye pressure fall into the low-risk group.

“This study has determined that close monitoring is an appropriate option for large numbers of people with ocular hypertension but no damage from glaucoma,” said Paul A. Sieving, director of the National Eye Institute of the National Institutes of Health, which funded the OHTS study. “This is a strong example of research that can result in more appropriate treatment at a lower cost.”

Early in the study, Brandt suggested adding an element: measuring corneal thickness. African Americans as a group appear to have thinner corneas and a slightly different anatomical structure to the optic nerve than people from other ethnic backgrounds. Because of the elevated risk, close monitoring may not be appropriate for many African American patients, and treatment may be indicated.

The study’s principal investigator, Michael A. Kass of Washington University said individual risk assessments should determine which patients receive treatment and which patients are followed.

“Glaucoma is about four times more common in African Americans than in people of European ancestry, and blindness from glaucoma is about six times more common in African-Americans,” Kass said. “Treatment does help, but we know from our study that even when treatment is identical, the risk for African Americans remains significantly greater.”

During the initial phase of the OHTS study, only 4.4 percent of Caucasian patients using drops developed glaucoma, compared with 8.4 percent of African American patients, and 16.1 percent of the African Americans who did not get the drops developed the disease over five years.

“In low-risk patients, close observation looks to be an effective approach,” Kass said. “But it’s important that all patients receive regular eye exams, to detect elevated pressure and to assess other risk factors for glaucoma. If you have high eye pressures with no glaucoma damage, speak to your eye doctor about your risk for developing glaucoma and whether you might benefit from preventative treatment.”

Anissa Routon is a senior writer for the UC Davis Health System.