Risk factors identified for progression of glaucoma

Gender, age, IOP and anticardiolipin antibody levels were shown as independent predictive influences.

Anticardiolipin antibody is highly predictive of glaucoma progression, and female gender, age and baseline IOP are other independently predictive influences identified in the Canadian Glaucoma Study.

Study author Balwantray C. Chauhan, PhD, said the novel finding was the link between positive anticardiolipin antibody (ACA) titers and the progression of glaucoma.

“It turns out that this [ACA] was probably the most highly predictive factor for progression,” Dr. Chauhan said in an e-mail interview with Ocular Surgery News, adding that patients with a positive result for this antibody were four times more likely to progress than those who did not have it.

“There are some important limitations,” Dr. Chauhan said. “The number of patients who actually tested positive for [ACA] was small.”

A negative ACA result does not mean that glaucoma will not progress, he said. Most patients have a negative titer, and there is still progression.

This is “a powerful finding,” he said, but because of the small number of patients in whom the positive titer is found, he does not advocate general testing of ACA titers.

Surprising IOP link

The Canadian Glaucoma Study (CGS) was conceived in 1992 as a multicenter prospective investigation, and the last patient examination was in 2005.

“We went to great pains to institute an interventional protocol that minimized the variation of IOP between the patients to attempt to reduce the influence of IOP and better elucidate other risk factors,” Dr. Chauhan said. “In spite of that narrow range of IOP among patients, it still turned out to be highly predictive. That was a big surprise.”

“The CGS is therefore in agreement with every major clinical trial in glaucoma over the past decade in confirming the potent effect of IOP on the progression of glaucoma across the spectrum of IOP,” the investigators said in study results published in the Archives of Ophthalmology.

Another finding was the lack of strong evidence linking vasospasm with glaucoma progression. About 15 years ago, there was evidence that certain vasculopathies, such as vasospasm, were linked to glaucoma progression. This association was studied in the CGS, but the evidence was not strong, Dr. Chauhan said.

Age and gender

The study investigated several other demographic variables, including age and gender. In this study, every year of age added a 4% increased independent risk of glaucoma progression.

Although twice as many women as men showed progression, the reasons are unclear and may be because of hormonal factors. For example, postmenopausal women may be susceptible to hormonal factors that predispose them to a higher risk of progression, the study said. In addition, endogenous estrogen may have a protective effect, as is suggested by the higher prevalence of glaucoma in early menopausal women. However, not all evidence supports the hypothesis that a lack of estrogen is a strong factor in glaucoma.

“We have a goldmine of data,” Dr. Chauhan said. “We know a lot more about progression — how to define and measure it. So the next step is going to be to look [at the existing data] to see how these different variables affect the rates of change in patients.”

The CGS investigators suggest that further investigation also be done in phenotyping patients with positive ACA results. – by Pat Nale

Reference:

• Chauhan BC, Mikelberg FS, Balaszi AG, LeBlanc RP, Lesk MR, Trope GE; Canadian Glaucoma Study Group. Canadian Glaucoma Study: 2. risk factors for the progression of open-angle glaucoma. Arch Ophthalmol. 2008:126(8):1030-1036.

• Balwantray C. Chauhan, PhD, can be reached at the Department of Ophthalmology and Visual Sciences, Dalhousie University, Centennial Building, Second Floor, 1278 Tower Road, Halifax, Nova Scotia, Canada B3H 2Y9; 902-473-3203; fax: 902-473-2839; e-mail: bal@dal.ca.