"But, glaucoma is a very complex disease. Pressure buildup is a risk factor, not the disease itself. In fact, there are multiple diseases which cause glaucoma and numerous risk factors for damage from it. As a result of these new insights, we are finally beginning to direct specific therapies to improve outcomes," he said.

Traditionally, the two broad categories of glaucoma have been defined as open-angle glaucoma, the most common form, and closed-angle glaucoma, which is caused by pupillary block, plateau iris or ciliary block. In recent years, Dr. Ritch has concentrated much of his research on the more common open angle glaucoma and its primary cause, exfoliation syndrome.

"Exfoliation syndrome (XFS), which deposits a fuzzy white substance on the lens of the eye, was for many years thought to be limited to Scandinavia. Now it is recognized as the leading cause of open-angle glaucoma worldwide, and it is an important and exciting area of research," said Dr. Ritch.

XFS: Underdiagnosed and Underappreciated

"Exfoliation syndrome is ten times more prevalent in glaucoma patients than previously thought," said Dr. Ritch. "It has been underdiagnosed for years. Even now, physicians miss the diagnosis 90 percent of the time because they don't recognize it and because they feel that with or without XFS, treatment for glaucoma is the same. Well, treatment should not be the same."

The incidence of XFS in glaucoma patients varies widely around the world, with some populations, such as those in Scandinavia, having a prevalence as high as 93 percent. In the United States, the incidence is 12 percent, yet among Russian Jews who have immigrated to the U.S., the figure is 75 percent. "Taking epidemiology studies as a whole, XFS appears to account for about 20-25% of open-angle glaucoma, making it the most common identifiable cause worldwide," said Ritch.

XFS causes glaucoma, but other eye diseases as well, including cataract. XFS is also reported, in preliminary studies, to be associated with high blood pressure, heart attack, and stroke. "The ramifications of this disorder appear to be far more important than ever before realized," said Dr. Ritch.

What is XFS and Can It Be Grown in Tissue Culture?

XFS is characterized by the production and progressive accumulation of a white, feathery material on the lens, the iris, cornea, zonules and other areas within the eye. While it can be observed using standard microscopy, it is generally underdiagnosed.

The biochemical make-up of exfoliation syndrome is unknown, and, until now, it has been very difficult to isolate enough of the insoluble fibrous material to analyze it.

Currently, Dr. Ritch and his colleague, Dan-Ning Hu, M.D., at The New York Eye and Ear Infirmary, are conducting laboratory experiments to grow XFS in tissue culture using iris cells that previously produced XFS.

"This is a very exciting area of research," said Dr. Ritch. "If we are successful in growing iris cells in tissue culture that produce XFS in quantities that can be analyzed, we can then begin to understand its etiology and perhaps a way to prevent it."

Tailoring Treatment for Glaucoma with XFS

Compared to patients with ordinary (primary) open-angle glaucoma, patients with glaucoma associated with XFS tend to respond less well to medical therapy, which is generally the first line of defense against glaucoma. Standard medications to reduce eye pressure include beta-adrenergic antagonists (beta blockers), alpha-adrenergic agonists, miotics (drugs that cause pupil contraction), prostaglandin analogs (Xalatan), and carbonic anhydrase inhibitors. These are not as effective on XFS patients.

Argon laser trabeculoplasty (laser surgery on the trabecular meshwork) is particularly effective, at least early on, in eyes with XFS versus COAG (chronic open-angle glaucoma). The initial drop in eye pressure is greater for XFS patients. The effectiveness of the laser surgery may be related to the increased trabecular meshwork pigmentation found in XFS. The results of trabeculectomy (surgical removal of the trabecular meshwork) are comparable between XFS and COAG.

SOURCE: The New York Eye and Ear Infirmary