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Post Info TOPIC: Genetic Testing for Keratoconus

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Date: Sun Jul 16 8:15 PM, 2006
Genetic Testing for Keratoconus

Genetic Testing for Keratoconus

 One of the most promising technologies to screen candidates for LASIK is a genetic test that may be able to differentiate between patients who are predisposed to develop keratoconus and those who are not. Yaron S. Rabinowitz, MD, director of ophthalmology research at Cedars-Sinai Medical Center and clinical professor of ophthalmology at the Jules Stein Eye Institute, UCLA School of Medicine, has been developing the test and holds a patent on it.

“We recently published a paper in Investigative Ophthalmology1 which shows that there’s a gene called aquaporin 5 that is suppressed in patients with keratoconus,” he explains. (See image, below, right.) “So far, we’ve shown that the test can differentiate between normal and keratoconus corneal transplant specimens, as well as between epithelial specimens from normal and keratoconus patients who have had PRK.

“Currently, we have two challenges. The first is to see whether keratoconus patients show differences in expression of this aquaporin early on, where the only indication is an abnormal-looking cornea, and whether the test is sensitive enough to pick up that difference. The second challenge is to be able to get a piece of corneal tissue from a patient that’s small enough to do a biopsy without affecting the patient. We can’t run the test on any other tissue because, unlike many genetic tests that look for mutations, this particular test looks for gene suppression. Cur­rently, we take a 1-mm piece of epithelium from the corneal periphery, close to the limbus. It’s pretty easy, and it grows back within seven or eight hours.”

Dr. Rabinowitz notes that there’s an advantage to testing for gene suppression rather than mutation. “This test may be able to detect any kind of keratoconus, whether the cause is genetic or not,” he says. “If the early stages show gene suppression, it won’t matter what the cause is.”

Dr. Rabinowitz hopes to develop the test for commercial distribution with an ophthalmological product manufacturer. “We plan to do some large-scale testing during the next couple of years,” he says. “The preliminary data looks pretty good. Then it will just be a question of getting it on the market.”

1. Rabinowitz Y, Dong L, Wistow G. Gene expression profile studies of human keratoconus cornea for NEIBank: A novel cornea-expressed gene and the absence of transcripts for aquaporin 5. Invest Ophthalmol Vis Sci. 2005;46:4:1239-46.

-- Edited by QuintriX at 20:16, 2006-07-16

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