Predicting glaucoma

Optometric Management, Sep 2002 by Quinn, Chris

The Ocugene test can tell the future.

Since the human genome project began, we've been speculating that one day we may be able to run a blood test and diagnose glaucoma or perhaps utilize gene therapy to actually treat it. Now a genetic assay is commercially available to test for the presence of mutations in the trabecular meshwork inducible glucocorticoid response protein (TIGR)/ MYOCILIN gene.

Beginning in 1997, a series of mutations in the TIGR/MYOCILIN gene were identified and associated with juvenile glaucoma. The gene codes for a protein that's formed in the trabecular meshwork (and other parts of the eye). Production of this protein is substantially increased when exposed to glucocorticoids and may resuit in an obstructive influence of the trabecular meshwork.

A mutation of the gene may lead to lack of proper regulation of the production of the TIGR/MYOCILIN protein and may play a role in primary open-angle glaucoma. A mutation has been identified in as many as 4% of primary open-angle glaucoma patients. One recent retrospective study has linked the genetic mutations for TIGR/MYOCILIN with both higher IOPs and more damaged visual fields in patients who have glaucoma.

Insite Vision, an ophthalmic therapeutics, diagnostics and drug-delivery company has released the Ocugene glaucoma genetic test. The test consists of a pair of buccal brushes that are used to obtain a sample of cells from the oral mucosa inside of the cheek. Obtaining the sample is painless and requires no anesthesia. After the patient rinses his mouth with fresh water, you gently brush the inside of his cheek with the brushes to obtain the sample. Firmly sweep and twirl between the upper gum and cheek for 30 seconds (you'll need to obtain a sample from both sides). The technique should collect cells but not draw any blood.

After you obtain the sample, seal it in the plastic container supplied with the kit and forward it to an analytical lab. The lab extracts DNA from the samples and analyzes for the specific genetic mutations. The test results are generally available in 2 weeks.

The kit comes with all the supplies you need to perform the test including instructions, swabs, transport tubes and an overnight shipping envelope with preprinted label. Your cost for the test kit, including the analysis, is $200.00. You need only obtain and label the sample, fill in the consent and test order form and ship the package.

Although the test won't be useful for all glaucoma patients, it may help in diagnostic evaluations of patients at high risk for glaucoma who haven't yet developed glaucomatous optic atrophy or visual field loss.

BY CHRIS QUINN, O.D., EA.A.O., Iselin, N.J.

Dr. Quinn is center director of Omni Eye Services, a regional optometric co-management center with offices in New Jersey. He's president of the New Jersey Society of Optometric Physicians.