Frequently Asked Questions

What is deCODE Glaucoma™?

deCODE Glaucoma™ is a reference laboratory DNA test for assessing an inherited risk factor for exfoliation glaucoma, a major subtype of the group of eye disorders termed Glaucoma. The test detects versions of markers called SNPs (single nucleotide polymorphisms) – a one letter variation in the sequence of the genome, more specifically on chromosome 15 - that deCODE has linked to an increased risk of exfoliation glaucoma.
deCODE´s research has in two independent study groups determined that two non-synonymous changes in exon 1 of the LOXL1 gene on chromosome 15q24.1 confer risk to exfoliation glaucoma, possibly through the exfoliation syndrome. In Iceland and Sweden, the high-risk haplotype is very common with an average frequency of about 50% in the general population. About 25% of individuals in the general population are homozygous for the haplotype with the highest risk, and their risk of suffering from exfoliation glaucoma is estimated to be about 100 times that of individuals carrying only the low-risk haplotype, or about 2.47 times that of the population average. Jointly, the two non-synonymous changes account for more than 99% of all exfoliation glaucoma cases. The product of the LOXL1 gene modifies elastin fibers that are a major constituent of the intraocular lesions in exfoliation glaucoma.

Back to top of page

What is this test based on?

The test is based on the results of deCODE’s study, published in Science in September 2007 (http://www.sciencemag.org/cgi/reprint/317/5843/1397.pdf). The study reports the discovery of two common SNPs that increase the risk of exfoliation glaucoma, a major subtype of glaucoma. The SNPs, allele G of rs1048661 and allele C of rs3825942, are located in the LOXL1 gene on chromosome 15. They raise the chances of developing exfoliation glaucoma (XFG) by 26-fold and 8-fold, respectively, and 100-fold together compared to the low-risk versions of the same markers. The deCODE team first analyzed more than 300,000 SNPs in Icelandic and Swedish glaucoma patients and control subjects, utilizing the Illumina Hap300 SNP chip. One SNP was strongly linked to exfoliation syndrome, in which fibrous deposits begin to accumulate in the front of the eye but have not yet begun to impair vision. The researchers then analyzed additional SNPs in public databases that were not included on the chip, thereby identifying the LOXL1 mutations.

Back to top of page

What is a genetic risk factor for a common disease and why is understanding inherited risk important?

A genetic risk factor for a common disease is a specific version of a marker in the sequence of the genome that causes or correlates with an increased likelihood of developing a given disease. Common diseases such as glaucoma occur at the interface of genes and the environment, as inherited as well as environmental and other health risk factors play important roles in the disease process. As a result, it is important to understand what carrying an inherited risk variant for a common disease means, and how that information can be used to develop and implement disease prevention strategies that can effectively reduce the likelihood of an individual ever developing the disease, or effectively manage the consequences of the disease.

In basic terms, carrying a genetic risk variant for a common disease does not mean that one will necessarily develop the disease; and not having a certain risk variant does not eliminate the possibility of getting the disease. Rather, for the common diseases, genetic risk variants impact the likelihood that one may develop the disease. Understanding this inherited risk is empowering information with potentially important clinical utility. By understanding inherited risk, it may be possible to take preventive action – through lifestyle modification or by taking certain medications, in general taking the preventive measures necessary to minimize the effects of the disease and maximize the chances of staying healthier longer.

Back to top of page

Should test results be interpreted differently for different ethnic groups?

Studies published so far have been limited to white Caucasians so the answer to this question is not known.

Back to top of page

Why is understanding inherited risk important for Glaucoma?

The discovery of glaucoma genes provides a method for early detection of glaucoma. Genetic testing is capable of identifying those at highest risk for developing glaucoma. Such patients would include family members of patients with known glaucoma gene defects and members of families with a strong history of inherited glaucoma. However, depending on the population, only about 10 - 30% of all glaucoma patients have the glaucoma LOXL1 gene defect. About 25 % of the general populations tested so far are positive for the test which implies that there must be other, inherited and/or environmental factors involved in the development of the disease, even though the mutations identified seem to be present in over in 99 % of exfoliative glaucoma cases. For these reasons, glaucoma gene testing of those who are at high risk for developing glaucoma may be of value.

Back to top of page

Who might benefit from having this test and why?

 Those at highest risk would include family members of patients with known glaucoma gene defects and members of families with a strong history of inherited glaucoma. Regular monitoring by a physician of the eye pressure of these individuals is recommended.

Back to top of page

Is deCODE Glaucoma™  an FDA approved test?

No, this is a reference laboratory test that has not been cleared or approved by FDA. The laboratory that conducts the test is registered as a high-complexity laboratory under the Clinical Laboratory Improvement Amendments (CLIA). The clinical utility of this test as a means of assessing inherited susceptibility to glaucoma, as presented on this site and elsewhere, is based upon published studies by deCODE and independent researchers demonstrating the correlation of carrying two copies of the risk variants and increased likelihood of exfoliation glaucoma. Back to top

What scientific publications support the value of this test?

deCODE is widely recognized as the world leader in the discovery of genes contributing to risk of common diseases. deCODE has also led the way in publishing its discoveries, a commitment that not only drives ongoing research but also enables independent researchers from around the globe to validate the company’s discoveries.

For a complete list of relevant publications, click here.

Back to top of page

What is a positive result?

An individual with two copies of the risk variants will receive a positive result for deCODE Glaucoma ™, and those with only one or no copy of the risk variants will receive a negative result for the test.

Back to top of page

How can I order the test?

 You can have any licensed physician order your deCODE Glaucoma™ following the simple steps outlined in Ordering deCODE Glaucoma™.

Back to top of page

Payment and Reimbursement
Payment can be made by any major credit card by the individual or by the ordering physician or clinic, by including the card details on the test request form. Samples submitted anonymously must be accompanied by a valid credit card number from the respective doctor or affiliated health care institution.

Is deCODE Glaucoma™ reimbursed?
deCODE plans to make the deCODE Glaucoma™ as widely available as possible and is working with physicians, patients, and their insurers on reimbursement for deCODE Glaucoma™. For more information contact customer service at diagnostics@decode.com, or by phone at 1-877-222-6510

Back to top of page

How can I get additional information?

If you would like additional information on deCODE Glaucoma™, you can contact deCODE at diagnostics@decode.com, or by phone at 1-877-222-6510 and a deCODE representative will respond promptly to your questions.

Back to top of page