We have known for a long time that there is a genetic component to glaucoma, since having a family history of glaucoma is one of the most important risk factors for developing the disease. Glaucoma is actually a group of diseases, including some starting at birth or in childhood, as well as the more common types that happen in adults, such as primary open angle glaucoma.
In some of the glaucomas of childhood, scientists can trace the cause to a single gene. For example, mutations in the gene for myocillin can cause juvenile-onset open angle glaucoma. And there are genetic tests available for some of these genes. These genetic tests, however, are helpful only for a subset of glaucoma patients. For most glaucoma patients, these tests don’t give us the answers we need.
In the types of glaucoma that happen in adults, both environmental factors and genetic factors contribute to whether or not someone develops the disease. This complex interplay of factors makes testing only one gene or a handful of genes not as helpful. For diseases like adult-onset open angle glaucoma, instead of having just one gene that is mutated and causing the disease, there are many genes involved. All these genes contain tiny differences, some potentially helpful and some potentially harmful. It is an individual’s mix of genes combined with the lifetime of complex environmental exposures, that determines whether he or she will get the disease. In the future, genetic tests that incorporate this group of genes will help doctors, patients, and families better understand their susceptibilities, and hopefully lead to prevention of vision loss from glaucoma.
Genetic testing has the potential to offer a lot of benefits, but is not without risk and unintended consequences. Genetic counselors are trained to help patients, families, and doctors navigate these areas.
For more information about glaucoma, visit www.nei.nih.gov/glaucoma.
Genetics of primary glaucoma. AO Khan. Current Opinion in Ophthalmology. 2011. 22(5):347-55