Eye genetics: A cheek swab away?
By Dr. Roxanna Potter, FLTN Columnist – Many people regard the field of medical genetics as futuristic or science fiction, but it’s actually very current and relevant, and affects the diagnosis and treatment of many common diseases right now. I have been routinely ordering genetic evaluations of patients with macular degeneration, and it has been very helpful in my clinical decision making regarding their care and treatment options. There are plenty of other eye diseases that are genetically influenced, and this is a rapidly evolving branch of medicine that will eventually shape how most, if not all, diseases are treated.
With macular degeneration in particular, numerous genetic variants have been implicated in the disease. Approximately 15 genetic variants across 12 genes have been targeted specifically, with two particular biological pathways that seem to possess the most risk in progression to severe macular degeneration. These pathways have been named CFH and ARMS2, and an individual’s risk of severe vision loss can now be predicted based on whether or not they have the high risk variants of these genes.
The test used in my office utilizes a simple cheek swab that collects a patient’s DNA, which is sent to a lab in Michigan that returns results in a few weeks. The results indicate the patient’s genetic type of only the AMD-specific genes, and give a percentage risk of severe disease progression over the next 10 years. I have seen results in patients ranging from less than five percent chance of vision loss to over 80 percent chance of vision loss, which has changed how I treat individual patients significantly. I can now be more or less aggressive with antioxidant therapy, follow-up and education as needed. Research that helps to determine which vitamin therapy is better for which genotype is already present and growing. Most insurance companies cover this test for patients with signs of macular degeneration.
While genetics have been estimated to be accountable for up to 70 percent of a person’s risk of macular degeneration, there are still other known risk factors that are more controllable. These include smoking, UV radiation exposure and BMI. Smoking is the most dangerous risk-inducing behavior, although it’s not known if it’s due to direct oxidative damage to the retina or if it simply acts to “turn on” the gene that then causes the damage. Regardless, a healthy lifestyle of diet and exercise, no smoking, and UV and HEV (blue light) protection can still serve to reduce risk of vision loss despite genetic predisposition to this disease.
If you or a loved one has early or intermediate macular degeneration, consider genetic testing to help determine the risk of progression to a more advanced, severe stage. It will help you and your doctor prepare for early detection and treatment of worsening disease.