Earlier this year, I presented a lecture on age-related macular degeneration (AMD) to a large group of fellow optometrists. During the lecture, I asked the audience how many of them have administered genetic testing for their AMD patients. If I had asked this question to the same audience two years ago, no one would have raised a hand, but this time around, several hands went up. Genetic testing in AMD is a relatively new focus for optometrists and an important one to ensure that we are getting a complete view of our patients’ risk for developing advanced AMD. Although we are making some progress, we still have work to do to gain a better understanding of how to incorporate its use into clinical practice. I expect many more hands to rise the next time I ask this question in a lecture.
Genetic testing for AMD is important on several fronts. Up to 71 percent of an individual’s risk of developing advanced AMD is tied to his genetics.1 This influence has a significantly greater impact in AMD than nearly any other disease, including obesity, cardiovascular disease, and even breast cancer, which we will discuss in greater detail. Genetic testing can help determine which patients are most at risk for developing advanced AMD and allow us to manage them accordingly. For example, if a patient faces a high level of genetic risk for AMD progression, we may want to examine that patient more frequently than we would if the patient showed similar signs and symptoms, but possessed a more favorable genetic profile. By adjusting our monitoring schedule based on risk, we can catch conversions to choroidal neovascularization (CNV) or wet AMD as quickly as possible and refer the patient for treatment sooner. As we know, earlier intervention with anti-VEGFs typically yields better long-term results.2
Additionally, there is some evidence that indicates genetic testing may predict patients’ response to certain treatments. In a study conducted by Peter J. Francis, MD, patients who had the CFH gene showed less improvement in their visual acuity while receiving ranibizumab therapy. Patients who had the C3 gene had reduced thickening and improved retinal architecture, and those who had vascular endothelial growth factor (VEGFA), FLT1, and CFH genes were reported to require fewer ranibizumab injections during the 12-month study.3 A second study by Hermann et al looking at the VEGFR2/KDR genes also seem to show difference in responses to ranibizumab based on genetic variation.4 The CATT Study, however, did not seem to demonstrate such a difference in response rates based on genetic variance.5
Conceptually, genetic testing may seem foreign to eyecare professionals, but this approach is employed quite frequently in other fields of medicine. For example, there are studies related to breast cancer indicating that certain genes, such as the BRCA 1 and 2 genes, may predict a person’s risk of developing breast cancer as well as what treatment may be most beneficial in certain cases.6 I have little doubt that within eye care, genetic testing will become more important as data establishes the benefit of predictive action regarding AMD.