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AMD: Embrace current knowledge, monitor ongoing research
An ancient Chinese proverb reminds us that “going beyond is as bad as falling short.” While succinct and simplistic, its implications are far reaching. Like many Chinese proverbs, it provides us guidance and, in this particular case, a reminder that we should pursue most everything in moderation. It is healthy advice for both personal and professional endeavors.
Unfortunately, professionally we are constantly confronted by clinical conditions that can derail our pursuit of moderation. Perhaps none is more demonstrative than that of age-related macular degeneration (AMD). We have all witnessed how insidious and aggressive AMD can be, often devastating patient and family alike. It is understandable why we are so compelled to be equally aggressive – and driven to take whatever steps necessary to mitigate AMD’s impact.
We identify risk factors, offer dietary and lifestyle counseling, embrace the most advanced diagnostics, and employ any and all treatment strategies. Unfortunately, sometimes not even this is enough to prevent vision loss. So, our quest for better ways to identify – perhaps even predict – who will develop AMD continues. Arguably, this is why genetic testing has such appeal.
The Human Genome Project and subsequent genetic testing has clearly resulted in a paradigm shift in health care. It has helped us understand the role genes play in a variety of disease states and it is providing a template for personalized patient treatments, and AMD is no exception. We now know there are genetic implications to AMD and that certain gene variants predispose individuals to AMD.
The relationship, however, is not a simple one, as there are almost two dozen identifiable gene variants influencing the risk of AMD. Further complicating issues is the fact that not all gene variants are equally impactful; certain rare variants have an apparently more predictive value, while more common variants are less well understood. The reality is that genetic testing for AMD is not binary with a simple “yes” or “no” outcome.
The vexing nature of AMD is that its clinical presentation is influenced by so much more than just genetics. Age, smoking, body mass index, diet, supplementation and inflammatory markers such as C-reactive protein all play important roles in phenotypic expression. The list of comorbidities and environmental risk factors continues to grow. Suffice it to say, each of these variables, intertwined with an individual’s genetic code, ultimately determines what we see in our offices.
Arguably, the genetics of AMD is still in its infancy, though ongoing research is providing us a better understanding of all aspects of AMD. For instance, Awh and colleagues have given us a glimpse of how certain risk alleles potentially influence the efficacy of various supplement formulations. While their conclusions have led to much debate, they have also created a healthy dialogue – a dialogue that will undoubtedly lead us to a better understanding of an individual’s risk for AMD as well as more targeted forms of treatment.
So, what should we as clinicians do? Should we “go beyond” and genetically test all patients for AMD or should we “fall short” and not test patients at all? The obvious answer lies somewhere in between – cautiously embracing what we know while being guided by ongoing research. After all, we should “be not afraid of growing slowly, be afraid only of standing still.”