Pupillary Pathways

Genetic Testing for Macular Degeneration

Posted by Amanda Dexter on Jan 8, 2016 9:00:00 AM
Amanda Dexter
Dr. Amanda K. Dexter received her optometric training at Southern California College of Optometry in Fullerton, California, where she was Class of 2010 Valedictorian. She also completed a residency in Primary Care and Ocular Disease at the Veteran's Affairs Hospital in San Diego, California. Dr. Dexter is the Manager and Program Coordinator for OptoPrep, the premiere online study resource for the NBEO Part I & II.

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Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss and blindness in Americans who are of retirement age. Studies have shown that approximately one in ten individuals in their 50s will display some retinal changes indicative of AMD, and about one in three people in their 70s will show observable AMD changes.

Approximately 20% of those who develop the early and intermediate form of AMD will progress to an advanced disease stage with loss of vision as they age, but the risk for progression is very difficult to predict. This advanced disease can be characterized by dry geographic atrophy (30% of advanced disease cases) or wet choroidal neovascularization (70% of individuals with advanced disease). 

Risk Factors for AMD

We are all very aware that age-related macular degeneration is a multifactorial disorder with both genetic and environmental risk factors. The most well established factors include age, smoking, BMI and positive family history. Although the inheritance pattern of AMD is very complex, we have made great progress in better understanding the genetic component over the past several years. This is very important as genetics can explain as much as 71% of the cause of AMD. This inheritance includes at least 12 genes that are associated with the progression of AMD to more advanced forms. These genes are involved with several biological processes including complement immunity and inflammation, oxygen metabolism, cholesterol metabolism, the stability of blood vessels, etc. 

Macula Risk PGx Genetic Test for AMD

Macula Risk PGx from Arctic DX is the most easily available genetic test for AMD on the market at this time. It a combined prognostic and pharmacogenetics DNA test designed to determine a patient’s risk of progression to advanced AMD and aid in the selection of appropriate supplement formulation for AMD based on the patient’s individual genetic risk profile. 

Macula Risk PGx combines a patient’s current AMD status, genetic predisposition, and non-genetic risk factors to determine his or her 2, 5 and 10-year risk for developing advanced AMD (either geographic atrophy or choroidal neovascularization). 

How is the Test Completed?

Once you sign up and register as a provider with Macula Risk, a testing supplies case will be sent to your office. It will include individual testing kits, complete instructions, and prepaid shipping envelopes. The patient sample is collected via a simple cheek swab taken in your office. There is also a Test Requisition Form that has certain demographic information that will need to be completed for your patient and submitted with the cheek swab. You will receive a laboratory report within four weeks. 

Interpretation of Test Results: Macula Risk Prognostic Results

The patient’s AMD prognostic data report has the following information: clinical information (age, smoking history, BMI, and AMD status), genetic results (genotype for 15 AMD-associated genetic markers and the Genetic Risk Subscore), and the patient’s 2, 5, and 10-year risk of progression to advanced AMD. 

Based on the 10-year risk of progression data, patients are then placed into one of the five Macula Risk (MR) categories (M1-M5). Each category has a percentage range that represents the risk for progressing to advanced AMD with vision loss within the next 10 years.

Interpretation of Test Results: Vita Risk Pharmacogenetics Result

In addition to the prognostic data result, a Vita Risk pharmacogenetics result is also included from the laboratory. Pharmacogenetics is defined as the science of the impact of genetic variation on an individuals response to a certain treatment. Pharmacogenetics is utilized to determine appropriate dosages for a patient, optimize therapeutic outcomes, and minimize harmful effects. 

In relation to AMD, a recent study showed that components of the AREDS formation vitamins can be harmful in certain populations’ genotype in the CFH and ARMS2 genes. Additionally, these researchers found that 49% of the AREDS study patients would have experienced a greater benefit from an eye supplement formulation other than the AREDS formulation. This study also concluded that a genotype-directed eye supplement formulation could have more than doubled the reduction in the AMD progression rate compared to the standard. AREDS formulation. 

The Vita Risk Report shows all of the genetic features, the result, and the risk for each. It also provides a vitamin recommendation for the patient based on CFH and ARMS2 genotyping. 

Is the Test Accurate?

According to Arctic, Macula Risk PGx has been validated in two large, independent populations where it was shown to have a 10-year predictive accuracy of 89.5%, with a sensitivity and specificity both > 80%. 

Who Should be Tested?

Macula Risk testing is intended to be used on patients who have a diagnosis of macular degeneration in at least one eye, as the goal of the test is to determine risk for progressing from mild to moderate AMD to advanced AMD with associated vision loss. It is not necessary to test those who do not show any current AMD changes, even though they may have risk factors (including a strong positive family history). Arctic states on their website that the test is covered by most insurance providers for patients with a diagnosis of AMD, but I did not further investigate this matter. 

Why is This Test Important?

We all know that there is a better likelihood that vision loss can be prevented or saved if AMD is detected at an early stage. We also know that it is very difficult to predict when, or to whom, vision loss will occur in this disease. A lot of patients also are not aware that they are at an increased risk of developing advanced AMD and don’t regularly visit their eye care provider as recommended. In many cases they may wait to visit a doctor until symptoms worsen, which may be too late to save or prevent further vision loss. 

If we as eye care providers have a better understanding of our patient’s risk for progressing to advanced AMD, we can better tailor our treatment and management plan for follow-up visits, and better educate the patient about their disease and prognosis. 

-Dr. Dexter 

The Top 15 Tips and Tricks for Studying for Part I of NBEO®

Top 15 Tips

We’ve put together a ton of great tips and tricks for studying for Part I of NBEO along with two tailored study programs that will help you thoroughly prepare for the big day. Remember, you’ve made it this far and you can totally do this!

Some of the Top 15 Tips include:

  • Familiarize Yourself with the Test Format
  • Tackle the Weak Subjects Early
  • Start Sooner and Ease Into It
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NBEO Part I Study Guide The Top 15 Tips and Tricks for Studying for Part I

Topics: Vision Loss, Testing, Blindness