GENETIC TESTING

Marc Bloomenstein, O.D., F.A.A.O.: Ben, do you regularly look to perform genetic testing on your patients? I heard about genetic testing for macular degeneration yet was reluctant to incorporate this into my practice.

Ben Gaddie, O.D., F.A.A.O.: While I understand genetic testing has its benefits, I haven’t warmed up to the notion that you have to tie a particular neutraceutical to the test, though many of my colleagues have built great business models off in-office vitamin sales.

I feel the same way about macular pigment density programs. Knowing a patient has low MPOD is great clinical information. Studies conclude those with lower MPOD levels are at a greater risk for AMD, and others show that MPOD levels can be increased through nutritional supplements. However, the conclusion that “supplementing” sometimes several decades in advance can reduce the risk of AMD is the individual clinician’s interpretation — no study has demonstrated a direct connection.

M.B.: Recently, I was approached about testing for Avellino corneal dystrophy, a rare form of granular dystrophy, for our refractive surgical candidates. The company marketing this device cited a study that implies incidence is one in 870. While I am all for preventing a condition from progressing, I have reservations about looking for a mutation on the genome based on research that it may cause scarring in the future without any biomarkers.

Some surgical centers state that using this test will prevent blindness. And a prominent corneal specialist from Jules Stein Eye Institute added, “Avellino is the most common corneal dystrophy in Korea, where Fuchs is uncommon. The opposite is true in the U.S. As far as I know, there have not been any studies to determine the prevalence of Avellino corneal dystrophy in North America, but when you look at indications for corneal transplantation in the U.S., all of the TGFBI dystrophies account for less than 5% of the grafts. Thus, the incidence is far less than 1 in 870.”

This appears to be different than tests that use traditional markers and biomarkers for diagnosis. For example, one such test shows some promise in the early diagnose of Sjögrens syndrome. Having a foothold on patients who will progress in a condition that I can treat makes a huge impact on my practice.

B.G.: I think you hit it there, Marc. Having a particular gene profile doesn’t mean that 100% of those people will express the disease — they are certainly at greater risk, but far from diagnostic.

Results from these tests can have a major impact on an individual’s anxiety and could result in more (positive screening result) or less (negative screening result) interaction with licensed healthcare professionals. For example, the FDA recently shut down a personal genetics company for improperly marketing the benefits of genetic testing. In particular, the FDA cited the negative consequences of false positive and false negative results.

As far as the Sjögrens test, which looks at antibodies and biomarkers of disease, I think it will identify a lot of people who have the disease and need early intervention to prevent morbidity down the road.

With that said, I think genetic testing will play a vital role in eye care in the next 20 years. OM