Genetic testing rare in ophthalmology but poised for bigger role
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At the present time, genetic testing remains controversial and is rarely utilized in ophthalmology.
The general indication for a physician to order genetic testing is that the results of the test be “medically actionable.” This means that the results of the genetic test will affect medical decision-making in a significant enough way to justify the potential emotional, social and financial risks of the test. We have one definite indication, which is testing for RPE65 mutations in children so that Luxturna (voretigene neparvovec-rzyl, Spark Therapeutics) can be injected into the eye to prevent the debilitating effects of congenitally inherited and potentially blinding Leber congenital amaurosis.
The American Academy of Ophthalmology has a Task Force on Genetic Testing guidance document that was written in 2014. It is generally unsupportive of genetic testing except in patients with diseases that are Mendelian in nature in which the test will assist in diagnosis and/or therapy. The task force is also not supportive of direct-to-consumer testing such as 23andMe. If genetic testing is ordered for a patient, genetic counseling by a certified genetic counselor or one expert in the field is encouraged by the task force.
While genetic testing is quite common in oncology, as it has proven to be medically actionable for many cancers, it is rarely used in ophthalmology. Until recently, I had never ordered genetic testing for a patient. Then Avellino developed the AvaGen test, which is useful in determining an individual’s risk for developing keratoconus. When screening potential refractive surgery patients, I discouraged 10% to 15% from proceeding with corneal refractive surgery because I was uncomfortable with their corneal diagnostics. Many of these patients were highly motivated to have corneal refractive surgery and willing to accept an increased risk. I offered some genetic testing with AvaGen in an attempt to quantify their risk of post-corneal refractive surgery ectasia and found it helpful. Screening siblings of those with the diagnosis of keratoconus who have no ocular findings on examination is another reasonable indication for select interested patients.
I anticipate that soon genetic testing will help us make therapeutic decisions in our glaucoma patients. Identifying the ocular hypertensive and glaucoma patients who are at greater risk for progressive optic nerve damage will influence our target IOPs and choice of therapy. In addition, as we develop therapies for geographic atrophy of the macula, it will be helpful to have insight into which patients might progress rapidly and which might not. Genetic testing promises to be helpful to the clinician and medically actionable, as the treatment of geographic atrophy with multiple intravitreal injections is moderately invasive and will have a meaningful social impact on patients and their families.
It is a positive to me that genetic testing is quite easy for the patient and the eye care professional as saliva or a buccal sample gathered with a Q-tip is usually sufficient. Cost is an issue as genetic testing is usually patient pay, but the cost for an AvaGen test is only about $300. I expect to see many more useful genetic tests that will be medically actionable in the near future.
I hope the AAO will reconvene another Task Force on Genetic Testing as much has changed since 2014. Genetic testing is likely to advance hand in hand with biologic therapeutics, much to the benefit of our patients.
- Reference:
- Recommendations for genetic testing of inherited eye diseases - 2014. https://www.aao.org/clinical-statement/recommendations-genetic-testing-of-inherited-eye-d. Published February 2014.
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