Use genetic testing with caution

May 1, 2012
Jennifer A. Webb

Ophthalmologists should not order routine genetic tests for patients with common disorders like age-related macular degeneration until there are specific therapeutic interventions available to treat the disease based on the genetic information.

San Francisco-Ophthalmologists should not order routine genetic tests for patients with common disorders like age-related macular degeneration (AMD) until there are specific therapeutic interventions available to treat the disease based on the genetic information, according to a task force of the American Academy of Ophthalmology (AAO).

The recommendation is part of a five-page set of guidelines issued earlier this year to help physicians weigh the ramifications and potential benefits of identifying genes associated with inherited eye diseases before ordering tests for their patients. The guidelines offer a framework for physicians to discuss the issue with patients.

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While testing can very clearly reveal the cause of a patient's disease in some situations, in others, a detected genetic variation may be only part of the explanation, he said.

Monogenic disorders, such as retinitis pigmentosa and sickle-cell anemia, are linked to alterations in a single gene and their presence can indicate a high probability of developing the disease. However, many disorders are complex and common, such as AMD and glaucoma, and involve the interaction of variations in a number of different genes. The presence of any one disease-associated variant is not highly predictive of disease development, the guidelines state.

For example, researchers have identified several genes strongly associated with AMD, but in an individual patient, the presence of variations in one or more of these genes is not as predictive of the development of disease as similar variations would be in genes that cause monogenic disease Dr. Stone said.

"In 2012, the risk of somebody having vision loss from macular degeneration is correlated much more strongly to what a physician sees in [his or her] retina than it is to anything one would see in [his or her] DNA," he said. And, without preventive treatments tied specifically to one genotype or another, testing a patient is of considerably less value than a comprehensive eye exam, he added.

"If you're going to recommend AREDS vitamins, Amsler grid monitoring, smoking cessation, and periodic follow-up for everybody who has a significant number of drusen, how will the presence or absence of a specific AMD risk allele affect the treatment of an individual patient?" Dr. Stone asked.

In addition, genetic risk information can cause some people to worry unnecessarily about their health, or not worry enough because they are falsely assured by negative findings of a test. However, the involvement of skilled counselors makes such negative outcomes much less likely, Stone said.

The guidelines recommend:

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