I have a patient who was recently diagnosed with Avellino corneal dystrophy via genetic testing, and was subsequently advised against LASIK surgery. To be on the safe side, should I start ordering this test for all my patients who are considering refractive surgery?
Avellino corneal dystrophy (ACD), also known as granular corneal dystrophy type 2 (GCD2), is a rare, autosomal dominant disease.1
The condition causes cloudiness in the form of gray-white deposits on various layers of the cornea, which may lead to significant vision loss. Following corneal reshaping surgery such as LASIK, patients with Avellino corneal dystrophy are at an elevated risk for vision loss and eventual blindness due to increased deposition of opacity in the anterior cornea following refractive laser surgery.2 So, detecting the presence of ACD before referring patients for refractive procedures is crucial.
The presence of ACD is the result of a mutation in the gene encoding keratoepithelin (TGFBI), which is located on 5Q31.1––the long arm of chromosome 5 in humans.3 A new test known as the Avellino Gene Detection System (AGDS) identifies whether a patient has the genetic mutation responsible for ACD. The test uses a simple mouth swab that is sent to a laboratory for molecular testing. The results are then sent back to the clinician within 24 to 48 hours.
“This can certainly confirm the exact dystrophy, or at least the mutation, but in clinical practice the dystrophy is usually detected while the patient is in their second decade of life,” says George Rosenwasser, MD, who specializes in cornea and external disease, corneal transplantation, cataract surgery and refractive surgery at Central Pennsylvania Eye Institute in Hershey.
“More severe cases can be detected even earlier, in the first decade of life,” adds Dr. Rosenwasser. “Without a direct family history, one could always examine the parents of the individual, but, in the absence of deposits in the cornea, it is unlikely that one will develop Avellino corneal dystrophy much later in life, or be affected by laser vision correction.”
Before conducting a test that is designed to detect a specific corneal dystrophy––especially one as rare as ACD––Dr. Rosenwasser suggests an exhaustive corneal evaluation.
“There is no substitute for a thorough corneal examination. A good family history as to where the patient’s family comes from may avoid some of the areas in which Avellino has been a hot spot, such as Italy or Korea,” says Dr. Rosenwasser.
Laurel Jensen, OD, clinical director of Nvision Laser Eye Centers in Ontario, says their practice conducts the AGDS test on every patient planning to undergo LASIK or PRK.
“If the results are normal, the patient can proceed with LASIK or PRK as planned,” says Dr. Jensen. “If the results are not normal, we do not recommend following through with the procedure.”
While the company says the AGDS test determines with 100% accuracy whether or not a person has the genetic mutation, Dr. Rosenwasser doesn’t believe routinely conducting the test is necessary or cost effective.
“I would not advocate the routine use of testing for a rare corneal dystrophy prior to laser vision correction,” says Dr. Rosenwasser. “This is a relative waste of resources and unnecessary.”
Large-scale clinical trials are needed to determine the clinical value of routine genetic testing in this patient population. For now, consider using the test for high-risk patients, such as those with a family history of ACD.
Because there is no cure for ACD, patients with the disease should be managed carefully.
“Patients who test positive are encouraged to wear lenses that protect against UV light,” Dr. Jensen adds. “This may postpone disease progression. They should be followed every six months by an eye care professional.”
Additional information is available at
1. Han KE, Kim TI, Chung WS, et al. Clinical findings and treatments of granular corneal dystrophy type 2 (Avellino corneal dystrophy): a review of the literature. Eye Contact Lens. 2010 Sep;36(5):296-9.
2. Jun RM, Tchah H, Kim TI, et al. Avellino corneal dystrophy after LASIK. Ophthalmology. 2004 Mar;111(3):463-8.
3. OMIM.org. Corneal dystrophy, Avellino type; CDA. Available at: http://www.omim.org/entry/607541. Accessed January 23, 2014.