The Pediatric Eye Disease Investigator Group (PEDIG), led by Jonathan M. Holmes, M.D., of the Department of Ophthalmology at Mayo Clinic in Rochester, Minn., addresses the need for evidence-based medicine in pediatric ophthalmology.
This network of pediatric eye care providers in both academic and private practice settings conducts randomized clinical trial and large-scale observational studies, funded by the National Institutes of Health.
PEDIG member sites have completed 14 studies to determine which treatments are most effective for patients with amblyopia. Twelve of the studies were conducted at Mayo Clinic. They address anisometropic, strabismic, combined and bilateral refractive amblyopia (but not unilateral deprivation amblyopia).
Amblyopia is the most common cause of unilateral vision loss in children and young adults. It is characterized by the brain's suppression of one eye, associated with anisometropia, strabismus or deprivation. Bilateral amblyopia is most often associated with high refractive error in each eye.
"We have discovered that most cases of amblyopia can be treated successfully with low-intensity treatment," says Dr. Holmes. "Treating first with spectacles alone substantially improves visual acuity in many children with anisometropic amblyopia, bilateral refractive amblyopia and even strabismic amblyopia."
If improvement with spectacles alone is incomplete, several treatment options are available. Each option gives the amblyopic eye an advantage by blurring or blocking the fellow, nonamblyopic eye. These options include:
PEDIG amblyopia treatment studies include head-to-head comparisons of treatments and evaluations of different treatment intensities. The studies showed that treating the fellow eye with a drop of atropine every day had a similar effect to patching the fellow eye for six or more hours each day.
Using a specially developed questionnaire, researchers also found that parents and children tended to prefer the atropine drop to the eye patch. After the initial study was completed, atropine drops became more widely used for the treatment of amblyopia.
In a PEDIG subsequent study, a third option — a blurring filter over the spectacle lens in front of the nonamblyopic eye — also was found to be effective.
PEDIG researchers completed a series of studies to investigate the needed amount of patching and the needed frequency of atropine drops. These studies indicated that the intense regimens routinely prescribed were not necessary for most children. Patching two hours each day or using the atropine drop twice weekly was effective in many cases.
"The study that has changed my practice the most and profoundly improved quality of life for children with amblyopia and their parents is the study that found two hours of daily patching effective for more than 60 percent of children," says Dr. Holmes.
Researchers at Mayo Clinic are conducting a study of levodopa, an oral medication that may prove to be an adjunct to patching for children ages 7 to 13 years. Earlier PEDIG studies found that many children with amblyopia in this age group were responsive to patching, but that the response often was incomplete at these ages.
Two additional PEDIG studies under way at Mayo address residual amblyopia. These studies investigate how often children respond to increased intensity patching or augmented atropine treatment, when improvement is incomplete with two hours of daily patching or twice-weekly atropine. Mayo is actively recruiting patients ages 7 to 13 years with amblyopia for the levodopa study and patients ages 3 to 6 years for the residual amblyopia studies.
Dr. Holmes is the Joseph E. and Rose Marie Green Professor of Visual Sciences at Mayo Clinic. He is the national network chair of PEDIG and leads Mayo's levodopa study and residual amblyopia studies.