"Lazy eye" is the leading cause of decreased vision among children and, if left untreated, the loss of vision can be serious. Traditionally, methods of correcting it have proved difficult. Now a new study — published in the Journal of the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) — shows how the use of "dichoptic therapy" — which presents different images to each eye separately — combined with popular children's movies, has improved the vision of young children.
The condition — known in scientific circles as amblyopia — is usually treated by covering the strong eye with a patch to force use of the weaker one. Doctors know, however, this can lead to binocular dysfunction. The brain constructs its view of the outside world by combining the slightly different perspective from each eye. When the information coming from the two eyes is radically different, the brain actively suppresses the image from the weaker eye in favor of the stronger. Though this will allow the sufferer to see, it is far from a perfect solution.
Though dichoptic techniques combined with perceptual-learning tasks or simple games have been shown to significantly improve things for amblyopia patients, children have found these tasks intensive and repetitive with up to 40 percent of them described as "noncompliant." In response to this, a team of researchers have looked at potentially more engaging methods. By using popular animated movies with complementary dichoptic stimulation they hope they can hold children's interest. Lead investigator Dr. Eileen E. Birch hopes that, if the results are good, the research could lead to "home-based binocular amblyopia therapy."
In the study, eight amblyopic children ages 4 to 10 watched three dichoptic movies per week for two weeks. For each child, each eye received an image that had irregularly shaped blobs masking different portions of the film. The blobs seen by one eye were the inverse of the blobs seen by the other meaning the entire screen could only be seen fully with binocular vision. To overcome suppression in the weak eye and allow binocular vision to form a complete picture, the image presented to the stronger eye was reduced in contrast.
The experiment appears to work. "Children achieved 1 to 4 lines of improvement in visual acuity with just six sessions (nine hours) of dichoptic movie viewing over two weeks," says Dr. Birch. "Patching, by comparison, requires 120 hours of treatment to achieve 1 line of improvement in amblyopic children who have already been treated with spectacles for 12 to 16 weeks." While the maximum improvement and the permanence of its effects remain to be determined, Dr. Birch is optimistic about both treatment and the way in which it could be delivered at home. "If these preliminary results are confirmed in a controlled clinical trial," she says, "passive viewing of dichoptic feature films could be useful as a primary, supplemental, or maintenance treatment for amblyopia."