Amblyopia study provides new insight for older children

March 1, 2007
Cheryl Guttman

Baltimore-Results from the Amblyopia Treatment Study 3 (ATS3) support offering amblyopia treatment to children aged 7 to 12 years and considering it as well for children aged as many as 17 years who have not been treated previously, reported Michael X. Repka, MD, at the Current Concepts in Ophthalmology meeting here.

ATS3 was a multicenter, randomized study undertaken by the Pediatric Eye Disease Investigator group that enrolled 507 children aged 7 to <18 years with unilateral strabismic or anisometropic amblyopia, said Dr. Repka, professor of ophthalmology and pediatrics, Johns Hopkins University School of Medicine, Baltimore. The study compared optical correction alone (control) versus optical correction augmented with patching and near vision activities (active treatment).

In addition, children <13 years old in the active treatment group received atropine 1% daily.

No difference in response rates was seen between the active treatment and control groups among children aged 13 to 17 years. Active treatment was beneficial, however, considering the subgroup that had no previous amblyopia treatment. Overall, the benefits of amblyopia treatment occurred with a low chance of complications, according to Dr. Repka.

Paradigm shift

"Prior to the mid-1990s, most experts would generally recommend not attempting to treat amblyopia once children reached 8 to 10 years of age based on the idea that the critical period for visual development had already passed," he said. "The question, however, of when the critical period is actually over in children had not been well-studied, and results of this randomized clinical trial support a change in clinical practice."

The ATS3 was funded by the National Eye Institute. First, however, a pilot study was conducted to evaluate the potential for treatment response in older children with amblyopia. It enrolled 66 patients aged 10 to 17 years and found that 27% of those children benefited with a 2-line or greater improvement in visual acuity after just 1 month of treatment with part-time patching combined with near visual activities. Analyses with the children divided into two subgroups by age (10 to <14 and 14 to <18) showed no decrease in response rate with older age. Then these data were used to create the ATS3 study.

The objectives of ATS3 were to determine the response rate to amblyopia treatment in children aged 7 to <18 years as well as the frequency of recidivism after successful treatment. Children were eligible if they had unilateral amblyopia associated with strabismus and/or anisometropia, best-corrected visual acuity (BCVA) ranging from 20/40 to 20/400 in the amblyopic eye and 20/25 or better in the sound eye with a minimum 3-line intereye difference, no more than –6 D of myopia in the amblyopic eye, no amblyopia treatment other than spectacles in the past month, and no more than 1 month of amblyopia treatment in the last 6 months. In addition, patients aged fewer than 13 years were required to have no more than –0.50 D of myopia in the sound eye.

Patients were followed every 6 weeks for 24 weeks following randomization. A treatment response was defined as a patient with a 10-letter or greater improvement from baseline in the amblyopic eye's acuity with confirmation with a second measurement by an examiner in masked fashion. The analysis of response rates showed improvement even with optical correction only. A significant additional benefit was seen for the augmented strategy in children aged 7 to 12 years, however. In that subgroup, 53% of patients receiving the augmented treatment had a response compared with 25% of those treated with optical correction only. Among the older children, about one-fourth of patients in both the active and control groups had a response.