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Orlando— A series of recent studies of amblyopia therapy seem to be suggesting that less aggressive or shorter treatments could be more effective than previously thought.
"That's been the direction of what we have found in almost all of the projects to date," said Michael X. Repka, MD, professor of ophthalmology and professor of pediatrics, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.
Dr. Repka led a workshop at the American Academy of Pediatric Ophthalmology and Strabismus annual meeting to review completed and ongoing projects in the Amblyopia Treatment Studies (ATS). These are randomized, multicenter trials of amblyopia therapy for children less than 18 years with strabismic, anisometropic, or combined amblyopia.
In a multicenter trial, 419 children younger than 7 years with amblyopia (20/40 to 20/100 in the affected eye) were assigned to receive either patching (6 or more hours a day) or daily atropine for 6 months. Between 6 months and 2 years, treatment was at the discretion of the investigator.
Outcomes 18 months after completion of the randomized portion of the trial showed that both therapeutic approaches produced similar improvement in children who were between the ages of 3 and 7 years at enrollment.
Mean improvement in visual acuity from baseline was 3.7 lines in the patching group and 3.6 lines in the atropine group.
In both groups, the mean amblyopic eye acuity was approximately 20/32.
However, the amblyopic eye acuity was on average approximately 2 lines worse than the sound eye.
Six-month results, reported in 2002, had also shown that children in both groups had about the same improvement, an outcome that held up through the more recent follow-up, Dr. Repka said.
Hours of patching
In another study of moderate amblyopia, investigators compared 2 hours with 6 hours of prescribed daily patching and found similar outcomes in both groups after 4 months of treatment. And in a study of children with severe amblyopia, they compared 6 hours of daily patching with patching all waking hours. Again, results indicated that both treatment groups had similar levels of improvement.
"These results were counterintuitive," Dr. Repka said. "Most people would have said that patching should be faster and better than atropine and that more hours should translate to better outcomes. We didn't see that."
The conclusion was similar in a study of two doses of atropine. In a comparison of atropine drops given every day versus 2 days a week, the investigators found that the doses were equally effective for treatment of moderate amblyopia.
"Less treatment seems to be as effective or is better than we could have hoped," Dr. Repka said.
He added that compliance issues could have influenced results in all of these studies if parents decided that they did not need to adhere to the prescribed length of patching time or drug-dosing schedule if they believed that the format of the trial was "less versus more."
The workshop also covered a recently published paper from Archives of Ophthalmology on amblyopia treatment in older children aged 7 to 17 years.2
At 49 clinical sites, 507 patients with amblyopic eye visual acuity ranging from 20/40 to 20/400 were provided with optimal optical correction and then randomly assigned to a treatment group (2 to 6 hours per day of prescribed patching combined with near visual activities for all patients plus atropine sulfate for children aged 7 to 12 years) or an optical correction group. Patients whose amblyopic eye acuity improved 10 or more letters (2 lines) by 24 weeks were considered to have a response.
Outcomes showed that children up to age 13 could get a sizable improvement in vision while those from 13 to 18 years of age could get better as well, although improvement might not be as substantial, said Dr. Richard Hertle, of Pittsburgh.