Occluding the sound eye in amblyopic patients provides rapid and lasting visual acuity improvement.
Dr. Repka reported on his participation in an ongoing randomized, controlled, multicenter trial. The NIH-funded study has two goals: to see if there is merit to the use of atropine in amblyopic patients, and also to see if the benefit derived from amblyopic occlusion therapy-whether from atropine or a patch-is sustained over time.
A total of 419 patients, all with either strabismic or anisometropic amblyopia, were enrolled in the trial. Follow-ups were at 6 months and 2 years after enrollment. A subgroup of 188 patients was followed up at age 10 years, and will be reexamined at 15 years of age.
At 6 months, the patients' mean acuity had improved to 20/30-2 in the atropine group and 20/30 in the patching group. The patients who underwent patching had faster improvement; at 5 weeks there was a statistically significantly better acuity in the patching group. However, both groups continued to have improvement for 6 months. At 6 months the visual acuity improvements were similar for both treatment groups.
The benefit of each treatment was similar in subgroups based upon cause of amblyopia, strabismus, anisometropia, and both combined.
"We didn't expect that patients with strabismic amblyopia would have success as often as those with anisometropia using atropine. We questioned whether the strabismic patient would switch fixation with atropine," Dr. Repka said. "And yet that's not what we saw. The patients with strabismus were as likely to have a successful outcome as the patients with anisometropia. That went against our clinical instincts."
Also, patients were as likely to have the same amount of improvement if they entered the study at 20/100 as those who entered at 20/40.
There were some detrimental effects on the sound eye with atropine, however: a transient decrease in visual acuity of 1 line or more occurred significantly more often in the atropine group (23%) than in the patching group (8%). Patients who used atropine were also more likely to experience light sensitivity than the patients who used patching.
The benefits of amblyopia treatment have persisted over time in both groups. "Remarkably, the mean improvement in both groups could not have been more similar 2 years after enrollment," Dr. Repka said. "About 85% of the overall patient population had achieved 20/32, or a three line or better improvement. So there was a substantial improvement from either therapy, and it's not limited to the first 5 weeks or the first 6 months."
According to Dr. Repka, the basic message is that there is lasting value in occluding the sound eye, and there are options such as atropine eyedrops.
"Atropine is an alternative to patching," he said. "I'm not advising one or the other as superior; it really is an opportunity for parents to try one or both and to be able to have some flexibility. I don't have a preference in my practice; I educate the parents about both and they decide which they prefer to try initially."
Dr. Repka added that if patching or atropine fail, there are other treatments that can be tried. "The important thing is to occlude the eye, so the best thing we can do is relay the fact that patients and their parents have options," he said.
Finally, Dr. Repka said, do not think of either patching or atropine as a "start it and forget it" type of therapy. "Be sure you follow up regularly with your patients and their parents," he said. "Amblyopia therapy is an ongoing process that requires supervision and monitoring."