Questions and Answers
A Randomized Trial Comparing Part-Time to
Minimal Time Patching for Moderate Amblyopia
May 12, 2003
This document was prepared by the Information Office, National Eye Institute, National Institutes of Health, in consultation with the study chairman and coordinating center director.
What is amblyopia?
Amblyopia, or lazy eye, is a condition of poor vision in an otherwise healthy eye because the brain has learned to favor the other eye. Although the eye with amblyopia often looks normal, there is interference with normal visual processing, which limits the development of the portion of the brain responsible for vision of that eye. Amblyopia usually begins in infancy or childhood, and is the most common cause of visual impairment in children.
The most common causes of amblyopia are misalignment of the eyes (strabismus), inwhich the eyes are crossed inward (esotropia) or turned outward (exotropia); and significant differences in refractive error, such as farsightedness, nearsightedness, or unequal astigmatism between the two eyes.
How many children have amblyopia?
It is estimated that as many as two to three percent of children in the US have vision impairment due to amblyopia.
How is amblyopia currently treated?
Many eye care professionals treat amblyopia by placing an opaque adhesive patch, or “eye bandage,” on the skin to cover the unaffected eye for many hours each day lasting from weeks to months. For moderate amblyopia (20/40 to 20/80), this can mean six hours or more each day. Patching the unaffected eye had been the mainstay of amblyopia treatment for decades. In March 2002, researchers reported the effectiveness of a second form of treatment, which involved using atropine eye drops that dilate the unaffected eye. Both treatments force the child to use the eye with amblyopia, stimulating vision improvement in that eye by helping the part of the brain that manages vision to develop more completely.
Is treatment more effective at certain ages?
Treatment for amblyopia should generally be started when the child is young, since amblyopia seems to be more effectively treated in children less than seven years old. Response to treatment in older children is less effective. Timely and successful treatment for amblyopia in childhood can prevent lifelong visual impairment.
Why was the Amblyopia Patching Regimen Study conducted?
Opinions varied widely on the number of daily hours patching should be prescribed. No prior study had provided conclusive evidence of the optimal number of patching hours.
What were the results of the Amblyopia Patching Regimen Study?
Children with moderate amblyopia who wore an adhesive patch daily for two hours over their unaffected eye showed the same improvement in vision in the eye with amblyopia as those who wore a patch for six hours. More specifically, after four months of treatment, 79 percent of patients in the two-hour group and 76 percent of patients in the six-hour group showed improvement. Both groups of children in the study combined the prescribed patching dose with one hour a day of “near” work, such as coloring, tracing, reading, and crafts.
Why are these results important?
These results are important because they will change the way doctors treat moderate amblyopia. The findings will make an immediate difference in treatment compliance and the quality of life for children with this eye disorder.
Prior to these results, many children with amblyopia had to wear an eye patch during school hours. For these children, the accompanying social and psychological stigma was very real. Many were stared at and teased by other children, which made them feel different. Now, children can look forward to attending school without the patch. The study found that parents of children who wore the patch for six hours were more concerned about social stigma than the parents of children who wore the patch for two hours.
Also, patching forces a child to use the eye that has poor vision, often making compliance difficult for active children. It is crucial for young children to comply with the recommended treatment because if amblyopia is not successfully treated in early childhood, visual impairment usually persists into adulthood. Reducing patching time from six hours to two hours for moderate amblyopia will make it much easier for parents to monitor their children, fit the patching into their schedules, and encourage children to successfully comply with treatment. Timely and successful treatment for amblyopia in childhood can prevent lifelong visual impairment.
How many children were involved in the Amblyopia Patching Regimen Study?
Between May 2001 and May 2002, 189 patients entered the trial, with 95 randomly assigned to the two-hour patching group and 94 assigned to the six-hour patching group.
What were the characteristics of the children in the study?
The average age of the patients was 5.2 years; 44 percent were female, and 85 percent were white. To avoid including in the study those patients whose prior treatment was unsuccessful, enrollment was restricted to children who had not been previously treated for amblyopia; or had not received patching treatment within six months of enrollment and had not received other amblyopia treatment of any type (other than eyeglasses) within one month of enrollment. After four months, 97 percent of patients in the two-hour group and 95 percent in the six-hour group completed the primary outcome exam.
How much did vision improve?
Patients in both groups showed substantial improvement in the eye with amblyopia. At four months, 79 percent of patients in the two-hour group and 76 percent of patients in the six-hour group had improved by two or more lines on the eye chart.
Why did the children in both study groups have to perform one hour of “close-up” work while wearing the patch?
Having the child perform one hour of “near,” or close-up, work per day while patched was a part of the prescribed treatment and are common instructions in clinical practice. It remains unclear if the same amount of visual improvement would occur with patching alone. A clinical trial to address the importance of near work in the treatment of amblyopia is being planned.
Were there any negative effects in the unaffected eye?
Vision in the unaffected eye decreased by either one or two lines on the standard eye chart in about 21 percent of patients in the two-hour group, and about 24 percent of patients in the six-hour group. However, this is normal for patients with amblyopia, and vision in the unaffected eye is expected to return to normal when treatment is completed.
What is the cost of patching?
Eye patches, assuming 1= patches every day, are estimated to cost about $100 over a six-month period.
Will the children in the study continue to be followed?
No.
How does patching the eye for two hours compare to using the atropine eye drops?
In terms of both compliance and the amount of improvement in vision, they would likely be very similar.
Will this treatment work for all children with amblyopia?
These results do not necessarily apply to all children with amblyopia. Children with more severe amblyopia, or who have amblyopia from causes other than crossed eyes or refractive error, may need a different treatment regimen.
Are there any other studies of amblyopia underway?
Yes. The Pediatric Eye Disease Investigator Group, which conducted this study, is currently conducting a clinical trial on children with severe amblyopia and expects the results will be available in the Fall of 2003. A second trial is evaluating different dosage regimens of an eyedrop to treat amblyopia. A third trial is examining the value of treatment in older children and teenagers.
Who funded and conducted the Amblyopia Treatment Study?
The study was funded by the National Eye Institute, one of the Federal Government’s National Institutes of Health, and conducted by the Pediatric Eye Disease Investigator Group at 35 clinical sites throughout North America. The study was coordinated by the Jaeb Center for Health Research in Tampa, Florida.