Eye Drops To Treat Childhood Eye Disorder Work As Well As Patching The Eye

After six months of treatment, researchers found that the drug atropine, when placed in the unaffected eye once a day, works as well as eye patching and may encourage better compliance. Compliance is an important factor in the success of amblyopia therapy. Treatment should be started when the child is young, since amblyopia is more effectively treated in children under seven years of age. Timely and successful treatment for amblyopia in childhood can prevent lifelong visual impairment.

“These results are important because they provide an effective alternative treatment that helps prevent permanent vision impairment for children with amblyopia,” said Paul A. Sieving, M.D., Ph.D., director of the National Eye Institute, one of the Federal government’s National Institutes of Health and the agency that sponsored the study. “Amblyopia is currently treated by wearing an eye patch over one eye for weeks to months. Children usually do not like this treatment approach because of quality of life issues, such as irritation of the skin and teasing by other children. This new study found that atropine eye drops had a higher acceptance rate and better compliance by children and their parents than did patching. This may well become a new standard treatment for some forms of 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 looks normal, there is interference with normal visual processing, that limits the development of a portion of the brain responsible for vision. The most common causes of amblyopia are misalignment of the eyes (crossed eyes) or significant differences in refractive error, such as farsightedness or nearsightedness, between the two eyes. Amblyopia usually begins in infancy or childhood. It is estimated that as many as three percent of children in the U.S. have some degree of vision impairment due to amblyopia.

Treatment for amblyopia is most effective when started in young children less than seven years old. Response to treatment in older children is much less effective. Most eye care professionals treat amblyopia by placing an opaque adhesive patch, or “eye bandage,” on the skin to cover the unaffected eye. This forces the child to use the eye with amblyopia, which stimulates vision in the eye with amblyopia and helps the part of the brain that manages vision to develop more completely.

However, many children do not like the appearance of the eye patch and the accompanying social and psychological stigma and will not fully cooperate, which can lead to treatment failure. Also, patching forces a child to use an eye that has poor vision, often making compliance difficult for active children. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children and young and middle-aged adults. Consequently, it is crucial for children to comply with treatment.

The atropine eye drop works by temporarily blurring vision in the unaffected eye, thereby forcing the eye with amblyopia to be used. This strengthens it and improves vision. The advantage of atropine treatment is that the parent simply places a drop in the child’s eye once a day. With patching, the parent must monitor the child wearing the patch for six or more hours each day for many weeks or months.

In the Amblyopia Treatment Study, 215 children were randomly assigned to receive patching, and 204 were assigned to receive atropine eye drops. Researchers found that 79 percent of those receiving the eye patch were treated successfully, and that 74 percent of those receiving the atropine were treated successfully. This difference is clinically insignificant. Although researchers found that vision in the amblyopic eye improved faster in the patching group, the difference in the two groups at six months was small and not significant.

“The daily burden to administer treatment for amblyopia falls on the parent,” said study chairman Michael Repka, M.D., professor of ophthalmology and pediatrics at the Wilmer Eye Institute of Johns Hopkins University School of Medicine in Baltimore. “This study shows that one drop a day of atropine works as well as patching the eye for some children with amblyopia. Since both patching and atropine work equally well, the choice of treatment can be made by the eye care professional in consultation with the parent.”

The children who were treated in this study will continue to be followed until April 2003, allowing researchers to learn whether there is any longer term advantage to treating amblyopia with either patching or atropine.

The study was conducted by the Pediatric Eye Disease Investigator Group at 47 clinical sites throughout North America. The study was funded by the National Eye Institute and coordinated by the Jaeb Center for Health Research in Tampa, Florida and the Wilmer Eye Institute of Johns Hopkins University in Baltimore.

BACKGROUND

Amblyopia Treatment Study

The term “amblyopia” derives from the Greek word for “dullness of vision.” It is estimated that amblyopia affects two or three of every 100 children in the United States. The disorder is caused by conditions that affect normal visual development. These conditions can include an imbalance in the positioning of the eyes, such as strabismus, in which the eyes are crossed inward (esotropia) or turned outward (exotropia). Amblyopia can also result from a major difference in the refraction between the two eyes, such as nearsightedness, farsightedness, or astigmatism.

Despite the common occurrence of amblyopia, there has been little quality data on its natural history or on the outcomes of two forms of treatment of this disorder — occlusion therapy (patching) and topical drug therapy. Patching the unaffected eye has been the standard treatment for amblyopia, despite the lack of meaningful data demonstrating its superiority over other treatments. Reported rates of compliance for patching widely range from 49 to 87 percent. There is evidence that compliance is an important factor in determining the level of success of amblyopia treatment.

An alternative treatment — drug therapy with a cycloplegic eye drop (atropine) that dilates the pupil and blurs the image seen by the unaffected eye — has been known for almost a century. This method has been widely used when occlusion treatment does not work. However, it has seen little use as a primary treatment for amblyopia.

Prior to this study, a few small studies had suggested that atropine eye drops might be useful for treating mild to moderate degrees of amblyopia. If this were true, atropine drug therapy might be preferred as an initial treatment for many children with amblyopia, since it appears to be more readily accepted by the children and their parents. However, the use of atropine as a primary therapy for amblyopia had gained only limited use among pediatric ophthalmologists. A 1997 survey by the Pediatric Eye Disease Investigator Group (PEDIG) found that only three percent of eye care professionals prescribed atropine eye drops as a primary treatment of amblyopia, while 97 percent preferred patching. A definitive study to compare the outcomes from occlusion therapy and drug therapy was justified to determine if new practice guidelines for treatment of amblyopia were needed.

The Amblyopia Treatment Study

The Amblyopia Treatment Study was conducted to determine whether atropine was as effective as patching for treating amblyopia in children less than seven years of age. The study was funded by the National Eye Institute and conducted by the PEDIG, a network of eye care professionals at universities in North America and in local community offices. The PEDIG professionals have a goal of determining the best treatment for various eye problems in children.

Between April 1999 and April 2001, 419 patients entered the trial. The average age of the children at the beginning of the study was 5.2 years; 47 percent were female; and 83 percent were white. Enrollment was restricted to children who had either not been previously treated for amblyopia or who had received no more than two months of treatment in the prior two years. Each patient was randomly assigned to either the patching or atropine groups. Ninety-seven percent of those assigned to the patching group and 95 percent of the assigned to the atropine group completed the study.

The minimal patching time was six hours per day; some children were patched during all waking hours. This time was reduced or increased, depending on the success of the treatment at 16 weeks. Researchers judged the compliance rate in the patching group to be excellent in 49 percent of the patients, good in 34 percent, fair in 13 percent, and poor in five percent.

Atropine eye drops were prescribed, one drop a day initially but the frequency could be reduced depending on the success of the treatment at 16 weeks. Sunglasses were provided to the children for use in sunlight due to light sensitivity from the dilated pupils. Researchers judged the compliance rate in the atropine group to be excellent in 78 percent of the patients, good in 18 percent, fair in three percent, and poor in one percent. On a questionnaire completed by the child’s parent or guardian, the acceptability of the atropine treatment was judged to be better than that of the patching treatment.

Side effects were minimal for either group. In the patching group, mild skin irritation was reported at least once in 41 percent of patients, with moderate or severe skin irritation at least once in six percent of patients. In the atropine group, light sensitivity was reported for 18 percent of patients, eye lid or corneal irritation for four percent, and eye pain or headache for two percent. In the atropine group, some of the normal eyes that received the atropine had a temporary decrease in visual acuity. The results are inconclusive about whether this was an effect of the atropine or was due to a need to change the eyeglass prescription.

Atropine therapy is likely to be less expensive than patching. Atropine treatment is estimated to cost about $10 over six months, where an eye patch would cost nearly $100. About 25 percent of atropine-treated patients may need to wear a special lens in their eyeglasses to compensate for the effect of the atropine, at a cost of about $50.

Data from the study will provide valuable information about the course of amblyopia treatment and help determine whether factors such as age and refractive error should be considered in determining which procedure is best for a given patient.

The NEI is part of the National Institutes of Health (NIH) and is the Federal government’s lead agency for vision research that leads to sight-saving treatments and plays a key role in reducing visual impairment and blindness. The NIH is an agency of the US Department of Health and Human Services.