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A child getting an eye exam. (Lenses are placed in a trial frame to help determine eyeglass prescription.)
Lazy eye in older children
From eNews, June 23, 2005
Amblyopia, more widely known as lazy eye, affects approximately 2 to 3 out of every 100 children in the United States. It is the most common cause of monocular (one-eye) visual impairment among children and young and middle-aged adults, according to the National Eye Institute. For the longest time, eye care professionals believed that if you didn't treat the problem in early childhood-that is, before you hit the ripe old age of seven-then there was little, if anything, you could do to save your vision.
Results from a recent nationwide clinical trial, however, show that age alone should not be used as a factor to decide whether or not to treat a child with amblyopia. Several researchers at the University of Minnesota participated in this study, in which 507 children at 49 eye centers participated. The study was the first large sample to show effective treatment for this eye condition.
The study's major findings are that the vision of 53 percent of children ages 7 to 12 years improved, compared with 25 percent of those children who did not receive treatment. Among children ages 13 to 17 who had not been previously treated for amblyopia, 47 percent of them had successful vision improvement.
"This is important news because an estimated 3 percent of children in the United States have some degree of vision impairment due to amblyopia, and many of these children do not receive treatment while they are young," says Stephen Christiansen, coinvestigator and a pediatric ophthalmologist at the U.
Amblyopia, which usually begins in infancy or early childhood, happens when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The affected eye may look crossed or be left wandering (strabismus), or both eyes may look normal but actually have significant differences between them in terms of refractive error, such as astigmatism, farsightedness, or nearsightedness.
A drop of a drug called atropine is placed in the stronger eye once a day to temporarily blur the vision so that the child will prefer to use the lazy eye. Patching involves wearing an opaque, adhesive patch over the stronger eye for weeks or months. This therapy forces the child to use the eye with amblyopia. Both treatments are meant to stimulate vision in the weaker eye and help the part of the brain that manages vision develop more completely.
Children in the study were divided randomly into two groups. One group was given new prescription glasses, while the other was fitted with glasses as well as an eye patch, or given an eye patch and special eye drops to limit the use of the unaffected eye. These children were also asked to perform near-vision activities that forced them to use the eye with amblyopia. Patching was prescribed for two to six hours daily, and the eye drops were administered daily for the children ages 7 to 12.
Successful vision improvement was defined as the lazy eye's ability to read at least two more lines on a standard eye chart. The investigators found that 53 percent of children ages 7 through 12 who received glasses and were treated with patches, eye drops, and near-vision activity met this standard, while only 25 percent of those children in this age group who only received glasses met the standard. For children ages 13 to 17 who were treated with both glasses and patches (these children did not get drops), 25 percent met the standard, while 23 percent of those who received only glasses met the standard.
Despite the benefits of the treatment, most children, including those who responded to treatment, were still left with some visual impairment. "[But] this study shows how important it is to screen children of all ages for amblyopia," says study cochair Richard Hertle of the Children's Hospital of Pittsburgh.
The study authors do not know if the vision improvement of the study participants will be sustained once treatment is discontinued. The National Eye Institute is currently supporting a one-year follow-up study to determine the percentage of amblyopia that recurs among the children who responded well to treatment.
The study was published in the April 2005 issue of Archives of Ophthalmology.