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 a 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 theimage 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.

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