Occlusion Versus Pharmacologic Therapy for Moderate Amblyopia

Amblyopia, or lazy eye, is the most common cause of visual impairment in children and often persists in adulthood. It is reported to be the leading cause of vision loss in one eye in the 20-70 year old age group, with a prevalence of 1-4 percent in various studies, indicating that both improved means of detection and treatment are needed.

Most of the available data on the natural history of amblyopia and success rates of its treatment with either patching or drug therapy are retrospective and uncontrolled. Despite the common occurrence of amblyopia, there is little quality data on treatment of this condition. Thus, there is much to be learned about the course of treated amblyopia, to provide more precise estimates of success rates and to identify factors that may be associated with successful and unsuccessful treatment.

Amblyopia, when diagnosed in children, is usually treated with occlusion (patching) of the sound eye. Occlusion therapy is subject to problems of compliance, due to the child's dislike of wearing a patch for visual, skin irritation, and social/psychological reasons. There is evidence that compliance may be one of, if not, the most important determinant of success of amblyopia therapy.

An alternative treatment, drug therapy with a cycloplegic drug (atropine) that dilates the pupils and blurs the image seen by the sound eye, has been known for almost a century. This method has been widely used for the management of occlusion treatment failures and for maintenance therapy. However, it has seen little use as a primary treatment for amblyopia. Clinical experience has found that it has a high acceptability to patients and parents, and hence high compliance. In addition to its acceptability, pharmacologic therapy has the known advantage over occlusion of providing a wider visual field with both eyes, which may have safety and other functional implications. There is also clinical and laboratory evidence suggesting that drug therapy may maintain and improve the ability to see with both eyes (binocularity).

Available data suggest that the success rate with drug therapy is as good as, if not better than, the success rate with occlusion therapy for mild to moderate degrees of amblyopia. If this is true, for many children with amblyopia, drug therapy may be the preferred initial therapy since it appears to be more readily accepted by the children and parents. Despite data to support the use of drug therapy as a primary therapy for amblyopia, it has gained only limited use among pediatric ophthalmologists. A definitive study comparing the outcomes from occlusion therapy and drug therapy is justified in order to determine if new practice guidelines for treatment of amblyopia are needed.

Regardless of whether the trial determines that one therapeutic approach is better than the other, the data that are collected will provide valuable information about the course of amblyopia treatment that is not presently available. The study also is expected to provide data that will help to determine whether factors such as age, refractive status, cause of amblyopia, or fixation pattern should be considered in determining which procedure is best for a given patient.

Extended Follow-up of Study Patients

The extended follow up study consists of annual visits prior to age 10, followed by a visit at age 10 years and a visit at age 15 years. There is no amblyopia treatment that is required during the extended follow up period.

Inclusion criteria

• Patients must be 7 years old or younger with amblyopia due to strabismus or anisometropia
• Visual acuity in the amblyopic eye must be between 20/40 and 20/100
• Visual acuity in the sound eye or 20/40 or better
• At least 3 lines of acuity difference between the two eyes

Exclusion criteria

• More than two months of amblyopia therapy in the past two years
• Myopia (more than -0.50 D)