decrease in best corrected vision in one or both eyes is referred to as amblyopia. In most cases it is preventable and treatable. Treatment should be initiated soon after the diagnosis is made and before the completion of the visual pathway in the patient (i.e., before the age of 9 years old). Younger patients often respond more favorably to amblyopia treatment. For a successful outcome both the amblyopia and its underlying etiology (e.g., strabismus, refractive error, or obstruction of the visual axis) must be treated.