The Amblyopia Treatment Studies: Implications for Clinical Practice

Amblyopia is the most common cause of monocular vision loss in children1 with an estimated prevalence of approximately 2% in the United States.2–4 A developmental disorder of spatial vision, amblyopia is clinically defined as decreased best-corrected visual acuity (VA) in one, or less frequently both eyes, in the absence of any obvious structural anomalies or ocular disease. It is associated with abnormal visual experience, most commonly strabismus, anisometropia, or form deprivation that occurs during a sensitive period of visual development in infancy or early childhood. Signs, Symptoms, and Quality-of-Life Concerns In addition to reduced best-corrected VA, there are a plethora of visual function deficits of the amblyopic eye, including abnormal contour interaction,5 reduced contrast sensitivity,6 positional uncertainty,7 spatial distortion,8 poor accommodation,9 abnormal eye movements,10 and suppression.11 Because of good vision in their non-amblyopic (sound) eye, persons with unilateral amblyopia typically do not complain of blurred or poor vision under habitual binocular viewing conditions; however, recent studies have reported reduced reading speed12 and compromised fine-motor skills13 even with both eyes open. There are important public health consequences when amblyopia is left untreated. Patients with amblyopia are more likely to become visually disabled because of an increased risk of their sound eye becoming visually impaired,14,15 with their estimated lifetime risk of visual impairment being at least 1.2%.15 Vision loss in the sound eye, often caused by trauma, can have a significant effect on quality of life with many employed individuals no longer being able to work because of inadequate visual function.15,16 Although amblyopic eye VA can sometimes improve in adults after vision loss of their sound eye, most remain visually disabled.17 Furthermore, the presence of unilateral amblyopia has a deleterious effect on binocularity, including stereopsis. Because good VA in each eye and/or normal stereoacuity are often prerequisite for careers in the military, aviation, surgery, law enforcement, firefighting, as well as obtaining a commercial driver’s license,18 amblyopic individuals are often precluded from participating in such occupations.19