Iris S Kassem MD PhD (

Dr. Kassem of the Medical College of Wisconsin has no relevant personal financial relationships to disclose. She is married to an employee of AbbVie.

James Goodwin MD, editor. (Dr. Goodwin of the University of Illinois at Chicago has no relevant financial relationships to disclose.)
Originally released January 30, 2003; last updated January 9, 2019; expires January 9, 2022

This article includes discussion of amblyopia and lazy eye. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Amblyopia is a reduction of vision produced by abnormal central visual processing. This common disorder occurs in an estimated prevalence of 2% (MPEDS 2008; Friedman et al 2009; Pai et al 2012; McKean-Cowdin et al 2013). Unless treated during childhood, the loss of vision is permanent. Amblyopia therapy often requires penalization of the normal eye. The daily amount of time and the best penalization methods are unsettled and controversial. In this article, the author describes studies that investigate to quantitate the time and methods of penalization required for treatment and the ages most appropriate for their use in childhood as well as newer treatment modalities.

Key points


• Amblyopia is a reduction in visual acuity in 1 or both eyes due to refractive error, strabismus, or visual deprivation.


• Treatment of amblyopia involves treatment of the underlying cause of vision loss with or without penalization by occlusion or optical penalization.


• Amblyopia treatment is most effective at younger ages.


• Vision loss from amblyopia can be permanent if it is not treated in a timely fashion.

Historical note and terminology

Amblyopia, or lazy eye, is the reduction in the best corrected visual acuity that occurs during childhood that cannot be explained by a known structural abnormality. The term “amblyopia” is derived from the Greek amblys, meaning “blunt,” and ops, meaning “eye,” indicating a “dullness” or incomplete loss of vision rather than complete blindness (Duke-Elder 1973). The early clinical understanding of this disorder can be traced to George Louis Leclerc, Comte de Buffon, who in 1743 proposed the use of occlusion of the sound eye to “force” the amblyopic eye to see better (Duke-Elder 1973). The scientific study of amblyopia was advanced by the work of Hubel and Wiesel, who won the Nobel Prize in 1981 for their work demonstrating physiologic and anatomic changes in the visual system of kittens and monkeys that had been visually deprived during the critical period of visual development (Wiesel and Hubel 1963; Wiesel and Hubel 1965). As a result of their work and subsequent studies by other investigators, the concept of amblyopia as a developmental visual disorder of childhood was established (von Noorden 1985; Lowel and Engelmann 2002; Schroder et al 2002).

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