Definition of Isometropia

Isometropia: The condition in which both eyes have equal refractive power. If, for example, one eye is myopic (nearsighted), so is the other. Or if one eye is hyperopic (farsighted), so is the other, or neither eye may have a significant refractive error.

The term "isometropia" is made up of three parts from the Greek: iso- (equal) + -metr- (measure) + -opia (vision). Literally, the measure of vision is equal. The opposite of isometropia is anisometropia in which the two eyes have unequal refractive powers.

Anisometropia is a serious concern in newborns and young children because it can lead to amblyopia (impaired vision in one eye). With a major degree of anisometropia, the brain cannot reconcile the difference in images coming from the two eyes. It develops a preference for the image coming from one eye and suppresses the image from the other eye and, in time, the brain loses the ability to "see" the image from the suppressed eye.


Last Editorial Review: 9/20/2012

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