anisometropic amblyopia
Also called refractive amblyopia (unilateral), anisometropia amblyopia
Anisometropic amblyopia is a lasting reduction in best-corrected acuity in the eye with the greater refractive error. It develops when anisometropia remains uncorrected during visual development, and no disease of the eye or visual pathway explains the loss1,2.
Both foveae are directed at the same object, but the eye with the greater refractive error receives a blurrier image. During visual development, the cortex suppresses that image in favor of the clearer image from the fellow eye. Persistent suppression can lead to amblyopia3.
A refractive difference of as little as 1 diopter can cause anisometropic amblyopia. Hyperopic anisometropia is the usual cause: the more hyperopic eye remains blurred at every distance2. Because the child sees well with the fellow eye and the eyes appear straight, the condition often goes unnoticed until vision screening3.
More detail
Because the two images share a visual direction, the loss extends to contrast sensitivity across the whole field, which distinguishes it from strabismic amblyopia; that form requires a deviation and more often shows eccentric fixation and crowding1,3. Isoametropic amblyopia is the related form in which both eyes carry a high and equal error and both are mildly amblyopic1. Acuity in the affected eye measures better with the other eye covered than with both eyes open, and many of these patients have a microtropia on careful testing3,4.
Sources (4)
- Scheiman and Wick, Clinical Management of Binocular Vision, ch. 17
- Kanski, Clinical Ophthalmology (2024), ch. 18
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 14
- Pickwell's Binocular Vision Anomalies, ch. 13
Reviewed October 2026