anisometropic amblyopia
Also called refractive amblyopia (unilateral), anisometropia amblyopia
Reduced best-corrected acuity in the more ametropic eye of an uncorrected anisometropia, a difference in refractive error between the two eyes, with no eye or pathway disease to account for it1,2. Both foveae point at the same object, but one image is sharp and the other blurred; the cortex inhibits the blurred foveal image, and inhibition held through the years of visual development becomes amblyopia3.
A difference of as little as one diopter can produce it, and hyperopic anisometropia is the usual cause, because the more hyperopic eye never receives a clear image at any distance2. The condition hides: the child has one clear eye, straight eyes and no symptoms, so it is found at 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