anisoiconia

An ocular condition in which the image of an object in one eye differs in size or shape from the image of the same object in the other eye.

Synonym(s): unequal retinal image

[G. anisos, unequal, + eikōn, an image]

An ocular condition in which the image of an object in one eye differs in size or shape from the image of the same object in the fellow eye.

[G. anisos, unequal, + eikōn, an image]

A difference in size and/or shape of the visual images of the two eyes. This may be due either to unequal axial lengths of the two eyes, to an unequal distribution of the retinal elements or an inequality of the cortical representation of the two ocular images (basic or intrinsic aniseikonia). It is most frequently induced by lenses of different power used in the correction of anisometropia (refractive aniseikonia). Symptoms include visual discomfort, visual distortion of space and sometimes difficulty in achieving binocular vision, as for example in spectacle corrected unilateral aphakia. Aniseikonia is measured with an eikonometer, although a simple test consists of separating the retinal images of a large target (e.g. a test chart) with prisms and comparing them: placing size lenses in front of one eye until the images appear equal will give an indication of the amount of aniseikonia. See aniseikonic lens; shape magnification; New Aniseikonia test; Turville infinity balance test.