aniseikonia


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Related to aniseikonia: anisophoria

aniseikonia

 [an″is-i-ko´ne-ah]
inequality of the retinal images of the two eyes.

an·is·ei·ko·ni·a

(an'ĭ-sī-kō'nē-ă),
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.
[G. anisos, unequal, + eikōn, an image]

aniseikonia

(ăn-ī′sī-kō′nē-ə)
n.
A condition in which the shape and size of the ocular image differ in each eye.

an·i′sei·kon′ic (-kŏn′ĭk) adj.

an·is·ei·ko·ni·a

(an'ī-sī-kō'nē-ă)
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]

aniseikonia

An ocular defect in which the size or shape of the retinal images are different in the two eyes. This is often the result of ANISOMETROPIA. From the Greek an , not iso , equal and eicon , an image.

aniseikonia 

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.
References in periodicals archive ?
If there is sufficient difference between the retinal image sizes (a difference of around 5% or greater may be problematic), (6) then stereoscopic fusion will be difficult and can result in poor binocular vision as a result of aniseikonia.
Due to the contact lens position remaining relatively stable with changes in gaze, anisometropic contact lens wearers will not be troubled by off-centre differential prismatic effects, and the magnification produced by contact lenses will be significantly reduced in comparison to spectacle lenses, (6) which in turn, will help combat aniseikonia.
Contact lenses can be a powerful tool to help patients with a variety of conditions, from diplopia to aniseikonia. As practitioners, it is important to explore various treatment options with patients to provide optimal care.
Following a cataract operation, a patient may be rendered anisometropic by the introduction of an intraocular lens, possibly inducing large degrees of aniseikonia until the second eye is attended to.
However, what we know about aniseikonia and the effect of refractive correction on amblyopia mean that contact lenses are the preferred mode of optical correction for patients with this condition.
02 Which of the following statements relating to aniseikonia is correct?
a Basic (or intrinsic) aniseikonia could be induced by different refractive powers used in each eye used for the correction of anisometropia
b Basic (or intrinsic) aniseikonia could be induced by differing axial lengths of the two eyes or disruption of the retinal photoreceptor mosaic
c Aniseikonia can only be considered clinically significant if the image size differential between the two eyes is over 4%
This may lead to problems with spectacle wear due to anisometropia and aniseikonia. With waiting times for cataract surgery being quite short in most areas, this is becoming less of an issue with patients being told to wait until both eyes have been treated (if appropriate) before getting spectacles updated.