Size lens set

How to use size lenses

Let us say that an aniseikonia test showed that a patient has 4% aniseikonia. By definition, this means that the image in the right eye (OD) needs to be magnified by 4% to cancel the aniseikonia.

To see what the effect of a 4% aniseikonia correction is for the patient, a 4% size lens can be held in front of the right eye with the concave side towards the eye (see top-left image).
Note that aniseikonia is a binocular condition and therefore a relative measure between the two eyes. Instead of magnifying the image in the right eye, equal image sizes are also obtained by minifying the image in the left eye (OS). A size lens minifies by flipping it as in the top-right image.
The lower two images give two more alternative ways to correct a 4% aniseikonia. They also show that with two size lenses, it is possible to correct a larger amount of aniseikonia. Using both the 7% and the 6% allows you to correct 13%!