The degree of
aniseikonia with the correction of unilateral
aphakia is mathematically and clinically much greater with glasses than with
contact lenses. It is not possible to estimate the resulting
aniseikonia on an individual basis from calculating the right-to-left difference between the
retinal image sizes. However, both calculation of the differences between the
retinal image sizes and the
aniseikonia point out the advantage of
contact lenses. Unilateral axial
myopia (more than 90% of anisomyopias are axial) shows the smallest differences between
retinal image sizes for glasses; however, measuring the
aniseikonia with the phase difference haploscope shows the smallest amount of
aniseikonia for
contact lenses. This apparent contradiction can be explained by the "expansion" of the "granularity of perception" of the more myopic eye. Because the amount of "expansion" varies widely between individuals and is not known in particular cases,
aniseikonia cannot be calculated but must be measured.
Aniseikonia proved to be one of the most important factors in the development of
amblyopia of the more myopic eye.
Contact lenses are the best means of reducing the amount of
aniseikonia in patients suffering from axial anisomyopia. In cases with minor anisomyopia it may be also possible to obtain a minor degree of
aniseikonia with glasses. Exceptions such as "useful" and "malignant" anisomyopia must be taken into consideration.