A determination of the prevalence of anisometropia has several difficulties. Frequently, amblyopia is associated with a combination of anisometropia and strabismus. One cause of significant anisometropia and subsequent aniseikonia has been aphakia. Vision loss can occur and is associated with strabismus, refractive errors, and anisometropia. Yoon was exempted from the national service due to anisometropia in 1982. Anisometropia in a patient can lead to a microtropia. Refractive amblyopia may result from anisometropia (unequal refractive error between the two eyes). Anisometropia is when two eyes have unequal refractive power. An estimated 6% of subjects aged 6 to 18 have anisometropia. Anisometropia exists when there is a difference in the power between the two eyes.