Mirror image hypermetropic anisometropia in a pair of monozygotic twins.

In monozygotic twins two embryos are formed from a single fertilized egg. In "mirror image twins" identical siblings have reverse asymmetric features in the right and left sides of the body. We report the case of twins with mirror-image hypermetropic anisometropia. They were referred to an ophthalmologist at the age of 3.5 years for amblyopia. Cycloplegic refraction of twin 1 was +1.00 in the right eye and +4.50 -0.75 ×180 in the left eye; of twin 2, +4.75 -1.00 ×180 and +1.25. Keratometry and axial length were measured with Lenstar LS 900 when the twins were 6 years of age. In twin 1, the axial length was 22.18 mm in the right eye and 20.97 in the left eye; in twin 2, 20.94 mm and 22.13. Keratomtry of both eyes of these twins was relatively equal.