Ocular anisometropia and laterality.

Purpose: To study the difference in refraction between right and left eyes (anisometropia) in different age groups, look for evidence of eye laterality (more refractive error in one eye) and compare the size of anisometropia in the myopic and emmetropic ranges.

Methods: The study was based on children in Hong Kong (examined at the age of 6 years and again at the age of 8.5 years) and their parents (aged 26-60 years).

Results: In all age groups the difference between right and left eyes in sphere and cylinder was modest, in most cases < or = 0.25 D. In both children and their parents a tendency towards spherical right eye laterality was found in the myopic individuals (p < 0.05). This was not the case with the cylinder. In the 8.5-year-old children and in their parents, the numerical size of spherical anisometropia increased with myopia (p < 0.05 and p < 0.01, respectively). Cylindrical anisometropia did not exhibit such an increase.

Conclusion: In Hong Kong children and their parents we found a tendency towards more spherical myopia in right eyes (laterality) in myopic cases. The numerical size of spherical anisometropia also increased in myopia in these groups. Cylindrical anisometropia appeared to be independent of spherical ametropia. In most cases right/left differences in both sphere and cylinder were small and our findings justify the use of data from one eye only in publications on refraction.