Higher-order aberrations and anisometropia

Myopia incidence is increasing around the world. Myopization is considered to be caused by a variety of factors. One consideration is whether higher-order aberrations (HOA) influence myopization. More knowledge of optics in anisometropic eyes might give further insight into the development of refractive error.

To analyze the possible influence of HOA on refractive error development, we compared HOA between anisometropes and isometropes. We analyzed HOA up to the 4th order for both eyes of 20 anisometropes (mean age: 43 ± 17 years) and 20 isometropes (mean age: 33 ± 17 years). HOA were measured with the Shack-Hartman i.Profiler (Carl Zeiss, Germany) and were recalculated for a 4 mm pupil. Mean spherical equivalent (MSE) was based on the subjective refraction. Anisometropia was defined as ≥1 D interocular difference in MSE. The mean absolute differences between right and left eyes in spherical equivalent were 0.28 ± 0.21 D in the isometropic group and 2.81 ± 2.04 D in the anisometropic group. Interocular differences in HOA were compared with the interocular difference in MSE using correlations.

For isometropes oblique trefoil, vertical coma, horizontal coma and spherical aberration showed significant correlations between the two eyes. In anisometropes, all analyzed higher-order aberrations correlated significantly between the two eyes except oblique secondary astigmatism and secondary astigmatism. When analyzing anisometropes and isometropes separately, no significant correlations were found between interocular differences of higher-order aberrations and MSE. For isometropes and anisometropes combined, tetrafoil correlated significantly with MSE in left eyes.

The present study could not show that interocular differences of higher-order aberrations increase with increasing interocular difference in MSE.