Features of high order aberration dynamics in laser correction of hyperopia

Purpose
The purpose of this study is to investigate the higher order aberration dynamics after hyperopic LASIK and LTK.
Method: There were examined 32 patients (49 eyes) with initial hyperopia from 1.5 to 4.0 D aged 35 to 45 years. Higher order aberration were evaluated using the OPD-Scan ARK-10000 (NIDEK). The RMSHO and Zernike coefficients were calculated with a special software available in device. Group 1 - 14 patients, 22 eyes, with mean hyperopia 2.6±0.27 diopters underwent LASIK. Group 2 - 18 patients, 27 eyes, with mean hypermetropia 1.46±0.03 diopters underwent LTK.
Results
After hyperopic LASIK the RMSHO increased from 0.36±0.05 to 0.54±0.05 when measured with a 6 mm pupil, as well as trefoil Х, coma Х and spherical aberration. After LTK the RMSHO increased from 0.32±0.05 to 0.45±0.04. Coma Y, trefoil Y were increased too. In the Group 1 LASIK changed the sign of spherical aberration from positive to negative. Absolute value of spherical aberration increased 2 times. In the Group 2 (LTK) positive spherical aberration increased insignificantly, remaining positive.
Conclusion: Both higher order aberration, generally, and negative spherical aberration were induced, correlated with the refractive change after LASIK. After LTK coma X and coma Y mostly were induced without special systematics. After LASIK the negative spherical aberration compensates with negative defocus and improves the near vision and also creates a multifocal effect with 1.5 D optical power difference.