Spherical aberration from myopic excimer laser ablation for aspheric and non-aspheric profiles

To evaluate the difference in the spherical aberration (SA) induced by an aspheric and a non-aspheric myopic ablation profile with the MEL80 excimer laser (Carl Zeiss Meditec).

This was a prospective randomized paired-eye controlled study of 15 patients (30 eyes) who underwent LASIK using the Hansatome microkeratome (160 μm) (Bausch & Lomb) and the MEL80 using a 6 mm optical zone. For each patient, one eye was treated with an aspheric (Aberration Smart Ablation [ASA]) profile and the other eye was treated with a non-aspheric (Tissue Saving Ablation [TSA]) profile, assigned at random. Patients were measured before and 3 months after LASIK with the wavefront supported custom ablation aberrometer (Carl Zeiss Meditec), and SA was measured with an analysis zone of 3 to 7 mm in 0.5 mm intervals. The area under the curve of SA plotted against analysis zone (RAWS) was calculated.

The mean spherical equivalent refraction was -2.43 ± 1.53 D for the ASA group and -2.54 ± 1.47 D for the TSA group (p = 0.87). There was a statistically significant increase in SA for an analysis zone of 6.0 to 7.0 mm for the ASA group and for an analysis zone of 4.5 to 7.0 mm for the TSA group. At the 6 mm zone, the increase in SA was 0.032 in the ASA group and 0.069 in the TSA group. The induction of SA per diopter was 0.024 μm/D in the ASA group and 0.035 μm/D in the TSA group. The RAWS parameter increased by 34.8% in the ASA group and 74.4% in the TSA group.

There was less induction of SA in myopic LASIK with an aspheric ablation profile than with a non-aspheric ablation profile.