[Aspheric ablation for the correction of myopia: clinical results after LASIK with a Bausch & Lomb 217 Z 100 excimer laser].

BACKGROUND

The aim of this study was to evaluate the clinical performance of the new aspheric ablation mode (Zyoptix Aspheric) in laser in situ keratomileusis (LASIK) using the Bausch & Lomb 217 Zyoptix 100 laser. This algorithm incorporates the asphericity of the cornea (Q-value), the corneal curvature (K-values) and the manifest refractive error to create an ablation pattern.

PATIENTS AND METHODS

Clinical outcomes of three ablation patterns were compared: Group TS: 20 eyes treated with Zyoptix tissue-saving (refraction and keratometry based); Group AS: 54 eyes treated with Zyoptix Aspheric; Group PT: 20 eyes treated with Zyoptix personalised treatment (wavefront aberration-guided). In addition to our conventional exclusion criteria for LASIK, eyes with an astigmatic error of more than -1.75 diopter (D) and above-average higher-order aberrations (HOA RMS > 0.35 microm, excluding spherical aberrations) were excluded.

RESULTS

After an initial nomogram adjustment of -0.25 D in the AS group, good refractive predictability was observed at the 3-month visit (mean spherical error 0.02 +/- 0.50 D, mean cylinder -0.35 +/- 0.30 D). Natural spherical aberrations could be maintained. Uncorrected contrast sensitivity with and without glare remained at spectacle-corrected levels before AS LASIK. The uncorrected low contrast visual acuity after AS LASIK was as good as the spectacle-corrected low contrast visual acuity before. The asphericity of the cornea was best preserved with AS. The efficacy index was 0.94 in both AS and PT, 0.86 in TS.

CONCLUSIONS

AS without cyclorotational eye tracking has a clinical performance equivalent to PT with cyclorotational eye tracking and better than TS in eyes with low astigmatism and below average HOA.