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.