Randomized prospective clinical study comparing induced aberrations with IntraLase and Hansatome flap creation in fellow eyes - Potential impact on wavefront-guided laser in situ keratomileusis

Purpose: To measure and compare the changes in objective wavefront aberration and subjective manifest refraction after laser in situ keratomileusis (LASIK) flap creation with a mechanical microkeratome and a femtosecond laser. Setting: Private practice refractive surgery center, Irvine, California, USA. Methods: This randomized prospective study comprised 9 patients (18 eyes) treated with a 2-step LASIK procedure: lamellar keratectomy with a Hansatome microkeratome (Bausch & Lomb) or the IntraLase ferntosecond laser in fellow eyes followed by non-wavefront-guided (standard) excimer laser treatment with the Technolas 217A (Bausch & Lomb) excimer laser 10 weeks later. Fellow eyes were matched to within 0.75 diopter (D) sphere and 0.50 D cylinder. Patients were followed for 3 months after excimer laser treatment. Preoperative and post-flap creation wavefront aberrometry using a Hartmann-Shack aberrometer and manifest refraction were compared between the 2 groups. The same tests were performed 3 months after excimer laser ablation. Results: Statistically significant changes were seen in defocus wavefront aberrations after Hansatome (P =.004) and IntralLase (P =.008) flap creation. A hyperopic shift in manifest refraction was noted in the Hansatome group after the creation of the corneal flap (P =.04); no statistically significant changes in manifest refraction were seen in the Intral-ase group. Statistically significant changes in total higher-order aberrations (HOAs) (trefoil and cluadrafoil Zernike terms) were seen after flap creation in the Hansatome group (P =.02). No significant changes in HOAs were noted after flap creation in the IntralLase group. After the flap was relifted and standard excimer laser ablation was performed, a statistically significant increase in coma occurred in the Hansatome group (P =.008). Standard refractive outcomes in the 2 groups were similar. Conclusions: The creation of the LASIK flap alone can modify the eye's optical characteristics in low-order aberrations and HOAs. A significant increase in HOAs was seen in the Hansatome group but not in the IntraLase group. This may have significant clinical implications in wavefront-guided LASIK treatments, which are based on measurements made before flap creation.