Comparison of Higher Order Aberrations After LASIK and LASEK for Myopia

PURPOSE: To compare the change in higher order aberrations (HOAs) after LASIK and laser epithelial keratomileusis (LASEK). METHODS: This prospective comparative study measured HOAs preoperatively and 3 months postoperatively in 65 eyes (41 patients) that underwent LASIK and 65 eyes (50 patients) that underwent LASEK. Preoperative refraction was limited to myopia up to -5.00 diopters (D) and astigmatism <=-0.75 D. Patients were matched for age, manifest refraction, and HOAs. All procedures were wavefront-guided using the VISX S4 Star excimer laser (Abbott Medical Optics). Laser in situ keratomileusis flap creation was performed with a Moria ONE Use-Plus disposable microkeratome creating a nasal hinge. Laser epithelial keratomileusis flap creation was performed with 18% v/v unpreserved ethanol instilled for 40 seconds. The epithelium was displaced with an epi-peeler, creating a 6- to 8-mm superior hinge. Higher order aberrations were measured with the NIDEK OPD-Scan II. RESULTS: Statistically significant (P <.05) changes in five Zernike polynomial terms following LASIK (Z(4)(-4), Z(4)(0), Z(4)(4), Z(5)(-3), Z(6)(0)) were noted. There was a decrease in Zernike term Z(5)(-3) and increases in the remaining four Zernike terms. Statistically significant changes in five Zernike polynomial terms following LASEK (Z(3)(-1), Z(4)(0), Z(5)(-5), Z(5)(-1), Z(6)(0)) were noted. There was a decrease in Zernike term Z(3)(-1) and increases in the remaining four Zernike terms. CONCLUSIONS: Wavefront-guided LASIK and LASEK caused increases in spherical aberration, with LASIK additionally causing increases in two fourth order HOAs and LASEK additionally causing increases to two fifth order HOAs. As the same laser treatment was applied, it is presumed that the differences relate to the method of flap creation. [J Refract Surg. 2010;26:45-51.] doi:10.3928/1081597X-20101215-07