Comparison of High Order Aberrations Included by Regular LASIK vs. Wavefront Guided LASIK at Various Optic Zones

Abstract

Abstract: : Purpose: To compare the effect of wavefront guided LASIK vs. standard LASIK on the high order ocular aberrations. Methods: 15 eyes of 8 myopic- astigmatic patients (- 1.12 D to –4.5 D), that underwent wavefront guided LASIK and 16 eyes of 8 myopic- astigmatic patients (-1.5 D to –5.0 D) that underwent standard LASIK (Wavelight-Allegretto scanning- spot laser) were examined using the Wavelight Wavefront analyzer (a Tscherning aberrometer) pre- operatively and 1 month and 3 month post-op. The aberrometry was performed at various optic zones (OZ) ranging from 4 to 6 mm (under cycloplegia). In addition subjective and objective refraction, corneal topography (Oculus) and pupilometry were performed. We looked at the Zernike decomposition of the wave aberration up to the 6 ^th order and compared the effects of the two types of LASIK on the root mean square (RMS) of the wavefront error for the high order aberrations (3 –6^th order) as well as coma and high spherical aberration. Results: While standard LASIK induced a significant increase in high order aberration (from a mean RMS of 0.19 ± 0.02 µm to 0.27±0.03µm). Wavefront guided LASIK did not induce such as increase (a mean RMS change from 0.16±0.02µm to 0.19±0.02 µm). Similarly, an increased in mean coma aberration (from 0.12 to 0.25 µm) was noted in patients treated with standard LASIK, but not with wavefront guided LASIK. A similar trend appeared in the high spherical aberrations. The difference in the RMS of high order aberrations was significantly larger when measured through a 6 mm OZ (0.08µm) compared to a 4 mm OZ (0.04µm). No such effect was noted with wavefront guided LASIK (0.03 µm in both OZ). Conclusions: While correcting defocus and astigmatism, standard LASIK induces a significant increase in high order aberrations and coma especially at optic zones beyond 5 mm, leading to deterioration in the quality of vision especially under mesopic conditions. Those effects can be prevented by wavefront guided LASIK.

Keywords: laser • refractive surgery: LASIK • refractive surgery