Effect of NIDEK optimized aspheric transition zone ablation profile on higher order aberrations during LASIK for myopia.

PURPOSE: To investigate the effect of the Optimized Aspheric Transition zone profile (OATz) that was devised to minimize the "red ring" in corneal topography on ocular higher order aberrations following LASIK for Myopia. METHODS: Laser in situ keratomileusis with OATz using the Nidek Advanced Vision Excimer Laser Platform (NAVEX) was performed on 22 eyes with a 4.5-mm optical zone and 8.0-mm transition zone (OATz group). Conventional LASIK was performed on 11 eyes with a 6.0-mm optical zone and 7.0-mm transition zone as a control (conventional group). The higher order aberrations for the central 6-mm diameter were measured at 1 month postoperatively using a Hartmann-Shack wave-front sensor. In addition to the spherical aberration, the magnitude and orientation of trefoil, coma, tetrafoil, and secondary astigmatism were compared between two groups using Zernike vector analysis. RESULTS: The mean magnitude (root-mean-square) of the total higher order aberrations in the conventional group (0.70 +/- 0.28 mu m) was significantly higher than that in the OATz group (0.51 +/- 0.15 mu m, P <.05, un-paired t test). For spherical aberration, the OATz group had significantly lower values (0.22 +/- 0,17 mu m) than the conventional group (0.38 +/- 0.23, mu m, P <.05). The magnitude of coma in the conventional group was also higher than that in the OATz group (P <.05), and the mean axis of coma was 8.6 degrees in-the conventional group and 64.3 degrees in the OATz group. No statistically significant differences were noted in the magnitude and axes of trefoil, tetrafoil, or secondary astigmatism between the two groups. CONCLUSIONS: The OATz profile may decrease the surgically induced, increase of higher order aberrations especially spherical aberration, following LASIK. However, a study with equivalent treatment groups and larger sample sizes is required for a definite conclusion. [J Refract Surg. 2009;25:331-338.]