Purpose: To determine the higher order aberrations at the corneal first surface after conventional LASIK for high myopia and high hyperopia.
Methods: This was a retrospective study using a convenience sample with subjects divided into five groups by level of refractive correction. Group 1 were normals, having no eye disease or previous surgery, but may have had refractive error. Group 2 had low myopia (-1.00 to -5.87 D), group 3 high myopia (> 6.00 D), group 4 low hyperopia (+1.00 to +3.87 D), and group 5 high hyperopia (> 4.00 D). LASIK was performed using a Technolas 217 laser. Corneal topography was taken with Orbscan II, and Placido data exported to VOLPro software v6.71. Wavefront aberrations were determined for a 6.0-mm pupil.
Results: The study included 264 subjects-group 1 (normal), n=204; group 2 (low myopia), n=20; group 3 (high myopia), n=20; group 4 (low hyperopia), n=10; and group 5 (high hyperopia), n=10. The spherical equivalent refractive error corrected (mean +/-SD) was 0.00 +/- 0.00 D in group 1, -3.92 +/- 1.47 D in group 2, -9.53 +/- 2.06 D in group 3, +2.49 +/- 0.51 D in group 4, and +5.54 +/- 1.22 D in group 5. The total higher order root-mean-square (RMS) wavefront aberration was 0.38 +/- 0.07 microm in group 1, 0.69 +/- 0.22 microm in group 2, 1.36 +/- 1.79 microm in group 3, 0.64 +/- 0.34 microm in group 4, and 1.76 +/- 0.54 microm in group 5. Spherical aberration was 0.25 +/- 0.06 mcirom in group 1, 0.45 +/- 0.11 microm in group 2, 0.64 +/- 0.29 microm in group 3, -0.11 +/- 0.15 microm in group 4, and -0.56 +/- 0.22 microm in group 5. The refractive correction (Rx) was highly correlated to total higher order RMS for myopic correction higher order RMS = 0.38 - 0.07 Rx, R2=0.52, and for hyperopic correction higher order RMS = 0.18 + 0.28 Rx, R2 = 0.75.
Conclusions: Conventional LASIK increases all corneal higher order aberrations with induced aberrations increasing with the magnitude of refractive correction. High refractive corrections, both myopic (>6.00 D) and hyperopic (>5.00 D), can lead to very high levels of corneal higher order aberrations.
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