Purpose: To determine the higher order aberrations at the corneal first surface after 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, previous surgery, but may have had refractive error. Group 2 had low myopia (-1.00 to -5.87), group 3 high myopia (>6.00D), group 4 low hyperopia (+1.00 to +3.87), and group 5 high hyperopia (>4.00D). LASIK was performed using a Technolas 217 laser. Corneal topography was taken with Orbscan II, and Placido data exported to VOLPro software v6.71 (Sarver and Associates). Wavefront aberrations were determined for a 6.0mm pupil.

Results: The population included 264 subjects, group 1, 204; 2, 20; 3, 20; 4, 10; 5, 10. The spherical equivalent refractive error corrected (mean±SD) was group 1, 0.00±0.00; 2, -3.92±1.47; 3, -9.53±2.06; 4, +2.49±0.51; 5, +5.54±1.22 diopters. The total higher order root mean square (HORMS) wavefront aberration was group 1, 0.38±0.07; 2, 0.69±0.22; 3, 1.36±1.79; 4, 0.64±0.34; 5, 1.76±0.54 microns. Spherical aberration was group 1, 0.25±0.06; 2, 0.45±0.11; 3, 0.64±0.29; 4, -0.11±0.15; 5, -0.56±0.22 microns. The refractive correction (Rx) was highly correlated to total HORMS for myopic correction HORMS=0.38 -0.07Rx, R²=0.52, and for hyperopic correction HORMS=0.18 +0.28Rx, R²=0.75.

Figure 2. Higher order aberrations by paired Zernike modes from 3rd through 6th orders for group 1 normal, group 2 low myopia, group 3 high myopia, group 4 low hyperopia, and group 5 high hyperopia.

Conclusions: Conventional LASIK increases all corneal higher order aberrations with induced aberrations increasing with the strength of refractive correction. High refractive corrections, both myopic (>6.00D) and hyperopic (>5.00D), can lead to very high levels of corneal higher order aberrations.

Key words: laser in situ keratomileusis, optics, ocular refraction, refractive errors, wavefront aberrations

J Refract Surg. 2005;21:S508-S512.

Konrad Pesudovs PhD
Department of Ophthalmology, Flinders Medical Center and Flinders University of South Australia, Bedford Park, South Australia, 5042, Australia

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