Effect of Laser in Situ Keratomieusis on Astigmatic Correction

ABSTRACT

We studied the effect of LASIK(laser in situ keratomileusis) on the correction of astigmatism for patients with simple myopia & compound myopic astigmatism. LASIK was performed on 147 eyes of 108 patients using VISX STAR. All the cases were divided into two groups by the amount of underlying astigmatism 64 eyes for simple myopic group(equal or less than 0.5D) and 83 eyes for compound myopic astigmatism group(more than 0.75D). The attemped correction for refractive error was determind by cycloplegic refraction. We evaluated the changes of refractive error, uncorrected visual acuity, best corrected visual acuity, corneal topography, corneal thickness and keratometry before operation, one day, one week,two months and six months after operation. Uncorrected visual acuity improved from 0.062+/-0.056 before operation to 0.821+/-0.215 at six months after operation in simple myopic group and from 0.069+/-0.068 to 0.735+/-0.224 in compound myopic group. Spherical equivalent was reduced from -8.135+/-2.096D before operation to -0.765+/-1.186D at six months after operation in simple myopic group and from -9.498+/-3.181D to -1.022+/-1.504D in compound myopic astigmatic group. Mean astigmatism increased from -0.300+/-0.205D before operation to -0.703+/-0.553D at six months after operation in simple myopic group and was reduced from -1.640+/-1.047D to -1.075+/-0.811D in compound myopic astigmatic group. Decentration of ablation from the pupil center was ranged between 0.00 and 1.42mm(mean 0.449+/-0.341mm) in all the patients by corneal topography. It was 0.446+/-0.333mm in simple myopic group and 0.452+/-0.353mm in compound myopic astigmatic group respectively. The patients with a decentration more than 1.00mm showed a statistically significant astigmatism than those with a decentration equal or less than 1.00mm.With these results it is suggested that LASIK with VISX STAR would be effective in correction of astigmatism equal or more than 0.75D. In contrast, it is not effective in correction of astigmatism equal or less than 0.5D.