Regression and its Mechanism after Laser In Situ Keratomileusis

ABSTRACT

We evaluated the degree and mechanism of regression after laser in situ keratomileusis[LASIK]on moderate to highly myopic eyes during the first postopserative 6 months. Betwwen January 1997 and October 1998, 61 eyes operated on with LASIK for myopia, with 2 diopter or more myopic regres-sion occuring during than first 6 months were included in this study. And 79 eyes in control group with less than 1 diopter were included. The attemped correction for refractive error was determined 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. In regression group, corneal thickness was significantly incresed from 0.425 +/-0.048millimeter at postoperative 1 week to 0.444 +/-0.050millimeter postoperative 6 month[p=0.003]and central corneal power was significantly increased from 36.45 +/-2.03 dopter at 1 week to 37.45 +/-5.52 diopter.[p<0.01]The larger sperical equivalent and cylinder were, the more amount myopic regression was in contrast with control group. Early regression of refractive effect after LASIK appears to be a consequence of an increase in corneal thickness associated with central corneal steepening.