Effect of preoperative keratometry on refractive outcomes after laser in situ keratomileusis

Purpose: To evaluate the effect of preoperative keratometry on the refracti ve outcome after laser in situ keratomileusis (LASIK) for myopia. Setting: University Eye Clinic, Prince of Wales Hospital, Hong Kong, China. Methods: In this retrospective study, the records of patients who had LASIK for myopia greater than -6.0 diopters (D) using the Chiron Automated Corne al Shaper and the Schwind Keratome-F excimer laser were reviewed. Results: Laser in situ keratomileusis was performed in 167 eyes of 103 pati ents (mean age 34.7 years +/- 7.5 [SD]). Preoperative myopic spherical equi valent (SE) refraction was -9.0 +/- 2.0 D (range -6.0 to -13.9 D). Three mo nths after surgery, SE refraction was -0.04 +/- 1.1 D (range +2.3 to -3.3 D ); uncorrected visual acuity greater than or equal to 20/40 was present in 91.8% of 110 eyes in which emmetropia was the postoperative goal. Mean preo perative keratometry was 43.9 +/- 1.5 D (range 40.3 to 48.1 D). When eyes w ere stratified by the degree of preoperative myopia in 1.0 D steps, a trend toward greater undercorrection was noted in eyes with preoperative keratom etry <43.5 D than in those with steeper keratometry (>44.5 D) in all myopia groups except the -7.0 to -7.9 D group. This difference was statistically significant in eyes with a preoperative SE of -10.0 to -10.9 D and -11.0 to -11.9 D. Conclusions: Preoperative keratometry appeared to influence the refractive outcome after myopic LASIK. Eyes with flatter corneas tended to have greate r undercorrection than eyes with similar myopia and steeper corneas. Valida tion of these findings in larger data sets using the methodology described may improve the predictability of current LASIK nomograms, particularly in eyes with high myopia. J Cataract Refract Surg 2001; 27:297-302 (C) 2001 AS CRS and ESCRS.