The Effect of Preoperative Keratometric Value on Corneal Flap Dimensions in LASIK

ABSTRACT

PURPOSE: To evaluate the effect of preoperative keratometric value on corneal flap dimensions, records of 81 eyes of 45 patients who had LASIK were analyzed retrospectively. METHOD: Corneal thickness and diameter , and keratometric value were measured preoperatively. RESULTS: In this study, SCMD Turbokeratome was set for making a corneal flap with 150 micron thickness and 8.25 mm diameter. In reality, however, the mean corneal flap thickness was 110.7+/-15.7 micron and the mean corneal flap diameter was 7.89+/-0.33 mm. The lower mean preoperative keratometric value, the thicker(r=-0.325, p=0.003) and the smaller(r=0.460, p=0.009) diameter flap was made. When we divided eyes into three groups according to their keratometric values, eyes with keratometric values lower than 42.5 D resulted in corneal flap with 116.70+/-12.6 micron thickness and 7.65(0.28mm diameter as opposed to 102.16+/-13.41 micron thickness and 8.05+/-0.37 mm diameter flap in corneas having keratometric values above 44.5 D(p<0.05). CONCLUSION: When a LASIK flap was made using SCMD manual keratome, steeper corneas tend to have larger and thinner corneal flaps. In conclusion, for making the corneal flap according to the intended thickness and diameter in LASIK, preoperative keratometric value should be considered carefully.