Regression after LASIK for the treatment of myopia: the role of the corneal epithelium.

Factors responsible for postoperative regression are still unknown but postoperative epithelial hyperplasia might play an important role. To evaluate the role of the corneal epithelium on regression after laser in situ keratomileusis (LASIK), the thickness of the epithelium was measured in 18 eyes preoperatively and at various postoperative intervals. Measurements of the epithelial thickness were taken using a high-frequency (50 MHz) ultrasound device and measurements were correlated with the postoperative refraction. In all eyes, preoperative epithelial thickness was between 34 and 44 microm. In contrast, after surgery, values were between 35 and 111 microm. In eyes with a refractive outcome of +/-1.0 diopter of that intended, there was an increase of the epithelial thickness of less than 5 microm postoperatively. In contrast, eyes with severe regression showed a significant increase in the thickness in the epithelium after LASIK. In our patient group, regression of the attempted correction was related to postoperative epithelial hyperplasia. Broadly speaking, an increase of 10 microm epithelial thickness resulted in a 1 diopter regression. Mechanical and/or pharmaceutical factors controlling postoperative epithelial hyperplasia would be beneficial.