Purpose: The aim of our study was to evaluate the predictability of flap thickness and changes in flap edema over time after laser in situ keratomileusis (LASIK).
Methods: LASIK was carried out in 30 eyes. The corneal flap was created with a Moria CB manual microkeratome with a flap thickness of 130 microm. Photoablation was performed with the Zeiss-Meditec MEL 70(G-Scan) flying spot excimer laser. Ultrasound pachymetric measurements were performed with the Humphrey Model 855 pachymeter.
Results: Preoperative mean corneal thickness was 568.43 +/- 34.6 microm. After LASIK, mean flap thickness was 133 +/- 26.4 microm. After excimer laser treatment, mean central corneal thickness decreased to a mean 392.4 +/- 37.4 microm. Five minutes after repositioning the flap, mean central corneal thickness was 572.1 +/- 43.4 microm. On the first postoperative day, it decreased to a mean 501.6 +/- 46.6 microm followed by additional decreases: mean 487.4 microm on day 5, 481.8 microm after 1 month, and 479.6 microm at 6 months. The actual photoablation depth was 10 microm less than the predicted depth (paired sample t-test, no statistically significant difference, P = .018). A significant linear correlation was found (Pearson, R =.725, P = .001) between predicted and measured photoablation depth.
Conclusions: Corneal flap thickness had greater variability than expected. After flap creation, stromal and flap edema occurred, but decreased during the first five postoperative days and stabilized thereafter.