Clinical Study Of Laser-assisited Subepithelial Keratomileusis For Myopia

Refractive surgery entered a new era with the introduction of the excimer laser. Since Trokel and coauthors introduce photorefractive keratectomy (PRK) in 1983, refractive surgery using 193nm argon fluoride excimer laser has become a reasonably predictable, effective, and safe method for treating low to moderate myopia. However, postoperative pain, cornea haze, and myopic regression are problems of PRK. Laser in situ keratomileusis (LASIK) may be preferable to PRK, especially in eyes with higher degrees of myopia. However, epithelial in growth, cornea-flap-related complications, and corneal ectasia are shortcomings of LASIK. Laser-assisited subepithelial keratomileusis (LASEK) was introduced by Camellin in 1999, excimer laser stromal ablation is performed under a hinged flap of corneal epithelium. No microkeratome is used, and no stromal lamellar cut is made. It is reported that LASEK combine the advantages and eliminate the disadvantages of PRK and LASEK.Purpose:Laser-assisited subepithelial keratomileusis (LASER) is a new approach for myopia. It is thought to not only have the advantages of photorefractive keatomy (PRK) and laser in situ keratomileusis (LASIK) but also avoid the disadvantages of the both. To assess its effectives we compared the clinical results (efficacy, safety, stability and postoperative pain) of LASEK and LASIK for correction of myopia. Methods:In the prospective comparative study, there were 62 eyes in 32 patients that the cornea thickness was thinner than 500um or the residual corneal bed thickness was less than 250um. All procedures were performed using the Technolas 217Z excimer laser(Bausch and Lomb Surgical) with a 5-6mm ablation optical zone. All the patients were followed-up more than 6 months. The UCVA, BCVA, and refraction were measured at Iweek, and 1,3,6 months. The corneal epithelium healing time and the subepithelial cornea haze were also detected. Results:Preoperatively, the mean spherical equivalent (MSB) was -9.20 0.02 D in the LASEK eyes and -8.40 4.06 D in the LASIK eyes. The difference was not statistically significant(p>0.05) Postoperatively, at 1 week, 1,3,6 months, the MSEs were 0.85 0.64D, 0.25 0.78D, -0.23 0.60D and -0.28 0.38D,respectively in LASEK group and 0.28 0.84D, -0.34 0.53D, -0.30 0.46D and -0.32 0.40D in LASIK group. The differences were not statistically significant at 3 and 6 months but statistically significant at 1 week and 1month. In LASER group, the mean UVCA at 1 week, 1,3,6 months were 0.78 0.18, 0.86 0.14,0.90 0.18.and 0.89 0.14 ; In LASIR group, the UVCA were 0.93 0.12, 0.94 0.16, 0.92 0.13,and 0.93 0.20, at 1 week, 1,3,6 months. There were no statistically significant between the two group in UCVA at 3 and 6 months. At 6 month, the efficacy index and safety index were no statistically significant either. Postoperative pain, discomfort were noted after LASER eyes. The corneal epithelium were healing in 5 days with mean time 3.12 days. Cornea haze score were 0.56 0.52, 0.78 0.42, 0.32 0.24 at 1,3,6 month respectively in LASER group. Conclusion:Laser epithelial keratomileusis (LASER) provided similar results with laser in situ keratomileusis(LASIR). It was safe and effective in treating in a wide range of myopia. The potential advantages of LASER over LASIR include the elimination of stromal flap complications and greater choice in patient selection. The disadvantages include varying degree pain 2 or 3days and blurry vision for several days postoperatively.