Factors Affecting the Anterior Displacement of Posterior Corneal Surface after Laser In Situ Keratomileusis

ABSTRACT

PURPOSE: To determine factors which influence forward displacement of the posterior surface of conea after performing LASIK with residual corneal thickness greater than 250 micro meter. METHODS: We studied 100 eyes of 50 myopic patients with an expected residual corneal thickness of greater than 250 micro meter after underwent LASIK. Residual corneal thickness, amount of laser ablation, intraocular pressure, spherical equivalent of cornea (keratometer), corneal diameter, corneal thickness, and anterior chamber depth were obtained at the preoperative stage, the postoperative one week, one month. Computed topography of cornea was performed between before and after LASIK. We evaluated the influence the forward displacement of posterior surface of conea by LASIK procedure. RESULTS: Average forward displacement of posterior surface of the cornea was 38+/-12 micro meter, and among preoperative factors, preoperative corneal thickness showed relatively high correlation with r=0.462 (P<0.001), having influence on the forward displacement. The displacement measured 1 month after LASIK was shown to decrease slightly (31+/-8 micro meter) compared that the displacement measured at 1 week after LASIK. CONCLUSIONS: Despite performing LASIK with residual corneal thickness of greater than 250 micro meter, if pre- operative corneal thickness is thin, one should be careful about anterior displacement of corneal posterior surface, and this change usually occurs within 1 week.