AIM: To evaluate the accuracy of central conreal thickness(CCT)using EX500 Excimer Laser workstation(EX500)in laser in situ keratomileusis(LASIK)patients.

METHODS: The CCT of 120 eyes(63 patients)who had LASIK between January 2013 and June 2013 were measured by A-scan and EX500. Three groups were classified: >550μm, 500～550μm, <500μm according the CCT value of A-scan. The CCT were measured again by corneal flap creating by moria SBK microkeratome. The thickness of the corneal bed stroma were measured by A-scan and EX500 after keratomileusis. All outcomes were analyzed with paired t test.

RESULTS: The average preoperative CCT value was 527.9±34.3μm measured by A-scan, 528.5±34.6μm measured by EX500. There was no significant difference between these two measurements(t=1.736, P=0.085). In group which CCT >550μm, the average preoperative CCT value was 571.4±17.3μm measured by A-scan, 572.7±15.7μm measured by EX500. There was no significant difference between these two measurements(t=1.857, P=0.072). In group which CCT 500～550μm, the average preoperative CCT value was 523.4±13.1μm measured by A-scan, 524.2±12.4μm measured by EX500. There was no significant difference between these two measurements(t=1.934, P=0.058). In group which CCT <500μm, the average preoperative CCT value 484.5±9.8μm measured by A-scan, 483.7±8.9μm measured by EX500. There was no significant difference between these two measurements(t=1.395, P=0.174). The average CCT value after corneal flap lifting was 401.3±34.2μm measured by A-scan, 393.4±38.9μm measured by EX500. There was a significant difference between these two measurements(t=6.669, P=0.000). The average thickness of the corneal bed stroma value after keratomileusis was 332.6±38.3μm measured by A-scan, 307.3±37.1μm measured by EX500. There was a significant difference between these two measurements(t=17.165, P=0.000).

CONCLUSION: There is no significant difference between preoperative CCT value measured by A-scan and EX500. After corneal flap lifting and keratomileusis, the CCT value measured by EX500 is smaller than measured by A-scan.