Study on Corneal thickness measurements with the Orbscan-II Topography and ultrasonic pachymetry before and after LASIK

Objective To investigate the difference on corneal thickness measurements using Orbscan-ⅡSystem and ultrasonic pachymetry before and after LASIK in myopic patients.Methods Orbscan-ⅡSystem and A-scan ultrasonography were used to measure the corneal thickness pre-and post-operative in 300 eyes of 150 cases that underwent myopic LASIK.The differences were evaluated by t tests.Results Pre-operatively,the mean corneal thickness was 535.17±32.352 μm with Orbscan-Ⅱsystem,and 545.43±29.079 μm with A-scan ultrasonography.Post-operatively,the mean corneal thickness with Orbscan-Ⅱsystem and with A-scan ultrasonography was 417.06±46.422 μm and 457.64±32.30 μm respectively,and the differences were statistically significant.Conclusion There is significant difference between the corneal thickness value measured by Orbscan-II topography system and ultrasonic pachymetry.Even high correlation between them has been showed,Orbscan-Ⅱsystem for corneal thickness measurement could not substitute A-scan ultrasonography completely.Certainly it still can be used as the very good reference for LASIK.