Comparison of Three Different Instruments Measuring Central Corneal Thickness before and after Laser in situ Keratomileusis

Objective To compare the difference in measurements of central corneal thickness(CCT) using A-scan,OrbscanⅡand Pentacam before and after laser in situ keratomileusis(LASIK).Methods Between October 2010 and March 2011,the CCT of 137 patients(274 eyes) were measured by A-scan,OrbscanⅡ and Pentacam,and the results were analyzed by paired t-tests and Pearson correlation.Results Before LASIK,the values of CCT measured by A-scan,OrbscanⅡ and Pentacam were(526.6 ± 34.1),(516.6 ± 34.2),and(539.8 ± 31.5) μm respectively;paired t-tests showed the CCT values obtained with Pentacam were significantly higher than those with other methods(P0.05),but there were no statistical significant differences between OrbscanⅡand Pentacam measurements(P0.05).Six months after LASIK,the values of CCT measured by A-scan,OrbscanⅡand Pentacam was(448.2 ± 48.5),(391.9 ± 58.5),and(451.5 ± 46.4) μm respectively;the CCT values obtained with A-scan and Pentacam didn't differ much from each other(P0.05),and the CCT values obtained with OrbscanⅡwere lower than those obtained with A-scan and Pentacam.There was a high correlation between A-scan and Pentacam measurements.Conclusion The these methods measuring CCT could not be used interchangeably,and A-scan and Pentacam after LASIK were more precise than OrbscanⅡ.