Comparison of central corneal thickness measured by Pentacam,Orbscan II and A-mode ultrasound

Objective To compare the difference of central corneal thickness (CCT) measured by Pentacam,Orbscan Ⅱ and A-mode ultrasound.Methods CCT in 148 eyes of 74 patients were measured by Pentacam,Orbscan Ⅱ and A-mode ultrasound before refractive surgery,respectively.The difference of CCT was compared,and the correlation and concordance of three measurements were analyzed.Results The mean CCT measured by Pentacam,Orbscan Ⅱ,and A-mode ultrasound were (540.00±27.47)μm,(528.00±25.29)μm and (537.82±24.34)μm,respectively.The CCT measured by Orbscan Ⅱ was obvious lower than that measured by Pentacam and A-mode ultrasound,there were statistical differences(both P0.05).There was a significant linear correlation in CCT measured by three measurements (P0.05),especially between Pentacam and A-mode ultrasound.The mean differences and upper/lower LOA for CCT measurements were (4.50±14.31)μm and 22.47 μm/-13.47 μm between Pentacam and A-mode ultrasound,(11.39±15.13)μm and 40.08 μm/-17.31 μm between Pentacam and Orbscan Ⅱ,(7.15±16.03)μm and 28.46 μm/-14.16 μm between A-mode ultrasound and Orbscan Ⅱ.None of the CCT values measured by three measurements was correlated with refraction spherical equivalent (P0.05).Conclusions Pentacam has better agreement with the gold standard A-mode ultrasound,as compared with Orbscan Ⅱ.The CCT measured by three measurements have certain correlation,but also have the differences,these instruments should not be used interchangeably for CCT measurement in clinic.