Table 2.

Comparison of matching error results of the first and second measurement between keratoconus and control groups.

Corneal surface	PreICP-RMS, μm	PosICP-RMS, μm	Misalignment ratio
Anterior	0.000**	0.000**	0.000**
Posterior	0.000**	0.000**	0.000**

Mann-Whitney U test was used to compared the tomography matching results of control and keratoconus groups. PreICP-RMS and PosICP-RMS represent the root-mean-square error of the coordinate differences of corneal surface between two successive measurement before and after tomography matching, respectively; Misalignment ratio = 1- (PosICP-RMS/PreICP-RMS); *means P < 0.05, ** means P < 0.01.