Figure 2: Curve estimation showed there was significant different between x-coma of anterior corneal surface and A.C.D, linear regression showed statistic differences between x-coma of posterior corneal surface (y=0.250-0.329x, r2 =0.108, p<0.000) and A.C.D, that of total corneal surface (y=0.076-0.317x, r2 =0.091, p<0.000) and A.C.D.