Figure 6: There was a curve fitting relationship between A.C.D and y-coma for posterior corneal surface, linear regression showed statistic differences between y-coma of anterior corneal surface (y=0.211x-0.354, r2 =0.045, p<0.000) and A.C.D, that of total corneal surface (y=0.430x-0.954, r2 =0.180, p<0.000) and A.C.D.