Fig. 1

Methods to determine the treatment zone decentration and treatment zone size. A Axial map at baseline; B tangential curvature map at the twelve-month visit; C difference map used to determine treatment zone decentration and treatment zone size. The red cross indicates the corneal apex, the white circle represents the fitted treatment zone, and the white cross indicates the center of the treatment zone. The distance between the white cross and red cross was defined as the decentration of the treatment zone. The radius of the white circle was defined as the treatment zone size. R: radius of treatment zone circle; r: the distance of treatment zone decentration