Study on the measurement error on corneal vergence for eyes after corneal refractive surgery

The radius of anterior and posterior corneal surface, central corneal thickness and Q value of anterior and posterior corneal surface are obtained. Based on the corneal data, the effects of equivalent refractive index and error in radius of curvature on the corneal vergence measurement after refractive surgery are studied theoretically. The measurement error induced by equivalent refractive index and error in radius of curvature increases with the Q value of corneal anterior surface (P<0.05). Both the equivalent refractive index and error in radius of curvature lead to the overestimation of the corneal vergence, and the additive effects of the equivalent refractive index and error in radius of curvature lead to the overestimation of the corneal vergence by the clinical instruments. In addition, the measurement error linearly relates to the Q value of anterior corneal surface (P<0.05). The error in radius of curvature as well as the equivalent refractive index should be considered in the corneal vergence measurement for eyes after refractive surgery.