Effect of Different Corneal Curvature on Corrected Power of Conductive Keratoplasty

Introduction Conductive Keratoplasty (CK) induce refractive change of cornea by peripheral deformation
^[1]
. The predictability of CK is still unsatisfactory, partly due to wound-healing response and refractive regression
^[2]
. Because the same surgery operation was performed on corneas of different curvature
^[3,4,5,6]
, we infer that different curvature of cornea may be one of the reasons for diverse surgery results. In this paper, the effect of different curvature of cornea on corrected power of conductive keratoplasty was evaluated. Methods Mathematical analysis was done on the assumption that front surface of deformation zone of cornea is spherical before and after surgery, back surface of cornea is stable before and after surgery. Results After surgical deformation, relative change of refractive power of front surface of cornea Δø / ø =((R-r)/r=-ΔR/h, where R is curvature radius of front surface of cornea before surgery, r is that after surgery, ΔR is the deformation of cornea at location of surgical operation, h is the difference of height between apex of cornea and location of surgical operation. Absolute change of refractive power of cornea Δϕ≈-2(n-l)ΔR/L
²
, where n is refractive index of cornea, L is the distance from the location of surgical operation to the axis of cornea. Calculation by the above formula with operation values of actual surgery shows that the absolute theoretical errors will be less than 0.1 diopter.