Paracentral Corneal Power Versus Standard Keratometry and Topography for Keratoconus
Purpose
To review the results of cataract surgery in keratoconus (KCN) and evaluate the accuracy of paracentral corneal power versus standard keratometry, topography, and tomography for lens power calculations.
Methods
26 eyes. Noncomparative case series of patients with KCN undergoing cataract surgery. Corneal powers derived from keratometry, topography, and tomography used to calculate predicted refraction and prediction errors using Holladay 2 formula.
Results
Surgeon specific algorithms delivered manifest spherical equivalence of -1.63 D with a prediction error of +1.0 D. Average absolute prediction error of optical biometer-derived keratometry, placido topographer-derived keratometry, scheimpflug tomographer-derived Equivalent K-Reading (EKR) and paracentral corneal power (EKR65) were 0.88 D, 1.02 D, 1.66 D, and 1.46 D respectively.
Conclusion
Lens power calculations using EKR65 are more accurate than those using EKR in patients with KCN. Lens power calculations using optical biometer-derived keratometry remains the most accurate.