Intraocular lens power calculations using a Scheimpflug camera to measure corneal power

Abstract

We measured corneal power using an Oculus Pentacam® to assess its accuracy for calculating intraocular lens (IOL) power after myopic refractive surgery. A series of corneal power measurements were performed on 22 patients (43 eyes) who had undergone myopic refractive surgery. In 37 of the 43 eyes, phacoemulsification and IOL implantation subsequently were performed. Conventional keratometry and three corneal measurements (mean true net power, central true net power, and 4.5 mm equivalent K reading) obtained using a Pentacam were analyzed and compared to values derived from the clinical history method. Prediction errors of three Pentacam corneal power measurements inserted in third generation IOL formulas also were compared. Analysis of the variance showed that only two Pentacam corneal measurements, mean true net power and central true net power, were not significantly different from those of the clinical history method. Mean true net power was correlated more closely with the clinical history method corneal power than other corneal power values. The one-sample t-test showed that of three Pentacam corneal measurements combined with third-generation formulas, only the mean true net power inserted in the SRK/T implant power calculation formula was not significantly different from zero. The percentages of eyes within ± 0.50 D and ± 1.00 D of the refractive prediction error of this method were 67.6% and 86.5%, respectively. Mean true net power inserted in the SRK/T formula can be used to calculate directly IOL power after myopic refractive surgery.