Corneal powers measured with a rotating Scheimpflug camera

Background/aim Keratometry measures the anterior corneal curvature only. Corneal power is calculated by multiplication with the keratometric refractive index, which takes into account the average negative posterior corneal power. The aim of this study was to calculate and compare various expressions for total corneal power assessed with Scheimpflug camera techniques, which also measure the posterior corneal curvature. Methods We used the Pentacam rotating Scheimpflug camera to measure the equivalent power, total corneal refractive power (based on Snell's law ray tracing), and simulated keratometry (keratometric refractive index=1.3375) over the central 3.0 mm zone in 951 eyes. The keratometric refractive index of the equivalent power and the total corneal refractive power was calculated as the ratio between these values and the anterior corneal curvature. Results The equivalent power, total corneal refractive power, and simulated keratometry all differed statistically significantly (analysis of variance, p