Comparison of the Pentacam equivalent keratometry reading and IOL Master keratometry measurement in intraocular lens power calculations

BackgroundTo compare the accuracy of the Pentacam Holladay equivalent keratometry readings with the IOL Master 500 keratometry in calculating intraocular lens power. DesignNon-randomized, prospective clinical study conducted in private practice. ParticipantsForty-five consecutive normal patients undergoing cataract surgery. MethodsForty-five consecutive patients had Pentacam equivalent keratometry readings at the 2-, 3 and 4.5-mm corneal zone and IOL Master keratometry measurements prior to cataract surgery. For each Pentacam equivalent keratometry reading zone and IOL Master measurement the difference between the observed and expected refractive error was calculated using the Holladay 2 and Sanders, Retzlaff and Kraff theoretic (SRKT) formulas. Main Outcome MeasureMean keratometric value and mean absolute refractive error. ResultsThere was a statistically significantly difference between the mean keratometric values of the IOL Master, Pentacam equivalent keratometry reading 2-, 3- and 4.5-mm measurements (P<0.0001, analysis of variance). There was no statistically significant difference between the mean absolute refraction error for the IOL Master and equivalent keratometry readings 2mm, 3mm and 4.5mm zones for either the Holladay 2 formula (P=0.14) or SRKT formula (P=0.47). The lowest mean absolute refraction error for Holladay 2 equivalent keratometry reading was the 4.5mm zone (mean 0.25D0.17D). The lowest mean absolute refraction error for SRKT equivalent keratometry reading was the 4.5mm zone (mean 0.25D +/- 0.19D). Comparing the absolute refraction error of IOL Master and Pentacam equivalent keratometry reading, best agreement was with Holladay 2 and equivalent keratometry reading 4.5mm, with mean of the difference of 0.02D and 95% limits of agreement of -0.35 and 0.39D. ConclusionsThe IOL Master keratometry and Pentacam equivalent keratometry reading were not equivalent when used only for corneal power measurements. However, the keratometry measurements of the IOL Master and Pentacam equivalent keratometry reading 4.5mm may be similarly effective when used in intraocular lens power calculation formulas, following constant optimization.