Determining corneal power using Pentacam after myopic photorefractive keratectomy
Article first published online: 15 MAR 2010
© 2010 The Authors. Journal compilation © 2010 Royal Australian and New Zealand College of Ophthalmologists
Clinical & Experimental Ophthalmology
Volume 38, Issue 4, pages 341–345, May/June 2010
How to Cite
Falavarjani, K. G., Hashemi, M., Joshaghani, M., Azadi, P., Ghaempanah, M. J. and Aghai, G. H. (2010), Determining corneal power using Pentacam after myopic photorefractive keratectomy. Clinical & Experimental Ophthalmology, 38: 341–345. doi: 10.1111/j.1442-9071.2010.02286.x
- Issue published online: 11 JUN 2010
- Article first published online: 15 MAR 2010
- Received 18 December 2009; accepted 23 February 2010.
- keratorefractive surgery;
- Pentacam Scheimpflug camera
Purpose: To assess the accuracy of Pentacam Scheimpflug camera for corneal power measurement in eyes with previous photorefractive keratectomy for myopia.
Methods: In this comparative interventional case series, 35 eyes of 35 patients who had myopic photorefractive keratectomy were studied. Corneal power was measured by conventional topography and Pentacam Scheimpflug camera, and equivalent keratometry readings (EKR) in different central corneal rings (0.5 to 4.5 mm), true net power and simulated keratometry (K) measurements as well as those obtained using Shammas no-history, Koch-Maloney and Haigis methods were compared with clinical history method.
Results: All corneal power measurements except for the topography simulated K and true net power values were statistically similar to the clinical history values. Simulated keratometry and 4.5-mm EKR values were more closely correlated with clinical history method. Shammas formula, Pentacam simulated K and 3-, 4- and 4.5-mm EKR provided a 95% confidence interval within ±0.50 D of the mean clinical history method value, among these, the width of the 95% limits of agreement (LoA) was narrower for Shammas and Pentacam simulated K and 4.5-mm EKR values; however, considerably large 95% LoA were found between each of these values and those obtained with the clinical history method. Estimated preoperative keratometry was statistically similar to the preoperative measurement; however, estimated refractive change was different from actual value.
Conclusions: The Pentacam 4.5-mm EKR and simulated keratometry may be used as an alternative to clinical history method to predict corneal power when pre-keratorefractive surgery data are unavailable; however, wide LoA should be considered in the calculations.