## Abstract

Recently Sicam *et al.* [J. Opt. Soc. Am. A **21**, 1300 (2004)
] presented a new corneal reconstruction algorithm for estimating corneal sag by Zernike polynomials. An equivalent but simpler derivation of the model equations is presented. The algorithm is tested on a sphere, a conic, and a toric. These tests reveal significant height errors that accrue with distance from the corneal apex. Additional postprocessing steps are introduced to circumvent these errors. A consistent and significant reduction in height errors is observed across the test surfaces. Finally, Sicam *et al.* used the conic *p*-value *p* as a measure of algorithm efficacy. Further investigation shows that the finite Zernike representation affected the reported results. The *p*-value should therefore be used with caution as an efficacy measure.

© 2007 Optical Society of America

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