Power of Zernike Polynomials for Eye Surface Reconstruction
Authors: Wei, Y., Lopes, B.T., Eliasy, A., Wu, R., Fathy, A., Elsheikh, A., and Abass, A.
Journal: Heliyon
Publication Date: Dec 2021
Zernike polynomial absolute fitting error Δz = |Zfit-Zsurf| for the anterior corneal surface of 27 years old keratotic female participant measured by the Pentacam HR tomographer.
Summary:
Our research focused on the potential of Zernike polynomials to reconstruct corneal surfaces captured by three different devices: Pentacam HR tomographer, Medmont E300 Placido-disc, and Eye Surface Profiler (ESP). We analysed clinical data from 527 participants and tested the fitting capabilities of Zernike polynomials for the measurements obtained by these devices.
Our findings revealed that Zernike polynomials of order 12 and 10 almost perfectly matched the raw-elevation data collected from Pentacam for anterior and posterior surfaces, respectively, for both healthy and keratoconic corneas. However, the Zernike fitting could not perfectly match the data collected from Medmont E300 and ESP.
It is important to note that these devices have different approaches and mathematical algorithms to reproduce corneal topography and tomography, and their final readings are not always comparable. Thus, understanding the data handling in each device and choosing a suitable mathematical algorithm to reconstruct the measured surfaces is crucial.
In conclusion, for analysts interested in wavefront analyses, high order aberrations, light raytracing, and other applications that require parametric continuous surfaces, using order 10 Zernike polynomial to fit Pentacam posterior corneal surface and order 12 Zernike polynomial to fit Pentacam anterior surface is an ideal option. Fitting Medmont E300 Placido-disc and ESP to Zernike polynomials is not recommended due to the relatively high RMS associated with this fit. However, if necessary, Medmont E300 Placido-disc's topography and ESP's corneal profile could be fitted to Zernike polynomial order 16 and 9, respectively, with an awareness of the possible effect of the fitting error.