Resumen de Fitting Zernike polynomials to ocular wavefront aberrations. Effect of the radial order on the fitting accuracy

Antonio J. del Águila Carrasco, José J. Esteve Taboada, Noelia Martínez Albert, Daniel Monsálvez Romín, Robert Montés Micó

• PURPOSE: To assess the accuracy of ocular wavefront aberration fits by means of Zernike reconstructions with different polynomial orders and different pupil sizes in normal healthy eyes.

  SETTING: Experimental study performed at the University of Valencia Department of Optics.

  METHODS: Ocular wavefront maps were obtained from 19 normal eyes using a ShackHartmann aberrometer. The tenth Zernike order fit was considered to be the real wavefront of the eyes. Different fittings from second to ninth Zernike orders were computed and compared with the tenth order. The ratio of the root mean square (RMS) error between the different fittings and the original wavefront was calculated, and a percentage value was given. This was performed for two pupil diameters: 3 and 6 mm.

  RESULTS: The accuracy of the fitting improved when the Zernike polynomial order used to describe the wavefront increased. This was very evident for the 6 mm pupil size. In order to obtain a reproduction with 99% of the RMS error of the original wavefront, four orders were required for the small pupil size (3 mm), whereas nine Zernike orders were necessary for a 6 mm pupil.

  CONCLUSIONS: The number of radial Zernike orders required to express ocular wavefront aberrations depends strongly on the pupil size. Four orders generally seem to be sufficient for small pupils, but for larger pupil sizes, more radial orders are needed if high accuracy is required.