Low Degree / High Degree polynomial decomposition in a large population of healthy normal eyes and how it compares to the Zernike polynomials: an observational study

Abstract Purpose: To evaluate and compare the ocular aberrations in healthy normal eyes with Zernike versus Low Degree/High Degree (LD/HD) coefficients using OPD-Scan III wavefront sampling.Methods: Retrospective case series. Ocular wavefront acquisition using automated skiascopy was performed in mesopic conditions on refractive surgery candidates. Root Mean Square (RMS) values were computed for 6 mm pupils and aberration data from the 1st to the 6th order were exported.A Principal Component Analysis was performed to investigate which of the two classifications explained better the variance of the wave aberrations for their respective higher order wavefront components.Results: Data from 3827 eyes of 2110 patients were analyzed. Z1-1 (horizontal tilt) and Z11 (vertical tilt) modes had a mean absolute RMS of 0.299 +/- 0.233 μm and 0.242 +/- 0.194 μm. G1-1 and G11 had a mean absolute RMS of 0.051 +/- 0.044 μm and 0.045 +/- 0.039 μm. Total Zernike coma (Z3-1, Z31, Z5-1 and Z51) had a mean absolute RMS of 0.168 +/- 0.089 μm. Total LD/HD coma (G3-1, G31, G5-1 and G51) had a mean absolute RMS of 0.488 +/- 0.261 μm. Zernike Spherical Aberration (SA = Z40) had a mean absolute RMS of 0.093 +/- 0.070 μm while LD/HD SA (Z40) had a mean absolute RMS of 0.642 +/- 0.481 μm. PCA demonstrated that the LD/HD classification provided a new set of basis functions that better fitted the variance of HOAs, compared with the Zernike classification.Conclusion: This study standardizes Zernike and LD/HD based wavefront reconstructions using the OPD-Scan III in mesopic conditions. LD/HD classifications appear to offer a more efficient description of the eye’s aberrations. The main differences of both classifications are expanded upon.