PURPOSE. The knowledge of corneal aberrations is important both for the development of improved contact lens designs and for the optimisation of refractive surgical procedures. Limited population data has been published, mainly testing the effect of the age. The purpose of the current study was to generate population information for the aberrations of the normal cornea. METHOD. Corneal topography was recorded using the Keratron videokeratoscope. The height data files generated by the instrument were analysed using CTView software to obtain the Zernike coefficients and the higher order wavefront error (WFE). The analysis was carried out for three apertures (3, 4.5 and 6mm), two higher order sets of Zernike coefficients (up to the 4th and 10th order), and two reference centres (corneal apex and pupil centre).
RESULTS. The current report, which concerns the first 100 (n=200 eyes) normally sighted subjects measured produced the following results: i) The mean WFE was slightly greater when the pupil centre (relevant to the optical correction) rather than the corneal apex was taken as a reference; ii) The mean WFE increased with increasing apertures, becoming significant at 6mm (Mean 3mm=0.006um; 4.5mm=0.038um; 6mm=0.225um). However, even within the normal population large intersubject differences were recorded with significant WFE present for some individuals at 4.5mm aperture; iii) Individual Zernike coefficients varied greatly within the population, particularly for 6mm aperture; iv) Spherical aberration produced the greatest change with aperture (Mean+/-SD: 3mm=0.019+/-0.011um; 4.5mm=0.082+/-0.028um; 6mm=0.245+/-0.077um); v) WFE and common individual Zernike were similar for the 4th order and 10th order analysis.
CONCLUSIONS. The corneal aberration WFE of the normal population is significant at 6mm diameter. However, very large inter-subject differences exist leading to the presence of significant aberrations at smaller apertures for some individuals. The benefit of correcting higher order corneal aberrations within the normal population will be highly patient dependent.