Abstract
Abstract: :
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 age. The purpose of the current study was to generate population information for the aberrations of the normal cornea and quantify their effect on visual performance. Methods: 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) with the pupil centre as reference centre. The higher order aberrations were compared to aberrations produced by lower order defocus normally correctable with spectacles. Results: The current report, which concerns the first 100 (n=200 eyes) normally sighted subjects measured, produced the following results: i) The mean WFE increased with increasing apertures, becoming significant at 6mm (Mean 3mm=0.006 µm; 4.5mm=0.042 µm; 6mm=0.252 µm); ii) Even within the normal population large inter-subject differences were recorded with significant WFE present for some individuals at 4.5mm aperture; iii) Mean higher order WFE for a 6mm pupil size was equal to the WFE produced by 0.40D of defocus. Conclusion: The corneal WFE of the normal population is significant at 6mm diameter. However, very large inter-subjects differences exist leading to the presence of significant aberrations at smaller apertures for some individuals.
Keywords: 599 topography • 370 cornea: basic science