Effect of higher-order aberration on modulation transfer function for the optical quality in normal myopic eyes

Abstract

Objective To analyze the changes of the modulation transfer function (MTF) with or without different mode higher order aberration in normal myopic eyes. Methods Two hundred and fifty-five patients (255 eyes) were included. An aberrometer with Hartmann-Shack sensor was used to measure the monochromatic aberration of eyes. MTF of optical system were calculated at various pupil sizes (3 and 6 mm) respectively and the difference between MTF with whole high order aberrations and MTF without different Zernike mode (C3-3-C33,C40) and different mode of higher-order aberration (S3, S4, S5, S6) with paired-t test. Results The MTF values improved at all spatial frequency [5-60 cycles per degree, (c/d)] without C3-3-C33, C40 respectively both at 3 mm and 6 mm pupil (P＜0.01). As for the effect of each Zernike mode, for a 3 mm pupil, MTF values got the most improvement without C3-1 and C3-3, following with without C31 and C33, and least without C40; for a 6 mm pupil, the improvement of the MTF without C40 was the most, secondly without C3-1 and C3-3,and thirdly without C31 and C33. As for the effects of each order aberrations, for a 3 mm pupil, MTFvalues got significantly improvement without S3 and S4 at all spatial frequency (5-60 c/d) (P＜0.01);for a 6 mm pupil, all MTF values got significantly improvement without S3, S4, S5 and S6 respectively at all spatial frequency (5-60 c/d) (P＜0.01), and without S3 and S4, MTF value increased more than without S5 and S6. Without S3, MTF value increased more than without S4 when the spatial frequency was 20 c/d or lower, and there were no significantly differences between MTF values without S3 and without S4 when the spatial frequency was higher than 20 c/d. MTF value decreased by a constant speed with the spatial frequency increasing at a 3 mm pupil, while at 6 mm pupil, MTF value decreased sharply below 30 c/d, and keep relative stable more than 30 c/d.Conclusion ①The MTF values improve at all spatial frequency (5-60 c/d ) without C3-3-C33 and C40 respectively at different pupil size. ②For a small pupil, coma (C3-1, C31) and coma-like (S3)aberrations make the MTF value lower at all spatial frequency. For a large pupil, spherical aberration (C40) show a more significant effects at all spatial frequency, and spherical-like aberration has a weaker effect than coma-like aberration at 20 c/d or lower, but there is no significantly difference between the effect of S3 and S4 at spatial frequency higher than 20 c/d. That means difference modes of high-order aberration at different pupil size give various effect on optical quality at different spatial frequency for the human eye. Key words: Wavefront aberration; Modulation transfer function; Optical; Pupil; Myopia