人眼高阶像差对正常近视眼调制传递函数影响的初步分析

摘要

目的 借助光学手段,分析不同高阶像差影响下近视患者调制传递函数(MTF)的变化,找出影响人眼光学质量的主要像差因素.方法 应用Hartmann-Shack原理的波阵面像差仪对255例(255眼)近视散光患者在不同直径瞳孔和不同空间频率下进行波阵面像差测量,应用光学常规数理统计方法分别进行MTF值计算和分析.应用配对t检验分析正常近视眼去除不同Zernike主要项C3-3～C33和C40及不同阶S3、S4、S5、S6等之后的MTF值与总高阶像差MTF值的差异.结果 无论是3 mm还是6 mm直径瞳孔,分别去除上述各Zernike项后各空间频率(5～60 c/d)下的MTF值均有相应提高,差异均具有统计学意义(P均＜0.01).其中,3 mm瞳孔下,C3-1和C3-3的影响最大,C31和C33次之,C40的影响最小;6mm瞳孔下,C40的影响最大,C3-1和C3-3次之,G31和C33影响最小.3 mm瞳孔下,除了去除S5、S6对MTF值影响不明显外,去除S3、S4后各空间频率下的MTF值均有相应提高(P均＜0.01);其中,S3对MTF值的影响最大.6 mm瞳孔下,去除各阶像差后MTF值均有提高(P均＜0.01);其中,在20 c/d及以下空间频率,S3的影响最大,从25 c/d开始,其与S4的差异无统计学意义(P＞0.05).随着空间频率的增加,3 mm瞳孔下的MTF值呈匀速降低;6 mm瞳孔下,空间频率为30 c/d及以下时,MTF值急剧下降,空间频率大于30 c/d时,MTF值变化趋于平稳.结论 ①不论大、小瞳孔下,C3-3～C33和C40等高阶像差均可降低各空间频率下的MTF值.②小瞳孔下G3-1、C31及S3对各个空间频率的MTF值影响较大;大瞳孔下C40对各空间频率的MTF值影响较明显;S3对20 c/d及以下空间频率的 MTF值影响较大,从25 c/d空间频率开始,S3和S4对MTF值的影响基本一致.即不同直径瞳孔下和不同空间频率下,高阶像差对人眼光学质量的影响不同.%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.