人眼角膜散光矫正的点扩散函数分析表达

The expression of the correction of corneal astigmatism in the point spread function analysis system of human eyes

目的探讨人眼点扩散函数（PSF）分析系统表达角膜散光眼的视网膜成像特性的可行性及角膜散光在不同矫正方式下的光学成像特征。方法前瞻性随机对照研究。利用PSF分析系统（PSF-1000）检查和评估26例近视散光患者（年龄18—28岁，球镜度数-3．00～-6．00DS，散光度数-0．75～-3．00DC）在配戴框架眼镜、散光软性角膜接触镜（TSCL）和透氧性硬性角膜接触镜（RGPCL）3种全矫状态下的视网膜成像质量，采用26只眼屈光介质调制解调函数（MTF）曲线中的12个点（即分别等同于对数视力表4．0—5．1的12个点）进行比较和统计学分析。设置中度近视无散光者26例为对照组。左右眼MTF值比较使用配对样本t检验，与对照组的比较使用独立样本t检验，3种矫正方式的差异用单因素方差分析，P〈0．05时再进行配对样本t检验。以P〈0．05为差异有统计学意义。结果左右眼的MTF表达具有镜像对称性。与对照组比较，瞳孔直径3．0mm时，在低空间频率无差异，在中、高频空间频率差异有统计学意义（t值范围：-2．237～-5．421，P〈0．05）；瞳孔直径6．0mm时，在12个空间频率差异均有统计学意义（t值范围：-2．893～-9．577，P〈0．01）。3种矫正方式在模拟3．0和6．0mm瞳孔直径下MTF值差异均有统计学意义。3．0mm瞳孔时，除了3．00、3．78、4．78、30．00和37．80周／度5个空间频率外，其余空间频率RGPCL和框架眼镜的MTF值高于TSCL（F值范围：3．229—4．123，P〈0．05）。6．01／mm瞳孔直径下，12个空间频率的3种矫正方式差异均有统计学意义（F值范围：5．609—9．610，P〈0．05），RGPCL的MTF值较高。同一矫正状态下，3．0mm瞳孔直径下的MTF值均高于6．0mm瞳孔直径下的MTF值。结论PSF分析方法能综合表达像差、衍射和散射对视网膜成像质量的影响，RGPCL所产生的泪液镜不仅矫正角膜散光，同时可改善眼的衍射、散射和其他像差效应，从而获得相对较好的成像质量。

Objective To investigate the ocular optical imaging quality among corneal astigmatism subjects under different corrections by using the Point Spread Function analysis system （PSF）. Methods PSF 1000 analyzer was used to measure retinal image quality of eyes of 26 subjects with corneal astigmatism （ sphere ranged from - 3.00 to - 6. 00 DS, cylinder ranged from - 0. 75 to - 3.00 DC） , who were fully corrected with three different methods respectively： spectacles （SPE）, rigid gas permeable contact lenses （RGPCL） and toric soft contact lenses （TSCL）. The modulation transfer function （MTF） curve was recorded and evaluated. 12 points of the MTF curve （ equivalent to the 12 points of Log Mar VA chart） were chosen for analysis. Equivalent moderate myopia 26 subjects without astigmatism were set up as control group. Results The MTF curve of each eye is enantiomorphous symmetrical. Compared with the control group （ 〈 -0. 75D）, with 3.0 mm pupil, there＇s no statistical difference under low spatial frequency, the difference between middle and high frequency is significant （ P 〈 0. 05 ）. With 6. 0 mm pupil, there is statistical difference in all frequencies （ P 〈 0. 01 ）. With simulated 3.0 mm pupil and 6. 0 mm pupil, MTF values of all these three methods are statistical different. With 3.0 mm pupil, the MTF value of eyes fitted with RGPCLs is higher than that fitted with TSCLs except in the following frequency 3.00 , 3.78,4. 78, 30. 00 and 37.80 c/deg （ P 〈 0. 05 ）. With 6.0 mm pupil, the three correction methods are statistical different in all frequencies （ P 〈 0. 05）. In all these three methods, MTF values with simulated 3.0 mm pupil are significantly higher than that with simulated 6.0 mm pupil （ P 〈 0. 01 ）. Conclusions PSF analytical method is available for offering objective data of retina imaging quality. RGPCL and its induced tear film is improved not only correcting the corneal astigmatism, but also enhances the ocular optical quality by reducing diffraction, dispersion and other high order of aberration.