点扩散函数法在人眼成像质量分析中的特征

目的采用点扩散函数（point spread function，PSF）分析系统，获得在人眼的视网膜成像质量表达中的各种特征，研究其在人眼成像质量评价中的作用。方法应用点扩散函数分析系统（PSF-1000），测量22例近视无散光者的视网膜成像质量，在瞳孔3mm和6mm状态下，取22眼调制传递函数（modulation transfer function．MTF）曲线中的12个点，分别等同于对数视力表4．0～5．1的12个点,针对PSF分析系统中的MTF参数进行比较和统计学分析。结果①PSF反映的是光强度大小和位置的偏差。PSF分析系统可直接采用屈光系统MTF曲线表达人眼的成像特征，该曲线MTF值从低频至中频迅速下降，高频趋向缓和至零，定量并客观地表达了人眼成像质量从低频至高频的改变。②左、右眼的MTF表达具有镜像对称性。⑧个体之间MTF值差异大（如空间频率为3．00c／d时，3mm瞳孔直径的MTF值为0．68-0．98，6mm瞳孔直径的MTF值为0．51～0．85）。④3mm和6mm瞳孔直径时的MTF值差异有统计学意义（P〈0.01）。结论点扩散函数分析系统既能表达总眼球成像的各种光学特性，又体现了像差、衍射和散射的共同影响。

The point spread function system and its value in optical image quality assessment

Objective To investigate the imaging characteristics of human eyes with the point spread function analysis system （PSF）. Methods A PSF 1000 analyzer was used to measure the retinal image quality of the myopic eyes of 22 subjects. The modulation transfer function （MTF） curve was recorded and evaluated for pupil sizes of 3 taro and 6 mm, Twelve points on the MTF curve of the PSF. which were equivalent to the 12 points of a LogMar VA chart （4.0-5.1）, were chosen for analysis. Results ①PSF reflects the deviation of light intensity distribution and position. The PSF analysis system could deseribe the imaging characteristics of the eyes with an MTF curve. The curve obviously declined from the low frequency to the middle frequency section, and was reduced to zero in the high frequency section, which objectively showed the change in imaging characteristics of the eyes from the low to high frequency areas. ②The MTF curve of each eye was enantiomor-phous symmetrical.③Individual MTF values were quite different （e.g., when the spatial frequency was 3.00 e/d, MTF values were from 0.68 to 0.98 for a 3 mm pupil size and from 0,51 to 0.85 for a 6 mm pupil size）.④MTF values measured with a simulated 3 mm pupil size were significantly different from those measured with a simulated 6 mm pupil. Conclusion PSF analysis expressed different kinds of optical imaging characteristics in human eyes. It integrated the impact of aberration, diffraction and dispersion, objectively evaluating the retinal imaging quality of the optic system.