School of Optometry, Indiana University, Bloomington, USA.
Ophthalmic Physiol Opt. 2013 Jul;33(4):444-55. doi: 10.1111/opo.12072. Epub 2013 May 19.
We tested the hypothesis that pupil apodization is the basis for central pupil bias of spherical refractions in eyes with spherical aberration.
We employed Fourier computational optics in which we vary spherical aberration levels, pupil size, and pupil apodization (Stiles Crawford Effect) within the pupil function, from which point spread functions and optical transfer functions were computed. Through-focus analysis determined the refractive correction that optimized retinal image quality.
For a large pupil (7 mm), as spherical aberration levels increase, refractions that optimize the visual Strehl ratio mirror refractions that maximize high spatial frequency modulation in the image and both focus a near paraxial region of the pupil. These refractions are not affected by Stiles Crawford Effect apodization. Refractions that optimize low spatial frequency modulation come close to minimizing wavefront RMS, and vary with level of spherical aberration and Stiles Crawford Effect. In the presence of significant levels of spherical aberration (e.g. C(4)(0) = 0.4 μm, 7 mm pupil), low spatial frequency refractions can induce -0.7 D myopic shift compared to high SF refraction, and refractions that maximize image contrast of a three cycle per degree square-wave grating can cause -0.75 D myopic drift relative to refractions that maximize image sharpness.
Because of small depth of focus associated with high spatial frequency stimuli, the large change in dioptric power across the pupil caused by spherical aberration limits the effective aperture contributing to the image of high spatial frequencies. Thus, when imaging high spatial frequencies, spherical aberration effectively induces an annular aperture defining that portion of the pupil contributing to a well-focused image. As spherical focus is manipulated during the refraction procedure, the dimensions of the annular aperture change. Image quality is maximized when the inner radius of the induced annulus falls to zero, thus defining a circular near paraxial region of the pupil that determines refraction outcome.
我们检验了这样一个假设，即瞳孔非均匀性是具有球差的眼睛中球镜折射的中央瞳孔偏倚的基础。
我们采用傅里叶计算光学，在瞳孔函数中改变球差水平、瞳孔大小和瞳孔非均匀性（斯泰尔斯-克劳福德效应），从这些点扩散函数和光学传递函数被计算出来。通过聚焦分析确定了优化视网膜成像质量的屈光矫正。
对于大瞳孔（7 毫米），随着球差水平的增加，优化视觉斯特雷尔比的折射反映了最大化图像中的高空间频率调制，并且都聚焦在瞳孔的近傍轴区域。这些折射不受斯泰尔斯-克劳福德效应非均匀性的影响。优化低空间频率调制的折射接近于最小化波前均方根误差，并且随球差和斯泰尔斯-克劳福德效应的水平而变化。在存在显著水平的球差（例如 C(4)(0) = 0.4 μm，7 毫米瞳孔）的情况下，低空间频率折射与高 SF 折射相比，可能导致 -0.7 D 的近视漂移，而最大化三周期/度方波光栅的图像对比度的折射可能导致 -0.75 D 的近视漂移相对于最大化图像清晰度的折射。
由于与高空间频率刺激相关的小景深，球差在瞳孔中引起的大的屈光度变化限制了有效孔径对高空间频率图像的贡献。因此，当成像高空间频率时，球差有效地诱导出一个环形孔径，定义了瞳孔中对清晰聚焦的图像有贡献的部分。随着球差在折射过程中的变化，诱导的环形孔径的尺寸也随之变化。当诱导的环形内半径降至零时，图像质量达到最大值，从而定义了瞳孔的近傍轴的圆形区域，决定了折射结果。
