Strang N C, Atchison D A, Woods R L
Centre for Eye Research, School of Optometry, Queensland University of Technology, Australia.
Ophthalmic Physiol Opt. 1999 Sep;19(5):415-26.
Defocus lowers the contrast sensitivity function (CSF), producing a complex function with local dips and peaks. Previously, we were able to predict the shape of the CSF with large pupils from measured transverse aberrations with hypermetropic defocus but not with myopic defocus (Atchison et al., 1998c, J. Opt. Soc. Am. A. 15, 2536). As there is no reason that myopic defocus should be more difficult to predict than hypermetropic defocus, we modified the procedure to try to improve CSF predictions with myopic defocus. Also, we extended the study to consider a range of pupil sizes. CSFs were measured for three subjects at three defocus levels (in-focus, -2D and +2D) and three pupil sizes (2 mm, 4 mm and 6 mm). Using a diffraction optics model, transverse aberration measures and in-focus CSF measures, we predicted the defocused CSFs. The predicted defocused CSFs were lower than the in-focus CSF as expected, and had complex shapes that varied with defocus and pupil size and between subjects. While a few predictions were poor, generally, the overall magnitude and shape of the defocused CSFs were well predicted and similarly so for myopic and hypermetropic defocus. Some further improvements in technique are indicated.
散焦会降低对比敏感度函数（CSF），产生一个具有局部凹陷和峰值的复杂函数。此前，我们能够根据远视性散焦时测量的横向像差来预测大瞳孔情况下CSF的形状，但近视性散焦时则无法做到（阿奇森等人，1998c，《美国光学学会志A》15卷，2536页）。由于没有理由认为近视性散焦比远视性散焦更难预测，我们修改了程序，试图改进对近视性散焦时CSF的预测。此外，我们还扩展了研究范围，考虑了一系列瞳孔大小。对三名受试者在三种散焦水平（聚焦、-2D和+2D）以及三种瞳孔大小（2毫米、4毫米和6毫米）下测量了CSF。利用衍射光学模型、横向像差测量值和聚焦时的CSF测量值，我们预测了散焦时的CSF。正如预期的那样，预测的散焦时的CSF低于聚焦时的CSF，并且具有随散焦、瞳孔大小以及受试者之间而变化的复杂形状。虽然有一些预测效果不佳，但总体而言，散焦时CSF的整体大小和形状得到了很好的预测，近视性散焦和远视性散焦的情况类似。文中指出了技术上的一些进一步改进方向。
