Enoch J M, Bedell H E
Am J Optom Physiol Opt. 1979 Jun;56(6):341-4. doi: 10.1097/00006324-197906000-00001.
An index to specify the directionality (spread) of Stiles-Crawford function and related retinal photoreceptor directional sensitivity data is proposed. This index, termed the half-sensitivity half-width (or angle) is the displacement in the pupil (or the change of angle of incidence at the retina) which results in a reduction of sensitivity to one-half that at the function maximum (0.3 log unit decrease). The half-sensitivity half-width or angle, unlike other currently used indices of retinal directionality, can be assessed empirically and is not intrinsically dependent upon curve-fitting assumptions or procedures.
提出了一个用于指定斯泰尔斯-克劳福德函数方向性（扩展）以及相关视网膜光感受器方向敏感性数据的指标。这个指标被称为半敏感性半宽度（或角度），是瞳孔中的位移（或视网膜处入射角的变化），它会导致敏感度降低至函数最大值时的一半（降低0.3对数单位）。与目前使用的其他视网膜方向性指标不同，半敏感性半宽度或角度可以通过实验评估，并且本质上不依赖于曲线拟合假设或程序。
