Smith G
Am J Optom Physiol Opt. 1982 Nov;59(11):885-9. doi: 10.1097/00006324-198211000-00006.
When the eye is defocused for any reason, the diameter of the blur disc may be used as a first approximation to estimate effects on visual acuity. More exact treatment must use physical optics which take diffraction effects into account. Traditionally, defocus calculations of blur disc diameters have started with a particular schematic eye and rays traced to find the retinal image diameter of the blur disc. The angular or perceived diameter of this disc is then found by calculation of the angular subtense of the retinal blur disc measured at the back nodal point. A formula is presented here which bypasses the need for a specific schematic eye and is valid for any level of accommodation. The formula, although it is approximate, is very simple and only contains a defocus or refractive error quantity and the pupil diameter.
当眼睛因任何原因出现散焦时，模糊斑的直径可作为初步近似值，用于估计对视敏度的影响。更精确的处理必须采用考虑衍射效应的物理光学方法。传统上，模糊斑直径的散焦计算始于特定的简化眼，并通过追踪光线来确定模糊斑的视网膜图像直径。然后，通过计算在眼球后节点处测量的视网膜模糊斑的视角来确定该模糊斑的角直径或感知直径。本文给出了一个公式，该公式无需特定的简化眼，并且对任何调节水平均有效。该公式虽然是近似的，但非常简单，仅包含散焦或屈光不正量以及瞳孔直径。
