眼底摄影或摄像的眼底图像如未经处理,其所测量结构及细节的结果与眼底的实际解剖大小或病理改变是不相吻合的,主要原因是受眼底照相机放大倍率、被检眼的屈光状态诸多因素的影响。活体眼底细节的真实大小无法直接测量,但却可以通过眼的光学系统在外界成像所形成的角的大小来间接测量眼底细节,根据可测量的角的大小(angular size)去推算眼底细节的真实大小需要了解眼屈光系统中的所有参数,包括角膜曲率、角膜厚度、前房深度、晶体曲率和厚度、眼轴长度以及眼底形状,这是一个非常复杂的三角几何计算过程,而且有关晶体和眼底形状的变化参数目前仍无法测量。 Littmann计算公式可以较满意地用于分析眼底图片的活体眼底细节,现就其原理及应用加以分 Fundus photography or camera fundus images without treatment, the measured structure and details of the results and the actual fundus anatomical size or pathological changes are not consistent, mainly due to fundus camera magnification, was seized refraction Status of many factors. The true size of living fundus details can not be directly measured, but the details of the fundus can be measured indirectly by the size of the angle formed by the optical system of the eye in the outside world, and the reality of the detail of the fundus can be calculated according to the measurable angular size The size of the ocular refractive system needs to understand all the parameters, including corneal curvature, corneal thickness, anterior chamber depth, the curvature and thickness of the lens, axial length and ocular fundus shape, which is a very complicated triangle geometry calculation process, and the crystal and The shape parameters of the fundus can not be measured at present. Littmann calculation formula can be more satisfactory for the analysis of fundus images of the fundus details, is the principle and application of points