Bobier W R, Campbell M C, McCreary C R, Power A M, Yang K C
University of Waterloo, School of Optometry, Ontario, Canada.
Ophthalmic Physiol Opt. 1992 Apr;12(2):147-52. doi: 10.1111/j.1475-1313.1992.tb00278.x.
Photorefractive methods allow rapid measures of the refractive and accommodative state of infants and young children whose brief attention and co-operation limit the use of more traditional methods such as retinoscopy and autorefraction. Three methods have been defined: orthogonal, isotropic and eccentric. We provide a common geometrical optical analysis for these three methods where the photorefractive pattern is defined at the plane of focus of the camera. Since this plane is conjugate with the detector plane of the camera then the critical optical parameters can be defined without reference to the design of the camera by simply determining the relative magnification of the projected image of an object photographed at the camera's plane of focus. Specifically the pattern width CF (mm) over a photorefractor's working range can be defined for the isotropic and orthogonal methods as: [formula: see text] and for the eccentric method as: [formula: see text] where: K is a myopic refractive error of the eye (dioptres) (K Less than 0); P the distance of the flash source to the eye (dioptres); L the distance in front of the eye of the camera's plane of focus (dioptres) (L less than 0); GH the pupil diameter (mm); e the eccentricity of the flash source from the camera aperture (mm); M magnification of the image measured relative to the camera plane of focus.
光折射方法能够快速测量婴幼儿的屈光和调节状态，这些婴幼儿注意力短暂且难以配合，限制了视网膜检影法和自动验光等更传统方法的使用。已定义了三种方法：正交法、各向同性法和偏心法。我们为这三种方法提供了一种通用的几何光学分析，其中光折射图案在相机的焦平面上定义。由于该平面与相机的探测器平面共轭，因此通过简单地确定在相机焦平面拍摄的物体投影图像的相对放大倍数，就可以在不参考相机设计的情况下定义关键光学参数。具体而言，对于各向同性法和正交法，在光折射仪工作范围内的图案宽度CF（毫米）可定义为：[公式：见正文]，对于偏心法可定义为：[公式：见正文]，其中：K是眼睛的近视屈光不正（屈光度）（K小于0）；P是闪光光源到眼睛的距离（屈光度）；L是相机焦平面在眼睛前方的距离（屈光度）（L小于0）；GH是瞳孔直径（毫米）；e是闪光光源相对于相机光圈的偏心距（毫米）；M是相对于相机焦平面测量的图像放大倍数。
