Bobier W R
School of Optometry, University of Waterloo, Ontario, Canada.
Am J Optom Physiol Opt. 1988 Dec;65(12):962-71. doi: 10.1097/00006324-198812000-00008.
When an eye is refracted by "eccentric photorefraction" with a flash source off-centered from a camera lens, a crescent of light is formed in the margin of the pupil. The size of the crescent varies directly with the eye's refractive error. This photographic method has been used in vision screening studies of young children where the appearance of a crescent indicated that the refractive error was above a certain threshold. Usually quantification of the refraction could not be achieved by the photorefractor but relied upon subsequent testing using retinoscopy. My research aimed to expand eccentric photorefraction so as to enable it to provide quantification of the eye's refractive error. This was achieved by varying the eccentricity of the flash source from the camera lens and then calibrating the instrument over a large range of refractive errors. The calibration modified a previously derived optical relation which defined the eye's refractive error in terms of the eccentricity of the source for a given pupil size. Eccentric photorefraction of 26 infants and children aged 7 to 48 months showed a good correlation with retinoscopy (r = 0.82). It is concluded that this method would be complementary to other photorefractive methods (e.g., isotropic) particularly as it is able to measure a large range of refractive errors once the astigmatic meridians of the eye are known.
当用偏离相机镜头中心的闪光光源对眼睛进行“偏心摄影验光”时，在瞳孔边缘会形成一个月牙形的光斑。月牙形光斑的大小与眼睛的屈光不正直接相关。这种摄影方法已用于幼儿视力筛查研究，月牙形光斑的出现表明屈光不正高于某个阈值。通常，验光仪无法实现对屈光不正的量化，而是依赖于随后使用检影镜进行的检查。我的研究旨在扩展偏心摄影验光技术，使其能够提供眼睛屈光不正的量化结果。这是通过改变闪光光源与相机镜头的偏心度，然后在大范围的屈光不正情况下对仪器进行校准来实现的。校准修改了先前推导的光学关系，该关系根据给定瞳孔大小下光源的偏心度来定义眼睛的屈光不正。对26名年龄在7至48个月的婴幼儿进行的偏心摄影验光结果与检影镜检查结果显示出良好的相关性（r = 0.82）。结论是，这种方法将与其他摄影验光方法（如各向同性）互补，特别是当已知眼睛的散光子午线时，它能够测量大范围的屈光不正。
