Visibility of transparent objects in the eye by retroillumination.
Visibility of transparent objects in the eye by retroillumination.
复制标题
通过逆光观察眼睛中透明物体的可见度。
DOI：
10.1136/bjo.55.8.517
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发表时间：
1971
影响因子：
4.1
通讯作者：
N. Brown
中科院分区：
文献类型：
--
作者：
N. Brown
后向照明是在裂隙灯处进行的，双目显微镜聚焦在物体上，由物体后面的一些结构反射的裂隙灯光束从后面照亮物体（沃格特，I930）。以这种方式观察角膜和透镜中的物体，并且所使用的反射器是虹膜、透镜或眼底。还描述了使用检眼镜对角膜进行后向照明（钱德勒，1945）。物体是可见的，因为它们通过阻挡、折射、反射（Berliner，1943）和反射与眼睛发出的光发生干涉。当物体的折射率高于或低于周围介质的折射率时，透明物体通过后向照明可见。主要原因是折射，但反射也起一定作用。所观察到的外观随着后向照明的方向和物体的折射性质而变化。从物体在不同的后向照明条件下的外观，可以得出关于物体折射性质的结论。虽然物体的形状和折射率的各种组合都是可能的，但这些组合只能分解为两种可观察到的效果：（i）物体作为发散折射器（透镜或圆柱体）。(2)作为会聚折射器（透镜或圆柱体）的物体。临床实例显示在宏观照片所作的技术先前描述（布朗，1970年）。图2所示为发散透镜（平凹）和会聚透镜（平凸）的对比照片。已经构建了一个模型来模拟眼睛中发现的物体。该模型有两个球形物体嵌入在一个明确的介质（明胶）：一个低折射率的对象（空气）作为一个发散透镜，和一个高折射率的（液体石蜡）作为一个会聚透镜。照片显示的模型在不同的照明条件下（图3，4和5）。
Retroillumination is performed at the slit-lamp with the binocular microscope focused upon the object which is illuminated from behind by the slit-lamp beam reflected off some structure posterior to the object (Vogt, I930). Objects in the cornea and lens are observed in this way and the reflectors used are the iris, the lens, or the fundus. The use of the ophthalmoscope for retroillumination of the cornea is also described (Chandler, I945). Objects are visible because they interfere with the emergent light from the eye by obstruction, refraction, respersion (Berliner, 1943), and reflection. Transparent objects are visible by retroillumination when the refractive index of the object is above or below that of the surrounding medium. The property mainly responsible is refraction, but reflection also plays some part. The observed appearance changes with the direction of the retroillumination and with the refractive nature of the object. From the appearance of an object under varying retroillumination conditions, conclusions can be drawn about the refractive nature of the object. Although a variety of combinations of shapes and refractive indices are possible in the object, these can be resolved into only two observable effects: (i) The object acting as a diverging refractor (lens or cylinder). (2) The object acting as a converging refractor (lens or cylinder). Clinical examples are shown in macrophotographs made by the technique previously described (Brown, I970). Photographs are shown for comparison of a diverging lens (plano-concave) and of a converging lens (plano-convex) (Fig. 2). A model has been constructed to resemble objects found in the eye. The model has two spherical objects imbedded in a clear medium (gelatin): one object of low refractive index (air) which acts as a diverging lens, and one of high refractive index (liquid paraffin) which acts as a converging lens. Photographs are shown of the model under varying conditions of illumination (Figs 3, 4, and 5).