Salyer David A, Twietmeyer Karen, Beaudry Neil, Basavanthappa Sreenivasa, Park Robert I, Chipman Russell
Optical Sciences Center, University of Arizona, Tucson.
Invest Ophthalmol Vis Sci. 2005 Jun;46(6):2120-4. doi: 10.1167/iovs.04-1020.
To quantify the reflectance of the swine fundus as a function of illumination angle and wavelength using a novel technique of intravitreal illumination.
Enucleated swine eyes were illuminated with a scanning monochromator coupled to a fiber-optic probe placed in the vitreous at several locations. Intravitreal illumination was used to reduce the effects of extraneous reflections and scatter from the anterior structures of the eye, including glints from the internal limiting membrane and blood vessels. Intravitreal illumination provided different light paths and additional information to apply to retinal reflectance modeling. A 25-mm(2) region of the illuminated fundus was imaged while the angle of illumination was varied over a maximum range of 22 degrees . Multispectral images from areas free of large blood vessels were acquired. The diffusely reflected intensity was integrated over the pupil with a solid angle of 0.028 steradians. The spectral reflectance function was calculated for multiple illumination angles.
Multispectral fundus image sets were obtained for two enucleated swine eyes by using intravitreal illumination. The fundus spectral reflectance function showed decreasing reflectance with increasing illumination angle, rapid changes in the 430- to 480-nm range, and a fairly consistent reflectance decrease for 480 to 700 nm.
Variations in fundus spectral reflectance with change in the illumination angle were found to deviate from Lambertian behavior, varying from Lambertian by 5% across the spectrum in one sample and 20% in a second sample. Intravitreal illumination resulted in markedly decreased extraneous reflections.
使用一种新型的玻璃体内照明技术，量化猪眼底反射率与照明角度和波长的函数关系。
将摘除的猪眼用与置于玻璃体中多个位置的光纤探头相连的扫描单色仪进行照明。玻璃体内照明用于减少来自眼睛前部结构的外部反射和散射的影响，包括来自内界膜和血管的反光。玻璃体内照明提供了不同的光路和额外信息，可应用于视网膜反射率建模。在照明角度在最大22度范围内变化时，对被照明眼底的25平方毫米区域进行成像。采集无大血管区域的多光谱图像。漫反射强度在立体角为0.028球面度的瞳孔上进行积分。计算多个照明角度下的光谱反射率函数。
通过使用玻璃体内照明，获得了两只摘除猪眼的多光谱眼底图像集。眼底光谱反射率函数显示，随着照明角度增加，反射率降低，在430至480纳米范围内变化迅速，在480至700纳米范围内反射率相当一致地降低。
发现眼底光谱反射率随照明角度变化而偏离朗伯行为，在一个样本中整个光谱范围内与朗伯行为的偏差为5%，在第二个样本中为20%。玻璃体内照明导致外部反射明显减少。
