van de Kraats J, Berendschot T T, van Norren D
Helmholtz Institute, Department of Ophthalmology, Academic Hospital Utrecht, The Netherlands.
Vision Res. 1996 Aug;36(15):2229-47. doi: 10.1016/0042-6989(96)00001-6.
We measured the spectral reflectance of the fovea of ten normal subjects in four conditions, i.e. under dark-adapted and bleached conditions and at two retinal angles of incidence. The objective was to study optical pathways through the photoreceptor layer, resulting in a model that simultaneously explains spectral, directional and bleaching properties of the fovea. On theoretical grounds, we propose that small reflections from the stack of discs in the cone outer segments are the origin of the directional component of foveal reflection. Non-directional reflection occurs at the inner limiting membrane and at all layers posterior to the outer segments. With four reflectance spectra as input, the model allows determination of the density of the photostable absorbers, the lens, macular pigment, melanin and blood. Because of the simplified modeling of the layers posterior to the photoreceptor layer, the values for the density of melanin and blood are not necessarily comparable to physiological data. The density of the visual pigment calculated with this model is consistent with psychophysical data, with estimates for the ten subjects ranging from 0.41 to 0.80. The long wavelength sensitive cone fraction is calculated as 0.56.
我们在四种条件下测量了10名正常受试者中央凹的光谱反射率，即暗适应和漂白条件下以及两个视网膜入射角时。目的是研究通过光感受器层的光学路径，从而建立一个能同时解释中央凹光谱、方向和漂白特性的模型。基于理论依据，我们提出，来自视锥细胞外段圆盘堆叠的小反射是中央凹反射方向分量的起源。非定向反射发生在内界膜以及外段后方的所有层。以四个反射光谱作为输入，该模型可以确定光稳定吸收体、晶状体、黄斑色素、黑色素和血液的密度。由于光感受器层后方各层的建模较为简化，黑色素和血液密度的值不一定与生理数据可比。用该模型计算出的视色素密度与心理物理学数据一致，10名受试者的估计值范围为0.41至0.80。长波长敏感视锥细胞比例计算为0.56。
