Abstract：
OBJECTIVE: The Beer-Lambert law suggests that visual pigment optical density (OD) should be linearly related to the length of photoreceptor outer segments (POSs). Mammalian studies indicate that visual pigment concentration increases with POS length, but the nature of this relationship may vary due to factors such as visual pigment packing density or retinal eccentricity, and may not necessarily be linearly related. The purpose of this study was to establish the relationship between OD and POS length in humans.
METHODS: Spectral domain optical coherence tomography (OCT) was used to image POS, and imaging retinal densitometry (IRD) was used to measure OD at corresponding locations in 19 healthy participants (age range 25-82 years). POS length and OD measurements were extracted from OCT and IRD images at 23 discrete locations spanning the central 9° of the retina. The averaged data from all participants were fitted with models based on the Beer-Lambert law to establish the relationship between OD and POS length.
RESULTS: Visual pigment OD increased monotonically with POS length, but the relationship was non-linear, and a straight-line fit, based on a simple interpretation of the Beer-Lambert law, provided a poor description. A model allowing for different rod and cone visual pigment concentrations provided a superior fit. Specifically, the data were well described by a model where the molar concentration of visual pigment in cones and rods were 3.8 × 10-3 mol/L and 1.8 × 10-3mol/L, respectively.
CONCLUSIONS: In accordance with the Beer-Lambert law, the results indicate that OD increases monotonically with POS length in humans, but the precise relationship is dependent on photoreceptor type. These results suggest that visual pigment concentration in rods is only about 48% of that found in cones. This may be due to the ubiquitous nature of artificial light that works to reduce the concentration of rhodopsin in rod photoreceptors.
METHODS: Spectral domain optical coherence tomography (OCT) was used to image POS, and imaging retinal densitometry (IRD) was used to measure OD at corresponding locations in 19 healthy participants (age range 25-82 years). POS length and OD measurements were extracted from OCT and IRD images at 23 discrete locations spanning the central 9° of the retina. The averaged data from all participants were fitted with models based on the Beer-Lambert law to establish the relationship between OD and POS length.
RESULTS: Visual pigment OD increased monotonically with POS length, but the relationship was non-linear, and a straight-line fit, based on a simple interpretation of the Beer-Lambert law, provided a poor description. A model allowing for different rod and cone visual pigment concentrations provided a superior fit. Specifically, the data were well described by a model where the molar concentration of visual pigment in cones and rods were 3.8 × 10-3 mol/L and 1.8 × 10-3mol/L, respectively.
CONCLUSIONS: In accordance with the Beer-Lambert law, the results indicate that OD increases monotonically with POS length in humans, but the precise relationship is dependent on photoreceptor type. These results suggest that visual pigment concentration in rods is only about 48% of that found in cones. This may be due to the ubiquitous nature of artificial light that works to reduce the concentration of rhodopsin in rod photoreceptors.
摘要：
目的：Beer-Lambert定律表明，视觉色素光密度（OD）应与感光体外段（POSs）的长度线性相关。哺乳动物研究表明，视觉色素浓度随着POS长度而增加，但这种关系的性质可能因视觉色素堆积密度或视网膜偏心率等因素而有所不同，并且不一定是线性相关的。这项研究的目的是建立人的OD和POS长度之间的关系。
方法：使用谱域光学相干断层扫描（OCT）对POS进行成像，在19名健康参与者(年龄范围25-82岁)中,使用成像视网膜光密度法(IRD)测量相应位置的OD.从跨越视网膜中央9°的23个离散位置处的OCT和IRD图像提取POS长度和OD测量值。来自所有参与者的平均数据用基于Beer-Lambert定律的模型拟合,以建立OD和POS长度之间的关系。
结果：视色素OD随POS长度单调增加，但是这种关系是非线性的，和直线拟合，基于对Beer-Lambert定律的简单解释,提供了一个糟糕的描述。允许不同的杆和锥视觉色素浓度的模型提供了优越的拟合。具体来说,数据由一个模型很好地描述，其中视锥和杆中视觉色素的摩尔浓度为3.8×10-3mol/L和1.8×10-3mol/L，分别。
结论：根据比尔-兰伯特定律，结果表明，在人类中，OD随POS长度单调增加，但是精确的关系取决于感光体类型。这些结果表明，视杆中的视觉色素浓度仅为视锥细胞中的48％。这可能是由于人造光的普遍存在的性质，可以降低视紫红质在视杆感光体中的浓度。
方法：使用谱域光学相干断层扫描（OCT）对POS进行成像，在19名健康参与者(年龄范围25-82岁)中,使用成像视网膜光密度法(IRD)测量相应位置的OD.从跨越视网膜中央9°的23个离散位置处的OCT和IRD图像提取POS长度和OD测量值。来自所有参与者的平均数据用基于Beer-Lambert定律的模型拟合,以建立OD和POS长度之间的关系。
结果：视色素OD随POS长度单调增加，但是这种关系是非线性的，和直线拟合，基于对Beer-Lambert定律的简单解释,提供了一个糟糕的描述。允许不同的杆和锥视觉色素浓度的模型提供了优越的拟合。具体来说,数据由一个模型很好地描述，其中视锥和杆中视觉色素的摩尔浓度为3.8×10-3mol/L和1.8×10-3mol/L，分别。
结论：根据比尔-兰伯特定律，结果表明，在人类中，OD随POS长度单调增加，但是精确的关系取决于感光体类型。这些结果表明，视杆中的视觉色素浓度仅为视锥细胞中的48％。这可能是由于人造光的普遍存在的性质，可以降低视紫红质在视杆感光体中的浓度。
