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S. R. Uhlhorn, D. Borja, F. Manns, J.-M. Parel; Species Variation of Human and Non-Human Primate Crystalline Lens Refractive Index Measured With Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3776. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if there are significant differences in the average refractive index of the crystalline lens between human and non-human primates.
Human and non-human primate (NHP) (cynomolgus monkey) crystalline lenses were isolated from whole cadaver globes (human: n=29, age range 23-82 years, post-mortem time <4 days, NHP: n=33, age range 3-11 years, post-mortem time <1 day) and placed in a preservation media-filled chamber resting on a soft rubber ring. Cross-sectional images of the isolated lenses were recorded with an optical coherence tomography system. From the recorded images, the average refractive index is calculated along the optic axis by measuring the optical thickness of the lens and the apparent location of the sample chamber window. These 2 parameters are used to calculate the axial thickness and group refractive index of the lens at the light source wavelength (825nm). The average group refractive index is first converted to the phase refractive index at 825 nm and then to the phase refractive index at 589 nm using lens dispersion data from the literature. The measured index was then analyzed as a function of age to determine whether any age-related differences exist.
The average refractive index along the optic axis was 1.407 +/- 0.004 (n = 29) for the human lenses and 1.414 +/- 0.009 (n = 33) for the NHP lenses. A linear regression of the human lens data as a function of age gave n = 1.414 - 0.00013*Age (R^2 = 0.19) and for the NHP data gave n = 1.410 + 0.00036*Age (R^2 = 0.15). The very small age coefficients and small regression coefficients (R^2) suggest there is little age-dependence in the average refractive index of both human and NHP lenses despite a significant decrease in the optical power with age.
There is little difference in the average refractive index of human and NHP species. These results provide further evidence that cynolmolgus monkey and other NHP species are well suited for use as an animal model for accommodation and presbyopia research.Support: R01 EY14225, P30 EY14801 (NIH Center Grant), F32 EY15362 (Kirschstein NRSA Fellowship), F31 EY15395 (Kirschstein NRSA Fellowship), Advanced Medical Optics, Santa Clara, CA, the Florida Lions Eye Bank, the Henri and Flore Lesieur Foundation, an unrestricted grant from Research to Prevent Blindness, and the Australian Federal Government CRC Scheme through the Vision Cooperative Research Centre.
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