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S.R. Uhlhorn, D. Borja, F. Manns, J.–M. Parel; Refractive Index Measurement of the Monkey Crystalline Lens Using Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2627.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the average refractive index of the primate crystalline lens using optical coherence tomography.
A long–range (12 mm) depth scanning optical coherence tomography system has been developed that acquires 10–20 A–lines/s. The system has a center wavelength of 830 nm, a bandwidth of 25 nm, and an axial resolution of 12 microns. The system measures the optical thickness of the lens, which is the product of the geometric thickness and the group refractive index at the source wavelength. Additionally, shadow photographs of the lens are recorded after the OCT measurements, and are analyzed to determine the geometric thickness. The average group refractive index is calculated by dividing the optical thickness from the OCT data by the geometric thickness from the shadow photographs. The lenses are prepared from donated whole globes by gluing a ring to the sclera of the eye near the lens equator. The posterior pole and cornea are removed from the mounted eye so the lens, zonules, and cilliary body remain intact, and the sectioned tissue is immersed in BSS and recorded by the OCT system. After the OCT measurements, the lens is extracted from the mount and shadow photographs are recorded. Measurements were performed on 5 lenses from 3 cynomolgus monkeys within 24 hours of euthanasia.
The average group refractive index was 1.386 (OS/OD, Male, 10 yo), 1.385 (OD, Male, 4 yo), 1.435 (OS/OD, Male, 4 yo), The average optical thickness for all eyes measured with the OCT was 5.487 +/– 0.374 mm, and the average axial thickness for all eyes measured from the shadow photographs was 3.90 +/– 0.26. The average group refractive index at 830 nm for all eyes is 1.405 +/– 0.028.
These measurements suggest that the average refractive index of the cynomogus crystalline lens is very close to that of the human crystalline lens.
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