Corneal group refractive index measurement using low-coherence interferometry

Stephen R. Uhlhorn; Fabrice Manns; Hassan Tahi; Pascal O. Rol; Jean-Marie A. Parel

doi:10.1117/12.309424

1 June 1998 Corneal group refractive index measurement using low-coherence interferometry

Stephen R. Uhlhorn, Fabrice Manns, Hassan Tahi, Pascal O. Rol, Jean-Marie A. Parel

Proceedings Volume 3246, Ophthalmic Technologies VIII; (1998) https://doi.org/10.1117/12.309424
Event: BiOS '98 International Biomedical Optics Symposium, 1998, San Jose, CA, United States

Abstract

Purpose: The goal of the study is to measure the group refractive index of the human cornea in vitro to improve the accuracy of corneal thickness measurements. Methods: Corneal buttons were trephined from 23 human cadaver eyes and the group refractive index of the cornea was measured at lambda equals 840 nm using a low-coherence Michelson interferometer and the technique proposed by Sorin and Gray (Phot. Tech. Lett. 4:105 - 107, 1992). The effect of dehydration on the measurement was studied by measuring the corneal optical thickness as a function of time. Results: Preliminary measurements of the group refractive index at 840 nm gave n_g equals 1.450 plus or minus 0.024 for the human cornea, which is much higher than a calculated group refractive index of n_g equals 1.387. Because of dehydration, the optical thickness of the cornea decreased at a rate of 5.5 micrometer/minute which led to an artificially high value for the group refractive index. Conclusion: The calculated group refractive index of n_g equals 1.387 appears to be an accurate value for the purpose of corneal thickness measurements using low-coherence interferometry, and corneal group refractive index measurements can be performed in vitro if the measurements are performed rapidly to avoid the effect of dehydration.

Citation Download Citation

Stephen R. Uhlhorn, Fabrice Manns, Hassan Tahi, Pascal O. Rol, and Jean-Marie A. Parel "Corneal group refractive index measurement using low-coherence interferometry", Proc. SPIE 3246, Ophthalmic Technologies VIII, (1 June 1998); https://doi.org/10.1117/12.309424

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