Measurement of gradient refractive index profile of crystalline lens of fisheye in vivo using optical coherence tomography

We report the use of optical coherence tomography (OCT) for noninvasive measurement of the refractive index profile of a crystalline lens of a fisheye. The approach exploits the fact that OCT provides a direct measurement of the optical path of the light traveled through the medium. The gradient refractive index profile for the crystalline lens was retrieved by iterative fitting of the optical path calculated by the ray tracing method with that experimentally measured using OCT. The estimated error in refractive index is approximately 1%. The measured gradient refractive index and Matthiessen's ratio (ratio of focal length to lens radius) are in good agreement with the previously reported values.