The invention provides a system and method obtaining the refractive index of the cornea. According to the invention, an optical coherence tomography system with a high numerical aperture lens. In a first position, radation is focused on the front surface of the cornea in a second position, focused on the back surface of the cornea. The distance the high numerical aperture lens moves corresponds to the thickness of the cornea. The OCT reference mirror signals in a first position correspond to the front surface of the cornea in a second position correspond to the back surface of the cornea. The distance between the first and second positions of the reference mirror corresponds to the optical distance of the cornea. Optical distance divided by physical distance provides the refractive index. Various alternate embodiments are taught.
