Chromatic dispersion based axial length estimation using retinal spectral domain optical coherence tomography.

We propose a method for extracting the axial length of the human eye from high-resolution spectral domain optical coherence tomography (SD-OCT) retinal scans. The method evaluates the chromatic dispersion introduced by the anterior segment and the vitreous of the eye. By analyzing sub-spectral scans, we quantify the axial shift caused by dispersion and relate it to the thicknesses of the media passed by the OCT beam. The method depends on accurate k-linearization and pixel-to-wavenumber calibration. First, we demonstrate the feasibility of our approach using a model eye with adjustable water chamber length. Subsequently, the method is explored for in vivo retinal OCT scans. Challenges are inter-subject variability and limited availability of exact chromatic dispersion data for ocular tissues in the relevant spectral range for OCT imaging. By interpolating the refractive indices of an established eye model from visible wavelengths to the infrared wavelengths of the OCT system using the dispersion of water and estimating refined dispersion properties of the lens, we improve the model's agreement with in vivo measurements.