Estimating the optical properties of corneal tissue from the OCT speckle

Estimating the scattering coefficient <i>μ</i> _<i>s</i> and scattering anisotropy factor <i>g</i> of the corneal tissue is currently limited to methods utilizing double integrating spheres or spectroscopic techniques, prohibiting such corneal tissue evaluation from being performed in a clinical setting. This paper presents a new concept of statistical matching between a given corneal optical coherence tomography (OCT) scan and a set of multi-reference phantom OCT B-scans, suitably simulated using the Monte Carlo method. The statistical matching that exploits the information present in the speckle includes an ensemble of distance measures. Using a set of OCT scans from 11 porcine eyeballs, for which epithelium was removed, it is demonstrated that the proposed statistical matching approach leads to a precise estimation of the optical properties of corneal stroma. The group mean of the scattering coefficient and the scattering anisotropy factor for the porcine stroma were <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow><mml:mover><mml:mi>μ</mml:mi> <mml:mo>¯</mml:mo></mml:mover> </mml:mrow> <mml:mi>s</mml:mi></mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.146</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.020</mml:mn></mml:math> mm^-1 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mover><mml:mi>g</mml:mi> <mml:mo>¯</mml:mo></mml:mover> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>0.893</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.021</mml:mn></mml:math> , respectively. These estimates match previously reported values established with other methods. The proposed approach of utilizing information present in the speckle can be readily extended to in vivo OCT imaging of human corneal tissue.