Imaging of polarization properties of the human cornea with phase-resolved polarization-sensitive optical coherence tomography

Polarization sensitive optical coherence tomography (PS-OCT) was used to measure and image retardation and birefringent axis orientation of in vitro human cornea. We used a two-channel PS-OCT system employing a phse sensitive recording of the interferometric signals in two orthogonal polarization channels. Using an algorithm based on a Hilbert transform, it is possible to calculate the retardation and the slow axis orientation of the sample with only one A-scan per transversal measurement location. While the retardation information is encoded in the amplitude ratio of the two interferometric signals, the axis orientation is encoded entirely in their phase difference. We present maps of retardation and slow axis distribution of normal and pathologic human cornea in longitudinal cross sections and en face images, obtained at the back sruface of the cornea. The results can be explained by a birefringence model based on stacked collagen fibril lamellae of different orientations.