The corneal polarization cross can be seen at the human cornea using crossed polaroids. The optical mechanisms for this phenomena include rotation and retardation of the light at the surface of the cornea due to the corneal curvature, as well as retardation due to an average circumferential orientation of the birefringent corneal collagen.
© 1978 Optical Society of America
W. T. Cope, M. L. Wolbarsht, and B. S. Yamanashi, "The corneal polarization cross," J. Opt. Soc. Am. 68, 1139-1141 (1978)