Cornea characterization using a combined multiphoton microscopy and optical coherence tomography system.

We present a multimodal imaging system which combines multiphoton microscopy and optical coherence tomography to visualize the morphological structures, and to quantify the refractive index (RI) and thickness of cornea. The morphological similarities and differences at different corneal layers across various species are identified. In the piscine and human corneas, the stromata exhibit thin fibers that indicate an overall collagen direction. Human corneas display collagen micro-folds which cause increased light attenuation. In the murine, porcine and bovine corneas, the stromata show interwoven collagen patterns. The Bowman's layer and the Descemet's membrane are also distinguished in some species. The RI and thicknesses are quantified for the epithelium and the stromal layers respectively, where the epithelium is found to have slightly higher RI than the stroma. The average epithelial and stromal RI are, respectively, 1.371 ± 0.016 and 1.360 ± 0.008 for the murine corneas; 1.502 ± 0.057 and 1.335 ± 0.011 for the piscine corneas; 1.433 ± 0.023 and 1.357 ± 0.013 for the human corneas; 1.476 ± 0.091 and 1.343 ± 0.013 for the porcine corneas; and 1.400 ± 0.007 and 1.376 ± 0.003 for the bovine corneas. The multimodal system can potentially provide a comprehensive characterization of the cornea.