A Wide-Angle X-ray Diffraction Study of the Developing Embryonic Chicken Cornea

Abstract

In terrestrial vertebrates the cornea is the main refractive component of the eye. Its remarkable mechanical toughness and almost 100% light-transparency are largely a consequence of the unique collagenous architecture of the corneal stroma. We have used WAXS methods to investigate stromal remodelling in the embryonic chicken cornea in the latter stages of development. Collagen organisation at day 13-15 of embryogenesis is dominated by a four-fold orthogonal arrangement of fibrils. Thereafter this preferential alignment recedes, seemingly because further collagen is deposited in a more isotropic manner, masking the initial orthogonal template. In contrast, the mean lateral spacing of fibril-forming collagen molecules remains unaltered over this developmental period. Our observations have important implications for the biomechanical strength and shape of the cornea.