ABSTRACT
The corneal stroma represents a unique connective tissue. Its collagenous structure is highly oriented and regular, and, due to this, it is a transparent tissue. This chapter demonstrates polarization microscopic findings obtained in embryonic human and chick corneas. These observations strongly suggest that glycosarninoglycans (GAGs) are oriented in the corneal lamellae, and the embryonic differentiation of the stromal lamellae—which occurs in a posterior-anterior direction—includes the oriented axiparallel deposition of the GAGs. It will be shown that the acellular primary cornea matrix has a spatially oriented microstructure. The differentiated cornea is a transparent tissue comprising a stratified squamous epithelium and its basement membrane anteriorly, an endothelial layer and its basement membrane on the posterior surface and an avascular stroma interposed between the epithelium and endothelium. Electron microscopy revealed a well ordered pattern of chondroitin sulfate-proteoglycan stained with ruthenium red in both the epithelial basement membrane and the collagen fibrils of the primary stroma in embryonic chick corneas.
