Morphological and biochemical analysis of intact and opaque cornea in dogs.

Cornea is mainly composed of anterior epithelium, sub­ stantia propria and posterior endothelium. In these main three layers, especially in the substantia propria, collagen types, amount and arrangement of cells, formation of collagen fibrils and components type of extracellular matrices are indispensable for transparency of cornea 2, . Major extracellular matrix components are various types of glycosaminoglycans (GAGs) linked to their core proteins with proteoglycans. GAGs consist chiefly of chondroitin sulfate, dermatan sulphate, heparan sulfate and keratan sulfate. Among these, while keratan sulfate plays a principal role in providing corneal clearness and maintaining a constant diameter of collagen fibril and interfibrillar space 6, , dermatan sulphate inhibits the in­ crease of collagen fibril diameter . Metabolic disorder of GAGs was reported to bring out collagen fibril malfor­ mation. As mentioned above, cloudiness of the cornea could be related to the abnormality of both cellular and non­cellular components, especially in the substantia propria. However, little attention to this particular aspect has been given to the point. In this study, clarification of the corneal opacity is to analyze morphology of collagen fibrils in the substantia propria together with biochemis­ try of some major extracellular substances.