LAUSR

The cornea is the front part of the eyeball and the transparent anterior segment of the globe of the eye that refracts light onto the retina. It is the first element in the eye’s optical system, contributing 2 ⁄ 3rd of the eye’s total focusing power, and must remain essentially clear for optimal vision to be achieved. The cornea is also the most sensitive tissue in the body (4). The cornea consists of five basic layers: the epithelium, Bowman’s layer, the stroma, Descemet’s membrane (caudal limiting membrane) and the endothelium (8, 7). Hayashi et al. (9) present comparative observations on corneas, with special reference to Bowman’s layer and Descemet’s membrane in mammals and amphibians. According to Nautschel (14), there is disagreement about the existence of Bowman’s layer in domestic animals. The structure of the stroma varies significantly between humans and animal species, such as cows, pigs, and rats (11). The cornea covers up to 30% of the rabbit eye. Due to its large size, the cornea is prone to trauma or other damages, including drying-out. The cornea, or the transparent front part of the eye, is a thin dense fibre-like structure characterized by 4 distinctive layers in rabbits: a keratinized layer of the epithelium (30 to 40 μm); the stroma formed by parallel bundles of collagen; Descemet’s membrane (7 to 8 μm); and a single layer of the endothelium, which is rich in Na+-ATPase pumps (3). The eyes of animals are frequently used in (animal and human) vision science studies, in pharmacodynamic studies of ophthalmic drugs, as well as in healing and surgery of traumatic eye injury (4, 5, 19, 20). Ocular diseases in food-producing animals play a significant role in economic losses (15). A large body of knowledge of corneal structures and functions is acquired from studying laboratory rodents, which are used as animal models for human research (17). However, the knowledge of corneal parameters in the pig, the cow and the rabbit is limited. Comparative morphological evaluation of animal corneal parameters