[Prognostic value of changes in the cornea and conjunctiva in diabetes mellitus]

Features of morphological and ultrastructural organization of the cornea (literature review)

The human cornea – the anterior fibrous membrane of the eye, is a unique ordered optical-biological system that is avascular, saturated with nerve endings, includes tissue-specific cells, consists mainly of various types of collagen. An exceptional feature of the collagen layers of the cornea, including the collagen plates of the stroma, is transparency, which provides physiological refraction and light transmission due to the stable supporting properties of the cornea. The data on the morphological structure of the cornea, which is an important element of the optical system of the eye, are of considerable interest not only from theoretical, but also from practical positions. This is due to the fact that the identification of the first signs of deviation from normal physiological morphological and ultrastructural criteria in the cornea allows us to establish the nature of its pathological changes, which can be caused by both hereditary predisposition and local and general disorders. It has been shown that the thinning of the layers of the cornea, a decrease in the density of endotheliocytes or keratocytes signal the development of dystrophic processes in it. In addition to evaluating quantitative morphometric data, changes in qualitative ultrastructural indicators play an important role. In particular it was found that a decrease in the density of endothelial cells is accompanied by an increase in their size and a decrease in the cell nucleus. In addition, a number of degenerative pathological conditions are characterized by a decrease in the diameter of collagen fibrils and a change in the density of fibrillary packaging.This literature review presents basic information, features of morphology, ultrastructural organization and functional purpose of layers and cells of the human cornea.