Photodegradation of hyaluronic acid and of the vitreous body.

Hyaluronic acid is a mucopolysaccharide. The chemical structure and properties of this group have been extensively studied (Brimacombe and Webber 1964; Schubert and Hamerman 1968; Mathews 1975; Laurent 1987). Hyaluronic acid is present in the connective tissue. It was discovered by Meyer and Palmer (1934) in the vitreous body tissue where its concentration ranges from 140 to 338 mg/dm (Laurent 1987). It has a number of physiological functions, including influence on the polymer-solvent interactions and on the diffusion processes (Wik 1979). Many of these functions have been proved to be closely related to the physicochemical properties of the compound (Laurent 1966, 1968. 1970). Recently, pathological processes in the eye due to luminous radation have come to the foreground of scientific interests (Lawwill 1982). X-rays and radiolysis of hyaluronic acid cause vigorous depolymerization and liquefaction (Caputo 1957; Ragan et al. 1947: Lai 1985). The vitreous body is a loose connective tissue built up of a collagen network and tied up with a molecularly dispersed glycosaminoglycan system to form an organized composite proteoglycan structure. It contains an aqueous solution of different species, including sodium chloride, metabolities and serum proteins. From the physiological point of view the vitreous body seems to be a large interstitial pre-lymphatic space inserted between the venous system of the ciliary body, which produces the chamber fluid, and the drainage system of the lamina cribrosa space. The present work examines the influence of UV-radiation on the photode-