[New approaches in clinical ophthalmology: UV absorbers and hindered amines covalently bound to contact lenses. Importance of enzyme histochemistry in studying their effectiveness in vivo].

UV absorbers developed by us are covalently bound in hydrophilic contact lenses. This is great advantage because UV absorbers cannot be diluted from contact lenses. In laboratory investigations and "in vivo" experiments it was found that contact lenses containing UV absorbents prevent the eye against the damaging effect of UV irradiation (UVA, UVB, UVC rays). The second new approach (mentioned in this paper) is the use of Hindered Amine Light Stabilizer (4-methakryloylamino-2,2,6,6-tetramethylpiperidine) covalently bound in the hydrophilic contact or therapeutic lenses--for the healing of the damaged eye. In laboratory measurements the cleavage of hydrogen peroxide (of various concentrations) by hindered amine light stabilizer was confirmed. In "in vivo" experiments it was examined histochemically and morphologically that Hindered Amines Light Stabilizer bound in contact lenses favourable influenced the healing of the damaged anterior eye segment of rabbits. The amount as well as enzyme activation (lysosomal hydrolases) of inflammatory cells was significantly reduced in the anterior eye segment. It is suggested that Hindered Amine Light Stabilizer reacts with reactive oxygen species (oxyradicals and hydrogen peroxide) present in the damaged anterior eye segment (e.g. released from inflammatory cells). During this reaction intermediate products appear and the resulting product is a nitroxide radical. All reaction products as well as resulting product are covalently bound in hydrophilic material. For the development and also evaluation of the efficacy of both new approaches perspective for the use in clinical ophthalmology, biochemical investigations and histochemical methods are employed. Enzyme histochemistry is very important for the evaluation of the efficacy of new therapeutic approaches "in vivo" and therefore the particular attention is devoted to it in this communication.