[Special indications for the use of soft contact lenses as a drug-release-system (author's transl)]

Research has been performed, both experimentally and clinically, to establish the value of the association of soft contact lenses and some types of eye drops. The use of soft contact lenses with eye drops may be useful in some special cases: a) more prolonged and more sustained effect compared with the usual way of administration of eye drops (especially antiglaucomatous substances, antimetabolites, mydriatics); b) possibility of reducing the concentration to avoid local discomfort or systemic side-effects, without loss of their effectiveness on the eye conditions to be treated. The combined use of soft lenses (12.5-15 mm in diameter) with eye drops may be obtained either by presoaking the lens in the liquid or by regular instillation of eye drops after insertion of the lens; the two techniques may of course be associated. In the present research the advantages of utilizing hydrophylic lenses with osmotically active substances, to obtain a better and more protracted dehydration of the cornea, were first examined, in vitro and in vivo. The following substances were tested: 10% propylenglycol, 10% glycerol, 10% glucose and 5% natrium chloride. The clearing effect of the different types of treatment was evaluated in 45 patients with edematous bullous keratopathy with an instrument which measured the infrared light emitted by an optic fiber and reflected by the cornea. The effects were more marked for the epithelial than for the stromal oedema. Another group of investigations was performed with two polypeptides with high molecular weight: Eledoisin, extracted from a mediterranean octopus, Eledone moschata, and Physalaemin, extracted from the skin of a south american batrachian, Physalaemus fuscomaculatus, both of these stimulate the lacrimal secretion and were previously successfully employed topically by the authors against keratoconjunctivitis sicca. The increase of the amount of fluid was however short-lived. Eledoisin at a concentration of 200 mug/ml, was examined in its effects both in vitro and in vivo, whereas physalaemin, at a concentration of 20 mug/ml, only in vitro, owing to the present shortage of the product. The clinical tests in 23 eyes of 14 patients with keratoconjunctivitis sicca proved satisfactory, since the lacrymal stimulating effect is not only greater, but lasts three times longer by combining the instillation of eledoisin with a presoaked soft lens. Some antiglaucomatous products (propranolol, clonidine, prostigmine) were, finally, used in association with a soft lens to reduce the concentration of the eye drops for a better tolerance locally (propranolol: a beta-adrenergic blocking agent) or generally (clonidine: alpha-adrenergic agent), also with the advantage of protracted release. With propranolol the concentration could be reduced to 0.01-0,10% (instead of 0.125 to 0.25%) and to 1.5% (instead of 3%) with prostigmine, when lenses were presoaked or instillations took place at regular time intervals, after insertion of the lenses.