A soft contact lens is used not only for the correction of refractive errors, but also for therapeutic purpose. Soft contact lens is hydrophilic, it takes up and releases medicaments so that it promotes and prolongs the penetration of drugs through the cornea. It has been also recently reported that´ a soft lens increases pressure lowering effect in pilocarpine therapy.
The purpose of this study is to evaluate the penetration rate of drugs immersed into a soft contact lens (Soflens) through the cornea. In this-study the authors used. 24NaCl and (3H) cortisol solution on the rabbit cornea with or without Soflens.
The results were as follows:
1. During four hours following the administration of 2-NaCl the pent ration rate into the anterior chamber when Soflens, immersed in 24NaCl solution for 2 minutes was applied, showed 2. 4 times higher than that of topical instillation. In topical instillation, the Soflens group revealed a higher penetration rate (1. 6 times) than non-Soflens group. It was revealed that Soflens promoted the penetration of 24 NaCl solution into the anterior chamber of rabbits.
2. Intracorneal penetration of 24NaCl solution was 1. 5 times higher in topical instillation in the Soflens group than the non-Soflens group. Meanwhile, the highest penetration (2. 2 times) was noted in the group of Soflens which were soaked in 24NaCl solution. The highest concentration in the iris (1. 5 times) was noted in the soaked Soflens group.
3. In topical instillation of cortisol solution in the group of Soflens without treatment and the group of Soflens immersed in cortisol solution showed much lower penetration rates into the anterior chamber with 0. 9 and 0. 5 times than those of the topical instillation group.
Based on the above results, it is clear that Soflens does not always promote the penetration of drugs into the anterior chamber. The drug-sponging effect is supposed to very according to various factors such as solubility, molecular weight of drug and physico-chemical properties of a soft contact lens.
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