One approach to reducing protein deposits is for the solution to contain a positively-charged element that effectively competes with the protein for the lens surface. Tear proteins are positively charged and are thus attracted to the lens surface. So much so that considerable effort has gone into developing solution elements that will prevent protein-binding on ionic lens materials, which carry a negative surface charge. Ionic lens materials, from which nearly 70% of soft lenses are made, have the greatest propensity to attract lysozyme. Rather, they are formulated to include other elements that help to remove protein and prevent it from binding to lens surfaces. Practitioners and patients alike misinterpret the "no separate enzyme required" phrase many multi-purpose solutions include in their labeling as meaning "enzyme included." These products do not include an enzyme. We can expect more of the latter with FDA approval of 30-night wear. Disposability may be the ultimate approach to avoiding lens deposit problems, but we know that many patients don"t dispose as regularly as we recommend, and they don"t always take their lenses out. A liquid form of the enzyme helped, but patients still had to thoroughly rinse lenses prior to insertion to avoid irritation. One catch is that our traditional enzymes can cause significant stinging and ocular irritation when they get in the eye, so the patient still needed a multi-step approach, usually involving separate enzyme soaking, to remove bound protein from the eye. The goal of a safe, effective single reagent system had merit, as well as enthusiastic consumer interest. Multi-purpose soft contact lens solutions simplified (revolutionized?) soft contact lens care. (On the other hand, had this discovery not taken place, we may have gotten to disposables much sooner.) For years, the use of papain, pancreatin and subtilisin made soft contact lens wear significantly less problem-prone. You could argue that the discovery that a proteolytic enzyme could extend the useable life of contact lenses saved the pre-disposable soft contact lens industry. Bound protein can decrease comfort and vision, and in some cases precipitate a giant papillary conjunctivitis. Over time, the protein (mostly lysozyme) can denature and firmly adhere to the lens surface. In the short term, this improves wettability and reduces friction, making lenses more comfortable. Solutions that do not include an enzyme are formulated to contain other elements that help to remove protein and prevent it from binding to lens surfaces.Ĭ ontact lenses become coated with a protein-rich film soon after being placed on the eye.
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