Contact lens solution
Contact lenses in wide use fall into two categories: the hard or rigid corneal type lenses formed from materials prepared by polymerization of acrylic esters, such as polymethyl methacrylate (PMMA), and gel, hydrogel or soft type lenses made of polymerized hydrophilic or hydrophobic monomers, such as 2-hydroxyethyl methacrylate (HEMA). Generally, a contact lens is liable to be stained with a secretion such as protein or lipid which is included in the tear fluid and which adheres to the surfaces of the contact lens while the contact lens is worn on an eye of the user. Contact lenses are subjected to the ocular environment for long periods of time each day. During the normal course of handling and wearing contact lenses, especially lenses made from hydrophilic materials, pathogenic agents or microorganisms typically accumulate and grow on the lenses. The presence of these pathogens on contact lenses oftentimes results in wearer discomfort and may even result in a contact lens wearer's eyes becoming infected. As a result of being in contact with the tear film and ocular debris, lenses have a tendency to build up surface deposits. The deposit may be formed from endogenous materials, such as proteins, lipids and mucins, but also may be the result of exogenous materials, such as cosmetic ingredients. To ensure comfortable wear and good vision, these surface deposits must be removed periodically, usually once a day for rigid gas permeable lenses and daily wear soft hydrogel lenses. For flexible wear lenses the cleaning may be less frequent. A solution for a contact lens contains a germicidal or preservative component to prevent contamination of the contact lens by molds and microorganisms such as bacteria, in addition to a cleaning component to remove deposits adhering to the contact lens such as protein and lipid which derive from tear fluid and lipid of the eye. The cleaning process for contact lenses can be either active, digital rubbing of the lens surface, or passive, soaking the lens in the cleaning solution. These cleaning processes may be combined, that is, the contact lens is removed from the eye, digitally rubbed with the cleaning solution, then placed in that same cleaning solution overnight to allow passive cleaning to occur.
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