Lens Cleaning Solution

In humans, a contact lens lies in the conjunctival sac of the eye. In a closed eye, this sac is a slitlike space between the conjunctiva-covered eyeball and the eyelids. Contact lenses are small polymer bowls that float on tears superficial to the corneal eye layer and correct existing visual deficiencies similarly to glasses. While the idea of the contact lens was formulated as early as 1508, it was not until the 1800s that contact lenses became a reality. Hard plastic contact lenses were invented around 1936, and although soft lenses were invented in 1960, they were not available on the commercial market until 1971. 

Solutions formulated to clean hard gas-permeable contact lenses are sterile and pH buffered. They are soaking solutions and include lens-hydrating (wetting) agents (e.g., cationic cellulose derivatives) and preservatives (e.g., edetate disodium, chlorhexidine gluconate). 

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Write a set of instructions that could be included in a package of contact-lens cleaning solution containing an enzyme. This enzyme catalyzes the breakdown of protein residues that adhere to the lenses. Include information about the structure and function of enzymes and the care that must be taken to avoid their denaturation during use. 

Other Uses Enzymes work outside your body, too. One class of enzymes, called proteases (PROH tee ay ses), specializes in protein reactions. They work within cells to break down large, complex molecules called proteins. The meat tenderizer shown in Figure 20 contains proteases that break down protein in meat, making it more tender. Contact lens cleaning solutions also contain proteases that break down proteins from your eyes that can collect on your lenses and cloud your view. 

Many different compormds are able to act as catalysts. The most powerful catalysts are those foimd in nature. They are needed to speed up the reactions necessary for a cell to function efficiently. These biological catalysts are called enzymes. Enzymes help your body use food for fuel, build up your bones and muscles, and store extra energy as fat. Enzymes are involved in almost every process in a cell. For example, proteases are enzymes that break down proteins, as shown in Figure 6.22. These enzymes occur naturally in cells to help with recycling proteins so their parts can be used over and over. Proteases are also used in many common products, including contact lens-cleaning solution and meat tenderizer. 

Proteases in contact lens-cleaning solutions help remove the grimy buildup on lenses that results from proteins secreted by cells around the eyes. 

Real-World Reading Link Some cleaning products, such as contact lens cleaning solution, contain enzymes. Did you ever wonder what an enzyme was ... 

Occupational allergic contact dermatitis to metallic mercury is rare and is mainly seen among dental personnel (Goh and Ng 1988 Ancona et al. 1982 Kanerva et al. 1993). The majority of positive patch-test reactions to mercury and to mercury compounds are related to non-occupational exposure, e.g., dental amalgam, mercury from broken thermometers, thio-mersal in vaccines, and contact lens cleaning solutions. 

The diminution of electrode fouling in oxido-reductive mode is shown in Fig. 22. Other ECL systems were also examined and sonoelectrochemical enhancement was observed for luminol (3-aminophthalhydrazide). This system has been thoroughly studied for the detection of low concentrations of residual hydrogen peroxide in contact-lens cleaning solutions. The ECL intensity of 9,10-diphenyl-anthracene in sonicated DMF solutions was increased by factors of 20-30 depending on the concentration of the solutions, ultrasound power, and fre-quencyT Similar effects were observed from l,5-diphenyl-3-styrylpyrazoline, rubrene, 9,10-dimethyl-anthracene, and perylene. ... 

After the PEM disk was dipped in each of the six hot solution beakers for an hour, it was then wiped with a piece of lint-free lens cleaning tissue, and air-dried in a clean place. 

Both preserved and unpreserved saline solutions are multifunctional solutions. In addition to thermal disinfection, they are also used to dissolve enzyme tablets in cleaning contact lenses, as a rinsing solution following cleaning and chemical disinfection, and as a lens storage solution. 

Some relatively simple blister packaging equipment is produced on a rotary table principle whereby a blister can be formed, hand filled, lidded and the completed blister pack removed after four 90° movements. Others work on a reciprocating bed principle of forming and lidding. These are often used for optic lenses and opthalmic-type solutions for lens cleaning. 

Two kinds of soft hydrogel contact lenses were cleaned with different lens care solutions (ECS) and analyzed by XPS. The elemental composition did not vary strongly between the different systems but the 0=C/0—C concentration ratio varied by a factor of 5. It was inversely correlated with the initial deposition rate measured in adhesion tests of P. aeruginosa performed in a laminar flow chamber. This revealed the adverse effect of compounds rich in O-C moieties adsorbed from the LCS. " After the contact lenses were worn, the presence of nitrogen-rich compounds and a much higher O /O—C concentration ratio were observed. The initial deposition rate of bacteria was lower on worn than on unworn contact lenses. ... 

Use of Duboscq-type colorimeter. The colorimeter must be kept scrupulously clean. The cups and plungers are rinsed with distilled water and either dried with soft lens-polishing material or rinsed with the solution to be measured. 

Another type of sterile ophthalmic product is the contact lens solution (section 4.5) however, unlike the other types, this is not used for medication purposes but merely as wetting, cleaning and soaking solutions for contact lenses. 

Most contact lenses are worn for optical reasons as an alternative to spectacles. Contact lenses are of two types, namely hard lenses, which are hydrophobic, and soft lenses, which may be either hydrophilic or hydrophobic. The surfaces of lenses mnst be wetted before nse, and wetting solntions (section 4.5.1) are nsed for this pnrpose. Hard and, more especially, soft lenses become heavily contantinated with protein material dnring nse and must therefore be cleaned (section 4.5.2) before disinfection (section 4.5.3). Contact lenses are potential sonrees of eye infection and conseqnentiy nticroorganisms should be removed before the lens is again inserted into the eye. Lenses mnst also be clean and easily wettable by the lacrimal secretions. Contact-lens solntions are thns sterile solutions of the varions types described below. Apart fiom... 

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