Contact lens care products

The final consideration, but by no means a minor one, is the design and evaluation of contact lens care products, which are regulated by the U.S. Food and Drug Administration (FDA) as medical devices since... 

Ocular sensitization to thimerosal has been well documented over the years [126-132]. Although thimerosal had at one time been referred to as the preservative of choice for soft contact lens care products [133-135], its use has been supplanted almost completely by the polyquaternium-1 and polybiguanide preservatives. 

Contact lens care products can be divided into three categories cleaners, disinfectants, and lubricants. Improperly cleaned lenses can cause discomfort, irritation, decrease in visual acuity, and giant papillary conjunctivitis (GPC). This latter condition often requires discontinuation of lens wear, at least until the symptoms clear. Deposits can also accumulate preservatives from lens care products and produce toxicity and can act as a matrix for microorganism attachment to the lens [317]. Thus, cleaning with the removal of surface debris, tear components, and contaminating microorganisms is one of the most important steps contributing to the safety and efficacy of successful lens wear [318]. 

Guidance for Industry Premarket Notification (510(k)) Guidance Document for Contact Lens Care Products. Center for Devices and Radiologic Health, FDA, Rockville, MD, 1997. 

Conjunctivitis caused by toxic agents can occur as either a primary or a secondary finding. Toxicity most commonly results from exposure to medications, contact lens care products, or cosmetics. However, any agent can cause a toxic response. Toxic conjunctivitis may have a wide variety of presentations. When superimposed over infection or allergic reaction, toxicity to a medication may complicate the diagnosis. 

The use of buffers and pH adjustment is an important consideration in lens care products. It is a general practice that all products which are likely to come in direct contact with ocular tissues should be buffered for ocular comfort around physiologic pH and preferably in the range 6-8.0. The most commonly used buffers in contact lens care products are phosphates and borates. Buffers used occasionally are acetate, citrate, and others. Besides buffers, sodium hydroxide and hydrochloric acid are generally used to achieve a desirable pH in the final product. They are also used to adjust the final pH in products, which do not have any buffering system. The selection of an appropriate buffering system should consider the pH necessary for optimal performance of the product, as well as products... 

As mentioned previously (and discussed in detail in section Contact Lens Care Products ), contact lens products have specific guidelines that focus on compatibUity with... 

Ophthalmic optics—Contact lenses and contact lens care products— Determination of biocompatibility by ocular study with rabbit eyes. ISO 9394 1998(E), 1998. 

ANTIMICROBIAL POLYMER, CONTACT LENS, AND CONTACT LENS CARE PRODUCTS... 

Contact lenses are made of polymeric materials designed and fabricated to correct vision. Because these lenses are removed from the eye after a prescribed wear time, lens care products are required to clean, disinfect and rinse them prior to reinsertion to avoid ocular infections and other complications. Lens care products are also required to enhance the comfort of lens wear. 

Marketed lens care products fall mainly into the following categories cleaners, disinfectants, lubricants, and multipurpose products. Cleaners are subdivided into daily or weekly cleaners. Disinfectants comprise solutions containing chemical antimicrobial agents, which do not require heating the lenses, and preserved or unpreserved saline solutions, which are used with an electrical thermal device for lens disinfection. These products are also used to rinse contact lenses. Lens lubricants are intended to enhance the comfort of lens wear and are used prior to insertion and during wear. Multipurpose solutions are intended to accomplish... 

Gossel, T.A Wuest, J.R. Contact lenses and lens care products. In Handbook of Non-prescription Drugs, 9th Ed. Feldmann, E.G., Ed American Pharmaceutical Association Washington, 1990 601-631. 

The polymer is prepared by homo- or copolymerising a vinyl phosphonium salt monomer, such as 2-methacryloxyethyltri-n-octylphosphonium chloride and has a wide antimierobial spectram and a sufficient antimicrobial effect, even with a short contact time. The lens and lens care products exhibit excellent optical properties and processabihty. 

This preservative is comparatively new to ophthalmic preparations and is a polymeric quaternary ammonium germicide. Its advantage over other quaternary ammonium seems to be its inability to penetrate ocular tissues, especially the cornea. It has been used at concentrations of 0.001-0.01% in contact lens solutions as well as dry eye products. At clinically effective levels of preservative, POLYQUAD is approximately 10 times less toxic than benzalkonium chloride [87,137], Various in vitro tests and in vivo evaluations substantiate the safety of this compound [137,141,142], This preservative has been extremely useful for soft contact lens solutions because it has the least propensity to adsorb onto or absorb into these lenses, and it has a practically nonexistent potential for sensitization. Its ad-sorption/absorption with high water and high ionic lenses can be resolved by carefully balancing formulation components [143],... 

C. Complications of Contact Lens Wear and the Need for Care Products... 

In the daily care of contact lenses, wearers are instructed to clean their hands with soap and to dry hands their hands with lint-free towels prior to handling their lenses. Selection of the specific soap product is important. In addition, to cleaning the hands thoroughly, it should be rinsing and should not cause ocular irritation even if residual amounts are transferred to the lens. With these considerations in mind, some hand soaps have, therefore, been designed specifically for contact lens users. 

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