Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing
Reexamination Certificate
2000-12-15
2004-10-19
Thornton, Krisanne (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
C422S005000, C422S028000, C422S029000, C422S040000, C523S106000, C523S107000
Reexamination Certificate
active
06805836
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to the surface treatment of medical devices including ophthalmic lenses, stents, implants and catheters. In particular, the present invention is directed to a simple, low cost method of modifying the surface of a medical device to decrease its capacity to sorb cationic antimicrobials.
BACKGROUND
Medical devices such as ophthalmic lenses can generally be subdivided into two major classes, namely hydrogels and non-hydrogels. Non-hydrogels do not absorb appreciable amounts of water, whereas hydrogels can absorb and retain water in an equilibrium state.
Hydrogels are widely used as soft contact lens materials. It is known that increasing the hydrophilicity of the contact lens surface improves the wettability of the contact lenses. This in turn is associated with improved wear comfort of contact lenses. Additionally, the surface of the lens can affect the overall susceptibility of the lens to deposition of proteins and lipids from the tear fluid during lens wear. Accumulated deposits can cause eye discomfort or even inflammation. In the case of extended wear lenses (i.e. lenses used without daily removal of the lens before sleep), the surface is especially important, since extended wear lenses must be designed for high standards of comfort and biocompatibility over an extended period of time.
Both daily-wear lenses and extended-wear lenses need to be periodically cleaned and disinfected. Formulating multipurpose solutions that not only clean and disinfect but are also ophthalmically compatible has proven to be a significant technical challenge. It has also been found that some contact lenses become less ophthalmically compatible with repeated cycles of wearing and cleaning. While the presence of lipid and protein deposits are important factors in predicting comfort, the presence or absence of these deposits alone fails to account for the observation that fresh contact lenses are typically more comfortable in the eye than lenses that have undergone one or more cleaning/disinfection cycles. Thus the cleaning and disinfection cycle appears to cause lenses to become progressively less comfortable, and the reduction in ocular comfort appears not to be attributable to imperfect cleaning.
In the area of contact lens wetting/conditioning solutions, it has been found that polyelectrolytes can bind to a lens surface of opposite charge and form polyelectrolyte complexes. Such polyelectrolyte complexes have commercially been demonstrated to give more comfortable lens materials because of the greater adsorption of surface bound water. Examples of materials useful for forming such polyelectrolyte complexes are taught in U.S. Pat. No. 4,321,261 to Ellis et al.; U.S. Pat. No. 4,436,730 to Ellis et al.; U.S. Pat. No. 5,401,327 to Ellis et al.; U.S. Pat. No. 5,405,878 to Ellis et al.; U.S. Pat. No. 5,500,144 to Potini et al.; U.S. Pat. No. 5,604,189 to Zhang et al; U.S. Pat. No. 5,711,823 to Ellis et al.; U.S. Pat. No. 5,773,396 to Zhang et al.; and U.S. Pat. No. 5,872,086 to Ellis et al.
The following references provide examples of typical contact lens care solutions. British Patent 1,432,345 discloses contact lens disinfecting compositions containing a polymeric biguanide and a mixed phosphate buffer.
U.S. Pat. No. 4,758,595 to Ogunbiyi et al. disclosed that a contact-lens solution containing a polyaminopropyl biguanide (PAPB) has enhanced efficacy when combined with a borate buffer. Such solutions are compatible with both non-soft and soft-type lenses, and are adaptable for use with virtually any of the commonly known disinfecting techniques, including “cold” soaking under ambient temperature conditions, as well as with high temperature disinfecting methods. These disinfecting and preservative solutions are especially noteworthy for their broad spectrum of bactericidal and fungicidal activity at low concentrations coupled with very low toxicity when used with soft-type contact lenses. Ogunbiyi et al. stated that biguanide polymers in the higher molecular weight ranges usually demonstrate lower toxicity levels than the lower molecular weight materials.
U.S. Pat. No. 5,453,435 to Raheja et al. discloses a preservative system that comprises a combination of chlorhexidine and the biguanide polymer polyhexamethylene biguanide. This preservative system, used in commercial products for rigid-gas-permeable lenses, was found to exhibit a combination of improved efficacy and relatively low eye irritation.
Compositions containing PAPB and borate, or other non-phosphate buffers, have been commercialized in various products, but at levels of about 1 ppm or less for use with soft contact lenses. It is generally desirable to provide the lowest level of a bactericide possible, while maintaining the desirable level of disinfection efficacy, in order to provide a generous margin for safety and comfort.
Some of the most popular products for disinfecting lenses are multipurpose solutions that can be used to clean, disinfect and wet contact lenses, followed by direct insertion (placement on the eye) without rinsing. The ability to use a single solution for contact-lens care is an advantage. Such a solution, however, must be particularly gentle to the eye because some of the solution will be on the lens when inserted and will come into contact with the eye.
Contact lens solutions that qualify as a “Chemical Disinfecting Solution”do not require rubbing to meet performance criteria set by the US Food and Drug Administration (FDA) under the Premarket Notification (510 k) Guidance Document For Contact Lens Care Produce, May 1, 1997, for destroying bacteria and fungi. However, they would generally require a more efficacious or stronger antimicrobial than a solution that requires rubbing. It is generally true that the stronger the bactericidal effect of a solution the more likely that it may exhibit toxic effects or adversely affect lens-wearer comfort. In fact, many very efficacious bactericides used in other contexts, such as mouthwashes, cosmetics, or shampoos, while being sufficiently safe for use in such products, are too toxic for ophthalmic use, especially for use with soft lenses because of the above-mentioned tendency of soft lenses to bind chemicals and the sensitivity of eye tissues. Similarly, the concentrations of certain bactericides may need to be within lower limits in solutions for use with soft contact lenses than in other products or in solutions for other types of lenses, especially when such solutions are not rinsed from the contact lens before placing the lens in the eye. Thus one way to decrease ocular irritation is to use a lower concentration of antimicrobial in solution, provided that the concomitant decrease in antimicrobial efficacy is acceptable. It would also be desirable to decrease ocular irritation without decreasing the concentration of antimicrobial in solution or its disinfecting efficacy.
Certain antibacterial agents have been found to be more compatible with contact lenses and exhibit less binding on lens surfaces. In one case, it was found that chlorhexidine, a biguanide, binds to soft lens material seven times less than benzalkonium chloride, but the presence of proteinaceous oily tear-film deposits on a lens can double the amount of chlorhexidine absorbed on the lens compared to a clean lens. U.S. Pat. No. 4,354,952 discloses very dilute disinfecting and cleaning solutions containing chlorhexidine or its salts in combination with certain amphoteric and non-ionic surfactants. These solutions were found to reduce the amount of binding of chlorhexidine on hydrophilic soft contact lenses.
Thus it would be desirable to inhibit the extent to which contact lenses, especially hydrogel contact lenses, progressively sorb antimicrobials during repeated cleaning/disinfection steps. Inhibiting sorption of antimicrobials by the contact lens during the cleaning/disinfection step would then decrease the amount of antimicrobial available to be desorbed from the contact lenses into the tear film when the lenses are returned to the wearer's
Ammon, Jr. Daniel M.
Hu Zhenze
Salamone Joseph C.
Bausch & Lomb Incorporated
Furr, Jr. Robert B.
Thomas John E.
Thornton Krisanne
Vacca Rita D.
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