Solution for preserving and sterilizing contact lenses

Details Solution for preserving and sterilizing contact lenses Solution for preserving and sterilizing contact lenses

1998-08-26

2001-02-13

Beisner, William H. (Department: 1744)

Chemical apparatus and process disinfecting, deodorizing, preser

Process disinfecting, preserving, deodorizing, or sterilizing

Using disinfecting or sterilizing substance

C514S839000, C514S840000

Reexamination Certificate

active

06187264

ABSTRACT:

TECHNICAL FIELD
This invention relates to a solution for preserving and/or disinfecting contact lenses.
BACKGROUND ART
Contact lenses are generally classified as hard contact lenses and water-containing soft contact lenses. Both types must be kept in their respective preserving solutions while they are not being worn, in order to preserve their delicate shape and performance. In particular, water-containing soft contact lenses should be stored in physiological saline to keep a constant water content thereby maintaining the characteristic softness that assures comfort in use.
Preserving solutions for contact lenses usually contain preservatives in concentrations of several parts per million to several percent, for the purpose of suppressing growth of bacteria and the like that enters through the opening of a container.
The preservatives must be harmless to the mucous membranes of the eyes and, at the same time, should not adversely affect the lenses. Benzalkonium chloride and chlorobutanol are effective antimicrobial agents currently and widely employed as such a preservative. They are used, of necessity, at concentrations safe to the eye mucosa. However, these preservatives are not suitable for certain water-containing soft contact lenses or hard contact lenses that have a high silicone content.
That is, in certain circumstances, the above-described preservatives penetrate into the inside of a lens and gradually concentrate in the inside. In the case of a water-containing soft contact lens, the inside concentration eventually reaches a level that might cause irritation to the eye mucosa. In the case of a high-silicone hard contact lens, the inside concentration is also problematical. Above all, the hydrophilic properties of the lens are reduced, which seriously impairs the comfort while the lens is being worn.
Water-containing soft contact lenses should be disinfected after use and before storage, to remove bacteria attached thereto while in use. Disinfection is usually effected by boiling. The microbicidal effect of hydrogen peroxide is also useful for disinfection.
However, in order to disinfect lenses by boiling, it is necessary for a user to procure a dedicated boiler and to secure a power source for operating the boiler, which is very inconvenient for a user especially when travelling.
This problem is avoided by using hydrogen peroxide instead of a boiler, but in this case a user must prepare two liquids, a preserving solution and a disinfectant, wherever he or she is (in places where such liquids are not available, a user must always bring the liquids with him or her). Further, disinfection with hydrogen peroxide should be followed by careful and certain neutralization of hydrogen peroxide remaining on the lenses.
Whichever disinfection technique is chosen, it has been an economical burden and an inconvenience for soft contact lens users to carry out storage and disinfection in separate systems.
In order to overcome these problems a solution for contact lenses with which disinfection and preservation (storage) can be effected simultaneously has recently been proposed, as an aqueous solution containing a polymer of a biguanide compound (see JP-A-61-85301 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)) and as an aqueous solution containing a polymer of poly(ammonium chloride) (see JP-W-A-83-501515 (the term “JP-W-A” as used herein means an “published Japanese national stage of international application”)).
However, biguanide compounds tend to decompose during long-term storage. Unless used up in a short time after the preparation, the solution will reduce its crystalloid, which raises the concern that not only the disinfecting ability but also the storage stability of the solution is reduced.
Further, poly(ammonium chloride) does not have sufficient heat resistance. Since water-containing soft contact lenses must be sterile when shipped from a manufacturing factory, containers containing lenses are usually sterilized by autoclaving at a temperature of 120° C. Poly(ammonium chloride) has a possibility of being decomposed by the high temperature. Eventually, two solutions, one for use in the sterilization and one for usual handling, should be prepared separately. Thus, a single solution is incapable of handling a contact lens from the shipment through the use.
An object of the present invention is to solve the above-described problems of conventional techniques and to provide a liquid for easy preservation and/or disinfection of a contact lens, which is applicable to any type of contact lenses and capable of preserving and disinfecting a contact lens, and which needs no special care after a disinfection.
DISCLOSURE OF THE INVENTION
The inventors have conducted extensive investigations in order to accomplish the above object. As a result, they have found that polylysine not only imparts storage stability to a solution for contact lenses containing the same, but also is effective in disinfecting contact lenses from bacteria that adheres thereto in use; on that basis, the present invention has been made.
The present invention relates to a solution for preserving a contact lens which is characterized by containing polylysine; a solution for disinfecting a contact lens which is characterized by containing polylysine; a solution for preserving and disinfecting a contact lens which is characterized by containing polylysine; and a method for preserving and/or disinfecting a contact lens which is characterized by using a solution containing polylysine.
THE BEST MODES FOR CARRYING OUT THE INVENTION
Polylysine is a polymer of L-lysine, usually composed of 20 to 50 lysine residues. It is obtainable through, for example, generally employed organic synthesis from L-lysine (see
Journal of the American Chemical Society,
Vol. 78, p. 764).
Polylysine can also be produced on an industrial scale by culturing a microorganism belonging to the genus Streptomyces according to applied biotechnology (see JP-B-59-20359, the term “JP-B” as used herein means an “examined Japanese patent publication”).
In addition, polylysine preparations are commercially available from Chisso Corp., which contain various adjuvants for potentiating polylysine.
Polylysine which can be used in the present invention includes &agr;-polylysine resulting from condensation between an &agr;-positioned amino group and a carboxyl group and &egr;-polylysine resulting from condensation between an &egr;-positioned amino group and a carboxyl group. The &egr;-polylysine is preferred.
The antimicrobial effect of polylysine is expressed in terms of minimum inhibitory concentration (MIC) against various bacteria. Polylysine inhibits the growth of bacteria, such as
Escherichia coli, Pseudomonas aeruginosa
, and
Staphylococcus aureaus,
at 100 ppm or lower, and the growth of black mold and yeasts at 300 ppm or lower.
Polylysine is approved as a food additive and in fact used as a preservative in many foods, such as fast food, deli food, convenience store food, etc. However, use of polylysine is currently confined to a food additive while its broad antimicrobial spectrum and safety to living bodies have been confirmed.
Because polylysine is, while solid per se, strongly deliquescent, it is usually used in the form of a very thick aqueous solution. Therefore, it dissolves in water in any concentration, and, for use as a solution for preservation and disinfection of contact lenses, the concentration of the solution can be adjusted arbitrarily.
The polylysine concentration of the solution used for preservation and/or disinfection of contact lenses preferably ranges from 1 ppm to 10%, while varying depending on the kind of microorganisms to be controlled. A more preferred concentration range is from 10 ppm up to 1%.
A particularly preferred concentration for lens preservation is from 10 to 1000 ppm, and for disinfection from 100 ppm to 1%.
In concentrations lower than 1 ppm, the antimicrobial effect is insufficient against some microorganisms. If the concentration exceeds 10%, no improvement-in

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