CONTACT LENS CLEANING AND DISINFECTION

Abstract: A method of treating a contact lens by means of hydrogen peroxide, which method comprises conducting the hydrogen peroxide treatment of the lens in the presence of an immobilized enzyme which catalyses the decomposition of hydrogen peroxide. The invention also provides apparatus and a kit for treating contact lens. Preferably the enzyme is catalase, which may be immobilized by adsorption, by absorption, by covalent binding or by antibody complexing.

Description: CONTACT LENS CLEANING AND DISINFECTION This invention relates to a method and apparatus for cleaning and disinfecting contact lenses and, in particular, to a method and apparatus for neutralizing the potentially toxic residues left after the cleaning and disinfection of contact lenses. Hydrogen peroxide is widely used to clean and disinfect contact lenses, normally generated in situ from effervescing tablets containing sodium percarbonate and citric acid. Hydrogen peroxide is effective for this purpose but any excess hydrogen peroxide can cause ocular irritation when the contact lens is re-inserted into the eye. To remove such excess hydrogen peroxide, repeated washings and rinsings of the lens are necessary but this is unacceptable in the case of soft contact lenses since undesirable leaching of isotonic solutions from the lenses can occur. An alternative procedure has been suggested is to neutralize the hydrogen peroxide by chemical means e.g. by treating the solution with slowly released sodium nitrite or sodium sulphite. Such a method however has the disadvantage of leaving the neutralizing chemicals in the lens-treating solution which may themselves cause ocular irritation. European Published Patent Application No 0082798A discloses a regime for the treatment of contact lenses SHEET by disinfecting and cleaning them with a hydrogen peroxide solution and then treating with catalase, firstly by adding catalose to the hydrogen peroxide solution, secondly by pouring off the hydrogen peroxide solution and adding a catalose solution or by transferring the lenses to another vessel containing a catalose solution. The methods disclosed in that European published Patent Application possess the severe disadvantage that the use of catalase as a solution requires the solution to be preserved; this means that extraneous preservative is in contact with the lenses and may therefore require its own removal regime before the lenses may be safely inserted into the eyes of a wearer. According to a first aspect of the present invention there is provided a method of treating a cont.ract lens by means of hydrogen peroxide, which method comprises conducting the hydrogen peroxide treatment of the lens in the presence of an immobilized enzyme which catalyses the decomposition of hydrogen peroxide. According to a second aspect of the present invention there is provided a method of decomposing hydrogen peroxide used for treating a contact lens which method comprises contacting the hydrogen peroxide with an immobilized enzyme which catalyzes the decomposition of hydrogen peroxide. According to a further aspect of the present invention there is provided apparatus for treating contact lenses with hydrogen peroxide which apparatus includes an effective amount of an immobilized enzyme capable of catalyzing the decomposition of hydrogen peroxide. The apparatus may comprise a container bearing a suitable quantity of a said immobilized enzyme, The enzyme capable of causing the decomposition of hydrogen peroxide, generally known as a peroxidase. is preferably catalase although any other suitable enzyme may be employed for the purpose. Immobilization of the enzyme may be by any of the techniques appropriate for this purpose. Such techniques include binding of the enzyme to a support material e.g. by adsorption, by absorption or by chemical (e.g. covalent) binding. Examples of surfaces upon which the enzyme may be adsorbed include alumina. bentonite. calcium phosphate gels, carbon, plastics, carboxymethyl cellulose, carboxymethylsephadex. collogen. glass and silica gel. The adsorbent surfaces may be continuous e.g. a coating upon the inside of a container or the actual material of which a said container is composed. The adsorbent surface may constitute the surface of a plurality of fixed beads or of a fixed disc or discs or the interstices of a fixed sponge or fritt. Examples of materials to which the enzyme may be covalently bound include supports with -OH. (e.g. celluloses) supports with -NH_ (e.g. epoxy resins), supports with CO H (e.g. methacrolates) and supports containing anhydrides. A preferred surface upon which to immobilize the enzyme has been found to be the surface of a plastics material such as polystynene, activated e.g. by gamma irradiation u.v. light or by corona discharge. Simple coating of the activated plastics surface with enyzme may suffice for the purposes of the present invention. As in the case of adsorbent surfaces, the supports may be a coating upon the surface of a container or the material of which a container is composed, etc. Very preferably however the enzyme is immobilized by use of an antibody. By this we mean that the enzyme is complexed with an antibody which regards the enzyme as an antigen and the complex is coated by means of the complexed antibody onto a suitable support surface. Preferably the support surface used in this and in the foregoing embodiments is the inner surface of a plastics container the surface of which may have been pretreated by u.v. light, corona discharge, irradiation, etc. to improve the coating ability of the enzyme or complexed enzyme. A suitable antibody may be obtained e.g. by injecting enzyme into a mouse and collecting resultant antibodies generated by the mouse immune-response system. The antibodies may be arranged by appropriate biotechnological techniques to be monoclonal in nature, e.g. by use of suitable hybridomas. By way of example only, embodiments of the present invention will now be described. EXAMPLE 1 Catalase is injected into suitable selected mice and antibodies to the catalase collected from the mice, concentrated and purified. The catalase and .the antibody are then contacted together in vitro to prepare a catalase-antibody complex. Thos complex is then coated onto the inner walls and base of a plastics contact lens container. The container so-coated may then be dried and stored in a sterile environment until required. Alternatively the coated container may be filled with a sterilized aqueous phase e.g. buffered saline solution and stored until required. The container preferably has means e.g. a screw threaded upper portion for receiving a lid provided with means for holding a contact lens. To prepare the solution of hydrogen peroxide for treating a said contact lens, an aqueous phase e.g. isoi.onic buffered saline is placed in the container and an effervescent tablet containing sodium percarbonate and citric acid added to the aqueous phase. The aqueous phase may be such that the resultant solution contains hydrogen peroxide at a 0.1 Molar concentration and is substantially isotonic. The hydrogen peroxide is present in solution in sufficient quantity (e.g. 0.1 Molar) to clean and disinfect the contact lens within a period of from a few minutes to a few hours. The complexed enzyme is present in a sufficient amount to cause decomposi ion of the hydrogen peroxide within a period of from say 1/2 hour to 8 hours. By this means substantially all excess hydrogen peroxide will be decomposed and substantially none of the enzyme will enter the aqueous phase and thus problems of ocular irritation or hypersensitization will be substantially avoided. EXAMPLE 2 A 10 ml polystyrene container or vial is irradiated with 2.5 Megarads of gamma irradiation to activate its surface. Into the containers is placed a solution of catalase powder in water at a concentration of 0.5 mg/ml (catalase activity: 24.000 units per milligram where 1 unit decays 1 icromole of hydrogen peroxide per minute at 25 C) and the filled container is then inculated at room temperature for 24 hours. Thereafter the vial is emptied, rinsed gently with distilled water and allowed to dry at room temperature. The dried, coated vial may then be stored for extended periods without significant loss of activity. For example it has been found that such vials remain effective even after storage at 45oC for 3 months. To such a dried, enzyme-coated vial there is added an aqueous hydrogen peroxide solution containing from 0.6 to 3% by volume of hydrogen peroxide. An modeuator, phenolphthalin, is also added to indicate the progess of hydrogen peroxide decomposition. It is found that after 1/2 hour no detectable hydrogen peroxide remains. The present invention provides a method and apparatus of treating a contact lens which mitigates the disadvantages of known contact lens treatment regimes. The present invention also consist... in a kit for treating contact lenses, which may include an enzyme-coated container as hereinbefore defined, a hydrogen peroxide release agent and a suitable aqueous phase. The coated containers may be arranged to be disposable single use items and more for example be supplied in sealed blister- or bubble-packs for removal and use as desired. The hydrogen peroxide release agent may be for example a tablet or capsule containing sodium prosphate and citric acid, which tablet or capsule may also contain an indinator, sufficient sodium chloride to render the residual solution isotonic and may also contain, if desired, an agent for removing free chlorine from the solution. In a preferred enbodiment of the apparatus of the present invention a strip of commuted plastics vials is provided, each vial being separable from the remainder and each coated internally with the enzyme. The vials may be disposed of after each has been used once. The vials may be accompanied by predetermined quantities of the hydrogen peroxide release agent, e.g. in the form of pellets, prills or granules. It will be apparent that although what has been described above is the use of an immobilized enzyme capable of causing the decomposition of hydrogen peroxide, the invention is not limited to the use solely of such an immobilized enzyme. The invention covers the use generally of immobilized enzymes to treat contact lenses. For example proteolytic emzymes are currently used to remove protein deposits from contact lenses but are used as solutions. The present invention embraces the case where such a proteolytic enzyme is, for example, coated onto the wall of a contact 3ens treatment container. Such immobilization will substantially eliminate the well-known problem of ocular hypersensitization due to the use of free proteolytic enzyme. The invention also covers all such changes and modifications to the method, apparatus and kit as would be apparent to one killed in the art.

Claims: CLAIMS 1. A method of treating a contact lens by means of hydrogen peroxide, which method comprises conducting the hydrogen peroxide treatment of the lens in the presence of an immobilized enzyme which catalyses the decomposition of hydrogen peroxide. 2. A method of decomposing hydrogen peroxide used for treating a contact lens which method comprises contacting the hydrogen peroxide with an immobilized enzyme which catalyzes the decomposition of hydrogen peroxide. 3. A method according to claim 1 or 2, wherein the enzyme is catalase. 4. A method according to claim 1, 2 or 3. wherein the enzyme is adsorbed onto a surface. 5. A method according to claim 4. wherein the surface is that of a container. 6. A method according to claim 4 or 5, wherein the surface is of a plastics material. 7. A method according to claim 6. wherein the plastics material has been activated by irradiation by corona discharge, or by u.v. light. 8. A method according to any of claims 1 to 3, wherein the enzyme is covalently bound to a surface. 9. A method according to any of claims 1 to 3. wherein the enzyme is in the form of a complex with an antibody coated on a surface. 10. A method according to claim 9 wherein the antibody is mouse anti-catalase antibody. 11. Apparatus for treating contact lenses with hydrogen peroxide which apparatus includes an effective amount of an immobilized enzyme capable of catalyzing the decomposition of hydrogen peroxide. 12. Apparatus according to claim 11 and in the form of a container upon the internal surface of which the enzyme has been immobilized. 13. Apparatus according to claim 13 wherein the container is composed of irradiated polystyrene. 14. Apparatus according to claim 12 and in the form of a bead. disc, sponge or fritt. 15. A kit for treating a contact lens which comprises apparatus as claimed in any of claims 12 to 14. together with a hydrogen peroxide release agent. 16. A kit according to claim 15 wherein the apparatus comprises a plurality of disposable vials each containing a quantity of said immobilized enzyme. 17. A kit according to claim 15 or 16. wherein said hydrogen peroxide release agent is present as granuales or in tablet or capsule form. 18. A kit according to claim 15 or 16 wherein said hydrogen peroxide release agent further includes at least one of sodium chloride in an amount sufficient to render residual solution isotonic. an indicator for indicating the presence or absence of hydrogen peroxide, and an agent capable of removing free chlorine from aqeoυs solution.

Inventors: KAY JOSEPH BRIAN, KAY, JOSEPH, BRIAN
Applicants: KELLWAY PHARMA, KELLWAY PHARMACEUTICALS LIMITED
Application year: 1986
Main classification: A61L2
IPC codes: A61L12, C11D3