GB2094992A

GB2094992A - Method and apparatus for sterilizing an object such as a contact lens

Info

Publication number: GB2094992A
Application number: GB8114801A
Authority: GB
Original assignee: Tomei Sangyo KK
Current assignee: Tomei Sangyo KK
Priority date: 1981-03-18
Filing date: 1981-05-14
Publication date: 1982-09-22
Also published as: FR2502011A1; CA1156420A; JPS57153653A; DE3131314A1; JPH0154060B2

Abstract

A method and apparatus for sterilizing an object such as contact lenses, scalpels, tweezers, injectors, artificial teeth and catheters, wherein the object is immersed in an aqueous solution of an alkali metal chloride, preferably sodium chloride, and a current is applied to the solution through two electrodes thereby to produce a hypochlorite for sterilizing the object.

Description

SPECIFICATION Method and apparatus for sterilizing an object such as a contact lens 1. Field of the Invention This invention relates to a method and apparatus for sterilizing such objects as contact lenses, artificial teeth, and scalpels and tweezers for medical use.

2. Description of the Prior Art The conventional hydrated contact lens principally comprising hydrophilic monomer such as 2hydroxyethyl methacrylate includes normally about more than 30% by weight of water. As a result, the hydrated contact lens itself is likely to constitute a favorable circumstance for various detrimental bacteria to be multiplied. Furthermore, it is very dangerous to wear the bacteria-infected contact lens on the eyes without treating in any way, since this practice may lead to a serious damage to the eye tissue, For this reason, therefore, it is essential for such a hydrated contact lens to be sterilized at every given period of time.

For example, the prior art, in sterilizing the hydrated contact lens, has employed a method of boiling the lens for a predetermined time which is extremely effective for sterilizing the lens but at the same time possesses not a few fatal disadvantages, as hereinafter described.

(1) The protein and other components in tear deposited on the lens undergo a thermal metamorphism through boiling operation and stick to the lens surface, thereby impairing the optical properties of the lens and remarkably reducing the wearing coziness on the eye.

(2) The sparingly cross-linked hydrophilic polymer, which is the material of hydrated contact lenses, is likely to be deteriorated through the repeated severe treatments of boiling. Thus, the lens is subject to discoloration and/or change in standard configuration, thereby resulting~in reduced useful life of the lens.

(3) The boiling disinfector is inconvenient to carry with in trip because of the related boiling heater requiring an alternating current, and especially, it cannot be used outdoors as in a camping site where no alternating current is available.

(4) No boiling sterilization may be applied for non-hydrated contact lenses which comprise polymethyl methacrylate and/or silicone rubber.

In order to alieviate the drawbacks associated with the boiling sterilization, the prior art has also employed a method of sterilization for the contact lenses wherein the lenses are sterilized by disinfectant fluids containing thimerosal or chlorohexadiene for example. In such a treatment, the sterilizing component will be readily be adsorbed into the lens body because of the large structural distance between molecules constituting the hydrated contact lenses. The adsorbed sterilizing component has the potential hazard of causing hypersensitive inflammation to the eye tissue.

The prior art has also proposed a method of detoxication whereby the lens is sterilized with 3% aqueous solution of hydrogen peroxide and the solution is catalized by platinum or the like to decompose the hydrogen peroxide into water and oxygen. This method has also disadvantages that it requires a considerably longer time in sterilization and is impractical because of its complicated operation.

Summary of the Invention An object of the present invention is to provide a method and apparatus for sterilizing contact lenses which renders no adverse influence to the material, standard and shape of the lenses.

Another object of the present invention is to provide a method and apparatus for sterilizing contact lenses, wherein the sterilizing operation may be accomplished extremely in a short time and yet extremely simply with the lenses held in protective containers.

A still further object of the present invention is to provide a method and apparatus for sterilizing contact lenses which is compact, lightweight, and easy to use; and yet may be used outdoors where no external power source is available.

A still further object of the present invention is to provide a method and apparatus wherein the sterilizing operation for contact lenses is accomplished while producing the disinfectant component, sodium hypochlorite through electrolyzation of the physiological salt solution which is a preserving liquid for the lenses, to thereby eliminate the need for an extra source of disinfectant liquid and allow for remarkable economy to users.

A still further object of the present invention is to provide a method and apparatus for sterilizing contact lenses wherein the lenses are free from harmful component because of spontaneous or operational dissolution of the sodium hypochlorite into sodium chloride and oxygen which are safe to the eye tissue.

A still further object of the present invention is to provide a method and apparatus for sterilizing contact lenses wherein the sodium hypochlorite is also effective to remove protein in tear which is deposited on the lens surface.

A still further object of the present invention is to provide a method and apparatus which may be adapted for sterilizing not only hydrated contact lenses but also such lenses as non-hydrated contact lenses containing polymethyl methacrylate, silicone rubber, etc., and artificial lenses to be grafted after cataract operation; and medical instruments such as scalpels, tweezers, injectors, artificial teeth and catheters.

Brief Description of the Drawings Figure 1 is a front elevational view of a direct current supplying apparatus according to one embodiment of the preF- nt invention; Figure 2 is a plan view thereof; Figure 3 is a plan view of the apparatus shown in Figure 1 with a cover removed; Figure 4 is a sectional front elevational view of a container for carrying a contact lens; Figure 5 is a plan view of the container; Figure 6 is a plan view of a tray for the contact lens; Figure 7 is a schematic diagram of the electrical circuit of the apparatus; and Figure 8 is a schematic view illustrating the operation thereof.

Detailed Description of the Preferred Embodiments The hydrated contact lenses are immersed and preserved in a 0.9% physiological salt solution which is isotonic with the tear fluid so as to confer affinity to the eye tissue when the lens is worn on the eye.

The present invention has positively utilized the above-mentioned fact, and has found and invented that, with the contact lens placed in the protective container filled with physiological salt solution, the lens may be sterilized through electrolyzation of the physiological salt solution in the container to produce an available quantity of sodium hypochlorite.

More particularly, the contact lens is immersed in a protective container filled with physiological salt solution, and an electric current is applied to the solution through an electrode disposed in the container. Because of the current thus applied, it is viewed that the chloric ions in the solution become chloric molecules through anodic oxidation, and the chloric molecules react with the sodium hydroxide formed in the solution through bonding of sodium ions and hydroxide ions, to thereby produce sodium hypochlorite.

This series of reactions is expressed by the following formula: Na+CI- + H20 < Na+OH- + T H2t + 2 C12t Cm2 + 2NaOh < NaClO + NaCI + H20 The sodium hypochlorite thus produced is effective for most of microorganisms such as virus, ordinary aposporic bacteria, acid-fast bacteria, bacterial spores, Hyphomycetes, Algae and Protozoa, and it accomplishes the sterilizing action in an extremely short time, about 30 to 1 80 seconds in a low concentration as of about 0.5 to 5.0 ppm.Furthermore, the sodium hypochlorite is feeble in its toxicity to the eye tissue although it has strong sterilizing characteristics, and from this point of view, it is an extremely ideal sterilizing agent for contact lenses.

The concentration of the sodium hypochlorite to be used for contact lenses preferably ranges from about 0.4 to 4.0 ppm. So long as the concentration of the sodium hypochlorite is in the above-specified range, a sufficient sterilizing effect may be expected, and after standing at the room temperature for about six hours, the sodium hypochlorite is spontaneously dissolved into sodium chloride and oxygen to be thereby brought into a concentration substantially innoxious to the eye. In consideration of the fact that contact lenses are sterilized generally before the user goes to bed and are left to the room temperature as they are in the container until the user put them on to his eyes next morning, it is reasonable and safe to the eye tissue to settle the concentration of sodium hypochlorite within the range above-mentioned.

it is also possible to decompose or reduce the sodium hypochlorite to an innoxious state in extremely short time by catalyzing the sterilized physiological salt solution with platinum etc., or by adding reducing agent. For this particular case, a higher concentration of sodium hypochlorite than specified above may be employed.

Such reducing agents include, for example, alkali or alkaline earth metal salts of thiosulfuric acid such as sodium thiosulfate, potassium thiosulfate and calcium thiosulfate; saccharides such as dglucose, I-glucose, lactose, d-fructose, d-xylose and d-arabinose; cysteins such as cystein and methionine; organic or inorganic peroxides such as sodium peroxide, barium peroxide, benzoyl peroxide, peracetic acid and peroxy propionic acid; acid or its alkali or alkaline earth metal salts such as sorbic acid, potassium sorbate, citric acid and sodium citrate; good buffers such as 3-(N-morpholino) propane sulfonic acid, N,N-bis (2-hydroxyethyl)-2-aminoethane sulfonic acid; sodium sulfite, sodium hydrogensulfite, ascorbic acid, isoascorbic acid, glutathione, and disodium ethylenediamine tetraacetate.

These reducing agents may be added to the sterilized physiological salt solution as discussed hereinbefore, but may be added likewise to the physiological salt solution prior to sterilization, depending on the type of reducing agents to be used. More particularly, in case of the reducing agents such as saccharides, cysteins, acid or its alkali or alkaline earth metal salts and good buffers, the action of sodium hypochlorite (sterilizing component) is generally more inactive to reducing agents than to microorganism, and therefore, the sterilized solution may be reduced without impairing the sterilizing action of sodium hypochlorite.

It should be noted that the decrease in salt concentration of the physiological salt solution caused by the production of available sodium hypochlorite is extremely small, that is, on the order of about 0.00001%, and thus no influence may be experienced to the function as a preserving fluid for contact lenses.

It is also to be noted that, throughout the description of this patent application, the use of the term "physiological salt solution" refers to an aqueous solution of sodium chloride which is isotonic with tear fluid and is physiologically innoxious, and it should be understood in a broader sense which is capable of including buffers and other components. Additionally, the term "salt solution" should be interpreted as an aqueous solution of not only sodium chloride but also potassium chloride, lithium chloride, etc. which may produce a sterilizing sodium hypochlorite through electrolyzation. The sterilizing action of potassium hypochlorite and lithium hypochlorite is well known, as with the sodium hypochlorite.

Turning now more specifically to the drawings which disclose an arrangement of one embodiment according to the present invention.

In the drawings, there is shown a pair of contact lens protective container 2 integrally formed with a connection portion 1 interposed therebetween, which are made of plastics such as polyethylene, polypropylene, polycarbonate and polysulfone, or of glass, which have a capacity of about 1 to 8 ml. The container 2 includes a cap 3 also made of plastics, the same material as mentioned above, and removably sealingly attached to the container 2 through a groove 4 formed on the outer periphery thereof and a protrusion 5 formed on the inner periphery of the cap 3. The containers 2 are filled with 0.9% physiological salt solution 6 for preserving a contact lens 7 which in turn is immersed therein on a lens tray 11 which is also made of the same plastics as mentioned above.The curved surface of the tray 11 on which the lens 7 is placed has a larger curvature than that of the lens 7 and has a plurality of apertures 8 and 9 to permit fluidity of the solution 6 between inside 10 and outside of the tray 11.

Additionally, on the bottom of each container 2, there is embedded an electrode 1 3 with the top surface thereof exposed to the inside of the container 2 and with the bottom surface thereof brazed to a brass, conductive plate 12 attached to the bottom surface of the container 2.

The material of the electrode 13 should be preferably platinum or gold, etc. which has a high ionization tendency in view of the fact that the anode is subject to a strong oxidization through the electrolyzation of the physiological salt solution, but it may be replaced by a metal such as copper and nickel or by plastics plated or vacuum-deposited with gold or platinum, etc. Additionally, the electrode 13 may be formed integrally with the conductive plate 12, and gold or platinum, etc. may be vacuumdeposited to the container 2 and the connecting portion 1 so as to serve as the electrode 13 and the conductive plate 1 2.

Reference numeral 14 represents the whole container unit for carrying the contact lenses arranged as mentioned above and adapted for connection with a direct current supplying unit 1 5 for delivering a current for electrolyzing the physiological salt solution 6 in the container 2 through the electrode 13. The direct current supplying unit 1 5 includes a case 1 6 which in turn has a plastic body 17 and a plastic cover 19 secured thereto with screws 18.On the upper surface of the cover 19, there are provided a sliding power switch 22 effective for turning on or off a battery 21 which is replaceably stored in the case 1 6 through a socket 20; a push-button type starter switch 23 to be used when the sterilizing operation for the contact lens 7 is initiated: a LED (Light Emission Diode) 24 adapted to light for confirmation of the on condition when the power switch 22 is turned on; and a LED 25 adapted to light by depressing the switch 23 for indication of the sterilizing operation being performed during the electrolyzation of the solution 6 in the container 2.

Furthermore, on the side face of the case 1 6 of the direct current supplying unit 1 5, there is formed an inlet 26 having a pair of guide grooves 27 provided on the right and left sides thereof for insertion of the portable container unit 14, which in turn has a pair of projecting edges 28 formed on the right and left sides of the container connecting portion 1. With the edges 28 engaged into the grooves 27, the container unit 14 is inserted into the case 16 from the inlet 26. Upon insertion of the unit 14, the conductive plate 1 2 exposed at the bottom of the unit 14 abuts under pressure with a phosphor bronze, elastic plate 30 secured to the case bottom by screws 29, and at the same time, the electrode 13 of the unit 14 is connected to a control device 31 secured inside the case 1 6 through the conductive plate 12 and the elastic plate 30.

Referring now to Figure 7 which illustrates an electrical circuit of the embodiment according to the present invention, a timer circuit 32 for a monostable multivibrator is connected to the battery 21 through the power switch 22. In the circuit, the monostable multivibrator is activated upon energization of the starter switch 23 to generate a trigger signal, and is adapted to energize each of transistors Tr1 and Tr2 by inverting the output from low to high for a given time determined by the resistance value of the variable resistance VR1. A constant-current circuit 33 is also connected to the battery 21, through the transistor Tr2 and the power switch 22. The constant-current circuit 33 comprises an operational amplifier Al, a zener diode ZD1, a transistorTr3, a resistance R1 and a variable resistance VR2.The circuit 33 is then connected to the one of electrodes 1 3 of each container 2 through the transistor Tr3 and the variable resistance VR2. Furthermore, the constant-current circuit 33 is connected to a lowerlimit-current setting circuit 34 which is effective for deenergization of the LED 25 by inverting the output of the operational amplifier A2 from low to high, when the voltage drop due to the current passing between the afore-mentioned one electrode 13 and another electrode 1 3 connected to the transistor Tr2 reaches below the specified voltage determined by the variable resistance VR3.

Additionally, it should be noted that the circuits 32, 33 and 34 are suitably connected to resistances R2 through R9 and condensers C1 and C2 to form a circuit configuration.

The operation and basic arrangement of the embodiment will now be described.

in Figure 8, a contact lens 7 is immersed in the physiological salt solution 6 in the protective container 2, and an electrical current is applied to the solution 6 from the battery 21 through the electrodes 13, variable resistance VR and power switch 22 so as to electrolyze the solution 6. The potential of the current is determined by the resistance value of the variable resistance VR, as already discussed above, and upon electrolyzation of the solution, a sodium hypochlorite substantially proportional to the potential is produced in the solution 6 to thereby effect sterilization of the contact lens 7. The current is then interrupted through the power switch 22 to thereby allow the sodium hypochlorite to be spontaneously dissolved into sodium chloride and oxygen which are entirely innoxious to the eye tissue.

More particularly, in order to accomplish a positive and effective sterilizing operation for the contact lens 7 by obtaining substantially constant production of the sodium hypochlorite during the operation, and to reduce the spontaneous dissolution time after completion of the sterilization operation, the circuits are arranged as follows: (1) The output of the timer is set at 30 seconds for example, through the variable resistance VR1:: (2) The ampere passing through the electrode 1 3 of each container 2 is set at 1.3 mA for example (2.6 mA for both electrodes), through the variable resistance VR2 of the constant-current circuit 33; (3) The lower-limit ampere is set at 2.0 mA for example, through the variable resistance VR3 of the lower-limit current setting circuit 34 adapted for obtaining a lower-limit ampere at which the output current from the constant-current circuit 33 is sufficient enough to produce the sodium hypochlorite required for the effective sterilizing operation when the potential is lowered due to the drain of the battery 21; and (4) the operational amplifier A2 is set so as to invert its output from low to high when the output current from the constant-current circuit 33 falls below 2.0 mA of the lower limit.

With this arrangement and under the normal condition where the battery is not drained, the contact lens tray 11 is placed in both protective containers 2, and a specified amount of 0.9% physiological salt solution 6 is poured into the containers 2. A pair of hydrated contact lenses 7 removed from the user's eyes are rinsed in the solution 6 and then immersed in the solution 6 while it is on the tray 11 in the container 2. The containers 2 are tight-closed with the caps 3 and the portable lens-container unit 14 is inserted into the case 1 6 of the direct-current supplying unit 1 5 from the inlet 26 thereof through the abutting engagement of the projecting edges 28 of the container unit 1 5 and the guide grooves 27 of the case 1 6.Upon insertion of the container 14, the conductive plate 12 of the container 14 abuts under pressure with the elastic plate 30 so as to allow the electrodes 13 of the containers 2 to be connected to the output terminal of the constant-current circuit 33. It is to be noted that under the condition the sterilizing operation for the contact lens 7 may be now initiated.

Accordingly, when the power switch 22 is turned on with the above setting completed, the LED 24 will illuminate because of the low output prior to the activation of timer 32, so as to confirm that the power is on. The starter switch 23 is then depressed, and the output is inverted from low to high to thereby energize each of the transistors Trl and Tr2. With this continuity, a given current in this instance, 1.3 mA, is passed between the electrodes 1 3 which is determined by the zener voltage of the zenerdiode ZD1 and the resistance value of the variable resistance VR2.Because of this large voltage drop caused by the current applied between the electrodes 1 3, The input voltage of the operational amplifier A2 is higher at the inverted side, and the output thereof is low so as to cause the LED 25 to light and confirm that an effective sterilizing operation is being performed. After pre-set 30 seconds, the output of timer 32 will be inverted from high to low to thereby deactivate each of the transistors Trl and Tr2. The output of the constant-current circuit 33 through the transistor Tr3 is turned off and the current passing between electrodes 1 3 is then cut off so as to complete the sterilizing operation for the contact lens 7. The LED 25 will go out to confirm the completion of the sterilizing operation, and the power switch is turned off to complete the whole sterilizing cycle. The lens container unit 1 4 is then allowed to stand for at least 30 minutes, and the sodium hypochlorite of the physiological salt solution 6 in the container 2 will be decomposed into sodium chloride and oxygen which are innoxious to the eye tissue.

Thus, the lenses 7 sterilized in the container 2 are ready for immediate safe use.

Alternatively, under the abnormal condition where the battery is drained, the portable lenscontainer unit 14 is inserted into the case of the direct-current supplying unit 15, and the power switch 22 and the starter switch 23 are turned on. At this time, if the output current of the constant-current circuit 33 falls below 2.0 mA which may not assure an effective sterilizing action, the input voltage of the operational amplifier A2 is higher at non-inverted side because of less voltage drop between the electrodes 13 and, because of the high output from the operational amplifier A2, the LED 25 will not illuminate, thereby enabling the operator to confirm that the sterilizing operation for the contact lenses 7 are being conducted effectively.

The present invention will be now further illustrated by the following non-limitative examples: EXAMPLE I In the contact lens protective container 2 (see Figure 8) having a pair of platinum electrodes 1 3 of 0.04 cm2 surface area, there was filled 2.2 ml. of 0.9% physiological salt solution. A hydrated contact lens 7 contaminated through actual use on the eye was then immersed in the solution 6. (It should be noted that if the immersed lens 7 directly overlies the electrode 13, especially on the cathode, the production of chloric ions from the cathode side will be hindered and the effective amount of sodium hypochlorite may not be obtained.) The container 2 was sealingly closed with a cap 3 and lightly shaken.Then, from the container 2 was taken 0.2 ml of physiological salt solution 6, into a sterilized test tube, which was used for a specimen to determine the number of bacteria. Next, in the remaining 2.0 ml of the solution 6 and through the platinum electrode 1 3 was passed a current of 1.3 mA for 30 seconds to thereby produce sodium hypochlorite of 1 ppm concentration in the solution 6.

Ten minutes later, each 1.0 ml out of the 2.0 ml physiological salt solution was inoculated in a thioglycolate medium (15 ml) for sterility test according to the Japanese Pharmacopoeia, Method of General Test 34, in order to examine the presence of bacteria.

The test was conducted to five subjects of contaminated, hydrated contact lenses 7. The results of the test are set forth in Table I.

TABLE I Number of bacteria Results of sterility Lens No. before sterilization* test after sterilization 1 1.7 x102/ml. Negative 2 1.2 x 102/ml. Negative 3 0.8 x 102/ml. Negative 4 2.9 x 102/ml. Negative 5 4.3 x 102/ml. Negative *The number of bacteria before sterilization was obtained by the following procedure: (1) Each 0.1 ml. of physiological salt solution was prepared from 0.2 ml. of unsterilized physiological salt solution picked beforehand.

(2) The 0.1 ml. solution was then inoculated on a plane of an agar culture medium and cultured at 370for24 hours.

EXAMPLE II The following specimen strains were cultured on a slant of an agar cuiture medium at 37 OC for 24 hours: (1) Escherichia Coli 0 : 55 K : 59 (2) Staphylococcus aureus 209P (3) Pseudomonas aeruginosa ATCC 9027 Each 103 cells/ml. of bacteria liquid was prepared with 0.9% sterilized physiological salt solution 6. Then, each 2 ml. of the liquid was poured into the same lens protective containers 2 as used in Example I. After the containers 2 were sealingly closed with a cap, there was applied a 1.3 mA of current through the platinum electrodes 13 for 30 seconds to thereby produce 1 ppm sodium hypochlorite.

Ten minutes later, each 1.0 ml. of test solution picked from the above three specimens was inoculated in a thioglycolate medium (15 ml.) for sterility test according to the above-mentioned Japanese Pharmacopoeia, Method of General Test 34, in order to examine the presence of bacteria. The results of the test are set forth in Table II.

TABLE II E. Coli S. aureus Ps. aeruginosa Number of bacteria before sterilization, cells/ml. 6,060 3,090 4,880 Results of sterility test after sterilization Negative Negative Negative EXAMPLE Ill An aqueous solution of 3.5 ml. was prepared by mixing the following acid and salts in the percent indicated: Trisodium citrate 0.562% Citric acid 0.006% Sodium chloride 0.9% The solution was filled in the contact lens protective container 2 (see Figure 2) having a pair of platinum electrodes 13 of 0.12 cm2 surface area. A hydrated contact lens 7 contaminated through actual use on the eye was then immersed in the solution 6, as with Example I already discussed. Next, from the container 2 was taken 0.5 ml of the solution 6 into a sterilized test tube, which was used for a specimen to determine the number of bacteria.Then, in the remaining 3.0 ml. of the solution 6 and through the platinum electrodes 13 was passed a current of 6 mA for 25 seconds to thereby produce sodium hypochlorite of about 5 ppm concentration in the solution.

Sixty minutes later, 2 ml of test solution was picked from 3 ml. of the solution and each 1.0 ml. of the test solution was inoculated in a thioglycolate medium (15 ml.) for sterility test according to the Japanese Pharmacopoeia, Method of General Test 34, in order to examine the presence of bacteria. On the other hand, the remaining 1.0 ml. of the solution 6 was determined with respect to the concentration of the residual sodium hypochlorite.

The test was conducted to five subjects of contaminated, hydrated contact lenses 7. The results of the test are set forth in Table Ill.

TABLE III Number of bacteria (per ml.) before Residual conc. of Lens No. sterilization Test results s. hypochlorite 1 3.1 x 102 Negative Less than 0.1 ppm 2 1.4 x 102 Negative Lessthan0.1 ppm 3 2.5 x 102 Negative Less than 0.1 ppm 4 9.0 x 102 Negative Less than 0.1 ppm 5 3.6 x 102 Negative Less than 0.1 ppm EXAMPLES IVANDV The sterilizing operations for contact lenses were conducted in the same manner as that of Example Ill except the test conditions were give as specified in Table IV. The test results are set forth in Table V.

TABLE IV Composition of pH of Current Applying Concentration of Time of Example solution (%) solution (mA) time s. hypochlorite picking d-glucose: 1% IV Sodium chloride: 0.9% 7.02 6 35 sec. 5 ppm After 30 min.

Sodium hydroxide: suitably 3-(N-morpholino) propane sulfonic acid: 0.4% V Sodium chloride: 0.9% 7.07 6 120 sec. 5 ppm After 60 min.

Sodium hydroxide: suitably TABLEV Number of bacteria Lens (per ml.) before Residual conc. of Example No. sterilization Test results s. hypochlorite 1 2.6 x 102 Negative 0 ppm 2 7.3 x 102 Negative 0 ppm IV 3 4.8 x 102 Negative 0 ppm 4 1.1 x 102 Negative Oppm 5 1.3 x 102 Negative Oppm 1 8.0 x 102 Negative Less than 0.1 ppm 2 3.9 x 102 Negative Less than 0.1 ppm V 3 2.7 x 102 Negative Less than 0.1 ppm 4 6.2 x 102 Negative Less than 0.1 ppm 5 4.6 x 102 Negative Lessthan0.1 ppm

Claims

1. A method of sterilizing an object which comprises immersing said object in an aqueous solution of an alkali metal chloride, and applying a current to said solution through two electrodes to produce an alkali metal hypochlorite in said solution and thereby sterilize said object

2. A method according to claim 1 wherein said object is a hydrated contact lens and said solution is a physiological salt solution for preserving contact lenses.

3. A method according to claim 1 or 2 wherein a current is applied for a predetermined time and said object is kept in said solution until the hypochlorite is dissolved after the interruption of said current.

4. A method according to claim 1, 2 or 3 wherein excess hypochlorite is reduced by adding a reducing agent to the solution.

5. A method according to claim 4 wherein said reducing agent is added to said solution before applying said current thereto.

6. A method according to claim 4 wherein said reducing agent is added to said solution after interrupting said current applied thereto.

7. A method according to claim 1 substantially as described in any one of the Examples.

8. An apparatus for sterilizing an object comprising a container for a solution for immersing said object therein, two electrodes oppositely disposed in said container and adapted for applying a current to said solution; and a current supplying means for connection to said electrodes.

9. Apparatus according to claim 8 wherein said object is an hydrated contact lens, said salt solution is a physiological salt solution effective for preserving said hydrated contact lens, and said container has a sealable lid thereon.

10. Apparatus according to claim 8 or 9 wherein said current supplying means includes at least one of a timer means for setting current-applying time and a constant-current means for maintaining current at a constant level.

11. Apparatus according to claim 8 substantially as described with reference to the accompanying drawings.