CA1156420A

CA1156420A - Method and apparatus for sterilizing an object such as a contact lens

Info

Publication number: CA1156420A
Application number: CA000377403A
Authority: CA
Inventors: Yasukichi Yanagihara; Kanbee Hotta; Eishun Tanaka
Original assignee: Tomei Sangyo KK
Current assignee: Tomei Sangyo KK
Priority date: 1981-03-18
Filing date: 1981-05-12
Publication date: 1983-11-08
Also published as: JPS57153653A; JPH0154060B2; FR2502011A1; GB2094992A; DE3131314A1

Abstract

Abstract of the Disclosure A method and apparatus for sterilizing an object such as a contact lens wherein the object is immersed in a salt solution, and a current is applied to the salt solution through two elec-trodes to thereby produce in the solution a sodium hypochlorite for sterilizing the object.

Description

1 ~ S~4~

METHOD AND APPARATUS FOR Sl'ERII.I~ING
AN OBJECT SUCH AS A CONTACT I,ENS

Background of the Invention 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 2-hydroxyethyl methacrylate includes normally about more than 30~ by weight of water. As a result, the hydrated contact lens itself is likely to constitute a favor-able 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 disadvan-tages, as hereinafter described.
- (1) The protein and other components in tear deposited on the lens undergo a thermal metamorphism through boiling operation .

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and stick to the lens surface, thereby irnpairing the optical properties of the lens anc~ remarkably reducing the weariny coziness on the eye.
(2) The sparingly cross-linked hydrophilic polymer, which is the material of hydrated contact lenses~ is likely to be deterio-rated 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 alter-nating 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 alleviate the drawbacks associated with the boiling sterilization, the prior art has also employed a method of sterllization for-the contact lenses wherein the lenses are -sterilized by disinfectant fluids containing thimerosal or chloro-hexadiene 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 1 1 5~42~

hydrogen peroxide and the solution is catalized by platinum or the like to decvmpose the hydroyen peroxide into water and oxygen. This method has also disadvantayes that it requires a considerably longer time in sterilization and is impractical because of its complicated operation.

Sumrnary of the Inven-tion An ob~ect 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 hypochlori~e through electrolyzation of the physiological salt solution which is a preserving liquid for the lenses, to there~y eliminate the need for an extra souxce of disinfectant liquid and allow for remarkable economy to users.

1 ~ ~ B4. 2 ~1 A still further object of the present invention is to provide a method and apparatus for steriliziny contact lenses wherein the lenses are free from harmful cornponent because of spontaneous or operational dissolution of the sodium hypochlorite into sodi.um 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 rernove protein in tear which is deposited on the lens surface.
A still further objéct of the present invention is to provide a method and apparatus which may be adapted for steri-lizing 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 .

~re~
Figure 1 is a front elevational view of a direct ~i~
supplying apparatus according to one embodiment of the present invention;
Figure 2 is a p:Lan v.iew thereof;
- Figure 3 is a plan view of the appara-tus shown in Figure 1 with a cover removed;
Figure 4 is a sectional front elevational view of a container for carrying a ccntact lens;
Figure 5 is a plan view of the container;

Fiyure 6 is a plan view of a tray for the contact lens;
Fiyure 7 is a schematic diag~am of the electrical cir-cuit of the appara-tus; and Figure ~ which is on the same sheet as ~igure 5 is a schematic view illustratiny the operation thereof.
Deta~led Description of the Preerred Ernbodiments The hydrated contact lenses are ir~nersed 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 utllized the above-mentioned fact, and has found and invented that, with the contact lens placed in the protec-tive container filled with physiological salt solution, the lens may be sterilized thorugh electrolyzation of the physiological salt solution in the container to produce an available quantity of sodium hypochlorite.
More particularly, the contact lens is imrnersed in a pro-tective 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 chloride ions in the solution become chloric molecules through anodic oxidation, and the chloride molecules re-act with the sodium hydroxide formed in the solutiorl through bond-ing of sodium lons and hydroxide ions, to thereby produce sodium hypochlorite.
This series of reactions is expressed by the following formula:

2 ~) 2 N~l ~ ~ 2 ~l2 t ~ 1 C~ t C12 ~ 2NaO~ NaClO ~ NaCl t H2V

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 180 seconds in a low concentration as of a~out 0.5 to 5.0 ppm. Furthermore, the sodium hypochlorite is feeble in its toxicity to the eye tissue althou~h it has strong sterilizing characteristics, and from this point of view, it is an extremely ideal sterilizing agent for contact lenses.
The concentra~ion of the sodium hypochlorite to be used for contact lenses preferably ranges from about 0.4 to 4.0 ppm.
5O 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 act 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 morniny, it is reasonable and safe to the eye tissue to settle the concentration of sodium hypochlorite within the range above-mentioned.

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It is also possible to decompose or reduce the sodium hypochlorite to an innoxious state in extremely short time by catalyz:ing -t:he steriliæed 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 exarnple, alkali or alkaline earth metal salts of thiosulfuric ac.id such as sodium thiosulfate, potassium thiosulfate and calcium thiosulfate; saccharides such as d-glucose, ~-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 m.ay be added to the sterilized physio-logical salt solution as discussed hereinbefore, but may be added likewise to the physiological salt solution prior to steri~ization, depending on the type of reducing agents to be used. More partic-ularly, 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 ger.erally more inactive to reducing agents than to microorganism, and _herefore, the sterilized solution may be 4 ~ V

reduced without impairing the sterili~ing ac~ion of sodium h~pochlorite.
It should be noted that the decrease in salt concentration of the physiological salt solution caused by the production o~
available sodium hypochlorite is extremely small, that is, on the order of about 0.00001%, and thus no influence may be experi-enced 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 lU salt solution" refers to an aqueous solution of sodium chroride which is isotonic with tear fluid and i5 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 lS of not only soaium 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 ~ormed with a connection portion 1 interposed therebetween, which are made of plastics such as polyethelene,polypropylene, polycarbonate and polysulfone, or of gla~s, 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 1 1 ~6~20 container 2 through a groove 4 forrned 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 B tray 11 on which the lens 7 is placed has a -~E~ curvature than that of the lens 7 and has a plurality of apertures 8 and 9 to permit fluidity of the solution 6 between i~side 10 and outside of the tray 11. Additionally, on the bottom of each container 2, there is embedded an electrode 13 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 ~ ionization tendency in view of the fact that the anode is subject to a strong oxidi-zation 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 vacuum~deposited to the container 2 and the~ connecting portion 1 so as to serve as the electrode 13 and the conductive plate 12.
Reference numeral 14 represents the whole container unit for carrying th~ contact lenses arranged as mentioned above and adapted for connection with a direct current supplying unit 15 1 lt'j~42~

for delivering a current for electrolyzing the phy~iological salt solu-tion 6 in -the container 2 through the elec-trode 13.
The direct current supplying unit 15 includes a case 16 ~1hich in turn has a plastic body 17 and a plactic cover 19 secured thereto with screws lB. 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 i.s replaceably stored in the case 16 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 confirmetion 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 lS solution 6 in the container 2.
Furthermore, on the side face of the case 16 of the direct current supplying unit 15, 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 12 exposed at the ba;ttom 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 16 through the conductive 2 ~3 plate 12 and the elastic plate 30.
Referring now to ~'igure 7 which illustratec3 an electrical circuit of the ernbodimerlt according to the present i.n~ention, a timer circui.t 32 ~or a monos-table multivibrator i~ connected to the battery 21 through the power switch 22. In the circuit, the monostable multivibrator is activated upon eneryization of the starter switch 23 to generate a trigger signal, and is adapted to energize each of transistors Trl and ~rr2 by inverting the output from low to high ~or a given time determined by the resist-ance value of the variable resistance VRl. A constant-c~rrent 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 ZDl, a transistor Tr3, a resistance Rl and a variable resistance VR2. The circuit 33 is then connected to the one of electrodes 13 of each container 2 through the transistor Tr3 and the variable resistance VR2. Furthermore, the constant-current circuit 33 is connected to a lower-limit-current setti.ng circuit 3~ 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 13 connected to the transistor Tr2 reaches below the specified voltage determi.ned 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 Cl and C2 to form a circuit con~iguration.
The operaticn and basic arrangement of the embodiment will be now described.

In Eigure 8, a contact lens 7 is immersed in the physio-logical salt solution 6 in the protective container 2, ar.d 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 curren-t is determined by the resistance value of the variable resistance VR, as already discussed above, and upon electrolyzation of the solution, a sodium hypochlorite substan-tially proportional to the potential is produced in the solution 6 to thereby e~fect 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 sodiùm chloride and oxygen which are entirely innoxious to the eye tissue.
More particularly, in order to accomplish a positive and effective sterili~ing operation for the contact lens 7 by obtain-ing substantially constant production of the sodium hypoch-lorit-e during the operation, and to reduce the spontaneous dissolution time after completion of the sterilization operation, the circuits are arranged as follows:
(1) The cutput of the timer is set at 30 seconds for example, through the variable resistance VRl;
(2) The ampere passing through the electrode 13 of each container 2 is set at 1.3mA for example (2.6mA for both electrodes), through the variable resistance VR2 of the constant-current circuit 33;
(3) The lower-limit am2ere is set at 2.OmA for example, through the variable resistance VR3 of the lower-limit current .

setting circuit 34 adapted for ob-talning a lower-limit a~npere at which the ou-tput current from the constant-cuxrent circuit 33 is sufficient enough to produce the sodium hypochlorite requirèd for the effective sterillzing operation when the po~ential is lowered due to the drain o 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 ~rom the constant-current circuit 33 falls below 2.0mA of the lower limit.
With this arrangement and under the norrnal condition where the battery is not drained, the contact lens tray 11 is placed in both protecti~e containers 2, and a specified amount o~ 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 16 of the direct-current supplying unit 15 from the inlet 26 thereof through the abutting engagement of the.projecting edges 28 of the container unit 15 and the guide grooves 27 of the case 16. 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 ~ 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.
~ ccordingly, when the power switch 22 is turned on with the above setting cQmpleted, the LED 24 will illuminate because of 4 2 ~

the low output prior to the activation o~ timer 32, 50 as to confirm that the power i8 on. The starter switch 23 is then depressed, and the output is inverted from low to high to thereby ~nergize each of the transistors Trl and Tr2. With this continuity, a given current, in this instance, 1.3mA, is passed between the electrodes 13 which is determined by the zener voltage of the zener diode ZDl and the resistance value of the variable resist-ance VR2. Because of this large voltage drop caused by the current applied between the electrodes 13, 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 Tr-2. The output of the constant-current clrcuit 33 through the transistor Tr3 is turned off and the current passing between electrodes 13 is then cut off so as to complete the sterilizin~ operation for the contact lens 7. The LED 25 will go out to confirm--the completion of the sterilizing operaticn, and the power switch is turned off to ~omplete the whole steri-lizing cycle. The lens container unit 14 is then allowed to stand for at least 30 minutes, and the sodium hypochlorite of the physiological salt solution ~ 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.
Alternativ~ly, under the abnormal condition where the battery is drained, the portable lens-container unit 14 is inserted into ' ' .

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the case of the direct-current supplying unit 15, and the power switch 22 and the s-tarter switch 23 are turned on. ~t this time, if the output current o the constant-current circuit 33 falls below 2.OmA 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 voltàge drop between the elec-trodes 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 ~3 is ho I
contact lenses 7 arc 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 13 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 hypoch'lorite 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.

, ~ 15 -1 2 ~

of the solution 6 and through the platinurn electrode 13 was passed a current of 1.3mA for 30 seconds to thereby produce sodilml hypochloxite of l ppm concentration in the solution 6.
Ten minutes later, each l.0 ml. out of the 2.0 ml. physio-logical salt solution was inoculated in a thioglycolate medium (15 ml.) for sterility test according to the Japanese Pharma-copoeia, Method of General Test 34, in order to examine the presence of bacteria.
The test was conducted to five subjects of contaminated, hyarated contact lenses 7. The results of the test are set forth in Table I.

Table I

. . ~
Lens No. Number of bacteria Results of sterility before sterilization* test after sterilization . _ _ . _ _ _ 15 l 1.7 x 10 /ml. Negative 2 1.2 x 10 /ml. Negative 3 ~ 0.8 x lO /ml. Negative 4 2.9 x lO /ml. Negative 4.3 x lO /ml. Negative * The number of bacteria before sterilization was obtained by the following procedure:
(l) 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 37C for 24 hours.

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Example II

The following specimen strains were cultured on a slant of an agar culture medium at 37C 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 1.3mA 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 examime 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, 6,060 3,090 4,880 cells/ml.
Results of sterility test after steriliza- Negative Negative Negative tion . _ . . _ ~

Example III

An aqueous solution oE 3.5 ml. was prepared hy mixing the following acid and salts in the percent i.ndicated:
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 cm 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 specimèn to deterrnine 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 6mA 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 tlS ml.) for sterilit~ 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, hydr.ated contact l~nses 7. The results of the test are set forth in Table III.

Table IIX

__ __ Lens No. Nurnber of hacteria Test results Residual conc. of (per ml.) before s. hypochlorite sterilization _ .
1 3.1 x 102Negative Less than 0.1 ppm 2 1.4 x 10Negative Less tha~ 0.1 ppm 3 2.5 x 10Negative - Less than 0.1 ppm 4 9.0 x 10Negative Less than 0.1 ppm 3.6 x 10Negative Less than 0.1 ppm .: _ Examples IV and V

The sterilizing operations for contact lenses were conducted in the same manner as that of Example III except the test conditions were given as specified in Table IV. The test results are set forth in Table V.

1 ~&~V

o,~ o o oa ~ rl r l It') r-l . '1~, O '~
.. a~ _ u ~ 0 U r~ X '~ O ~rl O _ ~ r~l 41 S l r~ O~n U ~ ~ U

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Table V

. ~
Example Lens Number of bacteria Test results Residual conc. o~
No. (per ml.) before s. hypochlorite sterili~ation 1 2.6 x 10 Negative O ppm 2 7.3 x 10 Negative O ppm IV 3 4.8 x 10 Negative O ppm 4 1.1 x 10 Negative O ppm 1.3 x 10 Negative O ppm . .
1 8.0 x 10 Negative Less than 0~1 ppm 2 3.9 x 10 Negative Less than 0.1 ppm V 3 2.7 x 10 Negative Less than 0.1 ppm 4 6.2 x 10 Negative Less than 0.1 ppm 4.6 x 10 Negative Less than 0.1 ppm . _ . _

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of sterilizing contact lenses comprising:
providing a container filled with a physiological salt solution and having electrodes disposed therein for passing a current in said physiological salt solution;
immersing said con-tact lenses in said physiological salt solution contained in said container;
passing a current in said physiological salt solution through said electrodes so as to produce a sodium hypochlorite for sterilizing said contact lenses in said physiological salt solution;
interrupting said current; and allowing said contact lenses to remain immersed in said physiological salt solution until said sodium hypochlorite concentration is lowered to a level substantially innoxious to the human eye tissue.

2. A method of sterilizing contact lenses comprising:
providing a container filled with a physiological salt solution and having electrodes disposed therein for passing a current in said physiological salt solution;
immersing said contact lenses in said physiological salt solution contained in said container;
passing a current in said physiological salt solution through said electrodes so as to produce a sodium hypochlorite for sterilizing said contact lenses in said physiological salt solution;
interrupting said current; and reducing said sodium hypochlorite remained in said physiological salt solution by using a reducing agent.

3. An invention as defined in claim 2 wherein said reducing agent is added to said physiological salt solution before applying said current thereto.

4. An invention as defined in claim 2 wherein said reducing agent is added to said physiological salt solution after interrupting said current applied thereto.

5. An invention as defined in claim 1,2 or 3 wherein said contact lenses are hydrated contact lenses.

6. An apparatus for sterilizing contact lenses comprising, a sealable container with a lid adapted to preserve said contact lenses and having means for immersing and holding said contact lenses in a physiological salt solution contained in said sealable container, said sealable container having electrodes disposed therein and adapted to pass a current in said physiological salt solution; and a current supplying means for passing a current through said electrodes so as to produce a sodium hypochlorite in said physiological salt solution.

7. An invention as defined in claim 6 wherein said contact lenses are hydrated contact lenses.

8. An invention as defined in claim 6 or 7 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.