Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND RIT FOR DI~INFECTION ~F CONTACT LENSE~
Field of the Invention
The present invention relates to methods and
apparatus for disinfection of contact lenses, particularly
plastic and rubber lenses.
Backqround of the Invention
Most contact lenses currently sold and used are
hydrophillic or soft contact lenses, as opposed to hydro-
phobic or hard lenses, due to the improved comfort of the
user of such lenses and reduced irritation of the eye.
However by their nature, it is necessary to maintain such
hydrophillic lenses in a sterile condition. Any steri-
lizing agent used must kill the bacteria on and in the
lens, be harmless to the eye and have no effect on the
shape or material of the lens. Improper disinfecting agents
can alter the shape of the contact lens which renders them
useless. A sterile saline solution is also used to store
the lenses when not in use.
Most substances used for sterilization of
contact lenses involve either substances which release
halogens, in particular chlorine, when dissolved in water,
or hydrogen peroxide. For example Canadian Patent No.
1,003,749 issued January 18, 1977 to Hydrophilics Interna-
tional, Inc. discloses the use of sodium dichlorocyanurate,
chlorinated trisodium phosphate, potassium dich-
lorocyanurate and trichloroisocyanuric acid in solution tosterilize soft contact lenses. The present inventor, in co-
pending Canadian application no. 2,044,072-4 filed June 7,
1991, discloses the use of a small but effective amount of
chloramine-T in concentration effective for disinfection
but non-damaging to the eye and to the contact lenses. The
use of chlorine alone may cause the lenses to be left with
a yellow stain, however. Other methods involve the use of
hydrogen peroxide as a sterilizing agent, but large quan-
tities of peroxide are required for adequate sterilization.
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Up to now both chlorine and peroxide have not been used in
combination for this purpose.
The sterilizing of contact lenses is generally
carried out in a sterile saline solution. Currently, users
are provided with a collection of bottles of sterile saline
to use over a period of time. This method of providing
saline is bulky and expensive. The present inventor has
disclosed in co-pending Canadian patent application 2,025,-
106 filed September 11, l99o and International application
lo no. PCT/CAgl/00056 a simple, portable device for storing
and dispensing sterile saline. It comprises a resilient
hollow container having a first outlet, a housing removably
mounted on the container and having a second outlet and a
passage communicating between the first and second outlet,
a liquid-sterilizing filter mounted in the housing in the
passage, and valve means for alternately opening and
closing the second outlet, whereby pressure applied to the
container forces a liquid stored in the container through
said filter and out the second outlet when the valve is in
an open position. This device permits sterile saline to be
produced readily from tap water. There is a need therefore
for a lens cleaning kit which incorporates this improved
device to eliminate the previously bulky components of the
prior art.
Summary of the Invention
The invention provides a method of disinfecting
contact lenses comprising immersing, for a period of time
sufficient to result in disinfection, the contact lenses in
a solution containing a chlorine-releasing agent, wherein
the amount of chlorine released is from 1 to 500 parts per
million, preferably between 10 and 20 ppm, and from 1 to
1,000 parts per million hydrogen peroxide, preferably 40 to
80 ppm.
The invention further provides a kit for steril-
izing soft contact lenses comprising a chlorine-releasing
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agent, hydrogen peroxide, an apparatus for producing a
sterile saline and a container for immersing the lenses in
the sterilizing solution.
Brief Description of_the Drawin~s
In a drawing which illustrates a preferred em-
bodiment of the invention:
Figure 1 is a schematic diagram illustrating the
kit of the invention.
Detailed Description of the Preferred Embodiment
According to the invention, a contact lens
disinfectant solution is prepared by dissolving a suffi-
cient amount of chloramine-T in a sterile saline solution
to produce between 1 and 500 parts per million of chlorine
in the water (preferably less than 200 ppm and between 10
and 20 ppm is preferred). Hydrogen peroxide in a strength
of less than 1000 ppm (40 to 80 ppm is preferred) is added
to the saline also. The soft, hydrophillic contact lenses
are immersed, for a period of time sufficient to result in
disinfection, in the solution, which is effective for
disinfection but non-damaging to the eye and to the contact
lenses. The further step may be taken of adding buffers
such as monosodium phosphate and dibasic sodium phosphate
to the solution described in a quantity sufficient to
neutralize the solution.
The irvention is used by way of a kit 1 illus-
trated schematically in Fig. 1. A suitable amount of a
chlorine-releasing agent (e.g. chloramine-T) is provided in
a pre-measured powder form in salt capsules or packets 3,
which also provide the salt for the saline solution in a
pre-measured amount. Hydrogen peroxide is provided in a 1
oz. spray atomizer container 5. A filter unit 7 of the type
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described in Canadian patent application 2,025,106 is
provided as is a contact lens washer/holder 9 of the type
disclosed in Canadian industrial design registration 67701
issued December 24, l99o. The lens or lenses are placed in
holder 9. A spray of peroxide from atomizer 5 is sprayed
into lens holder unit 9. Either distilled or tap water is
added to filter unit 7 in the appropriate measured amount
(use of distilled water results in improved filter life but
tap water may also be used). The salt packet with chlorine-
releasing agent is dissolved in the water in the filterunit 7 to the appropriate concentrations noted above. The
saline solution is then expelled from the filter unit as
described in the above-noted application, causing it to be
sterilized, into the lens washer/holder unit 9 which is
operated in the usual manner to clean and sterilize the
lens. Preferably the buffers noted above will be added to
the saline, either in unit 7 or in the holder 9, and the
lenses will be left overnight for sterilization (at least
4 hours is preferred, although sterilization may be a-
chieved in considerably less time). The resulting saline isof ophthalmic quality, non-irritating to the eye and can be
used for subsequent storage of the lenses.
The invention provides a number of advantages.
Chlorine alone in concentration tends to cause the lens to
~5 turn yellow due to partial oxidation of proteins. These
partially oxidized proteins are retained in the porous lens
material. The addition of peroxide apparently completes the
oxidation process and de-ionizes the protein. Use of
peroxide alone would require a much higher concentration of
peroxide. Also the peroxide oxidizes the residual active
chlorine which remains after disinfection. The xeaction
between H202 (hydrogen peroxide) and HOCl (hydrochlorous
acid) produces HCl (hydrochloric acid). The HCl is neutral-
ized by the buffering agent. The result is a saline that is
non-irritating to the eye while effectively maintaining the
lens sterile. The kit thus produces its own sterile saline
from water for sterilizing and storage purposes, which
saves considerable expense and storage size.
EXAMPLE
By way of example, 106 germs of type staph dermatitis
were added to 10 ml of water. Chloramine-T in powdered form
was added to the 10 ml. of water to provide 10 parts per
million of chlorine in the water. Hydrogen peroxide was
added in a concentration of 60 parts per million. After 4
hours the solution was cultured and no growth was reported
after 48 hours of incubation. A soft contact lens of class
4 material etasilicon - A (ACUVIEWTM) was tested clinically
in the solution for discolouration and no protein binding
or yellow discolouration was noted. The amounts of living
bacteria on the lens after removal were found to be mini-
mal, and there was no detected alteration of the lens shape
or material.
As will be apparent to those skilled in the art
in the light of the foregoing disclosure, many alterations
and modifications are possible in the practice of this
invention without departing from the spirit or scope
thereof. Accordingly, the scope of the invention is to be
construed in accordance with the substance defined by the
following claims.
