STABLE LIQUID ENZYME COMPOSITIONS AND METHODS OF USE IN CONTACT LENS CLEANING AND DISINFECTING SYSTEMS

The present application is a continuation-in-part of United States Patent

Application Serial No. 08/544753, filed October 18, 1995, which is a continuation-in-part

of United States Patent Application Serial No. 08/477001, filed on June 7, 1995.

Background of the Invention

The present invention relates to the field of contact lens cleaning and disinfecting.

In particular, this invention relates to liquid enzyme compositions and methods for

cleaning human-worn contact lenses with those compositions. The invention also relates

to methods of simultaneously cleaning and disinfecting contact lenses by combining the

liquid enzyme compositions of the present invention with a chemical disinfecting agent.

Various compositions and methods for cleaning contact lenses have been described in the patent and scientific literature. Some of these methods have employed compositions containing surfactants or enzymes to facilitate the cleaning of lenses. The

first discussion of the use of proteolytic enzymes to clean contact lenses was in an article

by Lo, et al. in the Journal of The American Optometric Association, volume 40, pages

1106-1109 (1969). Methods of removing protein deposits from contact lenses by means

of proteolytic enzymes have been described in many publications since the initial article

by Lo, et al., including U.S. Patent No. 3,910,296 (Karageozian, et al.).

Numerous compositions and methods for disinfecting contact lenses have also

been described. Those methods may be generally characterized as involving the use of

heat and/or chemical agents. Representative chemical agents for this purpose include

organic antimicrobials such as benzalkonium chloride and chlorhexidine, and inorganic

antimicrobials such as hydrogen peroxide and peroxide-generating compounds. U.S.

Patents Nos. 4,407,791 and 4,525,346 (Stark) describe the use of polymeric quaternary

ammonium compounds to disinfect contact lenses and to preserve contact lens care

products. U.S. Patents Nos. 4,758,595 and 4,836,986 (Ogunbiyi) describe the use of

polymeric biguanides for the same purpose.

Various methods for cleaning and disinfecting contact lenses at the same time

have been proposed. Methods involving the combined use of proteolytic enzymes and

peroxides to clean and disinfect contact lenses simultaneously, are described in U.S.

Patent No. Re 32,672 (Huth, et al.). A representative method of simultaneously cleaning

and disinfecting contact lenses involving the use of proteolytic enzymes and quaternary

ammonium compounds is described in Japanese Patent Publication 57-24526 (Boghosian,

et al.). The combined use of a biguanide (i.e., chlorhexidine) and liquid enzyme

compositions to simultaneously clean and disinfect contact lenses is described in

Canadian Patent No. 1,150,907 (Ludwig, et al.). Methods involving the combined use of

dissolved proteolytic enzymes to clean and heat to disinfect are described in U.S. Patent

No. 4,614,549 (Ogunbiyi). The combined use of proteolytic enzymes and polymeric

biguanides or polymeric quaternary ammonium compounds is described in copending,

commonly assigned United States Patent Application Serial No. 08/156,043 and in

corresponding European Patent Application Publication No. 0 456 467 A2 (Rosenthal, et

al.), as well as in U.S. Patent No. 5,096,607 (Mowrey-McKee, et al.).

The commercial viability of most prior enzymatic cleaning products has depended

on the use of stable enzyme tablets. More specifically, the use of solid enzymatic

cleaning compositions has been necessary to ensure stability of the enzymes prior to use.

In order to use such compositions, a separate packet containing a tablet must be opened,

the tablet must be placed in a separate vial containing a solution, and the tablet must be

dissolved in order to release the enzyme into the solution. This practice is usually

performed only once a week due to the cumbersome and tedious procedure and potential

for irritation and toxicity. Moreover, the enzymatic cleaning tablets contain a large

amount of excipients, such as effervescent agents (e.g., bicarbonate) and bulking agents

(e.g., sodium chloride). As explained below, such excipients can adversely affect both

cleaning and disinfection of the contact lenses.

There have been prior attempts to use liquid enzyme compositions to clean contact

lenses. However, those attempts have been hampered by the fact that aqueous liquid

enzyme compositions are inherently unstable. When a proteolytic enzyme is placed in an

aqueous solution for an extended period (i.e., several months or more), the enzyme may

lose all or a substantial portion of its proteolytic activity. Steps can be taken to stabilize

the compositions, but the use of stabilizing agents may have an adverse effect on the

activity of the enzyme. For example, stabilizing agents can protect enzymes from

chemical instability problems during storage in an aqueous liquid, by placing the enzymes

in a dormant physical conformation. This conformation is referred to herein as being

"partially denatured." However, such agents may also inhibit the ability of the enzymes

to become active again (i.e., become "renatured") at the time of use. Finally, in addition

to the general problems referred to above, a commercially viable liquid enzyme

preparation for treating contact lenses must be relatively nontoxic, and must be

compatible with other chemical agents used in treating contact lenses, particularly

antimicrobial agents utilized to disinfect the lenses.

The following patents may be referred to for further background concerning prior

attempts to stabilize liquid enzyme formulations: U.S. Patents Nos. 4,462,922

(Boskamp); 4,537,706 (Severson); and 5,089,163 (Aronson). These patents describe

detergent compositions containing enzymes. The detergent compositions may be used to

treat laundry, as well as other industrial uses. Such detergents are not appropriate for

treating contact lenses. The compositions of the present invention do not contain a

detergent, or other agents potentially damaging or irritating to the eye.

U.S. Patent No. 5,281,277 (Nakagawa) and Japanese Kokai Patent Applications

Nos. 92-370197; 92-143718; and 92-243215 describe liquid enzyme compositions for

treating contact lenses. The compositions of the present invention are believed to provide

significant improvements relative to the compositions described in those publications.

Summary of the Invention

The liquid enzyme compositions of the present invention contain critical amounts

of selected stabilizing agents. The stabilizing agents utilized are combinations of a borate

or boric acid compound and one or more 2-3 carbon polyols. The amounts of stabilizing

agents utilized have been delicately balanced, such that maximum stability is achieved,

while maximum activity is later obtained when the composition is put into use.

Furthermore, the borate or boric acid compound also preserves the liquid enzyme

compositions of the present invention from microbial contamination when the

compositions are packaged in multiple use containers.

The present invention also provides methods for cleaning contact lenses with the

above-described liquid enzyme compositions. In order to clean a soiled lens, the lens is

placed in a few milliliters of an aqueous solution and a small amount, generally one to

two drops, of the enzyme composition is added to the solution. The lens is then soaked in

the resultant cleaning solution for a time sufficient to clean the lens.

The liquid enzyme compositions of the present invention are preferably combined

with an aqueous disinfecting solution to simultaneously clean and disinfect contact lenses.

As will be appreciated by those skilled in the art, the disinfecting solution must be

formulated so as to be compatible with contact lenses. The antimicrobial activity of many

chemical disinfecting agents is adversely affected by ionic solutes (e.g., sodium chloride).

As explained below, the liquid enzyme compositions of the present invention are

substantially nonionic, and therefore do not adversely affect the antimicrobial activity of

such disinfecting agents. This is considered to be a major advantage of the present

invention.

The enzyme compositions of the present invention are formulated as concentrated,

multi-dose liquids, and consequently do not contain conventional enzyme tablet

excipients, such as sodium chloride (bulking agent) and bicarbonate (effervescent agent).

The liquid enzyme compositions of the present invention utilize an aqueous vehicle. The

primary components of the vehicle are one or more polyols and water. Both of these components are non-ionic. The liquid enzyme compositions of the present invention are

thus substantially nonionic, and therefore have very little impact on the ionic strength of a

disinfecting solution, and little to no effect on the antimicrobial activity of disinfecting

solutions.

The compositions and methods of the present invention provide greater ease of

use. This ease of use enables contact lens users to clean their lenses 2 to 3 times a week,

or more preferably, every day. It has been found that daily use of the liquid enzyme

compositions of the present invention results in dramatically better cleaning and safety, as

compared to the once-a-week enzyme cleaning regimens currently being utilized.

Brief Peggri ion of the Dr wings

Figure 1 is a histogram detailing the effects of a liquid enzyme composition of the present invention on Type III and Type IV lens deposits, when used daily during a 135

day clinical study; Figure 2 illustrates the frequency and reasons for lens replacements

during that study; and Figure 3 illustrates the safety of the liquid enzyme compositions of

the present invention relative to prior enzyme cleaner compositions, based on the

incidence of significant slit-lamp findings during the clinical study.

Detailed Description of the Invention

It has been found that the use of a polyol in combination with a borate or boric

acid compound achieves the stability and sustainable activity required in the liquid

enzyme compositions of the present invention. While Applicants do not wish to be bound

by any theory, it is believed that the stability of the enzymes utilized in the present

invention is enhanced by partially denaturing the proteins. The enzymes are partially

denatured by forming a complex with the stabilizing agents. The enzymes are denatured

to a point where the enzymes are inactivated, but where renaturation is easily achieved by

dilution of the denatured enzyme/stabilizing agent complex in an aqueous medium. It is

believed that the stabilizing agents compete with water for hydrogen bonding sites on the

proteins. Thus, a certain percentage of these agents will effectively displace a certain

percentage of water molecules. As a result, the proteins will change conformation

(partially denature) to an inactive and complexed (with the stabilizing agents) form.

When the enzyme is in an inactive form, it is prevented from self-degradation and other

spontaneous, chemically irreversible events. On the other hand, displacement of too

many water molecules results in protein conformational changes that are irreversible. In

order to obtain a stable liquid enzyme composition of significant shelf life and thus

commercial viability, a delicate balance point of maximum stability and maximum

reversible renaturation must be ascertained. Such a point has now been discovered.

The polyols utilized in the present invention are 2-3 carbon polyols. As used

herein, the term "2-3 carbon polyol" refers to a compound with 2 to 3 carbon atoms and at

least two hydroxy groups. Examples of 2-3 carbon polyols are glycerol, 1,2 -propane diol

("propylene glycol"), 1,3-propane diol and ethylene glycol. Propylene glycol is the

preferred 2-3 carbon polyol.

The borate or boric acid compounds which may be utilized in the present

invention include alkali metal salts of borate, boric acid and borax. The most preferred

borate or boric acid compound is sodium borate. As mentioned above, the borate or boric

acid compound also contributes to the antimicrobial preservation of the liquid enzyme

compositions of the present invention to a level effective for multi-use dispensing.

It has been found that certain amounts of a 2-3 carbon polyol and a borate or boric

acid compound are critical for obtaining the stability and sustainable activity required in

the liquid enzyme compositions of the present invention. It has been discovered that the

combination of 50-70% volume/volume ("% v/v") of a 2-3 carbon polyol and 4-8%

weight/volume ("% w/v") of a borate or boric acid compound is required to achieve the necessary criteria for efficacious and commercially viable liquid enzyme compositions, as described above. The combination of about 50% v/v of a 2-3 carbon polyol and about 7.6% w/v of sodium borate is most preferred. Examples 1, 2 and 3 below further

illustrate appropriate and inappropriate concentrations of these stabilizing agents.

The enzymes which may be utilized in the compositions and methods of the

present invention include all enzymes which: (1) are useful in removing deposits from

contact lenses; (2) cause, at most, only minor ocular irritation in the event a small amount

of enzyme contacts the eye as a result of inadequate rinsing of a contact lens; (3) are

relatively chemically stable and effective in the presence of the antimicrobial agents

described below; and (4) do not adversely affect the physical or chemical properties of the

lens being treated. The proteolytic enzymes used herein must have at least a partial

capability to hydrolyze peptide-amide bonds in order to reduce the proteinaceous material

found in lens deposits to smaller water-soluble subunits. Typically, such enzymes will

exhibit some lipolytic, amylolytic or related activities associated with the proteolytic

activity and may be neutral, acidic or alkaline. In addition, separate Upases or

carbohydrases may be used in combination with the proteolytic enzymes. For purposes of

the present specification, enzymes which satisfy the foregoing requirements are referred

to as being "ophthalmically acceptable."

Examples of ophthalmically acceptable proteolytic enzymes which may be

utilized in the present invention include but are not limited to pancreatin, trypsin,

subtilisin, collagenase, keratinase, carboxypeptidase, papain, bromelain, aminopeptidase,

elastase, Aspergillo peptidase, pronase E (from ≤ griseus). dispase (from Bacillus

polymyxa) and mixtures thereof. If papain is used, a reducing agent, such as N-

acetylcysteine, may be required.

Microbially derived enzymes, such as those derived from Bacillus. Streptomyces.

and Aspergillus microorganisms, represent a preferred type of enzyme which may be

utilized in the present invention. Of this sub-group of enzymes, the most preferred are the

Bacillus derived alkaline proteases generically called "subtilisin" enzymes.

The identification, separation and purification of enzymes is known in the art.

Many identification and isolation techniques exist in the general scientific literature for

the isolation of enzymes, including those enzymes having proteolytic and mixed

proteolytic/lipolytic/amylolytic activity. The enzymes contemplated by this invention can

be readily obtained by known techniques from plant, animal or microbial sources.

With the advent of recombinant DNA techniques, it is anticipated that new

sources and types of stable proteolytic enzymes will become available. Such enzymes

should be considered to fall within the scope of this invention so long as they meet the

criteria set forth herein.

Pancreatin and subtilisin are preferred enzymes, and trypsin is the most preferred

enzyme for use in the present invention. Pancreatin is extracted from mammalian

pancreas, and is commercially available from various sources, including Scientific Protein

Laboratories (Waunakee, Wisconsin, U.S.A.), Novo Industries (Bagsvaerd, Denmark),

Sigma Chemical Co. (St. Louis, Missouri, U.S.A.), and Boehringer Mannheim

(Indianapolis, Indiana, U.S.A.). Pancreatin USP is a mixture of proteases, lipases and

amylases, and is defined by the United States Pharmacopeia ("USP"). The most preferred

form of pancreatin is Pancreatin 9X. As utilized herein, the term "Pancreatin 9X" means

a filtered (0.2 microns) pancreatin containing nine times the USP protease unit content.

Subtilisin is derived from Bacillus bacteria and is commercially available from various

commercial sources including Novo Industries (Bagsvaerd, Denmark), Fluka Biochemika

(Buchs, Switzerland) and Boehringer Mannheim (Indianapolis, Indiana, U.S.A.). Trypsin

is purified from various animal sources and is commercially available from Sigma

Chemical Co. and Boehringer Mannheim.

The liquid enzyme compositions of the present invention will have an enzyme

concentration sufficient to provide an effective amount of enzyme to remove substantially

or to reduce significantly deposits of proteins, lipids, mucopolysaccharides and other

materials typically found on human-worn contact lenses when a small amount of a

composition is added to a diluent. As used herein, such a concentration is referred to as

"an amount effective to clean the lens." The amount of enzyme used in the liquid enzyme

compositions of the present invention will generally range from about 0.05 to 5% w/v.

The selection of a specific concentration will depend on various factors, such as: the

enzyme or combination of enzymes selected; the purity, specificity and efficacy of the

enzyme(s) selected; the type of lenses to be cleaned; the intended frequency of cleaning

(e.g., daily or weekly); and the intended duration of each cleaning.

During storage, some of the activity of the enzyme may be lost, depending on

length of storage and temperature conditions. Thus, the liquid enzyme compositions of

the present invention may be prepared with initial amounts of enzyme that exceed the

concentration ranges described herein. The preferred compositions of the present

invention will generally contain one or more enzymes in an amount of about 300-6000

PAU/mL. The compositions will most preferably contain about 900-2200 PAU/mL,

which corresponds to pancreatin in the range of about 1 to 2% w/v; subtilisin in a range of

about 0.1 to 0.3% w/v; and trypsin in the range of about 0.1 to 0.3% w/v. For purposes of

this specification, a "proteolytic activity unit" or "PAU" is defined as the amount of

enzyme activity necessary to generate one microgram (meg) of tyrosine per minute ("meg

Tyr/min"), as determined by the casein-digestion, colorimetric assay described below.

Casein-digestion assay

A 5.0 mL portion of casein substrate (0.65% casein w/v) is equilibrated for 10

minutes (min) ± 5 seconds (sec) at 37°C. A 1.0 mL portion of enzyme solution (0.2

mg/ml) is then added to the casein substrate and the mixture vortexed, then incubated for

10 min ± 5 sec at 37°C. After incubation, 5.0 mL of 14% trichloroacetic acid is added

and the resultant mixture immediately vortexed. The mixture is incubated for at least

another 30 min, then vortexed and centrifuged for 15-20 min (approx. 2000 rpm). The

supernatant of the centrifuged sample is filtered into a serum filter sampler and a 2.0 mL

aliquot removed. To the 2.0 mL sample is added 5.0 mL of 5.3% Na ₂ CO ₃ . The sample is

vortexed, 1.0 mL of 0.67 N Folin's Phenol reagent is added, and the sample is

immediately vortexed again, then incubated for 60 min at 37°C. The sample is then read

on a visible light spectrophotometer at 660 nanometers (nm) versus purified water as the

reference. The sample concentration is then determined by comparison to a tyrosine

standard curve.

The cleaning obtained with the liquid enzyme compositions of the present

invention is a function of the time. The soaking times utilized will generally vary from

about 1 hour to overnight. However, if longer soaking periods (e.g., 24 hours) were to be

employed, lower concentrations than those described above can be utilized.

The cleaning methods of the present invention involve the use of a small amount

of the above-described liquid enzyme compositions to facilitate the removal of proteins

and other deposits from contact lenses. The amount of enzyme composition utilized in

particular embodiments of the present invention may vary, depending on various factors,

such as the purity of the enzyme utilized, the proposed duration of exposure of lenses to

the compositions, the nature of the lens care regimen (e.g., the frequency of lens

disinfection and cleaning), the type of lens being treated, and the use of adjimctive

cleaning agents (e.g., surfactants). However, the cleaning methods of the present

invention will generally employ an amount of the above-described liquid enzyme

compositions sufficient to provide a final enzyme concentration of about 5-75 PAU/mL of

solution, following dispersion of the liquid enzyme compositions in a disinfecting

solution or other aqueous solvent. A final concentration of about 5-25 PAU/mL is

preferred.

As indicated above, the liquid enzyme compositions of the present invention

contain relatively minor amounts of ionic solutes. More specifically, the compositions do

not contain bulking agents, effervescent agents or other ionic solutes commonly contained

in prior enzyme tablets. The present compositions do contain the ionic solutes of borate

or boric acid compounds and hydrochloric acid and/or sodium hydroxide, but the

concentration of these solutes in the present compositions is relatively low. The

compositions are therefore substantially nonionic. Moreover, as a result of the fact that

the compositions are formulated as concentrated, multi-dose liquids, only a small amount

of the compositions, generally one or two drops, is required to clean a contact lens. The

present compositions therefore have very little impact on the ionic strength of disinfecting

solutions. As explained below, this feature of the present invention is particularly

important when the liquid enzyme compositions are combined with disinfecting solutions

which contain ionic antimicrobial agents, such as polyquaternium-1.

The antimicrobial activity of disinfecting agents, particularly polymeric

quaternary ammonium compounds such as polyquaternium-1, is adversely affected by

high concentrations of sodium chloride or other ionic solutes. More specifically,

polymeric quaternary ammonium compounds, and particularly those of Formula (I),

below, lose antimicrobial activity when the concentration of ionic solutes in the

disinfecting solution is increased. The use of solutions having low ionic strengths (i.e.,

low concentrations of ionic solutes such as sodium chloride) is therefore preferred. Since

both ionic solutes (e.g., sodium chloride) and nonionic solutes (e.g., glycerol) affect the

osmolality and tonicity of a solution, osmolality and tonicity are indirect measures of

ionic strength. However, the low ionic strengths preferably utilized in the cleaning and

disinfecting methods of the present invention generally correspond to

tonicities/osmolalities in the range of hypotonic to isotonic, and more preferably in the

range of 150 to 350 milliOsmoles per kilogram (mOs/kg). A range of 200 to 300 mOs/kg

is particularly preferred, and an osmolality of about 220 mOs/kg is most preferred.

The liquid enzyme compositions of the present invention demonstrate effective

cleaning efficacy while exhibiting minimal adverse effects or, more preferably, enhanced

effects on the antimicrobial activity of disinfecting solutions. It has unexpectedly been

discovered that the liquid enzyme compositions of the present invention enhance the

antimicrobial activity of disinfecting solutions containing polyquaternium-1, a polymeric

quaternary ammonium disinfecting agent. It has also been discovered that combinations

of the liquid enzyme compositions and polyquaternium-1 disinfecting solutions become

even more effective than the polyquaternium-1 disinfecting solutions alone when lenses

are treated for extended periods of approximately one hour to overnight, with four to eight

hours preferred. Since, for the sake of convenience, contact lenses are typically soaked

overnight in order to be cleaned with enzymes or disinfected with chemical agents, this

finding has practical significance. While Applicants do not wish to be bound by any

theory, it is believed that the above-described enhancement of antimicrobial activity is

due to the disruption or lysis of microbial membranes by the enzyme over time.

The cleaning methods of the present invention utilize an aqueous solvent. The

aqueous solvent may contain various salts such as sodium chloride and potassium

chloride, buffering agents such as boric acid and sodium borate, and other agents such as

chelating agents and preservatives. An example of a suitable aqueous solvent is a saline

solution, such as Unisol® Plus Solution (registered trademark of Alcon Laboratories).

The cleaning and disinfecting methods of the present invention utilize a

disinfecting solution containing an antimicrobial agent. Antimicrobial agents can be

oxidative, such as hydrogen peroxide, or non-oxidative polymeric antimicrobial agents

which derive their antimicrobial activity through a chemical or physicochemical

interaction with the organisms. As used in the present specification, the term "polymeric

antimicrobial agent" refers to any nitrogen-containing polymer or co-polymer which has

antimicrobial activity. Preferred polymeric antimicrobial agents include:

polyquaternium-1, which is a polymeric quaternary ammonium compound; and

polyhexamethylene biguanide ("PHMB") or polyaminopropyl biguanide ("PAPB"),

which is a polymeric biguanide. These preferred antimicrobial agents are disclosed in

U.S. Patent Nos. 4,407,791 and 4,525,346, issued to Stark, and 4,758,595 and 4,836,986,

issued to Ogunbiyi, respectively. The entire contents of the foregoing publications are

hereby incorporated in the present specification by reference. Other antimicrobial agents

suitable in the methods of the present invention include: other quaternary ammonium

compounds, such as benzalkonium halides, and other biguanides, such as chlorhexidine.

The antimicrobial agents used herein are preferably employed in the absence of mercury-

containing compounds such as thimerosal.

The most preferred antimicrobial agents are polymeric quaternary ammonium

compounds of the structure:

wherein:

R] and R ₂ can be the same or different and are selected from:

N ⁺ (CH ₂ CH ₂ OH) ₃ X ^" ,

N(CH ₃ ) ₂ or OH;

X ^" is a pharmaceutically acceptable anion, preferably chloride; and n = integer from 1 to 50.

The most preferred compounds of this structure is polyquaternium-1, which is also known

as Onamer M™ (registered trademark of Onyx Chemical Corporation) or as Polyquad ^®

(registered trademark of Alcon Laboratories, Inc.). Polyquaterniurn-1 is a mixture of the

above referenced compounds, wherein X ^' is chloride and R _l5 R ₂ and n are as defined

above.

The above-described antimicrobial agents are utilized in the methods of the

present invention in an amount effective to eliminate substantially or to reduce

significantly the number of viable microorganisms found on contact lenses, in accordance

with the requirements of governmental regulatory agencies, such as the United States

Food and Drug Administration. For purposes of the present specification, that amount is

referred to as being "an amount effective to disinfect" or "an antimicrobially effective

amount." The amount of antimicrobial agent employed will vary, depending on factors

such as the type of lens care regimen in which the method is being utilized. For example,

the use of an efficacious daily cleaner in the lens care regimen may substantially reduce

the amount of material deposited on the lenses, including microorganisms, and thereby

lessen the amount of antimicrobial agent required to disinfect the lenses. The type of lens

being treated (e.g., "hard" versus "soft" lenses) may also be a factor. In general, a

concentration in the range of about 0.000001% to about 0.01% by weight of one or more

of the, above-described antimicrobial agents will be employed. The most preferred

concentration of the polymeric quaternary ammonium compounds of Formula (I) is about

0.001% by weight.

Oxidative disinfecting agents may also be employed in the methods of the present

invention. Such oxidative disinfecting agents include various peroxides which yield

active oxygen in solution. Preferred methods will employ hydrogen peroxide in the range

of 0.3 to 3.0 % to disinfect the lens. Methods utilizing an oxidative disinfecting system

are described in U. S. Patent No. Re 32,672 (Huth, et al.), the entire contents of which are

hereby incorporated in the present specification by reference.

As will be appreciated by those skilled in the art, the disinfecting solutions utilized

in the present invention may contain various components in addition to the above-

described antimicrobial agents, such as suitable buffering agents, chelating and/or

sequestering agents and tonicity adjusting agents. The disinfecting solutions may also

contain surfactants.

The methods of the present invention will typically involve adding a small amount

of a liquid enzyme composition of the present invention to about 2 to 10 mL of an

aqueous solvent or disinfecting solution, placing the soiled lens into the enzyme/solvent

or enzyme/disinfectant solution, and soaking the lens for a period of time effective to

clean or clean and disinfect the lens. The amount of liquid enzyme composition utilized

can vary based on factors such as the amount of aqueous solvent or disinfecting solution

used, but generally it is about 1 to 2 drops. Preferred methods involve adding 1 drop

(approximately 30 μL) to 5 mL of aqueous solvent or disinfecting solution. The soiled

lens can be placed in the aqueous solvent or disinfecting solution either before or after the

addition of the liquid enzyme composition. Optionally, the contact lenses are first rubbed

with a non-enzymatic daily surfactant cleaner prior to immersion in the enzyme/solvent or

enzyme/disinfectant solution. The lens will typically be soaked overnight, but shorter or

longer durations are contemplated by the methods of the present invention. A soaking

time of 4 to 8 hours is preferred. The methods of the present invention allow the above-

described regimen to be performed once per week, but more preferably, every day.

The following examples are presented to illustrate further, various aspects of the

present invention, but are not intended to limit the scope of the invention in any respect.

Example 1

A preferred liquid enzyme composition of the present invention, and a suitable

disinfecting solution for use in combination with that composition, are described below:

A. Liquid Pancreatin Composition

The following liquid enzyme composition represents a preferred embodiment of

the present invention:

Ingredient amount

Pancreatin (9X) 2200 PAU/mL

Sodium borate 7.62% (w/v)

Propylene glycol 50% (v/v)

Water QS

Hydrochloric acid/sodium QS** hydroxide

** corresponds to an amount to adjust the pH to 6.0

Note: (w/v) means weight/volume; (v/v) means volume/volume; and QS means quantity sufficient.

The above formulation was prepared by first sequentially mixing propylene

glycol, purified water, hydrochloric acid and sodium borate together. The solution was

polish filtered (1.2 μm filter) into a sterile receiving tank, and then sterile filtered (0.2 μm

filter). The required amount of pancreatin (about 1-2% w/v) was then dissolved in an

appropriate amount of water and the solution was polish filtered (0.6 μm filter). This

enzyme solution was then sterile filtered (0.2 μm filter) into the sterile receiving tank

containing the sterilized propylene glycol/sodium borate solution. While mixing, the

contents of the receiving tank were then brought to volume with an appropriate amount of

water. The optimal pH of the above formulation is in the range of 6-7; a pH of 6 is most

preferred.

B. Disinfecting Solution

The following formulation represents a preferred disinfecting solution:

Ingredient % (w/v)

Polyquaternium- 1 0.001 + 10% excess

Sodium chloride 0.48

Disodium Edetate 0.05

Citric acid monohydrate 0.021

Sodium citrate dihydrate 0.56

Purified water QS

To prepare the above formulation, sodium citrate dihydrate, citric acid

monohydrate, disodium edetate, sodium chloride and polyquaternium- 1, in the relative

concentrations indicated above, were mixed with purified water and the components

allowed to dissolve by stirring with a mixer. Purified water was added to bring the

solution to almost 100%. The pH was recorded at 6.3 and adjusted to 7.0 with NaOH.

Purified water was added to bring the solution to 100%. The solution was stirred and a

pH reading of 7.0 was taken. The solution was then filtered into sterile bottles and

capped.

Example 2

Preferred liquid subtilisin and liquid trypsin compositions of the present invention

for use in combination with a suitable disinfecting solution, e.g. Example IB., are

described below:

I. Liquid Trypsin Composition

Ingredient amount

Trypsin 2200 PAU/mL

Sodium borate 7.62% (w/v)

Propylene glycol 50% (v/v)

Water QS

Hydrochloric acid/sodium QS** hydroxide

** corresponds to an amount to adjust the pH to 6.0

II. Liquid Subtilisin Composition

Ingredient amount

Subtilisin 900 PAU/mL

Sodium borate 7.62% (w/v)

Propylene glycol 50% (v/v)

Water QS

Hydrochloric acid/sodium QS** hydroxide

** corresponds to an amount to adjust the pH to 6.0

The above liquid subtilisin and trypsin compositions are made in the same manner as the

liquid pancreatin composition, described in Example 1.

Example 3

A comparative study of the effects of varying amounts of borate and propylene

glycol in liquid enzyme compositions was performed. Aliquots of the compositions were

stored in a controlled temperature room (26.7° ± 2°C). At 6 and 12 weeks, aliquots were assayed for enzyme activity by the casein-digestion method described above. Activity

levels were compared with initial levels and expressed as percent remaining activity.

Data demonstrating the criticality of the amounts of sodium borate and propylene glycol

used in liquid enzyme compositions of the present invention versus alternative percentage

amounts, as a function of enzyme stability, is given in Table I below:

TABLE I: COMPARISON OF THE STABILITY OF ALTERNATIVE LIQUID

ENZYME COMPOSITIONS VERSUS A COMPOSITION OF THE

PRESENT INVENTION

Composition 1 2 3 4 5 6

Pancreatin 9X % (w/v) 1.7 1.7 1.7 1.7 1.7 1.7

Boric Acid % (w/v) 0.155 0.155 0.155 0.155 0.155 —

Sodium Borate % (w/v) 0.035 0.035 0.035 0.035 0.035 7.62

Purified Water (qs) 60 50 40 30 10 50

Propylene Glycol % (v/v) 40 50 60 70 90 50

Activity at 6 weeks (% of 71.9 86.6 88.2 92.9 * 97.7 initial activity)

Activity at 12 weeks (% 44 66 65 74 * 98.4 of initial activity)

Initial values showed low activity

Composition 6 illustrates a preferred embodiment of the present invention.

Compositions 2, 3 and 4 contain propylene glycol in an amount required by the present

invention, but do not contain an amount of borate (sodium borate and boric acid) required

by the present invention. Compositions 1 and 5 contain amounts of propylene glycol and

borate outside the ranges required by the present invention.

Activity measurements obtained for compositions 2-4, containing from 50-70%

propylene glycol, showed that similar stability (86.6-92.9% at room temperature) was

obtained after 6 weeks of incubation, while compositions 1 and 5, containing 40 or 90%

propylene glycol, were significantly less stable (71.9% and an undetectable level,

respectively). Compositions 1-5, were less stable (71.9-92.9%) than composition 6

(97.9%) through 6 weeks of incubation. Moreover, composition 6 exhibited a greater

duration of stability, 98.4% at 12 weeks, as compared to a range of 44-74% for

compositions 1-5.

Example 4

Data demonstrating the stability of the liquid enzyme composition of Example 1 at

temperatures of typical storage were ascertained. Aliquots of the composition were stored

in a controlled temperature room (26.7° ± 2°C, RT), or in a chamber held to 35° C. At the

appointed time, aliquots were tested for enzyme activity by the casein-digestion method

described above. Activity levels were compared with initial levels and expressed as

percent remaining activity. The results are presented in Table II below:

TABLE II: EFFECT OF STORAGE TIME ON A LIQUID PANCREATIN COMPOSITION AT ROOM TEMPERATURE (RT) AND AT 35° C

% Remaining Activity

Time (Weeks) RT 35° C

2 94.4 83.0

4 94.0 76.5

6 97.7 81.1

8 99.0 80.2

12 98.4 78.3

The data presented in Table II confirm the stability of liquid enzyme compositions of the present invention. The data are based on a compilation of 4 separate lots and experiments. The data show virtually no deleterious effect on enzyme activity through 12

weeks at room temperature, the final measurement being 98.4%. The liquid enzyme

composition of Example 1 was also effective in maintaining activity at the elevated

temperature of 35°C for 12 weeks, showing approximately a 20% loss in activity.

Example 5

It has been found that one of the protease components of pancreatin, trypsin, is

significantly more stable than one of the other protease components, chymotrypsin. This

finding was confirmed by a study which compared the relative stability of liquid enzyme

compositions containing 0.3% w/v of trypsin and chymotrypsin, respectively. The

compositions were identical to the composition described in Example 1 above, except for

the enzyme component. Aliquots of the compositions were stored in a chamber

maintained at 35°C. At the appointed time, aliquots were tested for enzyme activity by

the azocasein digestion method described below. Activity levels were compared with

initial levels and expressed as percent remaining activity. The results of the study are

presented in Table III below.

Azocasein Method:

The following solutions are used in this assay:

1) Buffer solution: 0.05 M sodium phosphate buffer containing 0.9% sodium

chloride, pH 7.6.

2) Substrate solution: 2 mg ml azocasein in the buffer solution mentioned above.

The assay is initiated by mixing 1 ml of an appropriately diluted (such that the

enzyme activity is in the range of standard curve) enzyme composition in phosphate

buffer with 2 ml of azocasein substrate solution (2 mg/ml). After incubation at 37°C for

20 minutes, the mixture is removed from the incubator and 1 ml of trichloroacetic acid

(14% w/v) is added to stop the enzyme reaction. The mixture is vortexed well and

allowed to stand at room temperature for 20 minutes. After centrifuging at 2500 rpm

(with a Beckman GS-6R Centrifuge) for 15 minutes, the supernatant is filtered with a

serum sampler. 2 ml of the clear yellow filtrate is then adjusted to a neutral pH with 0.4

ml of 0.1 N sodium hydroxide and the absorbance of 440 nm wavelength light is

measured with a spectrophotometer. The amount of azocasein hydrolyzed is calculated

based on a standard curve of known concentrations of azocasein solution developed under

identical conditions. An enzyme ^" activity unit ("AZ U") is defined as that amount of

enzyme which hydrolyzes 1 μg of azocasein substrate/minute at 37°C.

TABLE III: COMPARISON OF THE STABILITY OF LIQUID ENZYME COMPOSITIONS CONTAINING TRYPSIN OR CHYMOTRYPSIN

STORED AT 35°C

% Remaining Activity

Time Trypsin Chymotrypsin

24 hours 100 79.8

1 week 100 7.3

2 weeks 96.0 —

3 weeks 93.2 *

4 weeks 93.2 *

* no measurements taken after 2 week time point, when all activity was lost

The trypsin composition demonstrated an excellent stability profile at 35°C, in

contrast with the chymotrypsin composition, an alternative composition not part of the

present invention. As such, liquid enzyme compositions containing trypsin alone, are the

most preferred compositions of the present invention.

Example 6

Data demonstrating the stability of the liquid trypsin composition of Example 2 at

various temperatures was ascertained. Aliquots of the composition were stored at room

temperature room ("RT"), or at 35°, 40° or 45°C. At the appointed time, aliquots were

tested for enzyme activity by the azocasein method described above. Activity levels were

compared with initial levels and expressed as percent remaining activity. The results are

presented in Table IV below:

TABLE IV: STABILITY OF A LIQUID TRYPSIN COMPOSITION STORED AT VARIOUS TEMPERATURES

% Activity Remaining

Temperature (°C)

Weeks RT 35 40 45

0 100.0 100.0 100.0 100.0

1 98.4 97.8 98.4 61.1

2 100.0 99.4 100.0 56.3

4 100.0 93.2 96.0 42.5

8 100.0 97.8 95.6

12 100.0 95.9 93.8

Example 7

The disinfecting efficacy of the present invention was evaluated by determining

the rate and extent of kill achieved with an aqueous system formed by combining the

liquid enzyme composition and disinfecting solution described in Example 1 above. The

system was tested against six microorganisms: Staphylococcus epidermidis. Pseudomonas

aeruginosa. Serratia marcescens. Candida albicans. Aspergillus fumigatus. and Herpes

simplex. The test procedures and results are described below.

For testing against Staphylococcus epidermidis. Pseudomonas aeruginosa. Serratia marcescens. Candida albicans. and Aspergillus fumigatus the following procedure was

used:

A 0.1 mL volume of inoculum (10 colony forming units/mL) was first added to a

10 mL volume of the disinfecting solution of Example 1, followed by the addition of 2

drops of the liquid enzyme composition of Example 1. A similarly inoculated 10 mL

volume of the disinfecting solution of Example 1 was used as a control. The solutions

were maintained at room temperature throughout the test. Each microorganism and test

solution was tested individually. Sets of four replicate (n = 8) samples were tested for

each organism.

At selected time intervals of 1, 2, 3, 4, 6, 8 and 24 hours, a 1 mL volume of the inoculated test solution containing Staphylococcus epidermidis. Pseudomonas aeruginosa.

Serratia marcescens. Candida albicans. or Aspergillus fumigatus was removed and

appropriate serial dilutions were made in sterile 0.9% sodium chloride solution dilution

blanks. Pour-plates were prepared with soybean-casein digest agar containing 0.07%

Asolectin and 0.5% Polysorbate 80. At Time 0, a 1.0 mL volume of the saline control

was removed and serial dilution pour-plates were prepared using the same recovery

medium and dilution blanks. The Time 0 saline control count was used as the initial

count. The pour-plates were incubated at 30°-35°C for appropriate incubation periods.

The number of surviving organisms at each time interval was then determined. The results are summarized in Tables V - IX below.

For testing against Herpes simplex the following procedure was used:

5 mL of the disinfecting solution of Example 1 containing one drop of the liquid

enzyme composition of Example 1, and a control solution containing 5 mL of the

disinfecting solution, were inoculated with 125 microliters of Herpes simplex to yield a

Tissue Culture Infective Dose-50 (TCID ₅₀ ) of approximately 1 x 10 ⁵ . At time intervals of

1, 2, 3, 4, 6 and 8 hours, an aliquot of the test or control solution was removed and

neutralized by mixing 1:1 with AOAC neutralizer (40 g Asolectin and 280 mL

polysorbate 80 in 1 liter of 0.25 M phosphate buffer at pH 7.2) and diluting 10-fold in

Minimum Essential Medium (MEM). One mL aliquots were plated into VERO

monolayers, 4 replicates per dilution and allowed to absorb for 30 minutes at 37° ± 1° C

in 5 ± 1% CO ₂ in air. The sample from each time point was run in duplicate. The results

are summarized in Table X below.

TABLE V: ANTIMICROBIAL ACTIVITY: S. EPIDERMIDIS

SAMPLE TIME LOG REDUCTION (HR)

Liquid pancreatin 1 2.7 ± 0.2 composition and disinfecting solution of Example 1

2 3.3 ±0.1

3 3.6 ±0.2

4 4.2 ± 0.2

6 4.8 ± 0.2

8 4.9 ±0.1

24 4.8 ±0.1

Control (disinfecting 1 2.2 ±0.1 solution of Example 1)

2 2.7 ±0.1

3 3.1 ±0.1

4 3.3 ±0.1

6 3.7 ±0.1

8 4.1 ±0.3

24 4.9 ±0.1

TABLE VI: ANTIMICROBIAL ACTIVITY: P. AERUGINOSA

SAMPLE TIME (HR) LOG REDUCTION

Liquid pancreatin 1 2.2 ±0.1 composition and disinfecting solution of Example 1

2 2.7 ±0.1

3 3.1 ±0.2

4 3.1 ±0.2

6 3.6 ±0.1

8 3.9 ±0.2

24 5.0 ±0.2

Control (disinfecting 1 1.7 ±0.1 solution of Example 1)

2 2.1 ±0.1

3 2.4 ±0.1

4 2.6 ±0.1

6 3.1 ±0.2

8 3.5 ±0.1

24 4.8 ± 0.4

TABLE VII: ANTIMICROBIAL ACTIVITY: S. MARCESCENS

SAMPLE TIME LOG REDUCTION (HR)

Liquid pancreatin 1 0.8 ±0.1 composition and disinfecting solution of Example 1

2 1.2 ±0.1

3 1.5 ±0.1

4 1.9 ±0.0

6 2.6 ±0.1

8 3.0 ±0.1

24 4.8 ± 0.6

Control (disinfecting 1 0.1 ±0.1 solution of Example 1)

2 0.4 ±0.1

3 0.6 ±0.1

4 0.9 ±0.1

6 1.1 ±0.1

8 1.4 ±0.1

24 3.3 ±0.1

TABLE VIII: ANTIMICROBIAL ACTIVITY: £ ALBICAT

SAMPLE TIME LOG REDUCTION (HR)

Liquid pancreatin 1 0.1 ±0.1 composition and disinfecting solution of Example 1

2 0.1 ±0.1

3 0.1 ±0.1

4 0.1 ±0.0

6 0.1 ±0.0

8 0.2 ±0.1

24 0.2 ± 0.0

Control (disinfecting 1 0.1 ±0.1 solution of Example 1)

2 0.0 ±0.1

3 0.1 ±0.0

4 0.1 ±0.0

6 0.1 ±0.0

8 0.1 ±0.1

24 0.1 ±0.1

TABLE IX: ANTIMICROBIAL ACTIVITY: A, FUMIGATUS

SAMPLE TIME LOG REDUCTION (HR)

Liquid pancreatin 1 0.1 ±0.1 composition and disinfecting solution of Example 1

2 0.1 ± 0.0

3 0.1 ±0.0

4 0.2 ±0.1

6 0.3 ±0.1

8 0.3 ±0.1

24 0.5 ±0.1

Control (disinfecting 1 0.1 ±0.1 solution of Example 1)

2 0.1 ±0.1

3 0.1 ±0.0

4 0.1 ±0.1

6 0.2 ±0.1

8 0.3 ±0.1

24 0.5 ±0.1

TABLE X: ANTIMICROBIAL ACTIVITY: HERPES

SIMPLEX

SAMPLE TIME LOG REDUCTION (HR)

Liquid pancreatin 1 0.9 ± 0.7 composition and disinfecting solution of Example 1

2 0.7 ± 0.5

3 1.4 ± 1.8

4 3.7 ± 0.4

6 3.7 ± 0.3

8 3.9 ± 0.1

Control (disinfecting 1 0.2 ± 0.2 solution of Example 1)

2 0.2 ± 0.3

3 0.2 ± 0.2

4 0.3 ± 0.2

6 0.2 ± 0.2

8 0.3 ± 0.4

As illustrated in Tables V-X, the log reductions achieved with the liquid

enzyme/disinfecting solution combination were generally greater than the log reductions

achieved with the disinfecting solution control. This difference was statistically

significant for £, _. epidermidis. aeruginosa. £ _* marcescens and ϋ. simplex. The

antimicrobial activity against C. albicans and A. fumagitus was about equal.

Example 8

The disinfecting efficacy of another embodiment of the present invention was

evaluated by determining the rate and extent of kill achieved with an aqueous system

formed by combining the subtilisin liquid enzyme composition of Example 2 and the

disinfecting solution of Example 1. The system was tested against Serratia marcescens.

The test procedure in Example 7 was followed. Sample times were 2, 4, 24 hours and 7

days, and log reductions were calculated for 4 and 24 hours. The test results, expressed as log reductions, are presented in Table XI below.

TABLE XI: EFFECTS OF A SUBTILISIN CONTAINING LIQUID ENZYME

COMPOSITION ON THE ANTIMICROBIAL ACTIVITY OF A

POLYQUATERNIUM- 1 DISINFECTING SOLUTION

LOG REDUCTION

Time Disinfecting Solution Liquid Enzyme (subtilisin) Control + Disinfecting Solution

4 hours 0.9 ± 0.1 1.3 ± 0.2

24 hours 3.7 ± 0.4 3.4 ± 1.0

As illustrated in Table XI, the liquid enzyme composition containing subtilisin had an

enhancing effect on the antimicrobial activity of the disinfecting solution of Example 1, at 4 hours.

Example 9

The disinfecting efficacy of a further embodiment of the present invention was

evaluated by determining the rate and extent of kill achieved with an aqueous system

formed by combimng the liquid trypsin composition of Example 2 and the disinfecting

solution described in Example 1. The system was tested against Serratia marcescens.

Staphylococcus aureus. Pseudomonas aeruginosa. Candida albicans and Fusarium solani.

The test procedure in Example 7 was followed. Sample times were 4, 6 and 24 hours.

The test results, expressed as log reductions are presented in Table XII below.

TABLE XII: EFFECTS OF A TRYPSIN CONTAINING LIQUID ENZYME

COMPOSITION ON THE ANTIMICROBIAL ACTIVITY OF A

POLYQUATERNIUM- 1 DISINFECTING SOLUTION

LOG REDUCTION

Liquid Trypsin Disinfecting

Microorganism Time Composition and solution (hours) disinfecting alone solution

S. marcescens 4 1.9 ± 0.1 1.3 ± 0.1

6 2.0 ± 0.6 1.5 ± 0.1

24 4.4 ± 0.8 3.4 ± 0.5

S. aureus 4 3.1 ± 0.2 2.6 ± 0.2

6 3.5 ± 0.3 3.0 ± 0.0

24 4.9 ± 0.0 4.6 ± 0.3

P. aeruginosa 4 3.8 ± 1.0 2.3 ± 0.9

6 4.2 ± 0.7 2.9 ± 1.0

24 4.9 ± 0.0 4.4 ± 0.5

C. albicans 4 0.1 ± 0.1 0.1 ± 0.2

6 0.1 ± 0.2 0.1 ± 0.2

24 0.1 ± 0.2 0.2 ± 0.3

F. solani 4 3.8 ± 0.6 3.4 ± 1.3

6 4.5 ± 0.4 3.6 ± 0.3

24 4.6 ± 0.2 4.3 ± 0.5

O 96/40854 PC17US96/09689

Example 10

The following comparative example demonstrates the effectiveness of the liquid

enzyme compositions of the present invention with different disinfecting agents. The

effect of the liquid enzyme compositions of the present invention, in particular the liquid

enzyme composition of Example 1 (referred to below as "Liquid Enzyme" or "LE"), on

the antimicrobial activity of a polyquaternium- 1 multi-purpose solution (Example IB

formulation) and a polymeric biguanide multi-purpose solution (ReNu ^® Multi-Purpose

Solution) was evaluated.

Two drops of Liquid Enzyme were added to 10 mL of either the polyquaternium- 1

disinfecting solution or the polymeric biguanide disinfecting solution. The respective

disinfecting solutions alone were also tested as controls. The protocol described in

Example 7 was followed. Microbiological data, in the form of log reductions achieved

against Staphylococcus epidermidis. Pseudomonas aeruginosa. Serratia marcescens.

Candida albicans. and Aspergillus fumigatus. were ascertained at 4 hours. The results are

presented in Table XIII below.

TABLE XIII: ANTIMICROBIAL ACTIVITY OF A POLYQUATERNIUM- 1 MULTI-PURPOSE SOLUTION AND A POLYMERIC BIGUANIDE MULTI¬ PURPOSE SOLUTION WITH LIQUID ENZYME*

** LE = the liquid pancreatin composition of Example 1

The results demonstrate no deleterious effects of Liquid Enzyme on the polyquaternium- 1

disinfecting solution, and an enhancement of the S marcescens. P _^ aeruginosa and

S. epidermidis kill after 4 hours. Conversely, the Liquid Enzyme composition had a

negative effect on the antimicrobial activity of the polymeric biguanide disinfecting

solution. These results illustrate the unexpected results obtained with a preferred method

of the present invention, wherein a polyquaternium- 1 disinfecting solution is combined

with a liquid enzyme composition of the present invention.

Example U

A 135 day study comparing the efficacy of the compositions and methods of the

present invention with other known compositions and methods was performed. Three

different clinical observations were made: 1) frequency of Type III and Type IV lens

deposits (Rudko grading system); 2) frequency and reasons for lens replacement; and 3)

frequency of significant slit-lamp findings. "Type III" and "Type IV" lens deposits are

considered as heavily deposited lenses. A "slit lamp finding" is defined as an abnormality

observed on the cornea, by a clinician using an optometrist's slit-lamp apparatus.

Three different cleaning formulations and their associated methods were compared

with a method of the present invention ("LE"): 1) "Historical control" - a data set

comprised of 5 different studies wherein the lens was cleaned daily with a surfactant cleaner followed by an 8 hour soaking in a disinfecting solution combined with a once per

week, 8 hour soaking of the lens in a disinfecting solution containing a dissolved

pancreatin tablet; 2) "Protocol 1" - a protocol utilizing a polyquaternium- 1 disinfecting

solution containing citrate (Example IB formulation) wherein the lens is rubbed daily for

several seconds with this solution and then soaked 8 hours in this solution, combined with

a once per week, 8 hour soaking of the lens in a polyquaternium- 1 disinfecting solution

(Example IB formulation) containing a dissolved pancreatin tablet; 3) "Protocol 2" - a

protocol utilizing a polymeric biguanide disinfecting solution containing a surfactant,

wherein the lens is rubbed daily for several seconds, then soaked in this solution for 8

hours, combined with a once per week soaking of the lens in a polymeric biguanide

disinfecting solution containing a surfactant and a dissolved subtilisin tablet for a

minimum of 15 minutes, followed by removing the lens and placing it in a fresh

polymeric biguanide solution containing a surfactant and soaking for 8 hours; and 4)

"LE" - a method and composition of the present invention wherein the lens is rubbed

daily with a surfactant cleaner, followed by an 8 hour soaking in 5 mL of a

polyquaternium- 1 solution (Example IB formulation) and 1 drop of the liquid enzyme

composition of Example 1 ("Liquid Enzyme"). Table XIV, below, provides a tabulated

comparison of the compositions and protocols of this study.

TABLE XIV: COMPARISON OF CLEANING AND DISINFECTING COMPOSITIONS AND PROTOCOLS

HISTORICAL PROTOCOL 1 PROTOCOL 2 LE

CLEANING Daily, with a Daily, with Daily, with ReNu ^® Daily, with a surfactant cleaner polyquaternium- 1 polymeric surfactant cleaner solution biguanide solution

DISINFECTING Daily (8 hrs) with Daily (8 hrs) with Daily (8 hrs) with Daily (8 hrs) with a disinfecting polyquaternium- 1 ReNu ^® polymeric polyquaternium- 1 solution solution biguanide solution solution

ENZYMATIC Weekly (8 hrs) Weekly (8 hrs) Weekly (min. of 15 Daily (8 hrs) with a

CLEANER with a with minutes) with polyquaternium- 1 disinfecting polyquaternium- 1 ReNu ^® polymeric solution containing solution solution containing biguanide solution 1 drop of Liquid containing a a dissolved containing a Enzyme dissolved pancreatin tablet, dissolved subtilisin pancreatin tablet no separate tablet, followed by disinfecting step disinfecting step

The results are presented graphically in Figures 1-3. The protocol including the

liquid enzyme composition of the present invention ("LE") demonstrated superior

efficacy in maintaining lenses free of Type III and Type IV deposits, as compared to the

other known methods and compositions. As shown in Figure 1, the present invention

eliminated Type III and Type IV lens deposits (0.0 % frequency) while the other protocols

exhibited a 6.5 - 8.4% lens deposit frequency.

Figure 2 further demonstrates the cleaning efficacy of the compositions and

methods of the present invention. Lenses cleaned with the LE composition needed

replacement, due to lens deposits, on a frequency of 0.3% as compared to a range of 1.4 -

8.5% for the other compositions and methods studied. The LE composition also

demonstrated lower slit-lamp findings as compared to the three other compositions and

methods (Figure 3).

The invention in its broader aspects is not limited to the specific details shown and

described above. Departures may be made from such details within the scope of the

accompanying claims without departing from the principles of the invention and without

sacrificing its advantages.