AU2004201867B2 - Process for cleaning and disinfecting contact lenses - Google Patents

Description

AUSTRALIA

Patents Act 1990 ALCON LABORATORIES, INC.

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Process for cleaning and disinfecting contact lenses The following statement is a full description of this invention including the best method of performing it known to us:- PROCESS FOR CLEANING ANMD DISINFECTING CONTACT LENSES Backeround-of the Invention: The present invention relates to the field of products for treating contact lenses.

More Particularly, the invention relates to an improved process wherein contact lenses can be cleaned and disinfected with a single product containing one or more polycarboxylates, polysulfonates or polyphosphates. It has been found that these agents effectively remove deposits of proteins and other materials from contact lenses.

Products for treating contact lenses have generally been classified based on the intended use or function of the products. Most products have been classified as either cleaners or disinfectants. However, there are also a number of associated products which can be generally classified as rewetting drops or conditioning solutions. Although there have been attempts to accomplish two or more functions with a single product, such is attempts have generally had limited success, because combining the components required to perform multiple functions in a single product tends to reduce the effectiveness of those components. For example, combining surfactants commonly used to clean contact lenses with antimicrobial agents commonly used to disinfect contact lenses may reduce the activity of one or both of these agents. Thus, from a purely scientific standpoint, the combining of two or more functions in a single product has been discouraged.

1A The perspective of the patient is much different from that of the scientist. The primary concerns of the patient are typically effectiveness and convenience. The latter concern is particularly important among wearers of disposable contact lenses, who tend to be highly motivated toward convenience. The emphasis that patients place on convenience has led to a rapid rise in the popularity of disposable contact lenses capable of supporting either daily or extended wear. Depending on the planned replacement and wearing, schedules, these lenses are most commonly cleaned and dis infected daily, and occasionally weekly or biweekly. The result is that many convenience-driven patients who originally sought relief from the rigors of lens care are being fitted with lenses that require daily, albeit less rigorous, care. Such patients place a premium on products that are simple and straightforward to use. By their very nature, frequent replacement lenses worn for daily wear are presumed to require the use of fewer or milder cleaning products.

Thus, both patient preference for convenience and the fitting of frequent replacement lenses for daily wear has created a desire for easy-to-use disinfectants that can also be is used to clean, soak and rinse lenses.

If the care of the patients' contact lenses becomes too complicated, the patients may fail to comply with the cleaning and disinfection instructions provided by their physicians. Such non-compliance is a major concern of ophthalmologists and optometrists. Repeated failures to clean and/or disinfect contact lenses properly can lead 2o to serious vision problems, such as corneal abrasions, infections, inflammation of the conjunctiva, and so on.

The use of a disinfecting solution to also clean contact lenses has been proposed previously. However, such disinfecting solutions have typically included one or more .2surfactants as the active cleaning component. A product of this type is currently marketed by Bausch Lomb as ReNu® Multi-Purpose Solution.

In view of the foregoing circumstances, there is a need for improved products and processes for cleaning and disinfecting contact lenses in an efficacious but convenient manner.

Summary of the Invention: Accordingly, in one aspect the present invention provides a use of at least one polycarboxylate or corresponding acid, or a combination thereof, as a protein removal agent and cleaning agent in an aqueous single solution for both cleaning and disinfecting a contact lens, said solution additionally comprising an opthalmically acceptable antimicrobial agent in an amount effective to disinfect the lens.

In a second aspect, the present invention provides a use of at least one protein removal agent and cleaning agent which consists essentially of a polycarboxylate or corresponding acid, or a combination thereof, in the manufacture of an aqueous single solution for both cleaning and disinfecting a contact lens, said solution additionally comprising an opthalmically acceptable antimicrobial agent in an amount effective to disinfect the lens.

In a third aspect, the present invention provides a use of an aqueous single solution in a process of both cleaning and disinfecting a contact lens, wherein the solution comprises: an opthalmically acceptable antimicrobial agent in an amount effective to disinfect the lens; at least one protein removal agent and cleaning agent which consists essentially of a polycarboxylate or corresponding acid, or a combination thereof, in an amount effective to facilitate the removal of protein deposits from the lens; and an aqueous vehicle therefor.

In a fourth aspect, the present invention provides a use of at least one polycarboxylate or corresponding acid, or a combination thereof, as a protein removal agent in the manufacture of a single solution for removing protein deposits from a contact lens.

In a fifth aspect, the present invention provides a use of a single solution in a process of removing protein deposits from a contacts lens, wherein the solution comprises: at least one protein removal agent which consists essentially of a polycarboxylate or corresponding acid, or a combination thereof, in an amount effective to facilitate the removal of protein deposits from the lens; and an aqueous vehicle therefor.

The ability to clean contact lenses effectively by means of such a solution is surprising, since prior products for cleaning contact lenses have typically contained one or more surfactants. The solution of the present invention preferably does not contain a surfactant, nor an enzyme. It has been discovered that a surfactant or an enzyme is not necessary to achieve a significant degree of cleaning on mildly deposited lenses. More specifically, it has been discovered that a solution which contains polycarboxylates citrate) or corresponding acid, but no surfactant and no enzyme achieves a significant degree of cleaning when utilized in accordance with the process of the present invention.

In a sixth aspect, the present invention provides a process for cleaning and disinfecting a contact lens with a single solution which comprises performing the following steps on a daily basis: rinsing the lens with the same single solution to remove all debris; and soaking the lens in the same single solution for a time sufficient to disinfect the lens; wherein the single solution comprises a protein removal and cleaning agent which consists essentially of a polycarboxylate or corresponding acid, or a combination thereof for removing protein deposits from the lens in an amount effective to clean the lens, an opthalmically acceptably antimicrobial agent in an amount effective to disinfect the lens; and an aqueous vehicle therefor.

In a preferred embodiment, a small amount of the single solution is rubbed onto the surface of the lens.

The polycarboxylate or corresponding acid utilised in the present invention is preferably selected from the group consisting of citric acid and salts thereof sodium, potassium or ammonium citrate, or mixtures thereof), succinic acids and salts thereof, tartaric acid and salts thereof, malonic acid and salts thereof, maleic acid and salts thereof, ethanol diglycinate and diethanol glycinate.

The use of citrate as a component of various types of cleaning products is known. For example, it has been used as a builder in laundry and dishwashing detergents, wherein it has generally been combined with surfactants to achieve cleaning. It has also been utilized in denture cleansers, dentifrices and mouthwashes. The use of citrate in solutions for disinfecting contact lenses is described in United States Patent No. 5,037,647. However, that patent describes the use of citrate as a complexing agent, so as to prevent binding between. polymeric quaternary ammonium compounds and contact lenses. It does not describe the use of citrate as a cleaning agent in a process of the type described and claimed herein. A rinsing, disinfecting and storage solution for contact lenses known as Opti-Free® (marketed by Alcon Laboratories, Inc.) contains a citric acid/sodium citrate buffer system, but this product has not been utilized in a process for cleaning and disinfecting contact lenses. Similarly, the following patent publications mention citric acid and/or salts thereof as possible components of products for treating contact lenses, but do not disclose the use of these substances in conjunction with a process for cleaning and disinfecting contact lenses with a single, surfactant-free solution: Japanese Patent Publication No. JP 59 45,399 (Kokai Tokkyo Koho); French Patent No. 2,544,880; and United States Patent Nos.

4,599,195; 4,609,493; and 4,614,549.

Citrate is believed to enhance the removal of protein and other deposits through complexation/solubilization actions. More specifically, citrates are known to complex with some biological molecules and to render them more water soluble because of such association. For example, the interaction of citrate with cationic organic molecules is well documented; this includes lysozyme, which is cationic at physiological pH values. Citrate has also been shown to have the ability to displace lysozyme bound by polymers. In terms of cleaning soft contact lenses, citrate is believed to counteract the binding of lysozyme by the lens, rendering the protein more soluble in the aqueous media of the cleaning solution via complexes ion pairs) or salt formation, thereby facilitating its removal from the lens such as when rubbed and/or rinsed. Additional removal of lysozyme may also take place during the time when lenses are subsequently soaked in the solution during the disinfection stage of the process.

Calcium is another common component of soft lens deposits, occurring as inorganic salts and/or as an element of mixed deposits. In the latter instance, calcium ions can act as a "cross bridge" through ionic bonding and link protein, lipid or mucus-type soilants as well as microbial cells containing the surface. While chelation of calcium by citrate effects removal of discrete inorganic deposits, it is believed that it may also have an impact on mixed deposits by disrupting intermolecular bridging, thereby weakening the structural integrity of the deposits and making them more susceptible to the shearing/dispersing/solubilizing effects of rubbing the solution on the lenses.

The cleaning effect achieved with the above-described solutions is accomplished by combining the solvent action of the water contained in the solution and the chemical cleaning mechanisms of citrate or other polycarboxylate or a polysulfonate or polyphosphate, and preferably by combining: the mechanical effect of rubbing the soiled lenses with a small amount of the above-described cleaning and disinfecting solution, the solvent action of the water contained in the solution, and the abovedescribed chemical cleaning mechanisms of citrate or the other polycarboxylates, polysulfonates and polyphosphates described herein.

Description of Preferred Embodiments: Although various antimicrobial agents may be utilized in the present invention, the preferred antimicrobial agent is a polymeric quaternary ammonium agent known as "polyquaternium-1". Polyquaternium-1, also known as "Onamer (registered trademark of Millmaster Onyx Group) and "Polyquad®" (registered trademark of Alcon Laboratories, Inc.), is a chloride salt of a polymeric quaternary ammonium compound having the chemical name of a-4-[l-tris(2-hydroxyethyl)ammonium-2-butenyl] poly[1dimethylammonium-2-butenyl] -o-tris(2-hydroxyethyl) ammonium chloride.

The use of this antimicrobial agent to disinfect soft, hydrophilic contact lenses is described in United States Patents Nos. 4,407,791; 4,525,346; and 5,037,647. The entire contents of the above-cited patents are hereby incorporated in the present specification by reference.

The solutions of the present invention will contain one or more antimicrobial agents in an amount effective to eliminate or substantially reduce the number of viable microorganisms present on the contact lenses being treated, in accordance with criteria established by the United States Food and Drug Administration and corresponding health authorities in other countries. Such an amount is referred to herein as "an amount effective to disinfect". The amount of antimicrobial agent required for this purpose may vary depending on the relative activity of the particular antimicrobial agent selected and other factors familiar to those skilled in the art, such as the tonicity of the solution. The preferred polymeric quaternary ammonium compounds described above are utilized in concentrations of from about 0.00001 to about 3.0 percent by weight, based on the total volume of the solution preferably from about 0.0001 to 0.1 w/v%.

The solutions of the present invention contain a cleaning agent selected from polycarboxylates and corresponding acids, in an amount effective to facilitate the removal of proteins, calcium and other materials from contact lenses. As utilized herein, the prefix "poly-" means that the molecule contains more than one acid/salt group. Polycarboxylates which may be utilized in the present invention include, for example, citrate, succinate, tartrate, malonate, maleate, ethanol diglycinate, diethanol glycinate, and other such compounds having a molecular weight of approximately 90 to 600.

The above-described polycarboxylates or corresponding acids are utilized in an amount effective to clean the lens. This amount will generally be a molar concentration ranging from 0.013 to 0.13 moles/liter for the salt forms of the compounds, and a molar concentration equivalent to that range for the acid forms of the compounds. The use of a concentration in this range is believed to be necessary in order to achieve cleaning of contact lenses, as described herein.

The cleaning and disinfecting process of the present invention preferably includes three basic steps: cleaning the lenses by means of rubbing a small amount one to four drops) of a surfactant-free, aqueous solution containing a disinfecting amount of an antimicrobial agent and one or more of the above-described cleaning agents over the surfaces of the lenses for at least 10 seconds, rinsing the lenses thoroughly to remove all debris, and soaking the lenses in an amount of the same solution sufficient to completely cover the lenses for a period of from at least four hours to overnight. Suitably the rubbing is performed by placing the lens in the palm of one hand, applying the cleaning solution to the lens, and then rubbing the cleaning solution over both surfaces of the lens with a finger of the other hand. The lenses are preferably allowed to soak in a closed container, such as a contact lens case, and are also preferably rinsed before being replaced in the eye. The above-described process should be repeated on a daily basis.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

In the specification, unless stated otherwise, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge, or any combination thereof, at the priority date, was part of the common general knowledge in the art.

The present invention is further illustrated by means of the following examples, which are presented for purposes of illustration only and should not be deemed to be limiting in any way.

Example 1 The following formulation is the preferred surfactant-free cleaning and disinfecting solution for use in the process of the present invention.

Polyquad® Sodium Chloride Disodium edetate Citric acid monohydrate Sodium citrate dihydrate Purified Water

W/VYO

0.001 10% excess 0.52 0.05 0.021 0.56 q.s.

This solution may be prepared as follows. The purified water, sodium citrate dihydrate, citric acid monohydrate, disodium edetate, sodium chloride and Polyquad® are combined and then dissolved by stirring with a mixer. Additional purified water is then added to bring the solution to 100%. The pH is then adjusted (if necessary) to pH The following examples demonstrate the cleaning effect of the citrate-containing formulations utilized in the present invention.

Example 2 An in vitro study was conducted to determine the cleaning effect of the solution described in Example 1 above Opti-Free® Rinsing, Disinfecting and Storage Solution) on lenses from the four FDA soft lens polymer groupings. The study compared the solution's cleaning ability to that of Bausch Lomb's ReNu® Multi-Purpose Solution to on heavily deposited soft contact lenses. ReNu® Multi-Purpose Solution (sometimes referred to herein as "ReNu®-MPS") is a sterile, isotonic solution that contains boric acid, edetate disodium, poloxamine, sodium borate and sodium chloride; it is preserved with DYMED (polyaminopropyl biguanide) 0.00005%.

New unworn) contact lenses of the following types were utilized in the study: Is Ls Lns Manufactur Polyer a tiupD Ham Content I Soflens Bausch Lomb Polymacon 38% n B&L 70 Bausch Lomb Lidoficon A Pernaflex CooperVision Surfilcon A 74 I Durasoft 2 Wesley-Jessen Phemfllcon A 38 Hydrocurve II SBH BufllconA IV Durasoft 3 Wesley-Jessen Phemfilcon A -9- *Group I Low-water-content, nonionic polymers Group UI High-water-content. nonionic polymers Group Mii Low-water-content ionic polymers Group IV High-water-content, ionic polymers The lenses were deposited with an artificial tear solution prepared to mimic common lens deposits. This artificial tear solution was prepared by dissolving sodium phosphate and sodium biphosphate in a beaker containing 90% of volume of purified water, USP. Dissolution was achieved by stirring on a magnetic stir plate with a magnetic stir bar for 10-15 minutes. Lysozyme in an amount to equal 0.05% final concentration by weight was added and allowed to dissolve, following which the solution was brought to 100% volume with purified water, LISP. The pH of the solution was approximately 7.4 with no adjustment.

The test lenses were rinsed -with sterile 0.9% sodium chloride solution and blotted dry with lint-free towels, after which the lenses were placed in clean glass vials. Five milliliters (mL) of the artificial tear solution was added to each vial. The vials were stoppered and clamped and placed in a preheated water bath and heated at 90'C for minutes. Following the water bath treatment, the vials were removed and allowed to cool to room temperature. The lenses were then removed from the vials, rubbed, and rinsed with 0.9% sodium chloride solution remove loosely bound protein. The lenses were placed in clean glass vials with 5 mL. of OPT-PUREO sterile saline and stoppered.

The test procedure consisted of an initial rating of the in vitro deposited lenses by two trained raters following the FDA recommended Rudko method. Mfter initial rating the lenses were transferred to a third person who perforned cleaning by following a procedure similar to that which is normally recommended for the daily cleaning of human 10 worn lenses: The lenses were placed in the palm of the hand and two drops of cleaning solution from the coded bottles were applied to each lens surface. The lenses were then gently rubbed for 40 seconds and subsequently rinsed thoroughly with the test solution.

Deposited Group IV lenses were put through three cleaning cycles for both solutions since neither produced significant cleaning with this group of lenses after just one cycle of cleaning. The lens deposits were then rated again using the Rudko method by the two raters not involved in the cleaning steps.

The in vitro deposited lenses were rated before and after rubbing and rinsing by two technicians who were masked with respect to solutions used. The ratings were converted into numerical scores. The numerical scores for all lenses in a set were then added to obtain a cumulative score, and that score was divided by the number of lenses in that set to obtain an average score for a lens in that set. The overall cleaning efficacy of each solution was computed as a percentage utilizing the average rating of cleaned lenses and that of deposited lenses prior to cleaning. The results are presented below: 1 5 CommpsieL of Comparative ing Effiacy of Opti-Fire® Rinsing. Disinfecting and Storage Solution and ReNu@ Multi-Purpose Solution Using Converted Rudko Numerical Scores GopI Pronduct .so, Opti-FMre ReNu® 36 I1 Grouol Pmduct B&L0 7 Permaflex Composite Opti-Free® 10 86 48 ReNu® 8 65 36 imu'p nr £mduct Dursoft 2 Hydocur II Composite Opti-Free® 39 54 46 ReNu® 77 45 61 Gmlup IV Durasoft 3 Product Cycle Cycle 2 Cycle 3 Opti-Free® 3 11 53 ReNu® 6 19 64 *NOTE: In a prior study with Group I lenses using the same procedures as those described herein, the composite cleaning scores for Opti-Free® and ReNu@ were 58 and respectively. The average cleaning of the Group I lenses based on these two studies is therefore 59 (Opti-Free®) and 63 (ReNu®).

The foregoing results show that both the solution of Example 1 and ReNu® Multi- Purpose Solution removed a substantial amount of protein from in vitro deposited soft contact lenses. The cleaning efficacy of these two solutions was found to be dependent on the lens brand for Groups II and EI. Overall, the cleaning efficacy of the two products in this study was comparable.

-12- A study was conducted to evaluate the role of citrate in cleaning Group IV contact lenses Durasoft This study compared the cleaning effect of the solution described in Example 1 above Opti-Free® Rinsing, Disinfecting and Storage Solution) with modified versions of that solution, and with ReNu® Multi-Purpose Solution. The composition of the solutions utilized in the study is presented in the following table: Table 1 Comparative Compositions of Test Solutions' Ingredient Citric Acid Monohydrate, USP Sodium Citrate, USP Disodium EDTA (Edetate Disodium),USP Sodium Chloride, USP Mannitol, USP Polyquad. NOC Sodium Hydroxide, NF and/or Hydrochloric Acid, NF 92245 0.021 w/v in Solutions 92-260 92-2601 None None None 0.05 0.48 None None q.s. to adjust pH to 7.0 q.s. 100 0.48 None None q.s. to adjust pH to 7.0 q.s. 100 None 0.05 0.48 1.0 None q.s. to adjust pH to 7.0 q.s. 100 92-263 None None 0.05 None None None q.s. to adjust pH to 7.0 Opti-Freeb 0.021 0.56 0.05 0.48 None 0.001 excess) q.s. to adjust pH to Purified Water, USP q.s. 100 q.s. 100 The test procedures used in the study are described below.

13- I. Preparation of Deposition Solution A. Phosphate Buffered Saline 1.311 g of sodium phosphate (monobasic, monohydrate), 5.749 g sodium phosphate (dibasic, anhydrous), and 0.9 g sodium chloride s were dissolved in distilled water and the solution was brought to volume (1000 mL) with distilled water. The final concentration of each component in the solution was: sodium phosphate, 0.05 M; sodium chloride, 0.14 M. The final pH was 7.4 (drops of NaOH or phosphoric acid may be added if pH adjustment is needed).

B. Dansyl-lysozvme Solution: 750 mg of dansyl-lysozyme was dissolved in 500 mL phosphate buffered saline. The final concentration of dansyl-lysozyme was mg/mL.

is II. Lens Deposition Procedure Each lens was immersed in a Wheaton glass vial (8 mL capacity) containing 5 mL of dansyl-lysozyme solution (1.5 mg/mL in PBS). The vials were closed with a plastic snap cap and incubated in a constant temperature water bath at 37 0 C for 24 hours. After incubation, each deposited lens was rinsed by dipping into three consecutive beakers containing 50 mL of distilled water to remove any excess of deposition solution and loosely bound dansyl-lysozyme, and blotted gently with a laboratory towel (KayPees). These lenses served as the soiled lenses for 14 total protein determination (control lenses) as well as for the evaluation of cleaning efficacies.

Ill. Protein Determination on Control Lenses Five deposited lenses were used as control lenses to determine the total dansyl-lysozyme deposition on the lenses. For this purpose, each deposited lens was extracted with 10 mL SDS extraction solution (0.1 M Tris-HCl, pH 8.0, containing 2% SDS, 0.1% Dithiothreitol, and 0.1 mM EDTA) in a screw-capped glass scintillation vial (20 mL capacity). The extraction was conducted by shaking the vial with a rotary shaker (Red Rotor) at room temperature for at least 48 hours. The amount of dansyl-lysozyme extracted from each lens was assessed by fluorescence measurement with a fluorospectrophotometer. The total protein was calculated based on the standard curve established for dansyl-lysozyme solution.

IV. Cleanin Procdure Lenses were placed in Wheaton glass vials (12 mL capacity) containing mL of test solution, with five lenses being used for each test solution.

The vials were capped with plastic snap caps and gently agitated on a rotary shaker at room temperature for six or twenty-four (24) hours.

The lenses were removed from their respective test solutions after soaking and were rinsed with distilled water as described previously under "Lens Deposition Procedure." The lenses were then subjected to an extraction procedure as described under "Protein Determination on Control Lenses." 15 Both the test soaking solutions and the lens extraction solution were subjected to fluorescence measurements for protein determination.

V. Protein Determination Quantitative determination of protein for the soaking solutions and the lens extracts were carried out by use of a fluorospectrophotometer. Two mL of solution were required for each measurement. The fluorescence intensity was measured by setting the excitation/emission wavelength at 252 nm/530 nm with excitation/emission slits of 2.0 nm/8.5 nm. Dansyllysozyme concentrations for each solution and extract were calculated 10 o based on the slope established from linear standard dansyl-lysozyme curves developed under the identical instrumental conditions for SDS-extraction buffer and phosphate buffered saline respectively.

The following table shows a summary of the cleaning results for the six and twenty-four (24) hours soaking for each test solution.

s1 Table 2 Dansyl-Lysozyme Removed (ullens RT S by Evaluated SolutionS n 2254 2600 92.2601 92-03 Oi-Free ReNu@-MPS 6 Hours 65.08 24.26 23.57 2430 71.83 36.79 ±1.66 t 0.90 1.25 ±1.60 ±2.15 2.53 24 Hours 87.67 28.01 28.64 37.92 100.92 44.53 1.60 0.85 1.23 3.08 1.85 3.61 16- The results of this study indicate that Opti-Free® and Solution 92-2545, both containing citrate, removed more dansyl-lysozyme from lenses than Solutions 92-2603,92-2600, and 92-2601, all of which contained no citrate. The differences were significant based upon statistical analysis (p 0.05). Opti-Free® and Solution 92-2545 (Opti-Free® minus Polyquad®) also removed more dansyl-lysozyme from the deposited lenses than did ReNu® Multi-Purpose Solution, evaluated under the same experimental conditions. These results were also statistically significant (p 0.05).

The cleaning results observed during a prior experiment involving the same solutions and procedures were substantially similar to the results presented above. The results observed during the prior experiment are presented in the following table: Table 3 Dansyvl-Lvsozvme Removed (gfllens SD) by Evaluated Solutions lime 92-2545 922600 92601 2-2 Opt i-Fr® ReNuO-MPS 6 Hours 6836 26.62 27.98 28.46 72.68 43.10 1.72 1.15 1.59 1.61 1.83 1.37 24 Hours 82.28 36.16 34.00 4732 92.12 45.00 ±7.87 ±1.55 ±1.12 ±1.28 ±3.71 ±0.88 Another study similar to the study described in Example 3 above, but which involved somewhat different procedures, was also conducted to further evaluate the role of citrate in cleaning Group IV contact lenses Durasoft The study evaluated the -17cleaning effect of four of the same solutions tested in Example 3 92-2545; 92-2600; 92-2601; and 92-2603). The procedures used in this study are described below.

1. Preparation of Deposition Solution A. £QMpMsiin ~Ingredients 3- Lysozyme 0.15 Sodium Phosphate, Basic 0.689 Sodium Chloride 0.9 Sodium Hydroxide, 5N q.s. pH 7.4 Purified Water q.s. 100 B. Procdure Sodium chloride was dissolved in a beaker containing 80% of the total required volume of purified water. Sodium phosphate was added and dissolved while stirring. Lysozyme was then added and allowed to dissolve. The pH of the solution was adjusted to 7.4 with sodium hydroxide, and the volume of the solution was adjusted with water.

II.iren Procedu1Q~~lre A. Stuhdy Design Lenses were numbered from one to ninety. After deposition, ten lenses were not cleaned and used as control lenses to determine average lysozyme uptake per lens. The remaining eighty lenses were divided into four groups of twenty lenses and each group was cleaned with the respective test solutions. Ten cleaning solution samples from each group were pulled for analysis after six hours and the remaining ten from each group after 24 hours.

18.- B. Lens DepositiorLProcedure Each lens was immersed in a glass vial containing 5 ml, of the deposition solution. Vials containing the deposition solutioni and lenses were incubated for 24 hours at 37 0 C. Each deposited lens was rinsed by dipping into three (3) consecutive beakers containing 50 ml, of purified water to remove any excess of deposition solution and loosely bound protein.

C. £sntil Ten deposited lenses were used as control lenses to determine lysozyme deposition on the lenses. After rinsing as described above these were gently blotted to remove any excess water and placed into screw cap glass culture tubes. The tubes were stored in the freezer until analysis. Additionally, five new lenses were included to provide non-deposited lens values for the ninhydrin procedure described below.

D. Cleaning Erose4Urr, Six HouL Smples Ten lenses per test solution were gently blotted to remove excess Water following rinsing. The lenses were placed in plastic vials containing 5 ml, of test solution. The vials and their contents were gently agitated for six (6) hours. The lenses were removed from their respective test solutions after cleaning and the solutions refrigerated until analyzed.

Twnty-four_ Hour Samples Ten lenses per test solution were gently blotted to remove excess water following rinsing. The lenses were placed in plastic vials containing 5 mL of 19 test solution. The vials and their contents were gently agitated for twenty-four (24) hours. The lenses were removed from their respective test solutions after cleaning and the 24 hour cleaning solutions along with the control lenses and six hour cleaning solutions were assayed for protein using the ninhydrin s procedure.

E. Protein Analysis of Solutions and Control Lenses The samples were evaluated by means of a ninhydrin assay procedure. In this procedure, proteins are hydrolyzed under alkaline conditions to their amino acid components which react with ninhydrin to form a colored complex. The latter can be quantitated by measuring absorbance at 570 nm. For this study a standard curve was prepared covering a range of 5.00 to 15.00 ig lysozyme.

The curve had a slope of 0.050 AU/gg, a y intercept of 0.021 AU and a Rsquared value of 0.9811. The quantity of protein in a sample was determined using this standard curve and multiplying by appropriate dilution factors.

The following table shows a summary of the cleaning data for the six and twenty-four (24) hours cleaning: Lysozyme Removed (jgens) by Evaluated Solutions 22-2545 92-2600 2-2601 92-2602 6 Hours 47.52 -6.40 15.02 2.20 24 Hours 52.92 -2.33 -11.08 19.62 This study shows that significantly (p <0.05) more lysozyme is cleaned from lenses when citrate is present than when it is absent. Thus, the results demonstrate that citrate has cleaning properties that are effective in removing lysozyme from contact lenses.

In another cleaning study, which used a HPLC assay procedure instead of the s above-described ninhydrin method, similar results were obtained, as shown in the following table: Lysozyme Removed (uglens) by Evaluated Solutions 22-2545 92-2600 92-2601 92-260a 6 Hours 39.0 6.6 6.2 3.7 24 Hours 95.3 10.6 7.7 While there is not absolute agreement between these two studies (in part due to substraction of large blank value and the lesser precision associated with the ninhydrin assay) with all solutions, both studies clearly show that the 92-2545 solutions contain significantly higher levels of lysozyme than the others. Thus, the importance of citrate in removing protein deposits is demonstrated by these studies.

21

Claims (14)

1. 2. The method according to claim i, comprising soaking the lens in the single solution for at least four hours to remove protein deposits attached to the lens.
2. 3. The method according to claim 1 or 2, further comprising applying the single solution to the lens for a time and under conditions sufficient to remove debris and disinfect the lens before soaking the lens in the single solution.
3. 4. The method of claim 3, wherein applying the single solution to the lens for a time and under conditions sufficient to remove debris and disinfect the lens comprises rubbing a small amount of the single solution over the surface of the lens. The method of claim 4, wherein rubbing a small amount of the single solution over the surface of the lens is for at least 10 seconds.
4. 6. The method according to any one of claims 1 to wherein said method further comprises rinsing the lens to thereby wash away the removed protein deposits. COMS ID No: ARCS-171950 Received by IP Australia: Time 15:33 Date 2007-12-11 11/12 2007 TUE 15:26 FAX +612 82311099 0010/018 0 23 0 O 7. The method according to any one of claims 1 to 6, wherein said method is performed on a daily basis.
5. 8. The method according to any one of claims 1 to 7, wherein the protein deposits are removed by virtue of the polycarboxylate or corresponding acid interacting ND chemically with the protein deposits. o
6. 9. The method according to any one of claims 1 to 8, wherein the single solution is surfactant-free. c 10. The method according to any one of claims 1 to 9, wherein polycarboxylate or corresponding acid is present in the single solution in an amount from 0.013 to 0.13 moles per litre.
7. 11. The method according to any one of claims 1 to wherein the polycarboxylate or corresponding acid is selected from the group consisting of citric acid, one or more salts of citric acid, succinic acid, one or more salts of succinic acid, tartaric acid, one or more salts of tartaric acid, malonic acid, one or more salts of malonic acid, maleic acid, one or more salts of maleic acid, ethanol diglycinate, diethanol glycinate and mixtures thereof.
8. 12. The method according to any one of claims 1 to 11, wherein the polycarboxylate or corresponding acid is citric acid, sodium citrate, potassium citrate, ammonium citrate or a mixture thereof.
9. 13. The method according to any one of claims 1 to 12, wherein the single solution comprises an opthalmically- acceptable antimicrobial agent. COMS ID No: ARCS-171950 Received by IP Australia: Time 15:33 Date 2007-12-11 11/12 2007 TUE 15:26 FAX +612 82311099 0011/018
10. 14. The method according to claim 13, opthalmically-acceptable antimicrobial polyquaternium-1. wherein the agent is
11. 15. The method according to any one of claims 1 to 14, wherein the contact lens is a soft lens polymer having a water content of at least about
12. 16. The method according to any one of claims 1 to wherein the contact lens is an ionic polymer.
13. 17. The method according to any one of claims 1 to wherein the single solution comprises about 0.02% (w/v) citric acid, about 0.056% sodium citrate, about 0.05% disodium EDTA, about 0.48% sodium chloride, about 0.001% polyquaternium-1 and wherein said single solution has neutral pH.
14. 18. The method according to any one of claims 1 to 17 substantially as described herein with reference to the examples. Dated this ELEVENTH day of DECEMBER, 2007 Alcon Laboratories, Inc. Patent Attorneys for the Applicant: F B RICE CO COMS ID No: ARCS-171950 Received by IP Australia: Time 15:33 Date 2007-12-11