Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L12/00—Methods or apparatus for disinfecting or sterilising contact lenses; Accessories therefor
  • A61L12/02—Methods or apparatus for disinfecting or sterilising contact lenses; Accessories therefor using physical phenomena, e.g. electricity, ultrasonics or ultrafiltration
  • A61L12/04—Heat

Definitions

• This invention relates to methods for cleaning contact lenses, particularly to methods involving the use of enzyme solutions, and more particularly to methods using enzyme solutions at elevated temperatures and to methods for accomplishing a one-step process for thermal disinfection and cleaning of contact lenses.
• Procedures include mechanical rubbing of the lens, ultrasonic cleaning, hypertonic solutions, surfactant cleaners, enzymatic cleaners, and oxidative cleaners.
• proteases or peptidases have long been known to degrade proteins. This function of proteases or peptidases has been used for cleaning soft contact lenses.
• Lo, Silverman and Korb, J. Am. Optom. Assoc., 40 (11) (1969) published a finding that commercial protease-containing detergents specifically removed protein from contact lenses.
• U.S. 3,910,296 describes the removal of proteinaceous material on the surface of contact lenses, especially soft contact lenses, by contacting the lens for a time sufficient to clean the lens with a substantially isotonic, aqueous solution containing an effective amount of a protease such as papain.
• Non-toxic compounds containing sulfhydryl groups are included to activate the papain.
• U.S.4,096,870 describes the removal of proteinaceous material on the surfaces of hydrophilic gel contact lenses (soft lenses) by contacting the lenses with an aqueous suspension of pancreatin without absorption of pancreatin into the lens structure.
• Pancreatin is an enzyme mixture purified from animal pancreas that contains protease, lipase (lipid or fat-digesting enzyme) and carbohydrase (carbohydrate-digesting enzyme) activities and is active without the addition of compounds containing sulfhydryl groups.
• the pancreatin is commercially formulated as tablets using sodium chloride and boric acid to provide a measured amount of pancreatin for cleaning contact lenses.
• U.S.4,285,738 describes the removal of proteinaceous matter lodged on the surface of a contact lens by immersion of the lens in an aqueous bypertonic composition containing urea or a salt of guanidine and a reducing agent such as a sulfite, a pyrosulfite, etc., and preferably by adding a proteolytic enzyme, even in an amount not effective when the enzyme is used in the absence of urea or a guanidine salt.
• a reducing agent such as a sulfite, a pyrosulfite, etc.
• European Patent Application Publication No. 0005131 describes hypertonic cleaning solutions for soft contact lenses wherein the solution contains a lipolytic enzyme (or lipase) and, optionally, a proteolytic enzyme (or protease). The resulting degradation products are removed by rinsing. The lenses are then disinfected by boiling in a physiological saline solution. Another description of cleaning solutions for contact lenses containing a combination of enzymes can be found in Japanese Kokai Tokkyo Kbho JP 82/48,712 (Chem. Abs.97:78933d).
• Enzyme cleaning of contact lenses typically is achieved by placing the lenses in an enzyme cleaning solution for a period varying from two hours to overnight. Generally the cleaning is then followed by disinfection of the lens in saline solution.
• the disinfection step is required because enzyme cleaning solutions are typically non-sterile and are potential growth media for microorganisms. Since the lens must be disinfected prior to insertion in the eye, disinfection must always follow this type of enzyme cleaning. Further, protein which is deposited on the lens is believed to be baked on when the heat disinfection process is used, making removal more difficult or impossible. An ideal cleaning and disinfection regime always would remove protein deposits prior to any heat disinfection step.
• the present invention provides a substantially more convenient and efficacious method for cleaning and disinfecting contact lenses, particularly soft or bydrophilic lenses.
• enzyme cleaning and thermal disinfection can be accomplished conveniently in one step. Any lens which can tolerate thermal disinfection temperatures can be treated in one step by this technique.
• This method can also clean contact lenses which were uncleanable by prior art methods.
• the method of the invention comprises contacting a contact lens with a solution containing a heat stable proteolytic enzyme at an elevated temperature, that is sufficiently high to soften lipid deposits on said lens, for a predetermined period of time to clean said lens.
• this invention surprisingly and conveniently cleans contact lenses, particularly soft contact lenses, having light to moderate deposits of protein and lipids during a normal heat disinfection cycle, making it extremely convenient to both clean and disinfect such lenses in one convenient step.
• heat disinfection prior to complete cleaning compromises both the lens and the eye because protein deposits are baked onto the lens by the elevated temperatures. Indeed, protein deposits do build up on lenses and become impossible to clean off by prior art methods, thus necessitating the discarding of such lenses.
• it now has been found that some lenses that would have been discarded as uncleanable by prior art methods are remarkably cleaned by the method of the present invention and can continue to be used.
• a "heat stable” (thermostable) enzyme is an enzyme that has a half-life of activity, tig, of fifteen minutes or more at 60°C.
• FIGS. 1A-1D are photographs taken at 320x of representative fields of sectors of a contact lens cleaned with solutions having various concentrations of enzyme in accord with the present invention.
• FIGS. 2A-2D are photographs taken as 320x of representative fields of sectors of another contact lens cleaned with solutions having various concentrations of enzyme in accord with the present invention.
• FIGS. 3A-3F are photographs of sectors of a contact lens which were cleaned by various methods for comparison and then stained with dye to visualize the amount of protein remaining on the lens sector.
• FIGS.4A-4F are photographs of sectos of another contact lens which were cleaned by variousmethods for comparison and then stained with dye to visualize the amount of protein remaining on the lens sector.
• proteinaceous and lipid materials on the surface of soft hydrophilic contact lenses are removed and the lenses disinfected by heating the lenses in a solution containing a heat stable proteolytic enzyme for a period of time sufficient to achieve both cleaning and disinfection.
• the proteolytic enzyme is employed in solution at a temperature sufficiently high and for a suitable period of time to:
• the cleaning solution is preferably isotonic or substantially isotonic.
• the lens can be rinsed briefly with saline and ready to wear. While it is desirable that the heating process meet the minimum requirements for heat disinfection, thereby achieving both cleaning and disinfecting in a one-step process, this technique can be utilized in temperatures lower than those required for disinfection providing that a temperature of at least 60°C is used. This may be necessary for certain types of lenses which cannot tolerate conventional disinfection temperatures.
• Any proteolytic enzyme that is heat stable or that can be stabilized in solution so that it has a t1 ⁇ 2 of fifteen minutes or more at a temperature of 60°C is useful for the practice of the present invention.
• Enzymes suitable for the practice of this invention are thermolysin, papain and chymopapain (available from Calbiochem Behring or Sigma Chemical Co.,) caldolysin, (see European Patent Application Publication No.0024182), aminopeptidase I, endopeptidase of Bacillus stearothermophilus thermitase, thermcmycolin, and the like.
• papain in its pure crystalline form or in its crude form has been found highly useful in the practice of the present invention. I have found that papain retains its activity in solution for a sufficient length of time at temperatures below about 82°C to obtain remarkable and rapid cleaning in accord with the invention.
• a temperature of at least 60°C should be used for cleaning contact lenses in accord with the method of the present invention.
• the temperature should be at least 70°C and, more preferably, 80°C or higher.
• the only limitations on temperature are those imposed by the nature of the contact lenses and by the thermostability of the enzyme utilized.
• the temperature should not be too high so that the lens is deformed or otherwise degraded, or so that the enzyme is denatured before cleaning can be accomplished. It is highly preferred that the temperature cycle used for cleaning be the same as that required for heat disinfection, i.e. at least 80°C for a minimum of 10 minutes.
• the time required for cleaning will vary depending upon the concentration of enzyme in the cleaning solution, the composition of the cleaning solution, the temperature used for cleaning, the amount of protein and lipid deposits on the lens, etc. It has been found that very good cleaning for normally dirty lenses can be obtained using the enzymes thermolysin, papain and chymopapain with the temperature cycle and time period for conventional heat disinfection processes (reaching at least 80°C for minimum 10 minutes). Heating for 15 minutes at 80°C using 1.0mg/ml crude papain (Prolase 300) has been found to clean most lenses. More than one cleaning cycle may be used to clean lenses having unusually heavy deposits.
• the cleaning solution can contain, in addition to the proteolytic enzyme, other agents to stabilize the enzyme, to enhance and/or facilitate the activity of the enzyme, facilitate the removal of enzyme degradation products, etc., or agents to enhance cleaning by other mechanisms.
• agents include, for instance, buffering agents, surfactants, solvents, hypertonic solution additives, sulfhydryl containing compounds, oxidizing agents, reducing agents, lipases, carbohydrases, and the like, etc.
• an amount of calcium ion in the range of 1 to 10mM is important for the thermostability of thermolysin and caldolysin. Cysteine has been found to enhance the cleaning activity of many proteases.
• Polyethylene glycol (PEG, MW: 4000-6000) has been found to be beneficial as a wetting agent in amounts as low as 0.02% (w/v).
• a simple borate-buffered isotonic saline solution containing a low concentration (5mM) of calcium ion has proved effective for enzymatic cleaning using thermolysin.
• a typical composition for this buffer (which is hereinafter called CBS buffer) is 0.9% Nad, 10mM boric acid, 0.4mM sodium borate, and 5mM CaCl 2 , which is hereinafter called CBS buffer.
• a conventional buffer system comprising 0.02% KH 2 PO 4 , 0.2% NaHCO 3 ; 0.08% Na 2 EDTA, 0.73% NaCl, 0.02% PEG 4000 and 0.1% cysteine hydrochloride (hereinafter PBS solution) has been found to provide highly effective cleaning.
• PBS solution 0.02% KH 2 PO 4 , 0.2% NaHCO 3 ; 0.08% Na 2 EDTA, 0.73% NaCl, 0.02% PEG 4000 and 0.1% cysteine hydrochloride
• thermostable buffer is meant a buffer which maintains a nearly constant pH when heated in the cleaning and disinfection cycle in accord with the present invention.
• a buffer which contains a heat unstable component such as NaHCO 3 , which decomposes liberating CO 2 ) is not thermostable.
• a suitable thermostable buffer system for use with papain comprises 10mM boric acid, 5mM to 10mM sodium borate, 2mM disodium EDTA (ethylenediaminetetra acetic acid), 125mM sodium chloride, 0.02% PEG 4000, and 0.1% cysteine.
• the particular buffer system preferably is chosen to control the pH of the solution for optimal cleaning and to provide a pH which is compatible with that of the patient's eye.
• This buffering function can be controlled in many ways.
• the buffer system may be a thermostable system or the amount of volatile or unstable components can be carefully controlled to keep variations of pH within acceptable limits.
• the buffer system used for cleaning solutions in accord with the present invention at least should provide control of pH in a range wherein: (1) the enzyme has good activity; (2) the components of the cleaning solution remain in solution; and (3) eye irritation is minimized even though the lens is not rinsed thoroughly.
• Enzymes preferred for the practice of this invention are natural proteases such as those listed above which have good activity within a broad range of pH.
• cysteine oxidizes to form cystine, which is quite insoluble between pH 2 and 8.
• the pH of tears is variable with the norm considered to be 7.4 to 7.5. However, it can be as low as 5.2 or as high as 8.35.
• a typical pH range of comfort for the average eye is considered to fall between 6.6 and 7.8.
• the approximate limits of pH outside of which tissue epithelial damage occurs are 4.0 and 10.0.
• thermolysin-based cleaning solution comprises 1.5mg thermolysin, 0.87mg boric acid, 1.2mg sodium borate .1H 2 O, 0.75mg calcium chloride .2H 2 O, 1.0mg cysteine hydrochloride, 7.3mg sodium chloride, and distilled H 2 O to make 1ml.
• 0.4mg of PEG 4000 also is added.
• the ingredients can be formulated in a tablet with or without the enzyme, the enzyme being supplied separately in a packet, if desired. Alternatively, the entire composition can be packaged as a powder to facilitate dissolution. Formulations may differ depending upon whether the intended use is for regular maintenance or heavy duty cleaning.
• a papain-based cleaning solution can be formulated from the following ingredients: 0.5mg cystalline papain or 5.0mg crude papain (commercially available as Prolase 300) , 3.1mg boric acid, 10.9mg sodium borate.1H 2 O, 3.7mg disodium EDTA, 36.5mg sodium chloride, 1.0mg PEG 4000, 5.0mg cysteine, and distilled H 2 O to make 5ml.
• this papain formulation can be provided as a powder or in tablet form. The enzyme can be included in the tablet or powder, or packaged separately.
• thermolysin, papain and chyraopapainrbased cleaning solutions The heating and disinfection which accompanies heat stable enzyme cleaning in accord with the present invention has additional benefit.
• Conventional enzyme solutions in physiological buffers are non-sterile. Because these solutions can support growth of microorganisms, the lens must be disinfected after enzyme cleaning prior to wearing. Debris from the growth of these microorganisms during the conventional cleaning step may renain and be baked onto the lens in the course of disinfection. Heat disinfection of the enzyme solution during cleaning in accord with the present invention prevents this problan.
• a Hydromarc hydrophilic soft contact lens which was heavily and uniformly coated during human use was treated first with Allergan commercial papain preparation and second with Alcon commercial pancreatin preparation according to the furnished directions. No cleaning was detectable by microscopic analysis.
• the lens was then divided by razor blade into four equal sectors, one piece being placed in each of four solutions of CBS buffer containing 0, 0.1, 0.4 or 1.6mg/ml thermolysin.
• the lens sectors were incubated at 80°C for 2 hours.
• the lens sectors were rinsed with saline, stained with Coomassie Brilliant Blue Stain for one minute, rinsed with an aqueous methanol solution and photographed at 320x magnification using 35 mm Kodak Plus-X-pan film.
• a photograph of a representative field from each piece is illustrated in FIG. 1A through 1D, respectively. It is readily seen that dramatic cleaning occurred with 0.4mg/ml thermolysin and almost complete cleaning occurred with 1.6mg/ml.
• a Syntex CSI hydrophilic soft contact lens was heavily and uniformly coated during human use.
• the lens was not cleaned by either Allergan's papain preparation or Alcon's pancreatin preparation. Subsequently, the lens was divided into sectors and the sectors incubated as in Example 1 with 0.0, 0.2, 0.4, or 1.6mg/ml thermolysin.
• the lens sectors were analyzed as in Example 1. Photographs of representative fields of the sectors cleaned with enzyme concentrations of 0, 0.2, 0.4 and 1.6mg/ml are shown in FIG. 2A through 2D, respectively. Again, increasing enzyme concentrations yielded increasingly clean lens sectors. A concentration of 1.6mg/ml thermolysin produced essentially clean lens surfaces.
• thermolysin concentrations of 0.2 - 0.4mg/ml produced essentially clean lenses.
• thermolysin (E) with 0.5mg/ml thermolysin (Calbiochem-Behring) dissolved in CBS buffer;
• thermolysin-treated lens sectors were designated by the letter E in Figures 3 and 4. Example 5.
• a Bausch & Lomb Softlens and a CSI lens were boiled for 30 minutes in a solution containing 0.1% Lysozyme (w/v) in a modified CBS buffer.
• the modified CBS buffer solution was formulated as follows: 14mM H 3 BO 3 ; 5.5mM Na 2 B 4 O 7 .10H 2 O; 5mM CaCl 2 .2H 2 O; 5.7mM Cysteine.HCl; and 125mM NaCl.
• the lenses were incubated at 84°C for 30 minutes in modified CBS buffer solution containing 0.5mg/ml of thermolysin.
• the denatured protein deposited from the Lysozyme solution was completely removed from both lenses.
• thermolysin solution 0.5mg/ml buffered with CBS containing 1mg/ml cysteine hydrochloride
• Control-Treatment (A) a course granular continuous coating
• Prolase 300-Treatment (C) same results as for treatment (B) as described above.
• Lens 2 another Hydromarc lens, and lens 3, a CSI lens, showed similar results to those for lens 1.
• Example 7 The experiment of Example 7 was repeated using additional sectors from each of the same three lenses.
• the cleaning solutions were the same as in Example 7 with the exception that 0.25mg/ml of crystalline papain was substituted for the Prolase 300 of treatment (C) . Results were virtually identical to those of Example 7.
• Thermolysin-Treatment (B) about 30% of the lens surface was still coated.

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• 1985
  • 1985-01-17 EP EP19850900894 patent/EP0168487A1/de not_active Withdrawn
  • 1985-01-17 AU AU38896/85A patent/AU3889685A/en not_active Abandoned
  • 1985-01-17 WO PCT/US1985/000079 patent/WO1985003247A1/en unknown

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