Abstract:
A composition for conditioning a contact lens comprising a surfactant comprising a copolymer of hydrophobe and hydrophile blocks the structure:  
     HO-(hydrophobe) x -(hydrophile) y -(hydrophobe) x -H  
     where x and y are integers reflecting the respective hydrophile and hydrophobe blocks of said copolymer.

Description:
STATEMENT OF RELATED APPLICATION  
       [0001]    This application claims the benefit under 35 U.S.C.§ 119(e) of United States Provisional application serial No. 60/332,065 filed Nov. 21, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to an improved contact lens conditioning solution. More particularly, it relates to a solution that renders the contact lens surface more wettable so that proteins, lipids, and other tear film substituents do not adhere and form deposits on the lens surface.  
           [0003]    Contact lenses are typically made of plastic and, therefore, are hydrophobic or water repellant. Since the use of the first contact lenses, there has been a recognized need to use conditioning agents for contact lenses to render the contact lenses more hydrophilic or “wettable.” The purpose of these conditioning agents is to render the lens surface more wettable so that proteins, lipids, and other tear film substituents do not adhere and form deposits thereon. Such deposits reduce the comfort and safety of the lens, and also interfere with optical clarity since it is important that the tear fluid spread evenly over the surface of the lens.  
           [0004]    Surface-active agents have been employed in conditioning solutions in an attempt to alleviate the problems associated with contact lens wear, such as insertion comfort and dry eye. Surface-active agents are adsorbed on the lens surface and allow ready spreading of tears when the lenses are inserted, thus making them more comfortable to wear. Representative wetting agents and viscosity modifiers have included: cellulose derivatives, such as cationic cellulosic polymers, hydroxypropyl methylcellulose, hydroxyethylcellulose and methylcellulose; polyols, such as polyethylene glycol, glycerine and polyethylene oxide (PEO) containing polymers; polyvinyl alcohol; and polyvinyl pyrrolidone. Such additives may be used in a wide range of concentrations as is known in the art. These types of agents, however, do not adsorb to a significant level to the lens, and therefore do not provide prolonged comfort.  
           [0005]    Polymers which provide a more prolonged comfort level typically need to be employed in high concentration to create a higher viscosity, and thereby prolong the retention of the polymer. The use of these high viscosity agents, however, may cause blurring of vision when the lens is first placed in the eye, and also creating a sticky feeling of the lens to the user, making lens insertion and handling difficult. More hydrophobic polymers can adsorb more readily to the lens, and can be formulated at lower concentrations to provide better lubrication. The disadvantage, however, of a more hydrophobic polymer is that the polymer may also act as a substrate for deposits and as a consequence, make the lens more prone to filming and lipid deposit.  
           [0006]    Therefore, there exists a need for a conditioning solution that renders a contact lens surface more wettable so that proteins, lipids, and other tear film substituents do not adhere thereto and form deposits. There is a further need for such a solution that may be used on hard, RGP and hydrogel (soft) contact lenses. Such a conditioning solution would greatly enhance the cleaning operations now required.  
           [0007]    Numerous presently known contact lens conditioning solutions contain multiple surface-active agents. While such solutions are effective, the necessity of multiple ingredients complicates the manufacturing and regulatory process. Thus, a solution containing only one surface-active agent that provides effective conditioning would be advantageous over multiple-component systems.  
           [0008]    For example, U.S. Pat. No. 5,773,396 to Zhang, et al. discloses a contact cleaning and wetting solutions containing two surfactants: one having an HLB below 18 and another having an HLB above 18. The solutions also contain an additional wetting agent, such as cellulosic materials. All of the polyoxyethylene-polyoxypropylene block copolymers disclosed therein are terminated in primary hydroxyl groups.  
           [0009]    U.S. Pat. No. 5,209,865 to Winterton, et al. discloses a contact lens conditioning solution containing two surfactants: one poloxamine having an HLB of seven or below and a poloxamer also having an HLB of seven or below. All of the polyoxyethylene-polyoxypropylene block copolymers disclosed therein are terminated in primary hydroxyl groups.  
           [0010]    Disinfecting solutions are known in the art containing only one surfactant. However, the surfactant is not employed to condition the lens, but to enhance the antimicrobial efficacy of the solution. Furthermore, none of the published references known to the applicant teach a conditioning solution containing a polyoxyethylene-polyoxypropylene block copolymer terminated in secondary hydroxyl groups.  
           [0011]    WO 92/16244 teaches a disinfecting solution having improved antimicrobial properties containing a non-ionic surfactant, preferably polyethylene glycol fatty alcohol ethers such as PEG 24®. No mention is made of improved conditioning properties or of any polyoxyethylene-polyoxypropylene block copolymers.  
           [0012]    WO 00/35500 teaches a disinfecting solution having improved polymeric biguanide stability. The solution contains a poloxamine surfactant having an HLB value of at least 27. No mention is made of improved conditioning properties or of any polyoxyethylene-polyoxypropylene block copolymers.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention relates to a conditioning solution for contact lenses that comprises a polyoxyethylene-polyoxypropylene terminated in secondary hydroxyl groups having the following structure:  
           HO-(hydrophobe) x -(hydrophile) y -(hydrophobe) x -H  
           [0014]    where x and y are integers reflecting the respective hydrophile and hydrophobe blocks of said copolymer.  
           [0015]    Such surfactants are generally known as “Poloxamers” and sold under the trademark “Pluronic R”® (BASF), and typically have a molecular weight of between and about 1,800 and about 9,000.  
           [0016]    The present surfactants provide the advantages of those known in the art because the more hydrophobic portions of the polymers can adsorb more readily to the lens, and can be formulated at lower concentrations to provide better lubrication. However, they overcome the disadvantages of known surfactants because the hydrophilic portions of the polymer will not act as a substrate for deposits. Thus, the solution according to the present invention forms a uniform hydrophilic film on a lens surface for which proteins and lipids have very little affinity. As such, a contact lens contacted by the solution will have a coating that provides a prophylactic effect to the lens.  
           [0017]    It is, therefore, an object of the present invention to provide a conditioning solution which renders a contact lens-surface more wettable so that proteins, lipids, and other tear film substituents are less likely to adhere thereto and form deposits.  
           [0018]    It is a further object of the present invention to provide for such a solution that may be used on hard, RGP, and soft contact lenses.  
         DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
         [0019]    The present invention provides a prophylactic action in preventing and/or retarding tear film deposits on the surfaces of contact lenses. The ingredients form a uniform hydrophilic film on the lens surface for which proteins and lipids have very little affinity. Furthermore, although some minor amounts of tear film substituents may adhere to the film, the protective film can be sacrificially removed, along with any adherence, by digitally cleaning the contact lens with any appropriate contact lens cleaner. The removal of the sacrificial film is virtually complete so that the contact lens is “renewed” to its native clean state. It is envisioned that the present solution may be used separately from other ophthalmic solutions, or may also be incorporated into a cleaning, conditioning or disinfecting solution, thus aiding in compliance with existing protocols rather than adding an extra solution, product or care step to achieve the desired prophylactic results.  
           [0020]    The conditioning solution for contact lenses according to the present invention comprises a polyoxyethylene-polyoxypropylene nonionic surfactant terminated in secondary hydroxyl groups.  
           [0021]    The polyoxyethylene-polyoxypropylene nonionic surfactant terminated in secondary hydroxyl groups is a surface-active agent which will be tolerated in the formulations. Such a surfactant exhibits a high affinity for hydrophobic (lipophilic) surfaces due to the presence of the secondary hydroxyl groups on the termina of the surfactant. Thus, these surfaces active agents strongly adhere to those hydrophobic regions of the contact lens and render them hydrophilic. This adherence forms a “barrier” to potential absorbance, and keeps them from the surface of the lens. Furthermore, this increase in hydrophilicity simultaneously decreases the thermodynamic driving force for protein and lipid absorption, thereby retarding tear film deposits.  
           [0022]    It has been surprisingly discovered that in contrast to the teachings of the prior art, even those surfactants having a hydrophile-lipophile balance (HLB) greater than seven are suitable for use in the conditioning solution of the present invention. Preferably, the HLB of the surfactant is between 7 and 18; most preferably about 12.  
           [0023]    The HLB of a surfactant is known to be a major factor in determining the emulsification characteristics of a non-ionic surfactant. In general, surfactants with lower HLB values are more lipophilic, while surfactants with higher HLB values are more hydrophilic. The HLB values of various polyoxyethylene-polyoxypropylene nonionic surfactants terminated in secondary hydroxyl groups are provided by BASF Performance Chemicals in published commercial literature, employed herein by reference.  
           [0024]    Such surfactants are polyoxyethylene/polyoxypropylene condensation polymers terminated in secondary hydroxyl groups. They may be synthesized by first creating a hydrophile (polyoxyethylene) of desired molecular weight by the controlled addition of ethylene oxide to ethylene glycol. In the second step of the synthesis, propylene oxide is added to create hydrophobic blocks on the outside of the molecule. Such block copolymers can be obtained commercially from the BASF Corporation under the trademark PLURONIC® R.  
           [0025]    Copending application Ser. No. 09/963,972, filed Sep. 26, 2001, also by the present inventor, discloses disinfecting solutions containing hydrogen peroxide and polyoxyethylene-polyoxypropylene block copolymers terminated in secondary hydroxyl groups. The surfactants are taught as enhancing the antimicrobial properties of hydrogen peroxide. In contrast to the above-mentioned copending application, hydrogen peroxide is not a required element of the present invention; and is preferably substantially absent from the solutions of the present invention. In fact, while such agents may be present in some embodiments, the solutions of the present invention are preferably substantially free of disinfecting effective (bactericidal) amounts of antimicrobial agents such as hydrogen peroxide, quaternary ammonium agents, polymeric biguanides, benzalkonium chloride, and thimerosal. However, preferred solutions may contain non-disinfecting amounts of such agents as a preservative (bacteriostatic). While exact bactericidal and bacteriostatic amounts of the various antimicrobial agents are easily determined by one of skill in the art, by way of non-limiting example, it is noted that a preservative amount of hydrogen peroxide is typically between 10 ppm and 0.1%, while a disinfecting amount is typically greater than 1%.  
           [0026]    The preferred surfactant is a block copolymer of ethylene oxide and propylene oxide having the formula:  
                         
 
           [0027]    wherein x and y are integers from 1 to 350 reflecting the respective polyethylene oxide and polypropylene oxide blocks of said copolymer. The polyoxyethylene component of the block copolymer constitutes from 10 to 90 weight percent of the block copolymer. Preferably, the polyoxyethylene component of the block copolymer constitutes from 10 to 50 weight percent of the block copolymer. In another preferred embodiment of the present invention, the polyoxyethylene component of the block copolymer constitutes less than 50 weight percent of the block copolymer. Most preferably, the polyoxyethylene component of the block copolymer constitutes about 40 weight percent of the block copolymer.  
           [0028]    Surfactants having a total molecular weight of 1000 to about 20000 are preferred. More preferred are those surfactants having a molecular weight of 1200 to 3100. Most preferred are those surfactants having a molecular weight of about 2650.  
           [0029]    The amount of surfactant component varies over a wide range depending on a number of factors, for example, the specific surfactant or surfactants being used, the other components in the composition and the like. Often the amount of surfactant is in the range of about 0.0005% or about 0.8% to about 10% or to about 20% or to about 40%. Preferably, the amount of surfactant is from about 0.01% to about 0.1% or to about 0.5% or to about 0.8% (w/v). Alternatively, the surfactant is present in an amount greater than 0.8%.  
           [0030]    The sequence and percent distribution of hydrophobic and hydrophilic segments in these block copolymers leads to important differences in surfactant properties. The surfactant is preferably a liquid at 20° C. The molecular weight of the polyoxypropylene block is preferably from about 1200 and about 3100. Preferably, molecular weight of the polyoxypropylene block is from about 1000 and about 2500. Most preferably, the molecular weight of the polyoxypropylene block is approximately 1700. Specific non-limiting examples of PLURONIC® R surfactants that are satisfactory include: PLURONIC® 31R1, PLURONIC® 31R2, PLURONIC® 25R1, PLURONIC® 17R1, PLURONIC® 17R2, PLURONIC® 12R3. Particularly good results are obtained with PLURONIC® 17R4 surfactant.  
           [0031]    The letter ‘R’ found in the middle of the designation of the PLURONIC® R series signifies that this product has a reverse structure compared to the PLURONIC® products, i.e., the hydrophile (ethylene oxide) is sandwiched between the propylene oxide blocks and that the surfactant is terminated in secondary hydroxyl groups, rather than primary hydroxyl groups. The numeric designation preceding the ‘R’, when multiplied by 100, indicates the approximate molecular weight of the propylene oxide block. The number following the ‘R’, when multiplied by 10, indicates the approximate weight percent ethylene oxide in that product.  
           [0032]    While, one of ordinary skill in the art will recognize that the surfactant of the present solution may be used in conjunction with one or more other surfactants, it is preferable to employ a polyoxyethylene-polyoxypropylene block copolymers terminated in secondary hydroxyl groups as the sole surfactant.  
           [0033]    The conditioning solution is ocularly compatible and may be used on hard, RGP, and soft contact lenses. The active ingredients may be in any of a number of carrier vehicles. For example, the solution may be used in a soaking conditioning solution with or without a preservative or disinfecting agent.  
           [0034]    The composition of the present invention preferably contains a buffer. The buffer maintains the pH preferably in the desired range, for example, in a physiologically acceptable range of about 4 or about 5 or about 6 to about 8 or about 9 or about 10. In particular, the solution preferably has a pH in the range of about 5.5 to about 8. The buffer is selected from inorganic or organic bases, preferably basic acetates, phosphates, borates, citrates, nitrates, sulfates, tartrates, lactates, carbonates, bicarbonates, tris, tris derivatives, fatty acid salts and mixtures thereof, more preferably basic phosphates, borates, citrates, tartrates, carbonates, bicarbonates and mixtures thereof. Typically, it is present in an amount of 0.001% to 2%, preferably 0.01% to 1%; most preferably from about 0.05% to about 0.30%.  
           [0035]    The buffer component preferably includes one or more buffers, for example, combinations of monobasic phosphates, dibasic phosphates and the like. Particularly useful phosphate buffers are those selected from phosphate salts of alkali and/or alkaline earth metals. Examples of suitable phosphate buffers include one or more of sodium dibasic phosphate (Na 2 HPO 4 ), sodium monobasic phosphate (NaH 2 PO 4 ), and potassium monobasic phosphate (KH 2 PO 4 ).  
           [0036]    The present invention can be formulated in a liquid form, a near gel form, or in a gel form. One of ordinary skill would readily recognize formulations encompassed by the present disclosure suitable to achieve each form. The preferred form is a liquid form.  
           [0037]    The solutions of the present invention preferably include an effective amount of a tonicity component to provide the liquid medium with the desired tonicity. Such tonicity components may be present in the solution and/or may be introduced into the solution. Among the suitable tonicity adjusting components that may be employed are those conventionally used in contact lens care products, such as various inorganic salts. Sodium chloride and/or potassium chloride and the like are very useful tonicity components. The amount of tonicity component included is effective to provide the desired degree of tonicity to the solution. Such amount may, for example, be in the range of about 0.4% to about 1.5% (w/v). If a combination of sodium chloride and potassium chloride is employed, it is preferred that the weight ratio of sodium chloride to potassium chloride be in the range of about 3 to about 6 or about 8. The preferred tonicity component is sodium chloride, or its equivalent present in the range of 0.50% to 0.90%.  
           [0038]    Typical tonicity builders for use in the invention include suitable water soluble salts compatible with ocular tissue, preferably alkali or alkali earth metal halide, organic polyols, such as sorbitol and mannitol, sulfates, nitrates, carbonates, borates, and phosphates, more preferably sodium or potassium chloride. The tonicity builder is present in an amount sufficient to provide a tonicity of the dosage regimen of 50 to 400 mosmol/kg, most preferably 250 to 350 mosmol/kg. When non-contact lens cleaning is the desired use, the tonicity builder may also be absent or in even greater amounts than set forth above.  
           [0039]    The lens could be soaked in the solution to allow the surfactant to absorb to the lens surface and/or the internal matrix. Alternatively, the solution may be placed in an eye drop solution, which may also be dispensed with or without a preservative or disinfecting agent. The drop would be applied to the lens while being worn on the eye. Furthermore, the conditioning solution may be placed within a contact lens cleaning solution, which would deliver the surfactant while the lens is being cleaned. In this type of formulation, the surfactant could also be used to clean, and other detergent agents would not also need to be provided, thus providing an additional advantage of that embodiment of this invention. 
       
    
    
     EXAMPLE 1  
     PRIOR ART  
       [0040]    A quantity of the following liquid composition was prepared by blending together the individual ingredients (in g).  
                                                       Hydrogen peroxide   35.0           Sodium Phosphate, Monobasic (monohydrate)   0.072           Sodium Phosphate, Dibasic (Anhydrous)   0.622           DEQUEST ® 2060   0.120           Sodium Chloride   8.655           USP Purified Water   QS to 1 liter                      
 
         [0041]    The resulting solution is an aqueous solution containing 3.5% hydrogen peroxide; 0.0072% sodium phosphate, monobasic (monohydrate); 0.0622% sodium phosphate, dibasic (anhydrous); 0.0120% DEQUEST® 2060; and 0.8655% sodium chloride. The pH was adjusted to between 6.3 and 6.6 with phosphoric acid.  
       EXAMPLE 2  
       [0042]    A quantity of the following liquid composition was prepared by blending together the individual ingredients (in g).  
                                                       Hydrogen peroxide   35.0           Sodium Phosphate, Monobasic (monohydrate)   0.772           Sodium Phosphate, Dibasic (Anhydrous)   1.555           DEQUEST ® 2060   0.120           Sodium Chloride   7.900           PLURONIC ® 17R4   0.500           USP Purified Water   QS to 1 liter                      
 
         [0043]    The resulting solution is an aqueous solution containing 3.50% hydrogen peroxide; 0.0772% sodium phosphate, monobasic (monohydrate); 0.1555% sodium phosphate, dibasic (anhydrous); 0.0120% DEQUEST® 2060; 0.79% sodium chloride; and 0.05% PLURONIC® 17R4. The pH was adjusted to between 6.3 and 6.6 with phosphoric acid.  
       EXAMPLE 3  
       [0044]    Studies were conducted to assess the contact angle of the Example 1 formulation versus the Example 2 formulation on Group I and IV soft contact lenses (FDA categories). Group IV is distinguished from Group I by having higher water content and being more ionic. Typically, Group IV lenses have a water content greater than 50% by weight. The contact angle of phosphate buffered saline was then measured. The second study evaluated the contact angle of “fresh” lenses directly out of the package. The contact angle of both the Example 1 formulation and the Example 2 formulation were measured. The results put forth in Tables 12 and 13 indicate that the formulation of Example 2 has better wetting than Example 1 in both studies.  
                               TABLE 1                                   Lens type   Example 2   Example 1                           Group IV, vifilcon A   38   66           Group I, tefilcon   36   45                      
 
         [0045]    [0045]                               TABLE 2                                   Lens type   Example 2   Example 1                           Group IV, vifilcon A   43   83           Group I, tefilcon   32   60                        
       EXAMPLE 4  
       [0046]    A quantity of the following liquid composition is prepared by blending together the individual ingredients (in g).  
                                                       Sodium Phosphate, Monobasic (monohydrate)   0.772           Sodium Phosphate, Dibasic (Anhydrous)   1.555           Sodium Chloride   7.900           PLURONIC ® 17R4   0.500           USP Purified Water   QS to 1 liter                      
 
         [0047]    The resulting solution is an aqueous solution containing 0.0772% sodium phosphate, monobasic (monohydrate); 0.1555% sodium phosphate, dibasic (anhydrous); 0.79% sodium chloride; and 0.05% PLURONIC® 17R4. The pH is adjusted to between 6.3 and 6.6 with phosphoric acid.  
         [0048]    The invention has been described in detail, with reference to certain preferred embodiments, in order to enable the reader to practice the invention without undue experimentation. However, a person having ordinary skill in the art will readily recognize that many of the components and parameters may be varied or modified to a certain extent without departing from the scope and spirit of the invention. Furthermore, titles, headings, definitions or the like are provided to enhance the reader&#39;s comprehension of this document, and should not be read as limiting the scope of the present invention. Accordingly, the intellectual property rights to this invention are defined only by the following claims and reasonable extensions and equivalents thereof.