US 3311577 A
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United States Patent O 3,311,577 UNDERWATER CONTACT LENS SOLUTION Billy F. Rankin, Rockville, Md., assignor to Burton Parsons Chemicals, Inc, Washington, D.C., a corporation of Delaware No Drawing. Filed Mar. 29, 1965, Ser. No. 443,693 11 Claims. (Cl. 260-17) This invention relates to contact lens treating compositions and more particularly to contact lens wetting solutions for underwater use. Specifically this invention is directed to a composition for use by swimmers and divers fitted with the new scleral type of underwater contact lens known as the SCAL lens (skindivers contact air lens).
One of the most unique developments in the eye contact lens field since the corneal contact lens is the special lens developed by Dr. Alan H. Grant in collaboration with Capt. Edward Beckman of the US. Naval Medical Research Institute for use underwater. By taking advantage of the unique properties of these lenses, skindivers and other underwater swimmers have, for the first time, been able to have substantially full peripheral vision under water, the restriction of a face mask being eliminated. This new type lens is described in such publications as Sports Illustrated, vol. 19, No. 25, Dec. 16, 1963, and since the lens, per se, only represents the environment of use for my invention, a complete discussion of its physical parameters will not be repeated here.
Although these new lenses have proven themselves already, their continued use has resulted in several problems not normally encountered with regular corneal contact lenses. Specifically it has been noted that with extended use of the SCAL lens the wearers view may become blurred or the eyes may be irritated. Specific problems manifesting themselves were the edema formed by immersion in a chlorinated swimming pool as evidenced by halo-syndrome, burning and stinging. Stinging also resulted from salt water contacts and in this latter environment actual blurring resulted upon prolonged immersion.
To combat these difficulties it was originally assumed that the regular corneal lens treating solution might be applied, such as that disclosed in my Patent 3,171,752 issued Mar. 2, 1965. However, this type of composition was only temporarily effective, its effectiveness being constantly diminished due to the washing action of the swimmers or divers environment. These environmental factors were even more deleterious to the lens wearers vision as the pressure increased with the depth of submersion.
Therefore it is a principal object of the present invention to provide a composition for use with underwater contact lenses which will suppress blurring and irritation due to their use environment.
It is a further object of the invention to provide a lens treating solution which will not be washed from the eye by fresh or salt water immersion or by pressure variation.
It is still a further object of the invention to provide a composition having the desideratum and which is inexpesive to manufacture and can be utilized by any lens wearer without expensive training or prolonged periods of accustornization.
These and other objects will become apparent from a "ice study of the following detailed description of my invention.
It has been discovered that a composition to provide the desired characteristics must broadly comprise, in a water base, a component for close viscosity control with subsidiary components which allow the viscosity control agent to be both compatible with the eye fiuids and resistant to attack by the use environment.
As a viscosity control agent it is preferred to use cellulosic derivatives such as methyl cellulose, hydroxy ethyl cellulose, hydroxy propyl cellulose, etc., each of which functions in the quantities utilized to maintain the viscosity of the overall composition between about 3000 cps. and 30,000 cps. at 20 C. as measured by a Brookfield Viscosimeter with a No. 6 spindle rotated at 10 r.p.m. Other cellulose derivatives which are utilizable include carboxy methyl cellulose, hydroxy propylmethyl cellulose (Methccel H.G.-Dow Chemicals Co.), etc.
Since cellulosic derivatives come in a multitude of molecular weights an exact range for the amount of cellulosic derivative to be included to provide the requisite viscosity cannot be given. However, as a specific example, it has been found that a range of about .8 to 2% is acceptable where hydroxy ethyl cellulose is utilized as supplied by Union Carbide Chemicals Co. under the trade name Cellosize (QP52,000). With lower viscosity grade (molecular weight) celluloses, the percentages would increase correspondingly while higher molecular weights reflect lower percentages. Although higher amounts will not leak or be washed out by the environment, it is necessary to have an upper viscosity (and corresponding percentage) limitation in order to obtain effective handling characteristics including sufiicient flowability for full lens coverage.
With the cellulosic derivatives it is necassary to combine components to provide eye compatibility and fluid retention. These functions are provided by the combination of polyalkylene glycols and buffers and preferably inclusions of polyvinyl pyrrolidone and compatible biocides.
The polyalkylene glycols serve a dual function in the composition: acting as a plasticizer for the cellulosic derivative while also combining therewith to provide an effective barrier to infiltration of environmental water such as the sea. Specifically, it has been discovered that polyalkylene glycols with the cellulose derivative forms a film barrier at the surface which not only keeps the cellulose in but keeps any diluents out. The preferred polyalkylene glycol utilized is polyethylene glycol such as Carbowax 4000 as supplied by Carbide and Carbon Chemicals Co. Other Carbowaxes may be utilized as well as other polyalkylene glycols such as polypropylene glycol, etc. Other alkylene groups may be included in the glycol composition but lower alkylene glycols are preferred because of their ready availability. The polyalkylene glycol is present in amounts of from about 30 to 200% based on the weight of .the cellulosic derivative (0.254% based on the weight of overall water based composition with hydroxy ethyl cellulose). Amounts less than 30% are ineffective for forming a sufiicient barrier film while amounts greater than about 200% may exhibit a salting out effect forming wax solid globules or particles. This efiect may not occur until the excess is over 200% and thus with some polyalkylene glycols greater amounts may be included. However, the effects desired are produced within the range specified and additional inclusions, although sometimes not deleterious, do not enhance these properties. The use of polyalkylene glycols as plasticizers for cellulosic derivatives has previously been recognized in film casting with amounts from 10 up to 30% based on the dry weight of the cellulosic derivative being suggested. However proportions of this nature are, as pointed out above, unsatisfactory for the instant invention wherein the polyethylene glycol must not only plasticize but also build a sufficient barrier film to balance the environmental condition. This is critical to the instant invention for besides the barrier layer, the cellulosic composition must be maintained in a flowable nature.
The basic composition, as defined, also must include a buffering combination to insure pH maintenance between about 7.4 and 8.2, preferably at about 7.6. The amount of buffers so utilized must be sufficient to maintain the pH even under the adverse effects of sea water so relatively high amounts are utilized when compared to the amount suggested for corneal lens uses. As buffering agents it is preferred to use a combination of phosphate such as mono sodium phosphate with disodium phosphate .to provide both acid and base control. Other phosphates of the alkali metals such as potassium are also satisfactory provided they are eye compatible. Anions such as borates, acetates and carbonates may similarly be substituted for the phosphates with the criteria of acceptability, as with the cations, being eye compatibility. The exact amount of buffering additions may range between about 1 and 4% for the dibasic component and about 0.0 and .5% for the monobasic component with the ratio of the components being balanced to provide the proper pH of the overall composition.
To the above defined mixture it is preferable to add specific subsidiary components which materially enhance the end properties of the products. Of these, the most important is polyvinyl pyrrolidone (such as Plasdone C, supplied by Antara Chemicals, Division of General Aniline & Film Corp.) which in the combination, provides a number of unique and desirable functions. Specifically it has been discovered that polyvinyl pyrrolidone (PVP) acts as a detoxicant whereby it Ibinds with any toxins which might be present in the eye fluids and renders them harmless. Such toxins might be produced by bacteria present in the eye fluids or in the lens treating solution per se. Further the PVP acts to protect the cellulose, water colloidal system by preventing its breakdown due to particle agglomeration and acts as a demulcent lubricant by a combination of adhesive and lubricating properties which aid in the spreading of the viscous cellulosic derivative water dispersion over the lens while also holding it thereto. The PVP combines the above properties while having little effect on overall composition viscosity. Further it aids in preventing blepharospasm (involuntary eyelid contraction). Besides these features, the PVP when formulated with the buffers closely simulates the human tear. PVP is desirably present in a range of up to 3% With a minimum of .5% exhibiting the desired properties. More than 3% may provide a transfer problem with possible corneal penetration due to the excess.
It is desirable to also include with the composition compatible biocides such as those disclosed in my Patent 3,171,752. Specifically polysodium diamine tetracetates as well as thimerosal (sodium ethylmercurithiosalicylate). The (11-, tri-, or tetra-sodium ethylene diamine tetracetates are of substantially equal effectiveness. The percentages of such biocides may vary over a broad range although it is preferred to use at least .01 up to 1% EDTA with from .001 to .01 thimerosal.
Having described the mandatory and preferred ingredients of my composition individually, in combination the following compositions fall within the scope of my in vention:
Percent by weight based on overall composition unless Component: noted otherwise.
Cellulosic derivative Sufficient amount to pro duce viscosity of 3000- 30,000 cps. Polyalkylene glycol 30200 (based on weight 1 Brookfieldat 20 C.10 r.p.m.-#6 Spindle. To pH of 7.4-8.2.
The method whereby the ingredients are combined insures stability and handling ease and generally comprises dissolving the buffers in distilled water and heating the buffered solution to about F. Thereafter the EDTA, the polyvinyl pyrrolidone and polyalkylene glycols are added and finally the thimerosal. The solution is rapidly stirred whereby a vortex is formed and the cellulosic derivative sifted slowly into the vortex with the agitation being maintained to provide maximum turbulence with minimum air entrainment. Slow cooling of the composition completes the process. Alternatively and preferably the buffers are combined with the cellulosic derivative to accelerate the solution rate and aid in the prevention of agglomeration.
Specific examples of compositions prepared and tested within this invention are as follows:
EXAMPLE I A mixture having the following composition was prepared by the above defined method with the hydroxyethyl cellulose being added with the buffers:
Hydroxy ethyl cellulose (Cellosize QP 52,000)
The product had a pH of 7.6 and a Brookfield viscosity of 4000 centipoises at 20 C. using a #6 spindle at 10 rpm. The composition was tested in the ocean by swimmers who placed two drops in each of their SCAL lenses. Submersion at depths of up to 300 ft. evidenced no infiltration of sea water with prolonged use and further no evidence of edema resulting halo syndrome. The composition was also tested in chlorinated pools and proved equally effective. Swimmers who continuously used the treated lenses over 3 hrs. in such pools reported no burning sensation or edema.
EXAMPLE II The following composition was prepared by first mixing the buffers in water and adding the EDTA, PVP, and Carbowax at 118 C. with the thimerosal being added thereafter and the hydroxy ethyl cellulose added during agitation:
Hydroxy ethyl cellulose (Cellosize QP 30,000)
grams .8 Polyethylene glycol (Carbowax 3000) do .8 Polyvinyl pyrrolidone (Plasdone C) do 1.5 Disodium phosphate do 1.4 Monosodium phosphate do .3 Disodium ethylene diamine tetracetate do .1 Thimerosal solution) cc .04 Distilled Water cc 100 The product had a pH of 7.6 and a viscosity of 25,000 centipoises at C. (Brookfieid#6 spindlel0 r.p.m.). It was effective in combating edema during use in both fresh and salt water but in view of the diminished amount of cellulosic derivative it failed to provide a sufiicient barrier to sea water infiltration after about 2 hrs. submersion.
The effectiveness of the instant invention was demon strated at the Summer Olympics in Tokyo during 1964 when the American swimming team was equipped with SCAL lenses and the composition of the instant invention used therewith. Swimmers reported good vision was maintained even on flip turns and the lens materially contributed to the success of the US. team.
Although the above composition has proved itself with the SCAL lens it has been recognized that the con1- position will also act as a wetting solution for standard corneal lenses and may be used therewith.
Also, it has been determined that with eye compatibility the composition has increased eye retention characteristics which make it very desirable as a medicament carrier for treatment of eye diseases wherein the composition is applied directly to the eye without being carried on a contact lens.
As many widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.
What is claimed is:
1. A composition for use with skindivers contact air lenses consisting essentially of (l) a cellulosic derivative selected from the group consisting of methyl cellulose, carboxy methyl cellulose, propyl methyl cellulose, hydroxy ethyl cellulose, and hydroxy propyl cellulose,
(2) unsubstituted polyalkylene glycol and (3) an alkali metal phosphate buffered water solution,
said composition having a pH of between about 7.4 and 8.2 and a viscosity of between about 3000 and 30,000 cps. when measured by a Brookfield viscosimeter at 20 C. with a #6 spindle at 10 r.p.m.
2. A composition according to claim 1 wherein compatible biocides ethylene diamine tetracetates and thimerosal are included.
3. A composition according to claim 1 wherein polyvinylpyrrolidone is included as a detoxicant, demulcent lubricant and antiblepharospasm agent.
4. An eye compatible composition suitable for use with contact lenses consisting essentially of a water base containing a cellulosic derivative selected from the group consisting of methyl cellulose, carboxy methyl cellulose, propyl methyl cellulose, hydroxy ethyl cellulose, and hydroxy propyl cellulose; from .25 to 4% unsubstituted poly.- alkylene glycol; a combination of alkali metal mono and dibasic bufiers to provide a pH of from about 7.4 and 8.2 and a viscosity of between about 3000 and 30,000 cps. when measured by a Brookfield viscosimeter at 20 C. with a #6 spindle at 10 rpm.
5. The composition of claim 4 including from .5 to 2.5% polyvinylpyrrolidone.
6. The composition of claim 5 including from .01 to .5 EDTA and .001.005% ethylmercurithiosalicylate as compatible biocides.
7. A composition in accordance with claim 4 wherein the polyalkylene glycol is polyethylene glycol.
8. A composition for use with contact lenses consisting essentially of a water base containing:
(1) about .8 to 2.0% of a cellulosic derivative selected from the group consisting of methyl cellulose, carboxymethyl cellulose, propyl methyl cellulose, hydroxy ethyl cellulose and hydroxy propyl cellulose;
(2) about .25 to 2% of an unsubstituted polyalkylene glycol; and
(3) a butter mixture of alkali mono and dibasic phosphates suificient to provide an overall pH of about 7.4 to 8.2; said composition having a viscosity of between about 3000 and 30,000 cps. when measured by a Brookfield viscosimeter at 20 C. with a #6 spindle at 10 rpm.
9. The composition of claim 8 which contains from .5
to 2.5% polyvinyl pyrrolidone.
10. The composition of claim 9 wherein the cellulosic derivative is hydroxy ethyl cellulose, the buffers are disodium phosphate and monosodium phosphate and the polyalkylene glycol is polyethylene glycol.
11. The composition of claim 10 which also contains a compatible biocide mixture of from .01 to 5% EDTA and .001 to 005% ethylmercurithiosalicylate.
References Cited by the Examiner UNITED STATES PATENTS 3,171,752 3/1965 Rankin 106-13 MORRIS LIEBMAN, Primary Examiner.
J. FROME, Assistant Examiner.