GB2055118A

GB2055118A - Cleaning contact lenses

Info

Publication number: GB2055118A
Application number: GB8020681A
Authority: GB
Original assignee: Polymer Technology Corp
Current assignee: Polymer Technology Corp
Priority date: 1979-06-25
Filing date: 1980-06-24
Publication date: 1981-02-25
Also published as: FR2459993A1; AU5931080A; GB2055118B; IT1131637B; DE3021034C3; JPS566215A; DE3021034C2; DE3021034A1; AU537744B2; CA1152843A; JPH0381136B2; FR2459993B1; IT8022938A0

Abstract

The present invention provides a method of cleaning an ophthalmic contact lens, which comprises applying a cleaning composition containing an abrasive and a surface-active agent to a surface of a lens and abrading the surface to remove unwanted surface deposits, if present, without changing the power of the contact lens. The present invention also provides a contact lens cleaning composition, consisting essentially of a surface-active agent, an inorganic abrasive, a suspending vehicle and means to maintain the surface-active agent and abrasive in substantially uniform suspension, the composition being capable of cleaning a contact lens without adversely affecting the lens.

Description

SPECIFICATION Contact lens cleaning composition The present invention is concerned with a contact lens cleaning composition and with a method of cleaning an ophthalmic contact lens.

It has long been recognised in the art that contact lenses must remain free of surface deposits in order to maintain their wearing comfort and optimum vision and reduce the potential for ocular change.

Unfortunately, contact lenses are susceptible to acquiring surface deposits from exogenous sources (mascara, hair spray, etc.) and endogenous sources (mucus, oily meibomian secretions, etc.). Siliconecontaining contact lenses are the most vulnerable of all contact lenses to the acquisition of tenacious, waxy surface deposits which are difficult, if not impossible, totally to remove without damaging the lens.

Previous hard and soft contact lens cleaning solutions have used a variety of water-soluble cleansing agents, in addition to water-soluble hydrating polymers in sterile homogeneous aqueous solution. Other cleaning agents have employed thixotropic, synthetic, water-soluble polymers and thixotropic synthetic clays with detergents to give stiff gels for cleaning hard contact lenses.

Abrasive materials have not previously been used in contact lens cleaning solutions perhaps because such abrasives would be considered to scratch the surface of the plastic contact lens, thus leading to a reduction in optical clarity, as well as enhanced eye irritation.

It is an object of the present invention to provide a contact lens cleaning composition which consists essentially of a surface-active agent, an inorganic abrasive and a suspending vehicle, which material is very useful as a cleaner, enabling superior cleaning of silicone-containing plastic contact lenses, while also useful as a cleaner and/or cleaner-polisher for other contact lens materials.

Another object of the present invention is to provide a method of cleaning an ophthalmic contact lens, which method comprises applying a cleaning composition containing an abrasive to a surface of the lens and abrading said surface to remove unwanted surface deposits if present, without changing the power of the contact lens.

Thus, according to the present invention, there is provided a contact lens cleaning material which consists essentially of a surface-active agent, an inorganic abrasive, a suspending vehicle, such as water or an organic liquid, and means to maintain the surface-active agent and abrasive in substantially uniform suspension, the composition being capable of cleaning a contact lens without adversely affecting the lens.

The composition is preferably in the form of a liquid solution but can also be in the form of a paste. The cleaner can have a polishing action when the abrasive materials are increased. The abrasive is preferably in a small particle size range so as not to scratch the lens when used.

According to the method of the present invention, an ophthalmic contact lens is cleaned by abrading the surface of the lens in the presence of a cleaning solution containing an abrasive, a surface-active agent, a liquid vehicle and a suspending agent. The cleaning solution is applied and the surface of the lens is abraded to remove unwanted surface deposits, if present, without changing the power of the contact lens. By increasing the abrasive and applying substantial pressure over a comparatively long time period, the material can be used as a polish, although it is preferred to use it as a cleaner polisher.

It is a feature of the present invention that there is multifold enhancement of the cleaning effectiveness of certain surface-active agents, increasing the friction produced as the surface-active agent is rubbed over the surfaces of the synthetic resin lens. This is accomplished by introducing into the surface-active agent solution solid abrasive particles, the size and concentration of which can be varied, according to the desired function of the cleaning composition. The particle size normally used is comparable to or smaller than the abrasive used to polish lens surfaces during manufacture, as is conventionally known. The particles remain uniformly suspended in the surface-active agent solution, without settling, since settling could vary the effectiveness of the cleaner, and without aggregating, which could cause scratches on the lens surface.

It is another feature of the present invention that the suspending agent for the abrasive particles is such that the overall suspension is stable for a substantially indefinite period of time. The cleaning solution may contain a sterilising and/or buffering agent, as well as a fragrance. In certain cases, it may be possible to use a surfactant both for suspending the abrasive particles and for providing a cleaning action. However, it is preferable to use a high concentration of a water-soluble salt or an organic polymer to act as a suspending agent.

Although the cleaning compositions according to the present invention are especially useful for cleaning and/or cleaning and polishing hard, gas-permeable contact lenses containing siloxanes, they are also useful for contact lenses made from polymethyl methacrylates, silicones and cellulose acetate butyrate, as well as other synthetic resins and other materials used for making ophthalmic contact lenses.

The preferred formulation of the contact lens cleaning composition of the present invention contains a surface-active agent with an abrasive for combined chemical and mechanical cleaning action and a suspending agent for the abrasive, such that a stable suspension is formed in an aqueous solution.

The preferred surface-active agents are detergents or surfactants, such as anionic sulphates having the general formula:- CnH2n+lO (CH2CH20), S03-R+ CnH2n+,O (CH2CH20)X S03 R wherein x is O or 1 to 10,n n is from 8 to 20 and R+ is Na+, K+, NH+4, Mg++ or HN+(CH2CH2OH)3.

Examples of such detergents include sodium lauryl sulphate, sodium cetyl sulphate, sodium octyl sulphate, sodium tridecyl sulphate, sodium oleyl sulphate, sodium tridecyl ether sulphate, triethanolamine lauryl sulphate, ammonium lauryl ether sulphate, sodium lauryl ether sulphate and magnesium lauryl sulphate.

The abrasive compound or compounds are water-insoluble inorganic compounds employed for their abrasive characteristics. The abrasive material is a hard, tough substance containing many sharp projecting cutting edges or points and in ordinary use is used for grinding, smoothing, and polishing. Such abrasives include various types of silica, alumina, manganese oxides, zirconium oxides and carbonates. It is preferred to employ abrasives with an average particle size of 10 microns or less. The preferred abrasives include, for example, silicas, aluminas, kaolin, calcium carbonate and zirconium oxide.

The suspending agent or agents in the composition must provide a stable suspension of the abrasive in the cleaning composition. Such suspension may, for example, be achieved by increasing the viscosity of the aqueous solution by adding soluble salts or hydrophilic polymers or by adding water-soluble neutral or ionic polymers which can interact with the surface of one or more inorganic abrasive particles, thus preventing or hindering the occurrence of precipitation.

Such suspending agents can, for example, be one or more of the following:- alkali metal halides (high concentration), alkaline earth metal salts (moderate concentration), polyvinyl alcohol, polyacrylamide, hydrolysed polyacrylamide, polyacrylic acid, xanthan gum, hydroxyethylcellulose, carboxymethylcellulose, cellulose sulphate, methyl cellulose, methyl hydroxyethylcellulose, methyl hydroxypropylcellulose, poly-Nvinylpryrrolidone, guar gum, carboxymethyl guar gum, hydroxyethyl guar gum, hydrolysed polyacrylonitrile starch, hydrolysed polyacrylonitrile 2-acrylamido-2-methylpropane sulphonate starch, clays, such as bentonite, montmorillonite and hectorite, non-ionic, cationic and anionic detergents, partially acetylated cellulose, gelatine, polyethylene glycol and oxide and K-carageenan.

Buffering agents which can be used are preferably those commonly employed in the art within a pH range of from 5 to 8 and usually of from 7 to 8. Such buffers include boric acid, sodium borate, phosphoric acid, disodium phosphate and sodium bicarbonate.

The use of salts as suspending agents generally renders the cleaning solution sterile. However, in cases where sterility must be imparted, anti-microbial compounds can be used, for example, chlorhexidine, benzalkonium chloride, phenyl mercuric acetate, phenethyl alcohol, methyl or propyl paraben, cetyl pyridinium chloride, thimerosal and the like, possibly together with ethylenediamine-tetraacetic acid.

Fragrances, such as wintergreen or peppermint, can be used, if desired.

In the simplest fashion, the contact lens is cleaned by immersing the lens in the cleaning composition or spraying the lens therewith and, by providing agitation of the solution, such as by rubbing, shaking or wiping the cleaning solution on the lens surface. The lens is then rinsed with water and inserted directly into the eye or it is placed in a soaking and/or wetting solution prior to insertion.

The following Examples are given for the purpose of illustrating the present invention: Example I Formulation: sodium tridecyl ether sulphate (30%) 80 gms distilled water 160 gms sodium chloride 20 gms silica (9 micron average size) 24 gms The surfactant was mixed with the water, then the sodium chloride was added and mixing was continued until a thick solution was obtained. The silica powder was added to the solution and blended thoroughly until a smooth, viscous suspension was achieved. No settling of the abrasive was observed after eight months of shelf storage.

Example II Formulation: sodium tridecyl ether sulphate (30%) 133 gms distilled water 267 gms sodium chloride 30 gms silica (9 micron average size) 8 gms The method of preparation was identical to that described in Example I.

Example IIl Formulation: sodium tridecyl ether sulphate (30%) 133 gms distilled water 267 gms sodium chloride 30 gms silica (9 micron average size) 1 gm The method of preparation was identical to that described in Example I.

Example IV Formulation: A B C sodium tridecyl ether 133 gms 133 gms 133 gms sulphate (30%) distilled water 267 267 267 sodium chloride 30 30 silica (9 micron average size) 12 - Cleaning solutions were prepared in the same manner as that described in Example I.

Contact lenses having a high silicone content characteristically develop a tenacious waxy surface deposit which is difficult and often impossible to remove with solvents, surfactants or polishing without damaging the surfaces of the lenses. Such deposits are best seen by examining a rinsed and dried lens against a black background, using a self-illuminating binocular microscope, and can be quantified by grading 1 to 4, according to surface area and thickness (opaqueness), a rating of 4 indicating a severe deposit. Sixty pairs of lenses having roughly symmetrical surface deposits of grade 2 or greater were subjected to the following procedure: one lens of each pair was cleaned manually using formulation "A". The companion lenses were divided up into three groups of twenty.One group was cleaned manually with formulation "B", the second group with formulation "C" and the final group with various commercial contact lens cleaners (solutions and gels). It was found that formulation "B" and "C" were equally effective but that formulation "A" was very much more effective than formulation "B" or "C" in all cases. In fact, formulation "B" and "C" were relatively ineffective in removing grade 4 deposits, whereas the formulation according to the present invention (formulation "A") was very effective in all cases. Finally, none of the commercial contact lens cleaners was more effective than formulations "B" and "C" and many were less effective. This demonstrates the usefulness of a suspended abrasive in providing an improved cleaning action in comparison with simple surfactant solutions.

Example V The cleaning solution described in Example Ill was given two a number of subjects at the commencement of their wearing newly made hard contact lenses containing silicone. They were instructed to clean their lenses nightly with this formulation. Their lenses were inspected after 6 months and compared with the lenses of a similar group of subjects who cleaned their lenses nightly with a variety of commercial contact lens cleaners.

The lenses of patients using the cleaning solution of Example Ill were significantly freer of surface deposits and were, as a rule, more comfortable.

The cleaning solution described in Example Ill was also given to a small group of conventional polymethyl methacrylate contact lens wearers who complained of blurred vision as the result of the development of "dry" spots on the front surface of their lenses which recurred when cleaned nightly with a variety of commercial contact lens cleaners, solvents or polishing. In all cases, the nightly use of this composition according to the present invention eliminated the hydrophobic or dry areas and the subjects' vision remained clear during their daily wearing schedule.

Example Vl The surfaces of all hard contact lenses eventually become scratched. Conventional polishes remove shallow scratches and smooth the ridges adjacent to deeper scratches, thereby improving the comfort and optics of the lenses. However, many of these scratched contact lenses also have significant surface deposits which are not removed by polishing. In fact, polishing contact lens surfaces which have heavy deposits may simply spread and redistribute the deposits, thereby reducing the surface wettability even further. The cleaning solution described in Example I combines the function of a cleaner (to remove surface film) and a polish (to remove surface scratches) and it is far more effective than using a cleaner and a polish in separate operations.A cleaner/polish such as that described in Example I is particularly useful for restoring the optics and wettability of hard contact lenses.

Example Vll Formulation: sodium tridecyl ether sulphate (30%) 100 gms 4% hydroxy ethyl cellulose solution 200 gms aluminium oxide (0.06 micron size) 10 gms 4% by weight hydroxyethyl cellulose ("Cellosize" QP-40, a product of Union Carbide Corp. of New York, New York) was dissolved in distilled water. The surfactant was then added and the solution well mixed. The aluminium oxide was then thoroughly blended into this solution until a smooth viscous composition was obtained.

This Example demonstrates the use of a water-soluble polymer to suspend the abrasive powder.

Example Vffl Formulation: sodium tridecyl ether sulphate (30%) 100 gms distilled water 200 gms hydrite 10 (kaolin clay) 30 gms sodium chloride 25 gms The method of preparation was identical to that described in Example I.

This Example demonstrates the use of kaolin, i.e. a material which imparts a "milder" abrasive action as compared to silica or alumina.

Example IX Formulation: sodium tridecyl ether sulphate (30%) 100 gms glycerol 200 gms silica (9 micron average size) 3 gms The surfactant was dissolved in glycerol and then the silica was blended into this solution.

This Example demonstrates the use of an organic liquid, in conjunction with the surfactant, to achieve a transparent cleaning solution.

Example Formulation: A B C sodium tridecyl ether 100 gms 125 gms sulphate (30%) ammonium lauryl ether - - 100 gms sulphate (27%) silica (4 micron average size) 30 gms - 35 gms hydrite 10 (kaolin clay) - 75 gms The abrasive powder was mixed with the surfactant, under moderate shear, to give a stable paste.

This Example demonstrates the use of the surfactant as a suspending agentforthe abrasive to form a paste cleaner.

Example Xl Formulation: triethanolamine lauryl sulphate (40%) 75 gms distilled water 520 gms xanthan gum 10 gms silica (4 micron average size) 18 gms The xanthan gum was dissolved in distilled water. The surfactant was then added and the solution well mixed. The silica was then blended thoroughly into this solution until a smooth viscous solution was obtained.

While specific Examples of the present invention have been given and described, many variations as possible. When the cleaning compositions of the present invention are used only as cleaners, the surface-active agents preferably comprise from 1 to 30% by weight of the material, the abrasive particles from 0.1 to 5% by weight and the carrier vehicle, such as water, from 98.9 to 69.9% by weight, with a suspending agent, based on 100 parts of the above, being from 5 to 25 parts when inorganic salts are used and from 1 to 10 parts when polymers are used. The same suspending agents are used when the cleaning composition is used as a cleaner-polisher but here the amount of surfactant may be from 1 to 30% by weight and the abrasive amount is raised to from 5 to 25% by weight, while the water or other suspending vehicle is used to make up to 100%.When a paste is desired rather than a free flowing liquid, the surfactant can carry from 15 to 40% by weight of the surface-active agent, from 20 to 50% by weight of an abrasive and the balance water or other solvent, which is water-soluble. Of course, one or more surface-active agents, abrasives or solvents can be used in a single composition, if desired.

The particle sizes of the abrasives can vary greatly but they are preferably that normally used for lens polishing in the ophthalmic industry. Particle sizes of silica, for example, with an average size of 9 microns and a size range of from 1 to 20 microns, with an upper limit of 30 microns in the form of "Syloid" 63 (a trade-marked product of Davison Chemical W.R. Grace Co. of Baltimore, Maryland, U.S.A.) can be used.

Other size ranges are also possible.

In all cases, the surface-active agent in the form of a detergent or surfactant acts, together with the abrasive, to combine the best qualities of both which can result in a synergistic action to clean contact lenses in accordance with the method of the present invention.

While certain surface-active agents have been specifically mentioned herein, other surface-active agents can also be used: such agents associate in water to form a colloidal particle known as a micelle. The structure is such that the hydrophobic hydrocarbon chains are inside the particle and remote from the solvent and the polar head groups are on the surface of the particle. The presence of micelles in an aqueous solution endows it with minute regions which are predominantly hydrophobic in nature. This provides for a high solubility in water and a good wetting of the materials.

Claims

1. A method of cleaning an ophthalmic contact lens, which comprises applying a cleaning composition containing an abrasive and a surface-active agent to a surface of a lens and abrading the surface to remove unwanted surface deposits, if present, without changing the power of the contact lens.

2. A method according to claim 1, wherein the cleaning composition used further comprises a suspending vehicle and means to maintain the surface-active agent and abrasive in substantially uniform suspension so that said composition is capable of cleaning a contact lens, without adversely affecting the lens.

3. A method according to claim 2, wherein the suspending vehicle is water and the suspending means is an inorganic salt or a hydrophilic polymer.

4. A method according to claim 1 of cleaning an ophthalmic contact lens, substantially as hereinbefore described and exemplified.

5. A contact lens cleaning composition, consisting essentially of a surface-active agent, an inorganic abrasive, a suspending vehicle and means to maintain the surface-active agent and abrasive in substantially uniform suspension, the composition being capable of cleaning a contact lens without adversely affecting the lens.

6. A contact lens cleaning composition according to claim 5, wherein the composition is in liquid form.

7. A contact lens cleaning composition according to claim 5, wherein the composition is in a semi-viscous paste form.

8. A contact lens cleaning composition according to any of claims 5 to 7, wherein the surfactant is present in an amount of from 1 to 30% by weight, the abrasive is present in an amount of from 0.1 to 5% by weight and the vehicle is water in an amount up to 100%, the suspending agent being an inorganic salt or a hydrophilic polymer.

9. A contact lens cleaning composition according to any of claims 5 to 7, wherein the surfactant is present in an amount of from 1 to 30% by weight, the abrasive is present in an amount of from 5 to 25% by weight and the vehicle is water in an amount up to 100%, the suspending agent being an inorganic salt or a hydrophilic polymer.

10. A contact lens cleaning composition accoding to any of claims 5 to 7, wherein the surfactant is present in an amount of from 15 to 40% by weight, the abrasive is present in an amount of from 20 to 50% by weight and the vehicle is water in an amount up to 100%, the suspending agent being an inorganic salt or a hydrophilic polymer.

11. A contact lens cleaning composition according to any of claims 5 to 10, wherein said abrasive is silica, alumina, kaolin, calcium carbonate, zirconium oxide or a mixture thereof.

12. A contact lens cleaning composition according to any of claims 5 to 11, wherein the surface-active agent has the general formula: CnH2n+1O (CH2CH2O)xSO3 R+ wherein xis 0 or 1 to 10, n is from 8 to 20 and R+ is Na+, K+, NH+4 1/2Mg++, HN+(CH2CH2OH)3.

13. A contact lens cleaning composition according to claim 12, wherein the surface-active agent is any one of those hereinbefore specifically mentioned.

14. A contact lens cleaning composition according to any of claims 5 to 13, wherein the suspending agent is any one of those hereinbefore specifically mentioned.

15. A contact lens cleaning composition according to any of claims 5 to 14, wherein there is also present a buffering agent buffering in the pH range of from 5 to 8.

16. A contact lens cleaning composition according to claim 15, wherein the buffering agent buffers in the pH range of from 7 to 8.

17. A contact lens cleaning composition according to any of claims 5 to 16, wherein an anti-microbial compound is additionally present.

18. A contact lens cleaning composition according to any of claims 5 to 17, wherein a fragrance is additionally present.

19. A contact lens cleaning composition according to claim 5, substantially as hereinbefore described and exemplified.