US3591329A - Apparatus for preserving hydrophilic gels,more particularly ocular contact lenses - Google Patents

Abstract

APPARATUS FOR THE STORAGE OF A SWELLABLE HYDROPHILIC POLYMERIC GEL BODY SUCH AS A CRONTACT LENS OR OTHER IMPLANT COMPRISES A LIQUID CONTAINER DIVIDED INTO AT LEAST TWO PARTS BY A POROUS WALL AND HAVING A PHYSIOLOGIC LIQUID CONTAINED THEREIN, ONE OF SAID CONTAINER PARTS BEING ADAPTED TO HOLD SAID GEL BODY IMMERESED IN SAID LIQUID, A CATION RESIN EXCHANGE MATEIAL IMPREGNATED WITH A SURFACE ACTIVE METALLIC SILVER, SAID MATERIAL BEING LOCATED IN THE OTHER OF THE CONTAINER PARTS AND BEING SOLUBLE BY SAID LIQUID TO RELEASE SURFACE SILVER IONS OVER A PERIOD OF TIME TO THEREAFTER, FREELY FLOW THROUGH SAID POROUS WALL INTO CONTACT WITH SAID GEL BODY.

Description

United States Patent 3,591,329 APPARATUS FOR PRESERVING HYDROPHELIC GELS, MORE PARTICULARLY OCULAR CON- TACT LENSES Richard Chromecek, an Vodr iansky, and Jiii Manych, Prague, Czechoslovakia, assignors to Ceskoslovenska akademie ved, Prague, Czechoslovakia No Drawing. Filed Mar. 13, 1968, Ser. No. 712,609 Claims priority, application Czechoslovakia, Mar. 15, 1967, 1,883/67 Int. Cl. A611 3/00 US. Cl. 21--6l Claims ABSTRACT OF THE DISCLOSURE Apparatus for the storage of a swellable hydrophilic polymeric gel body such as a contact lens or other implant comprises a liquid container divided into at least two parts by a porous Wall and having a physiologic liquid contained therein, one of said container parts being adapted to hold said gel body immersed in said liquid, a cation resin exchange material impregnated with a surface active metallic silver, said material being located in the other of the container parts and being soluble by said liquid to release surface silver ions over a period of time to thereafter, freely flow through said porous wall into contact with said gel body.

The present invention relates to a protective system for preserving and storing swelled hydrophilic polymeric gels as well as articles made therefrom, more particularly ocular contact lenses, which system consists of a room to receive hydrogel, separated by a permeable wall from a room designed for cation exchanger on which silver has been reduced.

In many cases hydrophilic gels have to be preserved or stored in swelled condition, most frequently under water or physiologic solution. In this manner hydrophilic gels are easily liable to get perished which is caused preponderantly by mildew organisms or fungi which grow not only on the surface of the gel but also through its interior and lead to permanent, irreversible degradation thereof. Fungi cause particular troubles in the preparation and application of ocular contact lenses on the basis of glycolmethacrylate gels. The degradation influenced by the growth of fungi is of an irreparable character so that it cannot be suppressed by any of conventional means. The possibility of mildew growth on hydrophilic gels, especially on ocular lenses is one of the main arguments pointed out against wide application of the same.

From the medical point of view this fact has to be carefully considered, since among prevailing saprophytic species of fungi some have been isolated (mostly of Aspergilus tribe) which are Well-known parent of serious mycotis effects. Nevertheless even the non-pathogenic species of fungi can cause in the delicate ophthalmic medium a hypersensitivity to some of their somatic components as well as to their metabolites.

The aforesaid problem cannot be solved in that the lenses would be offered for sale safely sterile in suitable well-protecting packing, or, on the other hand, that they would be vended in dry state. The main troubles with the lenses will arise in applying them, since the optician, or oculist is not in a position to keep a large store of lenses in open state with the danger that they become degraded by an attack of molds or fungi. After all in this case even the patient would have to sterilise his lenses every two or three days in boiling water. Such an operation is rather tedious both for the patient and the optician, since the lenses for their smooth surface have to be boiled off separate lest they might get fused.

A similar practice is to be kept if storing other products made of hydrogels, such as, for example, prostheses of blood vessels, mammae, urinal ducts, pharynx, some substitutes for filling somatic cavities, prostheses of peritonaeum and other membranes, or ophthalomologic prostheses, and the like. In some of the said applications the hydrophilic gel has not to be dried up even in the preparation stage, since especially porous. hydrogels lose permanently their porosity when dried.

conventionally employed fungicidal and disinfecting agents cannot be used for the medical application of hydrophilic gels, since when applied in effective concentrations they may cause heavy irritations of the human eye, and moreover some of them are well-known as causing frequently allergic effects which .in some cases may be fatal. This fact eliminates practically the application of all agents having general antimycotic effects. The hereinbefore said drawbacks are overcome according to the present invention by storing hydrophilic gels in a system consisting of a receptacle of which the inner room is divided at least into two compartments. In one of them the hydrophilic material is stored under water or an aqueous solution while in the other, separated from the former by a permeable partition and communicating therewith, there is deposited a water-swellable polymer containing surface-active silver. The shape and arrangement of the system for storing hydrophilic gels can vary according to different application purports.

EXAMPLE 1 The most simple system to be employed consists of a little bag made of a porous, for example textile fabric manufactured of e.g. polyamide, polyester, cotton, and the like, which bag is filled up with a strongly acidic styrene divinyl-benzene cation exchanger which has been saturated with a solution of silver nitrate whereupon silver was reduced for inst. by means of hydrazine hydrate. The bag of an appropriate size is then put in a receptacle, the hydrophilic gel being stored above the same. For storing ocular lenses by the patient there may preferably be used a double system comprising two compartments each to receive one lens, and a central compartment between two perforated walls designed for silvered cation exchanger, the receptacle being provided with stoppers on either side.

EXAMPLE 2 For opticians practice there may be recommended well known plain containers made of polystyrene, where silvered cation exchanger is deposited under a false bottom. Alternately, well-known receptacles made of plastic, such as, for example, polypropylene, can be used for storing. For processing conditions it is advantageous to employ, for instance, a tank provided with a false bottom, the silvered cation exchanger being kept in the lower part thereof, in a bag, or in bulk, as referred to in Example 1, while in the upper portion there is arranged a device for depositing, or hanging up the hydrophilic articles to be stored. The protective system can be attached to a machine for manufacturing contact lenses, or hydrogel prostheses, preferably adjacent the moulds, since the hydrophilic products may be attacked by fungi within a period of being taken off from the moulds. The reduction of silver is carried out by any of Well-known methods, such as, for example, by means of hydrazine hydrate in an alkaline solution, or by means of other strongly reducing agents.

EXAMPLE 3 Strongly acidic styrene divinylbenzene cation exchanger is regenerated in a column by 10 percent hydrochloric acid into Hplus form, and rinsed with diluted 5 percent nitric acid and finally With water up to the neutral reaction. Thereupon it is converted to Ag-form by reacting with diluted 5 percent silver nitrate and rinsed with distilled water. The cation exchanger will then be taken olf from the column and flooded with double volume of percent hydrazine sulphate solution in percent aqueous ammonia. After the nitrogen evolution has been finished the cation exchanger together with the reduced silver will be washed through by water-decanting up to the last of the reaction to ammonia. The water layer above the cation exchanger must not react to ammonia even after a fortnights standing. The reduction of silver can be performed even by other methods, such as, for example, by means of formaldehyde, hydroquinone, glucose, and the like.

As cation exchanger there may be used a sulphonated styrene divinylbenzene polymer, preferably macroporous, or a carboxylic cation exchanger, e.g. on the basis of a co-polymer of methacrylic acid with divinylbenzene. The polymeric ion exchanger lattice is absolutely insoluble, guaranteeing thus that human organism could not be affected. Phenolic polycondensed cation exchangers cannot be applied for the purpose without being previously tested, since they may make free phenols which penetrate into the surrounding solution.

The grain size of the cation exchanger is to be selected in a suitable range lest individual grains might penetrate through the bag walls. The bags may be manufactured in any of well-known manners, such as, for example, by stitching both edges of a plied endless belt lengthwise together, further by a number of spaced transverse stitches, by cutting the stitched belt lengthwise in the middle, filling up the bags formed in such a way with the respective cation exchanger, and finally by stitching both free remaining edges together again.

A very convenient form of silvered cation exchanger is a membrane which can be cut to pieces which are then lodged under the false bottom or between two perforated partitions of the receptacle. Another embodiment consists in lining at least a part of the receptacle for the hydrogel with a silvered cation exchanger. The effect of the silver cation exchanger can be proved by a number of tests as follows:

II Lenses in physiologic solution inoculated with a mold culture.

III Leuses in physiologic solution Lenses absolutely intact.

plus Ag-cation exchanger.

IV Lenses in physiologic solution Lenses absolutely intact inoculated with a mold without traces of fungi culture plus Ag-cation growth.

exchanger.

With the above reference Groups I and II an intense up to mass attack of the lenses by molds occurs. On the other hand, with the test Groups III and IV where Agcation exchanger was used the lenses were perfectly limpid and intact, both macroscopically and microscopically. Thus the silvered cation exchanger meets all conditions to be laid down with a protective agent for disinfecting the material to come into contact with human organism, e.g. with the eye. Moreover silver cannot be found in the solution by using any of conventional analytic methods, and also no harmful eifects thereof on human organism were recorded. The silver cation ex- 4 ing aqueous liquid and penetrate into the hydrogel so that even spores in the swollen gel are killed when budding.

In the preparation of the contact ocular lenses as well as of hydrophilic methacrylate gels in general, the use of the silver cation exchanger is connected with the following advantages:

(i) The interval between the preparation and packing of the lenses can be extended whereby it is possible to obtain far better liberation of the lenses from any undesirable soluble substances. The lenses are not threatened with attack of molds and fungi before being packed.

(ii) The method enables to save two or three packers over the methods used heretofore.

(iii) Colour shades on the lenses, eye-burning, and

changes of dioptric values are eliminated.

(iv) The lenses can be perfectly sterilized when used by the patient who need not now sterilize them by boiling.

(v) The opticians and oculists manipulation with the lenses is made easier, since heretofore it has been necessary to employ at least one assistant to sterilize the lenses ready for application.

(vi) The main argument against wide practical application of the lenses can be disproved.

(vii) When using silvered cation exchanger together with physiologic solution the lenses can be applied directly on to .the eye-ball without additional washing.

What we claim is:

1. Apparatus for the storage of a swellable hydrophilic polymeric gel body such as a contact lens or other implant comprising a liquid container divided into at least two parts by a porous wall and having a physiologic liquid contained therein, one of said container parts being adapted to hold said gel body immersed in said liquid, a cation resin exchange material impregnated with a surface active metallic silver, said material being located in the other of the container parts and being soluble by liquid to release surface silver ions over a period of time to thereafter, freely flow through said porous wall into contact with said gel body.

2. The apparatus according to claim 1 wherein said exchange material is formed as a plurality of soluble beads, said beads being held in a porous fabric bag. 7

3. The apparatus according to claim 1 wherein said exchange material is formed as a membrane sheet.

4. The apparatus according to claim 1 wherein the resin exchange material comprises a strongly acidic styrenedivinyl-benzene containing surface active metallic silver.

5. The apparatus according to claim 4 wherein said resin exchange material is macroporous.

References Cited UNITED STATES PATENTS 1,883,967 10/1932 Krause 21-91X 2,066,271 12/1936 Irwin 424132 2,121,875 6/1938 Kruse et al. 2158X 2,283,883 5/1942 Conconi 424132 2,347,567 4/1944 Kresse 424-132 2,595,290 5/1952 Quinn 424-132 3,092,552 6/1963 Romans 424-432 3,211,281 10/1965 Speshyock et al 2065A 3,220,960 11/ 1969 Wichterle et a1 351 MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner