IE54081B1 - Colouring contact lenses with reactive dyestuffs - Google Patents

Abstract

Contact lenses comprising polymeric lens materials are coloured by reactive dyestuffs covalently bonded to monomer units of the polymer backbone, said dyestuffs being reactive dyes capable of forming ether linkages with cellulose, and being reactive with hydroxyl, amino, amido or mercapto groups present in a hydrogel polymer to form the covalent bond therewith. The invention is of particular interest in the area of "soft" contact lenses (hydrogel lenses).

Description

This invention relates to tinted contact lenses and to a method for their preparation.

In particular, the invention concerns contact lenses comprising polymeric lens materials in which reactive dyestuffs have been covalently bonded to monomer units of the polymer backbone. The invention is of particular interest in the area of so-called hydrophilic or soft contact lenses, commonly referred to as hydrogel lenses.

Hany of the known methods for tinting or coloring plastic materials are unsuitable for practical coloring of contact lenses, in particular >0 of hydrophilic contact lenses. For example, those methods whereby a coloring agent- is dispersed in a plastic by dissolving or dispersing a dye or pigment in a monomer precursor or in the polymer matrix cannot be used to obtain satisfactory water-absorbable materials. This is because water induces a migration of the coloring agent within the '5 plastic material and a leaching of the colorant outside of it. This migration, moreover, can be accelerated during heat sterilization treatments as commonly used with hydrophilic lenses, since the heating process in most cases expands the poiymer matrix. Therefore, the most common method for preparation of hard contact lenses, in which the lens 20 blanks are tinted or colored, would not be feasible for the preparation of soft lenses.

One alternative approach for coloring plastic materials is che use of printing, transfer or coating methods. According to this process, a coloring agent is caused to adhere to the surface oi che plastic. This method is also unsuitable for coloring water-absorbable plastics, such as are used for the preparation of hydrophilic contact lenses. If a plastic material colored by this method is allowed to swell in water, che applied layer of coloring agent does not swell as much as the plastic itself. Consequently, the coloring agent will become dissociated from the surface of the plastic. In any event, a simple transfer coloring method does not obviate the problem of leaching and will always be limited by the degree of physical adhesion of coloring agent to the surface.

A number of methods have been disclosed in the literature whereby all or a portion of a soft contact lens is painted or printed using an implement such as a brush. For example, in Contact Lens Forum, volume 3, March 1978, pp. 13-17, a method is disclosed in which the surface of a lens is colored by a chemical printing process. This method, however, is not entirely satisfactory, as it is noted that the color tends to fade after several autoclavings.

The use of water-soluble dyes is also unsatisfactory for the preparation of, in particular, soft contact lenses. Water-soluble dyes will leach during repeated thermal sterilization treatments. Moreover, watersoluble dyes in long term contact with the eye might permenently stain the ocular tissue. Thus, the method disclosed in the American Journal of Optometry and Physiological Optics, Volume 54, pp. 160-164 (1977), Methods of Tinting Soflens (Trade Mark) Contact Lenses, would not provide a solution to the problem of preparation of practical tinted soft contact lenses.

In addition to the problems engendered by the use of hydrophilic plastic material for the preparation of these lenses, there is an addition complication introduced by the dimensions of the lens itself. ι _ 54081 Conventional hard contact lenses, generally prepared from formulations using as principal co-monomer methyl methacrylate, are in general fitted with a diameter which is less than the diameter of the cornea of the eye. It is therefore possible to use a lens uhich is colored over its entire extent. In contrast, soft contact lenses are most commonly fitted with a diameter larger than that of the cornea. Because of this feature, a uniformly-colored soft contact lens would appear quite prominently against the white sclera of the eye. In order to prepare a neutral appearing contact lens, it would therefore be necessary to have a 0 colored central area and a clear outer perimeter.

As noted in U.S. Patent 4,252,421, the preparation of such lenses leads to difficulties in fabrication. These must be no bleeding of color from the central portion into the outer, clear portion. Colored area and clear area should, moreover, be concentric and easily aligned during the preparation. Finally, it is essential that there be no leaching of color either into che tear fluid or into the sterilization solution.

U.S. Patent 4,252,521 discloses a method for preparation of soft contact lenses containing a tinted central core and an outer lens element which is usually clear. The colored central core is formed from a tinted button, which in turn is polymerized from a monomer mixture which includes a dye as co-monomer. Thus, the water-insoluble dye or dyes are part of the backbone of the polymer. Alternatively, a water-insoluble dye may be added to che co-monomer mixture and this combination poly25 merized, whereby the dye is entrained in the polymer matrix. Due to the insolubility of the dye, it will not bleed or leach from the polymerized button. Two methods are also disclosed for fabricating the contact lens. The first method involves polymerizing the tinted button, placing the tinted button in a mold and pouring a hydrogel co-monomer mixture around the tinted button and polymerizing this mixture. An alternative method for forming the lens is to polymerize the clear outer button initially and then to form a centrally-positioned aperture 5408 I through the button. The co-monomer mixture including the dye is then placed within the aperture and polymerized.

This method suffers from a number of substantial drawbacks. With respect to the method in which a water-insoluble dye is merely entrained in the polymer matrix,the difficulties enumerated above will be present. In contrast to the uniform composition of a conventional hydrophilic contact lens, the lenses produced according to U.S. Patent 4,252,421 are a combination of hard lens and soft or hydrogel lens materials. Moreover, the preparation of these lenses requires a number of separate fabrication and polymerization steps. In addition, lenses of this type must be specially prepared for each prescription.Therefore, a substantial inventory must be carried by the dispenser of contact lenses in order to cover the range of prescriptions and colors normally desired. Finally, the use of combination hard-soft lenses would generally lead to a wrinkling or crimping of the edge upon hydration, causing discomfort to the wearer.

U.S. Patent 4,157,892 discloses a method for coloring water-absorbable plastic which comprises four steps. The first step is manufacture of a coupler monomer or coupler polymer. A polymerization radical is introduced into a coupler agent to obtain a polymerizable coupler mono20 mer. from which a coupler polymer may be manufactured. Either of the couplers obtained in the first step is then copolymerized or polymerized with a water-absorbable plastic in the form of a monomer or a polymer in the presence of a polymerization initiator to produce a water-absorbable plastic capable of developing color. The material thus prepared is formed into a intermediate product having the same dimensions as those of the desired final product, such as a waterabsorbable contact lens. Finally, the intermediate product is colored by immersion of the lens in an aqueous solution of a diazonium double salt which acts as a developer. The inmersion is continued for a length of time required to cause the swelling of the intermediate product, thereby allowing the diazo-component to penetrate into the plastic.

Then, the solution is controlled to optimum pH value for causing a '5 4 0 81 coupling reaction to take place and to allow the azoic dye to devolop its color on the final product. The production of partially-colored intermediate products is possible through the application of ultraviolet radiation to those portions of the plastic which are not to be colored, whereby the diazo-cotaponents on those portions are broken down.

This method again has the disadvantage of being procedurally quite complicated. The procedure for preparation of the material in which the color is latter to be developed must be carried out in a series of discrete steps, and care must be taken that is no premature development of the azoic dye in the lens material. Moreover, the azoic dye precursor is dispersed throughout the lens material, which could lead to differences in color intensity dependent upon the thickness of the lens material. In order to provide colored lenses for a wide variety of prescriptions, it would again be necessary for the dispenser to keep a large inventory. In addition, it is clear that this method is only suitable for use with specially-prepared lens material, including a coupler. Therefore, it would not be feasible to use the method taught in U.S. Patent 4,157,892 with conventional hydrophilic lens materials currently in use. Finally, the use of couplers of the type described in this reference would be likely to lead to polymeric materials of inferior quality, compared to materials now in use for this purpose.

It is therefore a goal of the present invention to avoid the problems associated with the prior art methods. In particular, it is an object of the instant invention to provide a method of tinting or coloring contact lenses which can be carried out without the need for complicated procedures and specialized equipment. It is an additional object of the instant invention to provide a method of coloring lenses which can be kept in inventory in an untinted state, or uhich are already available on the market and/or have been prescribed to the patient.

Further objects of the invention include the development of a method for preparing a contact lens which appears completely natural as worn 5408) on che eye, i.e., lenses having a central colored portion covering che cornea and clear edges over the part of the lens covering the sclera.

It is additionally an object of che invention to provide contact lenses which will retain the color over long periods of time and repeated chemical and/or heat sterilization treatments. It is a further object of the invention to prepare contact lenses in a vide range of colors and color combinations through mechanically simple procedures.

One object of the invention is a contact lens at least a portion of it is colored, comprising a polymeric hydrogel material containing ° hydroxyl, amino, amido or mercapto groups to which at least one reactive dyestuff, capable of forming an ether group with cellulose, is covalently bonded external to the polymer backbone through ether, thioether, amino or amido groups.

A wide variety of polymers are suitable for use in the preparation of 15 the novel lenses. The only requirement is that the monomers contain at least one of the functional groups capable of reacting with a reactive dyestuff, either before or after polymerization of the monomers to form the polymer.

The composition of the lens material itself can vary within wide limits, the only requirement being the presence in the monomer mixture of at least one component which will provide the polymer with the required exoskeletal functional groups. Particularly suitable as monomers for this purpose are hydroxyalkyl esters of polymerizable unsatut3ted acids. Among such esters, hydroxyethyl methacrylete (KEMA) has been *> ε , . used quite extensively; lenses prepared trora such materials are disclosed, for example, in U.S. Patents 2,976,576 and Re 27,401.

In general, however, any polymeric material suitable for use in the preparation of a contact lens can also be used for the preparation of the inventive tinted lenses, with the proviso that at least one of the monomeric components uhich forms the material contains the exoskeletal functional group vhich can react vith Che reactive dyestuff molecule. Therefore, the instant invention can be employed wich a vide variety of known polymeric lens materials. This allows for the possibility, of preparing tinted contact lenses according to the invention from the wide range of materials already available, as well as novel contact lens materials yet to be developed or marketed.

In addition to hydroxyalkyl esters of unsaturated acids, the following monomeric materials may serve as typical examples of co-monomers which can be used in conjunction with monomers providing the required functio10 nal groups: acrylic and methacrylic acids; alkyl and cycloalkyl acrylates and methacrylates; N-(l,l-dimethyl-3-oxobutyl) acrylamide; and heterocyclic N-vinyl compounds containing a carbonyl functionally adjacent to the nitrogen in the ring, in particular N-vinyl lactams such as N-vinyl pyrrolidone. Moreover, one or more cross-linking agents may be used, as known in the art, in order to provide a polymeric material of optimal properties. Examples of such cross-linking agents include trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate (EDMA) and diethylene glycol bis-allyl carbonate.

Useful reactive dyes according to the instant invention are commonly referred to as reactive dyes forming ether linkages inasmuch as the reactive group or groups in this known class of dyes react with cellulose to form an ether linkage, as opposed to, for example, an ester linkage. Such reactive dyes forming ether linkages are generally described in FIBRE-REACTIVE DYES Chapter VI, by W.F. Beech, SAF International Inc,, New York (1970).

This class of reactive dyes are believed to react with hydroxyl, amino, amido or mercapto groups present in the hydrogel polymer network of contact lens materials primarily by nucleophilic addition to form a covalent bond therewith. 5408( A wide variety of commercially available dyes, reactive via nucleophilic substitution, are suitable for use in the preparation of the inventive contact lenses. In addition, virtually any desired shade or tint can be achieved through the use of a particular reactive dye or combination of reactive dyes.

Thus, dyes containing an activated double bond which is able to add to the functional group external to the polymer backbone can be used according to the invention. For example, exosketetal bond activated by a bridge member such as an -SO^-, -SO- or -CO- group are particularly suitable for use according to the invention. Similarly, dyes wich functional groups which can undergo addition reactions with exosketetal double bonds of the polymer may be employed.

Among the types of reactive dyes suitable for use according to the invention, the following general classes may be mentioned: reactive dyes containing vinyl sulfone precursors, such as β-sulfatoethylsulfonyl, β-sulfatoethylsulfonamido, β-hydroxyethylsulfonyl and β-hydroxyethylsulfonamido substituents, as well as suitable derivatives thereof, dyes containing acryloylamino, β-chloropropionylamino, and β-sulfatopropionylamino and related reactive groups; dyes containing β-phenylsulfonylpropionylamino groups; dyes containing β-sulfato- or β-chloroethylsulfamoyl groups; chloroacetyl dyes; α-bromoacryloyl dyestuffs; and a wide variety of other reactive dyes which have been developed for use in the dyeing of natural and synthetic fibers, in particular of cellulose and wool and function by nucleophilic addition. Although there are many examples in the art of the use of reactive dyestuffs with clothfiber materials, the application of these dyes to the preparation of tinted contact lenses has not bean disclosed until this time.

Some typical examples of commercially available dyes suitable for use according to the invention are: Dye-SO^-CH^-CH^-O-SO^Na (Remazol), Dye-SO^NKCH^CH^OSOjNa (I.evafix), Dye-’:K-OC-CH.CH,SO7CgH5 (Solidazol), (Lcvarix and Solidazol are Trace Marks) , Dve-HK-OC-CH-CR,Br (Lanasol), Dye-NH-OC-C-CH, , Dye-NHCHOH (Calcobond). I 2 | 4 Z Br Br Similarly, within the scope of the invention is che use of dyestuffs containing more than one reactive group capable of forming a covalent bond by nucleophilic addition with hydroxyl, amino, amido or mercapto groups present in the hydrogel polymer network of contact lens materials.

Preferred contact lenses of the invention are those in which the reactive dyestuff is covalently bonded to -0-, -HR2-, -CO-NR2 or -S- groups, wherein R2 is alkyl having 1 to 6 carbon atoms.

Preferred reactive dyestuffs capable of forming a covalent bond with the hydroxyl, amino, amido or mercapto groups present in the contact lens hydrogel material are those having the general formulae D - R - C « CH, 1 2 X (I) D - R - CH - CH, (II) wherein ck-ch2D is the radical of an organic dyestuff; R is a divalent organic electron attracting group capable Lng electron withdrawal of the C carbon atoms in the -C=CH,- or groups of formulae I and II, thus activating the same; X is hydrogen or halo; and Y is a leaving group; or mixtures thereof.

The radical D may advantageously be the radical of an azo, phthalocyanine, azomethine, nitro or anthraquinone dye.

The reactive dyestuffs of formula II will eliminate in the reaction media HY thus forming intermediates of formula I, which react then by nucleophilic addition. 091 The divalent group -R- is advantageously bonded directly to an aromatic nuclear carbon of D, or is bonded thereto via an aliphatic group such as an alkylene group, e.g., a lower alkylene group. Most preferably, -R- is directly bonded to a nuclear carbon atom of D.

Suitable divalent R groups include -CO-, -SO^-, -SO-, -NHCO-, -NHSO^-, -SO^NH- and the like. Most preferably, -R- is -SO.,-, -SO^NH-, -CO- or -NHCO-.

Uhen X is halo, it is most preferably chloro or bromo.

Suitable leaving groups Y include -Cl, -Brz -OH, di-lower alkylamino, +/’~\ - +,., -OCH^N^ /· Cl , -SOj-phenyl, -OSO^- Z wnere Z is a cation, -OSOqR^ of -OSO^R^ where in each case is alkyl, aryl, aralkyl or alkaryl.

Advantageously where R^ is alkyl, it is alkyl of 1 to 6 carbon atoms, preferably alkyl of 1 to 4 carbons, including for example, methyl, ethyl, isopropyl, butyl and the like. Where is aryl, it is preferably phenyl or naphthyl. Where R^ is alkaryl, it is preferably lower alkyl substituted phenyl, such as tolyl or xylyl, and where R^ is aralkyl, ic is preferably lower alkylenephenyl, such as bentyl or phenethyl.

The reactive dyes of the class known as chose forming ether linkages especially suitable for tinting hydrogel contact lens materials are those reactive dyes which form a covalent bond with the hydroxyl, amino, amido, or mercapto groups present in a hydrogel polymer network in an aqueous medium having pH of 9 or greater and a ccmperature of up co 4O°C. Such reactive dyes, especially those of formula (I) or (II), are capable of dyeing hydrogel contact lenses without any significant degradation or deformation of che hydrogel substrate, due co the mild reaction conditions. 409» The invention provides novel tinted lenses with exceptional color fastness and color uniformity. According to the requirements in a particular instance, the dyestuff can be applied to both surfaces of a lens or to one surface only. In addition, the lens may be colored only in a particu5 lar portion. Thus, it is possible without difficulty to prepare lenses uith, e.g., colored central portions and clear edges, or with an annular colored portion corresponding to the iris. The method can also be used, for example, for the application of identifying indicia on lenses, such as to indicate the concave or convex surface of a flexible lens.

Although tinting or coloring is effected by contacting one or both surfaces of the lens with an aqueous solution of the dyestuff, interior parts of the lens will also be tinted or colored to some extent due to the diffusion of the dyestuff during the reaction time. '5 In general, the formation of a covalent bond between the lens material and the reactive dyestuff is effected by a simple contacting of the dyestuff formulation, such as a mildly basic aqueous solution, with the lens material until reaction is complete. In a case where both surfaces of a lens are to be dyed, the lens is contacted on both surfaces with a formulation of the reactive dyestuff. The shade of color is controlled by the time of contacting with the dye formulation, as well as the reactivity of the eye with the surface of the lens. When it is desired to apply the dye to one surface only, or to a specific portion of the surface, the prepared lens may be placed on a fixture or in a mold, and the reactive dyestuff formulation applied only to a specific portion or portions of the lens surface. In view of the complicated methods generally employed in the art, this simple mechanical procedure for tinting contact lenses is an enormous advance over the known methods.

Moreover, where desired, deep, fast dyeings can be easily obtained, e.g. such that the lens has a light transmission oi 90 2 or less in the 4 091 desired visible color range, and substantially devoid of opacity, over the colored portion of the lens.

After the reaction of the lens material with the reactive dyestuff is efiected, unreacted dyestuff may be removed using any suitable solvent.

The choice of solvent for extraction or rinsing is, of course, dependent upon the solubility of the particular dyestuff. For the majority of dyestuffs in current use, lower alcohols such as methanol are suitable solvents. After the cleaning process, the tinted lens is freed of traces of the solvent, for example by boiling in distilled water.

For economic reasons, it is preferable to treat the already polymerized material with the dyestuff preparation. However, it would also be possible to treat a monomer such as HEMA with reactive dyestuff prior to polymerization, and subsequently to polymerize the reactive dyestuff - monomer units.

Because of the formation of a covalent bond between the polymeric material forming the contact lens and che reactive dyestuff, the lenses of the invention show a remarkable color fastness to all types of sterilization treatments commonly used for contact lenses,such as chemical, enzymatic and heat sterilizations. Moreover, since the coloring material is applied directly co the surface or surfaces of the lens, the shade is independent of lens thickness. This is in marked contrast to lenses prepared from plastic buttons in which pigment is entrained in che polymer matrix, since, in this case, the intensity of che shade is directly dependent upon the thickness of the lens. This is true, for example, with the contact lenses prepared according to U.S. Patent 4.157.872.

Moreover, since the inventive method allows for the introduction of the coloring material at any time during the preparation of the colored lenses, it is possible to tint lenses after filling a particu30 lar prescription with conventional clear lenses. Thus, it is not 4 0BI necessary to keep a large inventory of precolored lenses, a substantial drawback of many of the known methods for preparing tinted lenses.

After fitting conventional clear lenses, the color could be introduced as a final step before dispensing to the patient. Alternatively, previously prescribed lenses could be subsequently custom-tinted according to the desires of the wearer. Since the range of polymeric materials suitable for use according to the invention is sufficiently broad to embrace virtually all lens materials in current use, che inventive method is of an almost universal applicability. jq Another advantage of the invencive method is the extreme reduction in cost of preparation of the inventive contact lenses, relative to known methods for preparation of lenses containing at least a cencral portion which has been colored. Suitable reactive dyes are readily available, and the ease of application of these dyes to the lens materials makes unnecessary the use of complicated polymerization procedures or equipment Tests on the oxygen permeability of lenses treated according to the invention have shoun that there is virtually no change in oxygen permeability after treatment 3S can be seen from the following table: j- | Clear Lenses Tinted Lens (Blue) lOxygen Concentration *(P ) Transmittance Oxygen Cone. (P ) j Po "6·1θ) (at max. « 587nm) ft - 6.10) 0 jl. 1.68 68.3 Z 1.71 :2. 1.47 23.0 Z 1.30 ;3. 1.56 j 9.3 Z 1.51 ;4. 1.66 1 t 0.0 Z 1.60 1 * Tested under same technique as reported by M.F. Sefojo, F.J. Holly 2o and P.L. Leong, Contd. Intraocular Lens Med. J., 3(4) (1977) 27, An additional advantage of the inventive lenses is the fact that most of the dyestuffs employed foe tinting tend to absorb ultraviolet radiation, particularly of the wavelengths shown to be harmful to the eye, for example in Optical Management, Ultraviolet Radiation and the Ocular Media, January 1981, pp. 21-33. In particular, it has been reported that ultraviolet radiation may be directly linked to the development of cataracts.

The invention may be better understood through the following Examples: Example 1: Totally Blue on Both Sides of Tinted Lens A stock solution, stable for at least 5 weeks, is prepared by dissolving 0.1 g of a dyestuff of the formula HO NH, 1 1 2 0 ll <6 ά \ / ll HO.S-O-C-H.-S-·; \ \-m-< >-s-c,h-o-so.h 3 2 4« " i ii 2 4 3 / / \ A \ NaOjS · · SOjNa in 10 ml of 0.001M HCl solution. A clear HEMA lens is soaked in 1.0M sodi™ carbonate solution. The sodi™ carbonate soaked lens is then placed into 0.11 ml of the stock solution, k ml of 1.0M sodi™ carbonate solution is then added, and the lens allowed to remain in the solution for 53 minutes. The tinted lens is then neutralized vith a buffered saline solution (pH » 7.0). Then the tinted lens is extracted, with methanol as a solvent, in a solvent extraction apparatus, until there are no dye molecules leaching out. This may be readily determined, for example, by spectrophotometer. After the extraction process, the tinted lens is boiled in distilled water for one hour to get rid of any trace of methanol.Then the tinted lens is stored in a saline butter solution.

The transmittance of the tinted lens at wavelength 600 nm is 68 Z. 540β| Example 2: Totally Aquamarine on Both Sides of Tinted lens A stock solution, stable for at least 3 weeks, is prepared by dissolving 0.1 g of a dyestuff of the formula CuPhc in 10 ml of 0.001M HCl solution. The lens which has been soaked in 1.0M sodium carbonate for 10 minutes, is placed into 1 ml of the stock solution. Thus 4 ml of l.Oti sodium carbonate solution is added, and the lens soaked for the desired time. The procedures of washing, extracting and rinsing of the lenses are the same as in Example 1.

The transmittance of the tinted lenses at wavelength 670nm are 80 Z and 70 Z for tvo and four hour soakings, respectively.

Example 3: Totally Brown on Both Sides of Tinted Lens Three stock solutions are required for this process, all of which are stable for at least six weeks.

A) 0.0512 g of a dyestuff of the formula OH ίχ/ ^COCH, • · · I II I • · · in 5 ml of 0.00 lti HCl solution.

B) O.O574g of a dyestuff of the formula 4 0 91 in 5 ml of 0.001M HCl solution C) 0.0291 g of a dyestuff or the formula OH NH. I H-O3S-0-C2H4-S-< >-N-Nx ίχ / 11 ·»· · · · I II I • · / / \ ά \ NaO^S . ·ζ SO^a 11 >-S-C,H,-O-SO H Ζ I, 2 4 3 P in 5 ml of 0.00111 HCl solution.

The lens, which has been soaked in 1.0M sodium carbonate solution for minutes, is placed into O.1S ml of A, 0.12 ml of B and 0.2 ml of C stock solutions. 1 ml of 1.0M sodium carbonate solution is then added and for one hour allowed to stand. The transmittance of the tinted lens at wavelengths 400, 490 and 605nm are 45 2, 51 2 and 60 2 respecti10 vely.

Example 4: Totally Green on Both Sides of Tinted lens The lens, which has been soaked in 1.0M sodium carbonate for 10 minutes, is placed into 0.18 ml of solution C and 0.12 ml of solution B prepared according to Example 3. Then 1 ml of 1.0M sodium carbonate solution is U added, and the lens allowed to soak in the solution for 30 minutes. The transmittance of the tinted lens at wavelengths 580 and 385nm are 64 2 and 58 2, respectively.

Example 5: Edge Clear/One Side Tinted Lens The tinting procedures are the same as for the Examples 1-4. The only difference is that the clear lens sits in a fixture. A suitable dye solution is then put into a mold, rather than immersing the lens in the eye solution. The area to be colored only is then brought into contact with the dye solution. The final steps of the procedure are the same as in Example 1. 0 01 Preparation of a fixture suitable for preparing the specific type of partially-tinted lens desired is a mechanically simple task. One type of fixture found useful for preparing clear-edge lenses may be described as follows: The fixture has three interlocking pieces. The bottom piece is a dome upon which the lens is positioned. The curved surface of the dome has a diameter corresponding to that of the lens to be tinted. The top piece acts as a reservoir for the dye solution and has an elastic gasket. This gasket forms a seal on the surface of the lens at the edge of the area to be tinted. The third piece is a housing for the reservoir/gasket assembly. The entire fixture is Chen inserted in a clamp to hold the assembly firmly in place during the dyeing process.

The lens, which has been soaking in 1.0M sodium carbonate for 10 minutes, is placed in position on the dome. The reservoir portion of che fixture is positioned and clamped. The reservoir is filled with che desired concentration of dye and sodium carbonate solution. The solution is allowed to remain in contact with the lens until the desired shade is obtained. The reservoir is purged with water until all traces of the dye solution have been removed. The lens is then removed from the fixture.

Similarly good results may be obtained using, for example, dyestuffs of the following structures: \/ \Z \z Η ίί ΐ SOjNa \z \ / \ < B is./' XS02CH2CH70S03H -Cu-tf tJHCOCH^ -N-N· · · I II I Β40βΙ NaO HO,S-O-C_H,SO 3 2 4 2 ?CH3 < >-S03Na ·· 0CH. ia. z\ z\ ·« · HO.S-O-C.H.SO ’/-Ν-Ν-·' '«-NHCOCH, 2 4 2 \ / I II I 3 Na0/‘ W Many of these dyes are readily available on the market, and dyes of this type have been known in the art for many years. These Examples should be viewed as illustrative only, without in any way limiting tbe scope of the instant invention.

Claims (17)

1. CLAIMS;

1. A contact lens at least a portion of it is colored, comprising a polymeric- hydrogel material containing hydroxyl, amino, amido or mercapto groups to which at least one reactive dyestuff, capable of 5 forming an ether group with cellulose, is covalently bonded external to the polymer backbone through ether, thioether, amino or amido groups.

2. A contact lens according co claim 1, wherein said reactive dyestuff 2 2 2 is covalently bonded to -0-, -SB. -, -CO-HR or -S- groups, wherein R is alkyl of 1 to 6 carbon atoms. j_0

3. A contact lens according co claim 1, wherein said reactive dyestuff is bonded through a group of formula -CH-CH - or -tx-CH, wherein X is χ 2 3 halo or hydrogen, to the oxygen , nitrogen or thio group.

4. A contact lens according to claim 1, wherein said reactive dyestuff residue, bonded to the polymeric hydrogel, is of the formulae D-R-0-CH, (I) 15 X 3 or d-r-^h-ch 2 ~ (II) wherein D is the radical of an organic dyestuff; R is a divalent organic electron attracting group 20 capable of causing electron withdrawal of the C carbon atoms, thus activating the same; X is hydrogen or halo; or mixtures thereof.

5. A contact lens according to claim 4, wherein D is che radical of an 25 azo, phthalocyanine, azomethine, nitro or anthraquinone dye.

6. A contact lens according to claim 4, wherein R is -CO-, -SO -, -SO-, NHCO- or -NHSO^. 2

7. A contact lens according co claim 1, comprising a colored central portion and a clear annular edge. 5

8. A contact lens according to claim I substantially as described with reference co any of the Examples.

9. , A process for preparing a contact lens at least a portion of it is colored, comprising reacting at least one reactive dyestuff, capable of forming an ether group with cellulose, with hydroxyl, amino, amido

10. Or mercapto group present in the polymeric hydrogel contact lens material, and removing unreacted dyestuff from said lens material. )0. A process according to claim 9, wherein said lens material is in the form of a contact lens.

11. A process according to claim 9, wherein the reaction is conducted 15 in an aqueous medium having a pH of at least 9 and at a temperature of up to 40’C.

12. A process according to claim 9, wherein the reactive dystuff is applied to only a portion of said lens.

13. A process according to claim 9, wherein said dyestuff reacts by 20 nucleophilic addition to said hydroxyl, amino, amido or mercapto groups in the hydrogel material.

14. A process according to claim 13, therein the reactive group of said dvestuff is one of the formulae -C»CH_ or-CH-CH , wherein X is I - .II 2 X X Y hydrogen or halo and Y is a leaving group. 25 15. Λ process according to claia 9, wherein said reactive dyestuff is of the formula D-R-C-CH I 2 X or D-R-CH-CH, 1 I i X Y wherein D is the radical of an organic dyestuff i 5 R is a divalent organic electron attracting group capable of causing electron withdrawl of the C carbon atoms, thus activating the same; X is hydrogen or halo; and Y is a leaving group; 10 or mixtures thereof. 16 > A process according to claim 15, wherein R is -CO-, -SO^-, -SO-, -NHCO- or -NHSO 2 -. 17. A process according to claim 15,wherein D is the radical of an azo, phthalocyanine, azomethine, nitro- or anthraquinone dye.

15. IS, A process according to claim 15, wherein the leaving group is Cl, Br, OH, dialkylaaino, SO^-phenyl, OSO^ 2 where Z is a cation, OSO^R^ or here R^ is alkyl, aryl, aralkyl or alkaryl.

16. 19. A process for preparing a contact lens according to claim 9 substantially as described with reference to any of the Examples.

17. 20 20. A contact lens when prepared by a process claimed in any of claims 9to 20.