Method of Making a Contact Lens Material Which May Be Identified

Fluorescent dots have been applied to the front surface of the lens to identify the lens. It is sometimes difficult for the practitioner to identify the right and left contact lens. Fluorescent dots are applied to the edge of the right lens to aid in right and left lens identification.

The use of fluorescent materials in the bifocal segments of contact lenses has been in use since 1970. Fluorescent material added to the bifocal segment makes the segment visible to the contact lens fitter. With the use of an ultraviolet light source to cause the bifocal reading segment to brightly fluoresce the position and fit of the bifocal reading segment may be evaluated. Charles W. Neefe, U.S. Pat. No. 3,597,055, Aug. 3, 1971.

Fluorescent compounds in contact lenses aid to locate them in the dark. L. Gusewitch, U.S. Pat. No. 3,189,914, June 15, 1965.

An article by Charles W. Neefe, "Circle of Confidence Lens Identification", Contact Lens Forum, September 1981.

At this time many new and varied contact lens materials are becoming available to the practitioner and the necessity for material type identification becomes important. These new materials are alike in appearance and feel and may differ only in oxygen permeavility or wetting angle. The practitioner has no method to readily identify the material. Counterfeiting and substitution of lens materials and misleading advertising has become common place. A method is needed for the practitioner and laboratories to identify lens materials for duplication purposes and to prevent receiving materials other than those ordered.

A small amount of colored ultraviolet activated fluorescent material is evenly distributed throughout the lens. The fluorescence is of a low level and is not visible to the eye until the fluorescent light is concentrated at the lens edge. This concentration of fluorescent light can occur only when the lens is dry and off the eye. When immersed in tears having a refractive index of 1.337 which is close to the lens refractive index of 1.49, no concentration of light will occur as the critical angle of refraction at the lens surface is too low. When the dry lens is in air having a refractive index of 1.0 the critical angle of refraction will be much higher and the fluorescent light will be totally reflected at the lens surface back into the lens. Polished optical surfaces above the critical angle act as mirrors and reflect light back into the lens structure. The critical angle is the angle of incidence beyond which refraction is impossible and the optical surface becomes a total reflecting surface. This phenomena makes fiber optics possible and is the principal upon which this invention functions. Polished surfaces such as prisms and fiber optics become almost perfect mirrors with little loss of light above the critical angle. The two lens surfaces act as a wave guides containing the fluorescent light between the lens surfaces and allowing the light to exit only at the lens edge. The fluorescent light eminating from within the lens is concentrated at the lens edge and is visible in a darkened room as a colored light at the periphery of the lens.

To the mixture of lens monomer the required transparent colorants are added, generally gray, blue, green and brown colorant are used in contact lens.

FD and C Green #6, Leeben Color Blue LA-589, Brown LS-595, Green 16128 and Violet LS-611.

The acid dyes known as azo dyes containing nitrogen to nitrogen bonds--N.dbd.N--may be used to practice the invention as may the dyes known as reactive dyes and the sulphur dyes. The sulphur dyes are fixed of made fast by removing the sodium sulphide which made the dye soluble. Reactive dyes require no special fixing step, only extraction of unreacted dye as they react chemically with the material and are thus made permanent. The properties of the dyes are well known to the art.

Fluorescence is a process of photo-luminescence by which light of short wavelengths, either in the ultra-violet or the visible regions of the electromagnetic spectrum, is absorbed and reradiated at longer wavelengths. The re-emission occurs within the visible region of the spectrum and consequently is manifested as color.

Fluorescent pigments are transparent organic resin particles containing dyes which are capable of fluorescing while in a solid state solution.

Certain substances, especially a number of organic dyes, have the property of fluorescing under ultraviolet light. The fluorescence of these organic dyes is associated with the individual dye molecules; and in order for them to fluoresce efficiently, they must be dissolved in fairly low concentrations in a solvent for the dyes. Due to the nature of the dyes used, it is necessary to have an organic medium or carrier to put them into solution; and in order to have a pigment, it is necessary that this medium be a solid. The type of material which meets these requirements for a carrier or matrix for the dyes is a transparent organic resin.

The physical structure of the pigments is amorphous, or non-crystalline. In contrast to most other pigments, they are not formed by precipitation and do not consist of particle agglomerates, but rather of individual nonporous particles. This and the fact that they are powdered organic resins makes their dispersion into the lens material relatively easy.

The particle size range of fluorescent pigments is sub-sieve, or finer than 325 mesh (44 microns).

Fluorescent pigments are stable to indoor light or conditions of outdoor light other than direct sunlight.

It is possible to mix more than one fluorescent pigment and a nonfluorescent colorant in the same formula.

To the liquid monomer mixture a small amount of a colored fluorescent material is added. These trace amounts of fluorescent materials do not alter the visible color of the lens. This mixture of monomers, transparent colorants, and fluorescent pigments are polymerized to produce blanks for the manufacture of contact lenses. The fluorescent colorants are secured in the polymer structure and will not leach from the material. The fluorescent colors are red, blue, green, gold, etc. The concentration of the fluorescent material is extremely low, ranging from 0.0003 to 0.009 parts by weight of lens monomer. In a darkened room the lens is placed concave side up and the convex surface on a dark flat surface and an ultraviolet lamp irradiates the lens. No fluorescence is visible in the central lens area, a ring of colored light is seen at the edge where the light eminating within the lens by fluorescence is concentrated. THE HARD GAS PERMEABLE LENS MATERIAL IS MADE AS FOLLOWS:

The permeable silane-methacrylate coppymer is made as follows: 100 milliliter of a reactive monomer such as monomeric methylmethacrylate is placed in a holding flask. 2 to 150 milliliter of a reactive organosilane such as Y-methacryloxypropyltrimethoxysilane (CH.sub.2 =COCH.sub.3)CO.sub.2 (CH.sub.2).sub.3 Si(OCH.sub.3).sub.3) having a molecular weight of 196.3 is placed in a second vessel and heated to 80.degree. C. and a catalyst such as benzoyl peroxide 0.50% by weight of the Y-methacryloxypropyltrimethoxysilane is slowly added. Stirring is continued until polymerization is noted by a slight increase in viscosity. The temperature is reduced to 50.degree. C. and the silane is allowed to thicken to a syrup state. The polymerized silane syrup containg large molecules is slowly added to the monomeric methylmethacrylate monomer and 0.008 parts by weight Radiant Green 31 thoroughly mixed. The mixture is purged of atmospheric oxygen and placed under a nitrogen blanket in a 55.degree. C. water bath of 24 hours.

A material is prepared by polymerizing 50 parts by of 1,1,1-tris(trimethysiloxy)methacryloxypropylsilane,40 parts by weight of methylmethacrylate, 3.5 parts by weight of Bis(methacryloxypropyl)tetramethyldisiloxane and 6.5 parts by weight of beta-styrene sulfonate, .0.009 parts by weight Radiant Red No. 35 in the presence of 0.25 parts by total weight benzoyl peroxide. The mixture is placed in the mold and placed in a 70.degree. C. water bath for 12 hours and post cured at 85.degree. C. for 24 hours. Contact lenses are fabricated by lathe cutting the concave and convex surfaces. The lenses are edged by conventional techniques and are hard, transparent, highly oxygen permeable, and wettable.

This example demonstrates the polymerization of the siloxanyl alkyl ester 1,1,1-tris(trimethylsiloxy)-methacryloxypropylsiloxane and the oxygen permeable crosslinking agent Bis (3-glycidoxypropyl)tetramethyldisiloxane.

The material is prepared by polymerizing 45 parts by weight of 1,1,1-tris(trimethylsiloxy)methacryloxypropylsiloxane, 45 parts by weight of methylmethacrylate, 5 parts by weight of Bis(3-glycisocypropyl)tetramethylsisiloxane and 5 parts by weight of dimethylamionoethyl methacrylate 0.007 Parts by weight Radiant Blue No. 39 in the presence of 0.25 parts by weight of benzoyl peroxide. The mixture is placed in the mold and placed in a 70.degree. C. water bath for 12 hours, and post cured at 85.degree. for 24 hours. Contact lenses are fabricated by lathe cutting and polishing the surfaces. Lenses are edged by conventional techniques and are hard, transparent, wettable, and highly oxygen permeable.

Methylmethacrylate monomer 96 parts by weight

Ethylene dimethacrylate 3.799 parts by weight

Salicyladehyde Azine Yellow 0.001 parts by weight

Benzoyl Peroxide 0.2 parts by weight

The monomers are polymerized by heating to 45.degree. C. for eight hours and post curing at 90.degree. C. for ten hours and a contact lens is lathe cut and polished from the material. Other fluorescent materials may be used in combination to produce red, blue, pink, or orange colors to identify lens materials.

Violet=ZnS:Ag Emission Peak 460 nm

Blue=ZnS:Ag Emission Peak 505 nm

Blue-Green=(Zn,Cd)S:Ag Emission Peak 485 nm

Green-Blue=(Zn,Cd)S:Ag Emission Peak 532 nm

Green=(Zn,Cd)S:Ag Emission Peak 560 nm

Green-Yellow (Zn,Cd)S:Ag Emission Peak 593 nm

Yellow=(Zn,Cd)S:Ag Emission Peak 625 nm

Orange=(Zn,Cd)S:Ag Emission Peak 660 nm

Red=(Zn,Cd)S:Ag Emission Peak 675 nm

Dark Red=(Zn,Cd)S:Ag Emission Peak 695 nm

Purple=(Zn,Cd)S:Ag Emission Peak 576 nm

Flesh-Color=ZnS:Mn Emission Peak 450/550/580

White=ZnS:Af+(Zn,Cd)S:Ag

White 101 =(Zn,Cd)S:Ag,Au,Ce

Red CS=CaSiO.sub.3 :Mn Emission Peak 620 nm

Green ZS=Zn.sub.2 SiO.sub.4 :Mn Emission Peak 529 nm

Yellow-Orange=ZnS:Mn Emission Peak 580 nm

L Blue=Terephthalic acid, 2,5-dihydroxydiethylester

Emission Peak 470 nm

L Yellow-Green=Zinc-8-oxyquinoline Emission Peak 500 nm

L Yellow=Salicylaldehydeazine Emission Peak 543 nm

L White-Yellow=C.sub.21 H.sub.16 N.sub.2 O.sub.4 S Emission Peak 545 nm

Sources for colors useful to practice the invention are:

Leeben Color Chemical Co.

E M Chemicals

Sun Chemical Co.

Allied Chemical

Ciba Geigy

Day Glo Corp.

Colorcon, Inc.

American Hoechst

In this manner each material manufacturer by using a different color fluorescence can provide a positive identification for his contact lens material. The practitioner may then know what lens material the patient is wearing and supply the correct duplicate lens in the event of loss.

Various modifications can be made without departing from the spirit of this invention or the scope of the appended claims. The constants set forth in this disclosure are given as examples and are in no way final or binding. In view of the above, it will be seen that the several objects of the invention are achieved and other advantages are obtained. As many changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.