CA1214899A - Soft contact lens - Google Patents
Soft contact lensInfo
- Publication number
- CA1214899A CA1214899A CA000407896A CA407896A CA1214899A CA 1214899 A CA1214899 A CA 1214899A CA 000407896 A CA000407896 A CA 000407896A CA 407896 A CA407896 A CA 407896A CA 1214899 A CA1214899 A CA 1214899A
- Authority
- CA
- Canada
- Prior art keywords
- soft contact
- contact lens
- weight
- monomethacrylate
- fluorine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A soft lens is obtained from a composition compris-ing, in specified amounts, a monomethacrylate of an alkylene glycol, a fluorine-containing methacrylate, preferably tri-fluoroethyl methacrylate and/or hexafluoroisopropyl methacry-late, and one or more compounds selected from unsaturated carboxylic acids, monomethacrylates of polyhydric alcohols with three or more hydroxyl groups and alkyl methacrylates.
The resulting soft contact lens has the same optical proper-ties and elasticity as conventional soft contact lenses, and is very superior to the conventional ones in resistance to deposit and in shape stability.
A soft lens is obtained from a composition compris-ing, in specified amounts, a monomethacrylate of an alkylene glycol, a fluorine-containing methacrylate, preferably tri-fluoroethyl methacrylate and/or hexafluoroisopropyl methacry-late, and one or more compounds selected from unsaturated carboxylic acids, monomethacrylates of polyhydric alcohols with three or more hydroxyl groups and alkyl methacrylates.
The resulting soft contact lens has the same optical proper-ties and elasticity as conventional soft contact lenses, and is very superior to the conventional ones in resistance to deposit and in shape stability.
Description
4~3991 This invention relates to a soft contact lens.
The soft contact lens of the invention is prepared from a monomer mixture preferably containing trifluoro ethyl methacrylate and/or hexafluoroisopropyl methacrylate and, when used, is wette~l with tears or the iike only with dif~iculty The invention makes it possible to provide a soft contact lens having excellent mechanical strength and elasticity which can retain its lens shape wi-th sufficient stability even when processed into a thin lens.
In recent years, soft contact lenses (hereinafter referred to as "soft lenses") have come to be widely used in place of conventional hard contact lenses because of their comfort of wearing. Most soft lenses are composed mainly of 2-hydroxyethyl methacrylate (HEMA) or N-vinylpyrrolidone (NVP), and have a water content within as a wide range as from about 20 to 85~. Soft lenses vary in physical proper-ties such as mechanical strength, refractive index, oxygen permeability, specific gravity and the like depending on the water content of the materials. In general, with in-crease in the water content, the oxygen permeability in-creases, but the mechanical strength decreases. Further the refractive index and the specific gravity decrease and approach the values for water.
Since the materials for soft lenses are high in affinity for tears, the surfaces of the lenses are easily wetted. Consequently, while soft lenses are used, resist-ance to sof-t lenses on the epithelium of a cornea and on the inner surface of an eyelid is reduced, so wearers of soft lenses are relieved of discomfort due to the lenses as toreign bodies. Further, sof-t lenses permit, to a certain extent, -the supply of oxygen to a cornea epithelium through -their own materials, and hence have a function of relieving want of oxygen in a cornea to some degree.
Increase in the water content of soft lenses leads to improvement in we-ttability and oxygen permeability through the lenses, but results in lowering of the mechani-cal strength of the materials, so that the lenses become ~7 ~ZP41~9'9 easier to break while handled. Ano-ther method for supplying more oxygen to a co~nea, involves making the soft lenses thinner. This method is advantageous in that wearers of soft lenses are relieved of discomfort due to the lenses acting as foreign bodies. However, according to this method, the front side and the back side of the lense are difficult to distinguish from each other when the lense is handled, and -the lense tends to fold in two and the two halves ad-here to each other when the lense is handled, so that the lense can be very inconvenient when attached to an eye.
As a general problem in soft lenses, there is a problem of contamination on the lenses. Contamination on soft lenses is due to the adhesion of proteins, lipids, mucoids and the like in tears; the denaturation, precipita-tion and adhesion thereof by boiling; and the adhesion ofproteins, lipids and the like from fingers during handling of the lenses. The lenses stained therewith show white turbidity, color change to yellow and the like. Further, when the precipitated and adhered matters form a layer, the layer of these matters tends to crack, so that the surface of the lense becomes uneven. Consequently, the surface of the lense becomes water-repellent and is lowered in oxygen permeability, so that the wearing comfort deteriorates.
Further, the formation of said layer facilitates propaga-tion of fungi, bacteria and the like. When soft lenses areseriously deposited, the effect of improving visual acuity by the lenses is greatly lessened and the discomfort due to the lenses acting as foreign bodies becomes very serious.
The lenses sometimes become unusable. Further, the lenses sometimes cause cornea disease of their wearers and hence contamination is a serious problem in soft lenses. As one mode of employment of a soft lens, it is sometimes attempt-ed to provide, for continuous wear, a soft lens having a high water content for a patient after a cataract operation.
3'~ llowever, in this case, since a material having a high water content is used, tear composition is ap-t to penetrate into -the material, and -the lens is liable to be contaminated 39~
because it cannot be washed everyday, which causes shorten-ing of life of the lens.
When contamination of soft lenses is caused by a tear composition, the contamination of the lenses varies depending upon the di~ference in composition of tears among wearers, but, in gelleral, there is strong suspicion of the origin against proteins, particularly lysozyme present in tears. Further, mucoids, lipids and the like appear to ad-here complexly to the lysozymes.
As a treatment for contamination on soft lenses, there are now used a washing treatment with a cleaner and a treatment with an enzymatic agent, however, in a sense, these are only passive countermeasures for removing deposits.
Further, these treatments sometimes cause deposits on the lenses when the subsequent washing is insufficient.
In consideration of these facts, the present in-ventors have attempted to impart deposit resistance to the material itself for a sof-t lens without reducing its physi-cal properties, and to developing a soft lens that retains its lens shape sufficiently even when its thickness is small, and is convenient for handling.
An object of this invention is to provide a soft lens to which proteins, lipids, mucoids and the like from tears and the like do not readily a~here.
Another object of this invention is to provide a soft lens which retains its lens shape sufficiently even when its thickness is small.
Accordingly, the present invention provides a soft contact lens comprising a copolymer obtained by polymerizing a composition comprising (~) at least 50% by weight of a-t least one monomethacrylate of an alkylene glycol, (B) from 5 to 35% by weight of at least one fluorine-containing meth acrylic ester wherein the ester moie-ty contains up to 4 car-bon atoms, and (C) less than 40'~ by weight of one or more compounds selected from the group consisting of an unsa-turat-ed carboxylic aci-i having one or more carboxyl groups in the molecule, a monomethacrylate of a polyhydric alcohol having 9~
-three or more hydroxyl groups, and an alkyl me-thacrylate, the percentages of (A), (B) and (C) being calculated on the basis of the total weight of (A) + (B) -~ (C), and the sum of the percentages of (A) + (B) + (C) being 100?6.
The fluorine-containing methacrylic ester is advantageously a fluorine-containing alkyl ester wherein the alkyl group contains at least one terminal -CF3 group Trifluoroethyl methacryla-te (hereinafter abbreviated as "TFEM" ), wherein the trifluoroethyl group has the formula -CH2CF3, and/or hexafluoroisopropyl methacrylate (herein-after abbreviated as "HFIPM" ), wherein the hexafluoroiso-propyl group has the formula -CH (CF3) 2' are preferably used as the fluorine-containing methacrylic ester, and the invention is thus primarily discussed in terms of these com-pounds. Other fluorine-containing methacrylic esters which may be used include pentafluoro-n-propyl methacrylate, wherein the pentafluoro propyl group has the formula -CH2CF2CF3, and pentafluoro-n-butyl methacrylate, wherein the pentafluoro-n-butyl group has the formula -CH2CH2CF2CF3.
The composition used in accordance with the in-vention contains at least 50% by weight of component (A), based on the total weight of (A) + (B) + (C1. The amount of component (A) should not exceed 95% by weight. Componen-t (C) must be present; that is the proportion of component 25 (C) cannot be zero.
The soft contact lens of the invention is prefer-ably obtained by subjec-ting to casting polymerization by a continuous and/or stepwise temperature raising method a com-position as specified above, mechanically processing and polishing the resulting polymer to give thereto a lens shape, and then hydrating and swelling the shaped polymer. A
continuous and/or stepwise temperature raising method of from 35 C to 110C is preferably used.
Advan-tageously the soft lens of this inven-tion is 35 obtained by subjecting to casting polymerization by a con-tinuous or stepwise temperature-raising method from 35C to 110 C, a composition comprising 50 to 94?6 by weight of a 121489~
monomethacrylate of an alkylene glycol, 5 to 35~ by weight of trifluoroethyl methacrylate "TFEM" and/or hexafluoroiso-propyl methacrylate, and less than '~0~ by weight of one or more compounds selected from the group consisting of an un-saturated carboxylic acid having one or more carboxyl groupsin the molecule, a monomethacrylate of a polyhydric alcohol having three or more hydroxyl groups, and an alkyl metha-cryla-te; finishing the resulting polymer by mechanical pro-cessing and polishing to give thereto a lens shape; and then subjecting it to a hyclration and swelling treatment involv-ing an alkali treatment.
Since at least one fluorine-containing monomer such as TFEM or HFIPM is used in the soft lens of this in-vention, foreign matter adheres less to the surface of the soft lens, so that the soft lens is greatly reduced in sus-ceptibility to color change to yellow and in white turbidity as compared with conventional soft lenses. Further, the lens can sufficiently retain its normal lens shape even when processed so as to be thin, which is also a new property ob-tained by the addition of at least one fluorine-containing monomer such as TFEM and HFIPM.
The production of a soft lens by use of a fluorine-containing acrylic or methacrylic ester has conventionally been known (Louis Plambeck Jr.; Japanese Patent Appln. Kokai (Laid-Open) 29,660/1978, U.S. Patent 4130706). However, this process uses a fluorine-containing ester in which the ester moiety is a straight chain having 5 or more carbon atoms and uses no fluorine-containing ester in which the ester moiety is short, for example with less than 5 carbon atoms, such as TFEM and HFIPM used in this invention. It has been confirmed that a hydroxyl group-containing monomer and the fluorine-containing monomer used in the above-mentioned patent are poor in miscibility with respect to each other and ~ive only an opaque polymer by the usual bulk polymerization. However, TFEM and HFIPM used in this inven-tion can give a transparent polymer and lens without causing white turbidity and opaqueness, by bulk polymerization with L48~9~
the hydroxyl group containing monomer, which is a novel finding by the presen-t inventors. Further, unlike this in-vention, the above-mentioned patent does not aim at ob-taining a deposit-resistan-t soft lens. When at least one fluorine-containing monomer such as TEEM, HFIPM or the like is used as a copolymer component as in this invention, a soft lens good of shape stability, elasticity and mecha-nical strength can be obtained even when the thickness of -the lens is small. Therefore, there could be obtained an ideal soft lens which advantageously supplies oxygen to the cornea of a lenswearer and gives only slight discomfort due to the lens acting as a foreign body.
lt has become clear that, as compared with conven-tional fluorine-free soft lenses, the soft lens of this invention gives rise to reduced deposits of proteins, lipids and mucoids. In particular, deposit with protein was measured by use of lysozyme labeled with 125I to show a significant difference in adsorption of the lysozyme between the soft lens of this invention containing at least one fluorine-containing monomer and a fluorine-free soft lens having the same water content as that of the soft lens of this invention.
Further, even when the thickness of the lens of this invention was adjusted so as to be about one-third of the conventional thickness (about 0.05 mm in central thick-ness), the lens retained its shape, the phenomenon of a lens becoming folded into two and stuck was not observed, and the lens could be handled without inconvenience. This was an unexpected result, and was the result of -the dis-covery of a novel effect brought about by the employment ofat least one fluorine-containing monomer.
The fluorine-containing monomer is used in an amount of 5 to 35% by weight. TFEM and HFIPM can be used alone or simultaneously. However, when the added amount of the fluorine-containing monomer is less than 5% by weight, the effect of the monomer on antideposit is insufficient, and with increase of the added a~ount, the effect on an-ti-~2~4~9~
-- 7deposit is heigh-tened, but the elasticity of the resulting soft lens is reduced. When the added amount exceeds 35%
by weight, elasticity required of a soft lens becomes un-obtainable. Preferably, an amount of from 10 to 20% by 5 weight is employed.
rlhe monomethacrylate of an alkylene glycol is, for example, the monomethacrylate of ethylene glycol, propylene glycol, die-thylene glycol, tetraethylene glycol or a poly-ethylene glycol, and is the main constituent of the soft lens of this invention. As the monomethacrylate, e-thylene glycol monomethacrylate, i.e., 2-hydroxyethyl methacrylate (2-HEMA) is preferably used. Simultaneous use of 2-hydroxyethyl methacrylate and propylene glycol monomethacry-late is also preferred.
Representative examples of the unsaturated car-boxylic acids having one or more carboxyl groups in the molecule include acrylic acid, metAacrylic acid, itaconic acid and the like, and the unsaturated carboxylic acid is a constituent for increasing the water content by a hydra-20 tion and swelling treatment involving an alkali treatment and for imparting elasticity required for a soft lens. As the unsaturated carboxylic acid, methacrylic acid is par-ticularly preferred.
As the monomethacrylate of a polyhydric alcohol 25 having three or more hydroxyl groups, glyceryl methacrylate or monomethacrylate of pentaerythritol is preferably used, and this constituent contributes to an increase of the water content and to the elasticity.
The preferred alkyl methacrylate is the methyl 30 ethyl, n-propyl or n-butyl ester of methacrylic acid, and is a constituent for improving the strength, processability and shape stability of the resulting soft lens.
In addition to these constituents, there may be used, as cross linking agents, polyfunctional monomers 35 such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dime-thacrylate, butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, propylene :9l;2~41~9$i glycol dimethacrylate, diethylene g]ycol bisallylcarbonate, trimethylolpropane -trimethacrylate, bisphenol A dimethacry-late, methylenebisacrylamide, and the like. N-vinylpyrroli-done, acrylamide, methacrylamide or the like may be used as a constituent for increasing the water content.
As the polymerization initiator, there may be used any suitable radical-ge}lerating agents, for example, benzoyl pero~ide, lauroyl peroxide, cumene hydroperoxide, di-tert-bu-tyl peroxide, bis-4-tert-butylcyclohexyl peroxy-dicarbonate, diisopropyl peroxydicarbonate azobisisobutyro-nitrile, azobisisovaleronitrile and the like, and initiators generating a radical at low temperatures are more preferable.
rn a preferred method for making the lenses of this invention, the desired constituents are mixed and then poured into a mold made of a metal, glass or plastics, after which, while the resulting mixture is hermetically sealed, polymerization is completed in an electric furnace by a continuous-temperature-raising method of from 35 to 110 C. After completion of the polymerization, the result-ing polymer is taken out of the mold and finished ~y usualmechanical processing and finishing to give thereto a lens shape. In order to hydrate and swell the finished lens, the lens is immersed in a physiological saline containing sodium carbonate, sodium hydrogencarbonate, potassium hydro-gencarbonate, and/or the like, at room temperature or with hea-ting, and then immersed in a physiological salt solution and allowed to stand at room temperature or heated while the physiological salt solution is renewed several times, so as to be hydrated and swollen.
The thus produced soft lens has the same optical properties and elasticity as those of conventional soft lenses, and enjoys such an effect from the content of at least one fluorine-containing monomer that it is less susceptible to adhesion of deposits due to proteins, lipids and mucoids than conventional soft lenses. Fur-ther, a soft lens retaining a lens shape sufficiently stably could be ob-tained even when the thickness of the soft lens was small.
This invention is further explained below in more detall with reference to the Examples and Comparative Examples, which are not by way of limitation but by way of illustration. In the Examples and Comparative Examples, parts are by weigh-t.
Example L
To a mixture of 89.7 parts of 2-hydroxyethyl metha-crylate, 10 parts of TFEM and 0.3 part of methacrylic acid was added 0.1 part of azobisisobutyronitrile as a polymeri-zation initiator, and the resulting mixture was sufficientlystirred and mixed, poured into a mold made of plastics, and then hermatically sealed up therein. The mixture was then subjected to polymerization in a continuous-temperature-raising furnace of from 35 to 110C, and the resulting transparent polymer was processed by cutting and polishing to give thereto a lens shape. The thus obtained lens was treated in a physiological saline containing 1.2% of sodium hydrogen-carbonate at 80 to 90C for 1 hour and then in a physiological salt solution at 80 to 90 C for 1 hour, whereby the lens was allowed to absorb water and swell and at the same time, the unpolymerized monomer was eluted from the lens. The thus obtained soft lens had a water content of 35% and a tensile strength of about 850 g/mm2, was comfortable to wear, and, as shown in Table 1, adsorbed only very small amount of protein (lysozyme) as compared with a conventional soft lens having the same water content, though it was equal in optical properties to the conventional soft lens. Eurther, the soft lens, even when its thickness was made smaller, had the same shape stability as did those having a conventional thickness.
Example 2 To a mixture of 84 parts of 2-hydroxyethyl metha-crylate, 15 parts of TFEM and 1 part of methacrylic acid was added 0.1 part of diisopropyl peroxydicarbonate, and the same procedure as described in Example 1 was followed to obtain a soft lens having a water content of 36%. As shown in Table 1, this lens adsorbed only very small amount of the 121489g protein as compared with the conventional soft lens having the same water content and containing no fluorine compound.
Example 3 To ~ mixture of 70 parts of 2-hydroxyethyl meth-acrylate, 10 parts of TFEM and 20 parts of glyceryl meth-acrylate was added 0.1 part of bis-4-tert-butyl-cyclohexyl peroxydicarbonate, and polymerization and lens processing were carried out in the same manner as in Example 1, after which the thus obtained lens was treated in a physiological salt solution at 80 to 90C for 2 hours to produce a soft lens having a water content of 36%. This soft lens had excellent resistance to deposit.
Examples 4 to 14 Soft lenses having various compositions and water contents were produced by the same technique as in Examples 1 to 3. All the soft lenses were colorless and transparent, had the same optical properties, mechanical processability and strength as conventional soft lenses, and were less susceptible to deposit with proteins. The soft lenses had good shape stability even when they were thin.
Comparative Examples 1 to 4 By the same technique as in Examples 1 to 3, soft lenses were produced from individual polymers having various compositions containing no fluorine-containing monomer, and were used as controls.
Each of the soft lenses obtained in the above Examples and Comparative Examples was immersed in a solution of egg white lysozyme labeled with radioactive iodine (125I) (concentration 500 ~g/ml; pH 7.3; 0.05 M borate buffer), and taken out of the solution after 2.5 hours, 24 hours, 3 days and 10 days, and the lens surface was washed with flowing water. Thereafter, the amount of egg white lysozyme adhered to the lens was measured by a method by which y-rays were detected by means of a well-type scintillation counter. As shown in Tables 1 to 4, the amounts of lysozyme adhered to the lenses of the comparative examples 1 to 4 containing no fluorine-containing monomer as a copolymer component are taken as 100%, and those in the examples are shown in com-parison therewith.
The shape stability is expressed by ~ , o, ~ or x (explai.ned below) based on the observation of the elasti-city, ability to restore the original shape during handling,and shape stability during handling of a thin lens (central thickness:0.05 mm). The tensile strength is expressed in terms oE g/rnm .
~ : Greatly excellent shape stability and elasticity o : Excellent shape stability and elasticity L~ : A little :inferior shape stability and elasticitv x : Inferior shape stability and elasticity ~z~
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~ ~o x x u - --When trifluoroethyl methacrylate and/or hexafluo-roisopropyl methacrylate, which are fluorine-coII-taining monomers, are included in a monomer mixture for producing a soft contact l.ens, -the resultin~ soft contact ]ens has the same optical properties and elasticity as conventional soft contact lenses, and is very superior -to the convention-al ones in resistance to deposit and in shape stability.
The soft contact lens of the invention is prepared from a monomer mixture preferably containing trifluoro ethyl methacrylate and/or hexafluoroisopropyl methacrylate and, when used, is wette~l with tears or the iike only with dif~iculty The invention makes it possible to provide a soft contact lens having excellent mechanical strength and elasticity which can retain its lens shape wi-th sufficient stability even when processed into a thin lens.
In recent years, soft contact lenses (hereinafter referred to as "soft lenses") have come to be widely used in place of conventional hard contact lenses because of their comfort of wearing. Most soft lenses are composed mainly of 2-hydroxyethyl methacrylate (HEMA) or N-vinylpyrrolidone (NVP), and have a water content within as a wide range as from about 20 to 85~. Soft lenses vary in physical proper-ties such as mechanical strength, refractive index, oxygen permeability, specific gravity and the like depending on the water content of the materials. In general, with in-crease in the water content, the oxygen permeability in-creases, but the mechanical strength decreases. Further the refractive index and the specific gravity decrease and approach the values for water.
Since the materials for soft lenses are high in affinity for tears, the surfaces of the lenses are easily wetted. Consequently, while soft lenses are used, resist-ance to sof-t lenses on the epithelium of a cornea and on the inner surface of an eyelid is reduced, so wearers of soft lenses are relieved of discomfort due to the lenses as toreign bodies. Further, sof-t lenses permit, to a certain extent, -the supply of oxygen to a cornea epithelium through -their own materials, and hence have a function of relieving want of oxygen in a cornea to some degree.
Increase in the water content of soft lenses leads to improvement in we-ttability and oxygen permeability through the lenses, but results in lowering of the mechani-cal strength of the materials, so that the lenses become ~7 ~ZP41~9'9 easier to break while handled. Ano-ther method for supplying more oxygen to a co~nea, involves making the soft lenses thinner. This method is advantageous in that wearers of soft lenses are relieved of discomfort due to the lenses acting as foreign bodies. However, according to this method, the front side and the back side of the lense are difficult to distinguish from each other when the lense is handled, and -the lense tends to fold in two and the two halves ad-here to each other when the lense is handled, so that the lense can be very inconvenient when attached to an eye.
As a general problem in soft lenses, there is a problem of contamination on the lenses. Contamination on soft lenses is due to the adhesion of proteins, lipids, mucoids and the like in tears; the denaturation, precipita-tion and adhesion thereof by boiling; and the adhesion ofproteins, lipids and the like from fingers during handling of the lenses. The lenses stained therewith show white turbidity, color change to yellow and the like. Further, when the precipitated and adhered matters form a layer, the layer of these matters tends to crack, so that the surface of the lense becomes uneven. Consequently, the surface of the lense becomes water-repellent and is lowered in oxygen permeability, so that the wearing comfort deteriorates.
Further, the formation of said layer facilitates propaga-tion of fungi, bacteria and the like. When soft lenses areseriously deposited, the effect of improving visual acuity by the lenses is greatly lessened and the discomfort due to the lenses acting as foreign bodies becomes very serious.
The lenses sometimes become unusable. Further, the lenses sometimes cause cornea disease of their wearers and hence contamination is a serious problem in soft lenses. As one mode of employment of a soft lens, it is sometimes attempt-ed to provide, for continuous wear, a soft lens having a high water content for a patient after a cataract operation.
3'~ llowever, in this case, since a material having a high water content is used, tear composition is ap-t to penetrate into -the material, and -the lens is liable to be contaminated 39~
because it cannot be washed everyday, which causes shorten-ing of life of the lens.
When contamination of soft lenses is caused by a tear composition, the contamination of the lenses varies depending upon the di~ference in composition of tears among wearers, but, in gelleral, there is strong suspicion of the origin against proteins, particularly lysozyme present in tears. Further, mucoids, lipids and the like appear to ad-here complexly to the lysozymes.
As a treatment for contamination on soft lenses, there are now used a washing treatment with a cleaner and a treatment with an enzymatic agent, however, in a sense, these are only passive countermeasures for removing deposits.
Further, these treatments sometimes cause deposits on the lenses when the subsequent washing is insufficient.
In consideration of these facts, the present in-ventors have attempted to impart deposit resistance to the material itself for a sof-t lens without reducing its physi-cal properties, and to developing a soft lens that retains its lens shape sufficiently even when its thickness is small, and is convenient for handling.
An object of this invention is to provide a soft lens to which proteins, lipids, mucoids and the like from tears and the like do not readily a~here.
Another object of this invention is to provide a soft lens which retains its lens shape sufficiently even when its thickness is small.
Accordingly, the present invention provides a soft contact lens comprising a copolymer obtained by polymerizing a composition comprising (~) at least 50% by weight of a-t least one monomethacrylate of an alkylene glycol, (B) from 5 to 35% by weight of at least one fluorine-containing meth acrylic ester wherein the ester moie-ty contains up to 4 car-bon atoms, and (C) less than 40'~ by weight of one or more compounds selected from the group consisting of an unsa-turat-ed carboxylic aci-i having one or more carboxyl groups in the molecule, a monomethacrylate of a polyhydric alcohol having 9~
-three or more hydroxyl groups, and an alkyl me-thacrylate, the percentages of (A), (B) and (C) being calculated on the basis of the total weight of (A) + (B) -~ (C), and the sum of the percentages of (A) + (B) + (C) being 100?6.
The fluorine-containing methacrylic ester is advantageously a fluorine-containing alkyl ester wherein the alkyl group contains at least one terminal -CF3 group Trifluoroethyl methacryla-te (hereinafter abbreviated as "TFEM" ), wherein the trifluoroethyl group has the formula -CH2CF3, and/or hexafluoroisopropyl methacrylate (herein-after abbreviated as "HFIPM" ), wherein the hexafluoroiso-propyl group has the formula -CH (CF3) 2' are preferably used as the fluorine-containing methacrylic ester, and the invention is thus primarily discussed in terms of these com-pounds. Other fluorine-containing methacrylic esters which may be used include pentafluoro-n-propyl methacrylate, wherein the pentafluoro propyl group has the formula -CH2CF2CF3, and pentafluoro-n-butyl methacrylate, wherein the pentafluoro-n-butyl group has the formula -CH2CH2CF2CF3.
The composition used in accordance with the in-vention contains at least 50% by weight of component (A), based on the total weight of (A) + (B) + (C1. The amount of component (A) should not exceed 95% by weight. Componen-t (C) must be present; that is the proportion of component 25 (C) cannot be zero.
The soft contact lens of the invention is prefer-ably obtained by subjec-ting to casting polymerization by a continuous and/or stepwise temperature raising method a com-position as specified above, mechanically processing and polishing the resulting polymer to give thereto a lens shape, and then hydrating and swelling the shaped polymer. A
continuous and/or stepwise temperature raising method of from 35 C to 110C is preferably used.
Advan-tageously the soft lens of this inven-tion is 35 obtained by subjecting to casting polymerization by a con-tinuous or stepwise temperature-raising method from 35C to 110 C, a composition comprising 50 to 94?6 by weight of a 121489~
monomethacrylate of an alkylene glycol, 5 to 35~ by weight of trifluoroethyl methacrylate "TFEM" and/or hexafluoroiso-propyl methacrylate, and less than '~0~ by weight of one or more compounds selected from the group consisting of an un-saturated carboxylic acid having one or more carboxyl groupsin the molecule, a monomethacrylate of a polyhydric alcohol having three or more hydroxyl groups, and an alkyl metha-cryla-te; finishing the resulting polymer by mechanical pro-cessing and polishing to give thereto a lens shape; and then subjecting it to a hyclration and swelling treatment involv-ing an alkali treatment.
Since at least one fluorine-containing monomer such as TFEM or HFIPM is used in the soft lens of this in-vention, foreign matter adheres less to the surface of the soft lens, so that the soft lens is greatly reduced in sus-ceptibility to color change to yellow and in white turbidity as compared with conventional soft lenses. Further, the lens can sufficiently retain its normal lens shape even when processed so as to be thin, which is also a new property ob-tained by the addition of at least one fluorine-containing monomer such as TFEM and HFIPM.
The production of a soft lens by use of a fluorine-containing acrylic or methacrylic ester has conventionally been known (Louis Plambeck Jr.; Japanese Patent Appln. Kokai (Laid-Open) 29,660/1978, U.S. Patent 4130706). However, this process uses a fluorine-containing ester in which the ester moiety is a straight chain having 5 or more carbon atoms and uses no fluorine-containing ester in which the ester moiety is short, for example with less than 5 carbon atoms, such as TFEM and HFIPM used in this invention. It has been confirmed that a hydroxyl group-containing monomer and the fluorine-containing monomer used in the above-mentioned patent are poor in miscibility with respect to each other and ~ive only an opaque polymer by the usual bulk polymerization. However, TFEM and HFIPM used in this inven-tion can give a transparent polymer and lens without causing white turbidity and opaqueness, by bulk polymerization with L48~9~
the hydroxyl group containing monomer, which is a novel finding by the presen-t inventors. Further, unlike this in-vention, the above-mentioned patent does not aim at ob-taining a deposit-resistan-t soft lens. When at least one fluorine-containing monomer such as TEEM, HFIPM or the like is used as a copolymer component as in this invention, a soft lens good of shape stability, elasticity and mecha-nical strength can be obtained even when the thickness of -the lens is small. Therefore, there could be obtained an ideal soft lens which advantageously supplies oxygen to the cornea of a lenswearer and gives only slight discomfort due to the lens acting as a foreign body.
lt has become clear that, as compared with conven-tional fluorine-free soft lenses, the soft lens of this invention gives rise to reduced deposits of proteins, lipids and mucoids. In particular, deposit with protein was measured by use of lysozyme labeled with 125I to show a significant difference in adsorption of the lysozyme between the soft lens of this invention containing at least one fluorine-containing monomer and a fluorine-free soft lens having the same water content as that of the soft lens of this invention.
Further, even when the thickness of the lens of this invention was adjusted so as to be about one-third of the conventional thickness (about 0.05 mm in central thick-ness), the lens retained its shape, the phenomenon of a lens becoming folded into two and stuck was not observed, and the lens could be handled without inconvenience. This was an unexpected result, and was the result of -the dis-covery of a novel effect brought about by the employment ofat least one fluorine-containing monomer.
The fluorine-containing monomer is used in an amount of 5 to 35% by weight. TFEM and HFIPM can be used alone or simultaneously. However, when the added amount of the fluorine-containing monomer is less than 5% by weight, the effect of the monomer on antideposit is insufficient, and with increase of the added a~ount, the effect on an-ti-~2~4~9~
-- 7deposit is heigh-tened, but the elasticity of the resulting soft lens is reduced. When the added amount exceeds 35%
by weight, elasticity required of a soft lens becomes un-obtainable. Preferably, an amount of from 10 to 20% by 5 weight is employed.
rlhe monomethacrylate of an alkylene glycol is, for example, the monomethacrylate of ethylene glycol, propylene glycol, die-thylene glycol, tetraethylene glycol or a poly-ethylene glycol, and is the main constituent of the soft lens of this invention. As the monomethacrylate, e-thylene glycol monomethacrylate, i.e., 2-hydroxyethyl methacrylate (2-HEMA) is preferably used. Simultaneous use of 2-hydroxyethyl methacrylate and propylene glycol monomethacry-late is also preferred.
Representative examples of the unsaturated car-boxylic acids having one or more carboxyl groups in the molecule include acrylic acid, metAacrylic acid, itaconic acid and the like, and the unsaturated carboxylic acid is a constituent for increasing the water content by a hydra-20 tion and swelling treatment involving an alkali treatment and for imparting elasticity required for a soft lens. As the unsaturated carboxylic acid, methacrylic acid is par-ticularly preferred.
As the monomethacrylate of a polyhydric alcohol 25 having three or more hydroxyl groups, glyceryl methacrylate or monomethacrylate of pentaerythritol is preferably used, and this constituent contributes to an increase of the water content and to the elasticity.
The preferred alkyl methacrylate is the methyl 30 ethyl, n-propyl or n-butyl ester of methacrylic acid, and is a constituent for improving the strength, processability and shape stability of the resulting soft lens.
In addition to these constituents, there may be used, as cross linking agents, polyfunctional monomers 35 such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dime-thacrylate, butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, propylene :9l;2~41~9$i glycol dimethacrylate, diethylene g]ycol bisallylcarbonate, trimethylolpropane -trimethacrylate, bisphenol A dimethacry-late, methylenebisacrylamide, and the like. N-vinylpyrroli-done, acrylamide, methacrylamide or the like may be used as a constituent for increasing the water content.
As the polymerization initiator, there may be used any suitable radical-ge}lerating agents, for example, benzoyl pero~ide, lauroyl peroxide, cumene hydroperoxide, di-tert-bu-tyl peroxide, bis-4-tert-butylcyclohexyl peroxy-dicarbonate, diisopropyl peroxydicarbonate azobisisobutyro-nitrile, azobisisovaleronitrile and the like, and initiators generating a radical at low temperatures are more preferable.
rn a preferred method for making the lenses of this invention, the desired constituents are mixed and then poured into a mold made of a metal, glass or plastics, after which, while the resulting mixture is hermetically sealed, polymerization is completed in an electric furnace by a continuous-temperature-raising method of from 35 to 110 C. After completion of the polymerization, the result-ing polymer is taken out of the mold and finished ~y usualmechanical processing and finishing to give thereto a lens shape. In order to hydrate and swell the finished lens, the lens is immersed in a physiological saline containing sodium carbonate, sodium hydrogencarbonate, potassium hydro-gencarbonate, and/or the like, at room temperature or with hea-ting, and then immersed in a physiological salt solution and allowed to stand at room temperature or heated while the physiological salt solution is renewed several times, so as to be hydrated and swollen.
The thus produced soft lens has the same optical properties and elasticity as those of conventional soft lenses, and enjoys such an effect from the content of at least one fluorine-containing monomer that it is less susceptible to adhesion of deposits due to proteins, lipids and mucoids than conventional soft lenses. Fur-ther, a soft lens retaining a lens shape sufficiently stably could be ob-tained even when the thickness of the soft lens was small.
This invention is further explained below in more detall with reference to the Examples and Comparative Examples, which are not by way of limitation but by way of illustration. In the Examples and Comparative Examples, parts are by weigh-t.
Example L
To a mixture of 89.7 parts of 2-hydroxyethyl metha-crylate, 10 parts of TFEM and 0.3 part of methacrylic acid was added 0.1 part of azobisisobutyronitrile as a polymeri-zation initiator, and the resulting mixture was sufficientlystirred and mixed, poured into a mold made of plastics, and then hermatically sealed up therein. The mixture was then subjected to polymerization in a continuous-temperature-raising furnace of from 35 to 110C, and the resulting transparent polymer was processed by cutting and polishing to give thereto a lens shape. The thus obtained lens was treated in a physiological saline containing 1.2% of sodium hydrogen-carbonate at 80 to 90C for 1 hour and then in a physiological salt solution at 80 to 90 C for 1 hour, whereby the lens was allowed to absorb water and swell and at the same time, the unpolymerized monomer was eluted from the lens. The thus obtained soft lens had a water content of 35% and a tensile strength of about 850 g/mm2, was comfortable to wear, and, as shown in Table 1, adsorbed only very small amount of protein (lysozyme) as compared with a conventional soft lens having the same water content, though it was equal in optical properties to the conventional soft lens. Eurther, the soft lens, even when its thickness was made smaller, had the same shape stability as did those having a conventional thickness.
Example 2 To a mixture of 84 parts of 2-hydroxyethyl metha-crylate, 15 parts of TFEM and 1 part of methacrylic acid was added 0.1 part of diisopropyl peroxydicarbonate, and the same procedure as described in Example 1 was followed to obtain a soft lens having a water content of 36%. As shown in Table 1, this lens adsorbed only very small amount of the 121489g protein as compared with the conventional soft lens having the same water content and containing no fluorine compound.
Example 3 To ~ mixture of 70 parts of 2-hydroxyethyl meth-acrylate, 10 parts of TFEM and 20 parts of glyceryl meth-acrylate was added 0.1 part of bis-4-tert-butyl-cyclohexyl peroxydicarbonate, and polymerization and lens processing were carried out in the same manner as in Example 1, after which the thus obtained lens was treated in a physiological salt solution at 80 to 90C for 2 hours to produce a soft lens having a water content of 36%. This soft lens had excellent resistance to deposit.
Examples 4 to 14 Soft lenses having various compositions and water contents were produced by the same technique as in Examples 1 to 3. All the soft lenses were colorless and transparent, had the same optical properties, mechanical processability and strength as conventional soft lenses, and were less susceptible to deposit with proteins. The soft lenses had good shape stability even when they were thin.
Comparative Examples 1 to 4 By the same technique as in Examples 1 to 3, soft lenses were produced from individual polymers having various compositions containing no fluorine-containing monomer, and were used as controls.
Each of the soft lenses obtained in the above Examples and Comparative Examples was immersed in a solution of egg white lysozyme labeled with radioactive iodine (125I) (concentration 500 ~g/ml; pH 7.3; 0.05 M borate buffer), and taken out of the solution after 2.5 hours, 24 hours, 3 days and 10 days, and the lens surface was washed with flowing water. Thereafter, the amount of egg white lysozyme adhered to the lens was measured by a method by which y-rays were detected by means of a well-type scintillation counter. As shown in Tables 1 to 4, the amounts of lysozyme adhered to the lenses of the comparative examples 1 to 4 containing no fluorine-containing monomer as a copolymer component are taken as 100%, and those in the examples are shown in com-parison therewith.
The shape stability is expressed by ~ , o, ~ or x (explai.ned below) based on the observation of the elasti-city, ability to restore the original shape during handling,and shape stability during handling of a thin lens (central thickness:0.05 mm). The tensile strength is expressed in terms oE g/rnm .
~ : Greatly excellent shape stability and elasticity o : Excellent shape stability and elasticity L~ : A little :inferior shape stability and elasticitv x : Inferior shape stability and elasticity ~z~
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~ ~o x x u - --When trifluoroethyl methacrylate and/or hexafluo-roisopropyl methacrylate, which are fluorine-coII-taining monomers, are included in a monomer mixture for producing a soft contact l.ens, -the resultin~ soft contact ]ens has the same optical properties and elasticity as conventional soft contact lenses, and is very superior -to the convention-al ones in resistance to deposit and in shape stability.
Claims (15)
1. A soft contact lens comprising a copolymer obtained by polymerizing a composition comprising (A) at least 50% by weight of at least one monomethacrylate of an alkylene glycol, (B) from 5 to 35% by weight of at least one fluorine-containing methacrylic ester wherein the ester moiety contains up to 4 carbon atoms, and (C) less than 40% by weight of one or more compounds selected from the group consisting of an unsaturated carboyxlic acid having one or more carboxyl groups in the molecule, a monometha-crylate, of a polyhydric alcohol having three or more hydroxyl groups, and an alkyl methacrylate, the percen-tages of (A), (B) and (C) being calculated on the basis of the total weight of (A) + (B) + (C), and the sum of the percentages of (A) + (B) + (C) being 100%.
2. A soft contact lens according to Claim 1, wherein the monomethacrylate of an alkylene glycol is the monomethacrylate of ethylene glycol, propylene glycol, diethylene glycol, tetraethylene glycol or a polyethylene glycol of the formula HO(CH2CH2O)nH, in which n = 5 to 20.
3. A soft contact lens according to Claim 1, wherein the unsaturated carboxylic acid is acrylic acid, methacrylic acid or itaconic acid.
4. A soft contact lens according to Claim 1, wherein the monomethacrylate of a polyhydric alcohol is glyceryl methacrylate or monomethacrylate of pentaery-thritol.
5. A soft contact lens according to Claim 1, wherein the alkyl methacrylate is the methyl, ethyl, n-propyl or n-butyl ester of methacrylic acid.
6. A soft contact lens according to Claim 1, 2 or 3, wherein the unsaturated carboxylic acid is used in an amount of 10% by weight or less.
7. A soft contact lens according to Claim 1, 2 or 4, wherein the monomethacrylate of a polyhydric alcohol is used in an amount of 30% by weight or less.
8. A soft contact lens according to Claim 1, 2 or 5, wherein the alkylmethacrylate is used in an amount of 20% by weight or less.
9. A soft contact lens as claimed in Claim 1, 2 or 3, wherein the fluorine-containing methacrylic ester is a fluorine-containing alkyl ester wherein the alkyl group contains at least one terminal -CF3 group.
10. A soft contact lens as claimed in Claim 1, 2 or 3, wherein the fluorine-containing methacrylic ester, or one of said esters, is trifluoroethylmethacrylate.
11. A soft contact lens as claimed in Claim 1, 2 or 3, wherein the fluorine-containing methacrylic ester, or one of said esters, is hexafluoroisopropyl methacrylate.
12. A soft contact lens as claimed in Claim 1, 2 or 3, wherein the fluorine-containing methacrylic ester is used in an amount of from 10 to 20% by weight.
13. A soft contact lens obtained by subjecting to casting polymerization by a continuous and/or stepwise temperature raising method a composition as specified in Claim 1, mechanically processing and polishing the result-ing polymer to give thereto a lens shape, and then hydrating and swelling the shaped polymer.
14. A soft contact lens as claimed in Claim 13, wherein a continuous and/or stepwise temperature raising method of from 35°C to 110°C is used.
15. A method preparing a soft contact lens, which comprises subjecting to casting polymerization by a continous-temperature raising method of from 35° to 110°C, a composition comprising from 50 to 94% by weight of a monomethacrylate of an alkylene glycol, from 5 to 35% by weight of trifluoroethyl metha-crylate and/or hexafluoroisopropyl methacrylate, and less than 40% by weight of one or more compounds selected from the group consisting of an unsaturated carboxylic acid having one or more carboxyl groups in the molecule, a monomethacrylate of a polyhydric alcohol having three or more hydroxyl groups, and an alkyl methacrylate; mechanical-ly processing and polishing the resulting polymer to give thereto a lens shape; and then hydrating and swelling the shaped polymer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000407896A CA1214899A (en) | 1982-07-23 | 1982-07-23 | Soft contact lens |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000407896A CA1214899A (en) | 1982-07-23 | 1982-07-23 | Soft contact lens |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1214899A true CA1214899A (en) | 1986-12-02 |
Family
ID=4123271
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000407896A Expired CA1214899A (en) | 1982-07-23 | 1982-07-23 | Soft contact lens |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1214899A (en) |
-
1982
- 1982-07-23 CA CA000407896A patent/CA1214899A/en not_active Expired
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