CA1260196A - Soft, with a low hydrophility contactoptical articles - Google Patents
Soft, with a low hydrophility contactoptical articlesInfo
- Publication number
- CA1260196A CA1260196A CA000497138A CA497138A CA1260196A CA 1260196 A CA1260196 A CA 1260196A CA 000497138 A CA000497138 A CA 000497138A CA 497138 A CA497138 A CA 497138A CA 1260196 A CA1260196 A CA 1260196A
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-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
- G02B1/041—Lenses
- G02B1/043—Contact lenses
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F226/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Eyeglasses (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
SOFT, WITH A LOW HYDROPHILITY CONTACTOPTICAL ARTICLES
A B S T R A C T
The present invention relates to contactoptical shaped articles in particular contact lenses and scleral lenses, of water-absorbing cross-linked copolymers of olefinically unsaturated monomers having a softening point in the hydrated state below 35°C, characterized in that the copolymer has.
(a) a water-absorbing capacity at 25°C of 4 to 50 %, by weight, based on the hydrated state; and (b) a glass transition temperature in the dry state of 25 to 55°C.
A B S T R A C T
The present invention relates to contactoptical shaped articles in particular contact lenses and scleral lenses, of water-absorbing cross-linked copolymers of olefinically unsaturated monomers having a softening point in the hydrated state below 35°C, characterized in that the copolymer has.
(a) a water-absorbing capacity at 25°C of 4 to 50 %, by weight, based on the hydrated state; and (b) a glass transition temperature in the dry state of 25 to 55°C.
Description
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SOFT, WITH A LOW HYDROP~ILITY CONTACTOPTICAL A~TICLES
This invention relates to new contactopticalshaped ar-~cles, in parti~lar contact lenses and scleral lenses, of cross-linked copolymers of olefinically unsaturated compounds whichhave a water-absorbing capacity of 4 to 50 ~ by weight, in the hydrated state,and of which the glass transition temperature is be~Jeen 25 and 55C in the dry state and below 35C in the hydrated state. In the dry state, the shaped articles may be machined at room temperature and only change into a soft lens in the hydrated state on the eye.
Scleral caps, also called scleral lenses, were already developed towards the end of the nineteenth century. The starting material used was glass which, because of its hardness, was not satisfactorily tolerated by the eye. An improvement was made in the thirties of this century through the introduction of polymethyl methacrylate (PMMA) whi~h was easier to process and more readily tolerated than glass. Although the mechanical strain imposed on the eye tissue by the cap covering it could be considerably reduced by PMMA, the high tolerance required for relatively long wearing times of the lenses could only be partly achie~ed.
Further considerations led in the fifties ~o the develop-ment of a small lens resting mainly on the cornea, the contact lens.
By reduction of the contact area between the contact lens and the eye, tolerance was considerably improved. However, because of the hardness of PMMA, lenses of that material also caused irritations which could not be overcome by dimensional changes. Accordingly9 the search for softer materials was taken up. About fifteen years ago, so-called hydrogel lenses introduced a new development in the field of contact lenses.
Hydrogel lenses are hydrophilic polymer networks based on water-soluble monomers which are capable of absorbing up to 70%, by weight, of water~ based on the hydrated form, Le A 23 271 :
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and of softening as a result of the absorption of water.
Among the water-soluble monomers, N~vinyl lactams in com-bination with polyallyl cross-linkers have become parti-cularly important. The prior art which may be mentioned includes, for example, US-PS 4,158,089, European Patents Nos. 79 720, 79 721 and 106 650 and Shell Polym. 7 (1983) No. 3, pp 69 to 71.
By virtue of their softer consistency and the lower mechanical strain which they impose on the eye tissue, hydrogel lenses are more comfortable to wear, but have the disadvantage that they are easily damaged, require intensive care and are capable of taking up and absorbing metabolism products, lens-care preparations and bacteria.
Recent years have seen the development of new lenses of rigid and semi rigid materials, for example poly-silyl methacrylates, cellulose acetobutyrate, which have a low water-absorbing capacity and which have meanwhile claimed a sonciderable share of the market.
High tolerance, easy care and good optical proper-ties of the material are primarily responsible for this.
Although the development of these lens materialsmay be considered to be positive, there has long been a demand for a soft, rubber-elastic material having low water absorption, in particular for PWT (prolonged wearing time) lenses. This demand was partly satisfied by lenses of sili-cone rubber. However, silicone lenses involve wettability problems. In addition, they have to be cast in a specialised production process. The less expensive lace cutting process cannot be used for silicone rubber.
A major difference between the shaped articles according to the present invention and commercial soft lenses based on HEM~ (2-hydroxyethyl methacrylate) or PVP
(polyvinyl pyrrolidone) lies in their higher glass transition temperature in the hydrated state. Although the prior art HEMA and PVP materials have a glass transition temperature Le_A 23 271 ~
.
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above 100C in the dry state they soften in the hydrated state at temperatures far below 20C. The shaped articles accordin to the invention, however, soften at between 20 and 35C in the hydrated state.
It has now been found that these requirements may be satisfied by cross-linked copolymers which have a low hydrophility, but which nevertheless have a glass transition temperature below 35C in the hydrated state.
The present invention relates to contactoptical articles, in particular contact lenses and scleral lenses, of water-absorbing, cross-linked copolymers of olefinically unsaturated monomers having a softening point in the hydra-ted state below 35C, preferable between 20 and 35C~ cha racterised in that the copolymer has:
(a) a water-absorbing capacity at 25C of 4 to 50 %, by weight, preferably 5 to 20 % by weight, based on the hydrated state; and (b) a glass transition temperature in the dry state of 25 to 55C, preferably 28 to 45C.
A further difference lies in the considerably lower water-absorbing capacity which leads to a reduced risk of inclusion of lens-care preparations, metabolism products and bacteria.
The increase in thickness which the contactoptical articles according to the invention undergo at 20C as a : result of hydration is 2 to 20 %, in particular 3 to 10, : based on the dry state the content of water extractable components is preferably below 0.5 %, by weight, in par-ticular below 0.1 %, by weight.
Copolymers suitable for the contactoptical ar-: ticles according to the invention can be obtained by poly-merisation of two or more olefinically unsaturated mono-: ~ mers in known manner, the monomers and the qualltitative ratios in which they are used being selected in such a way that the copolymer has a glass transition temperature in the :~ : Le A 23 271 :~:
~ .
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''` -'''' '' - , above-mentioned range. This is simple for those skilled in the art to achieve by virtue of the substantially linear relation between the glass transition temperature and the mole fraction of the components of a copolymer. Glass transi-5 tion temperatures of a vari~ty of homopolymers may be found,for example, in Immergut, Polymer Handbook, Interscience ~ lishers New York, 1966.
Another factor to be taken into account in the choice of the monomers is that the copolymer has high transparency lO (preferably >95 %, particularly preferably >98 % permeabi-lity to light at a layer thickness of 0.5 mm, disregarding the light loss by total reflection) and its water absorbing capacity at 25C is between 4 and 50 %, by weight, prefexably from 5 to 35 %, by weight, particularly preferably between lS 6 and 20 ~, by weight, based on the hydrated state. Both pro-perties may be determined by simple preliminary tests.
Examples of copolymers to be used according to the invention are those based on the following monomers:
n-butyl acrylate/methyl methacrylate (ratio, by weight, 1:4
SOFT, WITH A LOW HYDROP~ILITY CONTACTOPTICAL A~TICLES
This invention relates to new contactopticalshaped ar-~cles, in parti~lar contact lenses and scleral lenses, of cross-linked copolymers of olefinically unsaturated compounds whichhave a water-absorbing capacity of 4 to 50 ~ by weight, in the hydrated state,and of which the glass transition temperature is be~Jeen 25 and 55C in the dry state and below 35C in the hydrated state. In the dry state, the shaped articles may be machined at room temperature and only change into a soft lens in the hydrated state on the eye.
Scleral caps, also called scleral lenses, were already developed towards the end of the nineteenth century. The starting material used was glass which, because of its hardness, was not satisfactorily tolerated by the eye. An improvement was made in the thirties of this century through the introduction of polymethyl methacrylate (PMMA) whi~h was easier to process and more readily tolerated than glass. Although the mechanical strain imposed on the eye tissue by the cap covering it could be considerably reduced by PMMA, the high tolerance required for relatively long wearing times of the lenses could only be partly achie~ed.
Further considerations led in the fifties ~o the develop-ment of a small lens resting mainly on the cornea, the contact lens.
By reduction of the contact area between the contact lens and the eye, tolerance was considerably improved. However, because of the hardness of PMMA, lenses of that material also caused irritations which could not be overcome by dimensional changes. Accordingly9 the search for softer materials was taken up. About fifteen years ago, so-called hydrogel lenses introduced a new development in the field of contact lenses.
Hydrogel lenses are hydrophilic polymer networks based on water-soluble monomers which are capable of absorbing up to 70%, by weight, of water~ based on the hydrated form, Le A 23 271 :
,: ,, ~ " ,, ",, , .,:
~.
.
:
, ~
.~ , ~6~
and of softening as a result of the absorption of water.
Among the water-soluble monomers, N~vinyl lactams in com-bination with polyallyl cross-linkers have become parti-cularly important. The prior art which may be mentioned includes, for example, US-PS 4,158,089, European Patents Nos. 79 720, 79 721 and 106 650 and Shell Polym. 7 (1983) No. 3, pp 69 to 71.
By virtue of their softer consistency and the lower mechanical strain which they impose on the eye tissue, hydrogel lenses are more comfortable to wear, but have the disadvantage that they are easily damaged, require intensive care and are capable of taking up and absorbing metabolism products, lens-care preparations and bacteria.
Recent years have seen the development of new lenses of rigid and semi rigid materials, for example poly-silyl methacrylates, cellulose acetobutyrate, which have a low water-absorbing capacity and which have meanwhile claimed a sonciderable share of the market.
High tolerance, easy care and good optical proper-ties of the material are primarily responsible for this.
Although the development of these lens materialsmay be considered to be positive, there has long been a demand for a soft, rubber-elastic material having low water absorption, in particular for PWT (prolonged wearing time) lenses. This demand was partly satisfied by lenses of sili-cone rubber. However, silicone lenses involve wettability problems. In addition, they have to be cast in a specialised production process. The less expensive lace cutting process cannot be used for silicone rubber.
A major difference between the shaped articles according to the present invention and commercial soft lenses based on HEM~ (2-hydroxyethyl methacrylate) or PVP
(polyvinyl pyrrolidone) lies in their higher glass transition temperature in the hydrated state. Although the prior art HEMA and PVP materials have a glass transition temperature Le_A 23 271 ~
.
.
~ ' ::
, . . .
above 100C in the dry state they soften in the hydrated state at temperatures far below 20C. The shaped articles accordin to the invention, however, soften at between 20 and 35C in the hydrated state.
It has now been found that these requirements may be satisfied by cross-linked copolymers which have a low hydrophility, but which nevertheless have a glass transition temperature below 35C in the hydrated state.
The present invention relates to contactoptical articles, in particular contact lenses and scleral lenses, of water-absorbing, cross-linked copolymers of olefinically unsaturated monomers having a softening point in the hydra-ted state below 35C, preferable between 20 and 35C~ cha racterised in that the copolymer has:
(a) a water-absorbing capacity at 25C of 4 to 50 %, by weight, preferably 5 to 20 % by weight, based on the hydrated state; and (b) a glass transition temperature in the dry state of 25 to 55C, preferably 28 to 45C.
A further difference lies in the considerably lower water-absorbing capacity which leads to a reduced risk of inclusion of lens-care preparations, metabolism products and bacteria.
The increase in thickness which the contactoptical articles according to the invention undergo at 20C as a : result of hydration is 2 to 20 %, in particular 3 to 10, : based on the dry state the content of water extractable components is preferably below 0.5 %, by weight, in par-ticular below 0.1 %, by weight.
Copolymers suitable for the contactoptical ar-: ticles according to the invention can be obtained by poly-merisation of two or more olefinically unsaturated mono-: ~ mers in known manner, the monomers and the qualltitative ratios in which they are used being selected in such a way that the copolymer has a glass transition temperature in the :~ : Le A 23 271 :~:
~ .
' . ' ~ .
''` -'''' '' - , above-mentioned range. This is simple for those skilled in the art to achieve by virtue of the substantially linear relation between the glass transition temperature and the mole fraction of the components of a copolymer. Glass transi-5 tion temperatures of a vari~ty of homopolymers may be found,for example, in Immergut, Polymer Handbook, Interscience ~ lishers New York, 1966.
Another factor to be taken into account in the choice of the monomers is that the copolymer has high transparency lO (preferably >95 %, particularly preferably >98 % permeabi-lity to light at a layer thickness of 0.5 mm, disregarding the light loss by total reflection) and its water absorbing capacity at 25C is between 4 and 50 %, by weight, prefexably from 5 to 35 %, by weight, particularly preferably between lS 6 and 20 ~, by weight, based on the hydrated state. Both pro-perties may be determined by simple preliminary tests.
Examples of copolymers to be used according to the invention are those based on the following monomers:
n-butyl acrylate/methyl methacrylate (ratio, by weight, 1:4
2~ to 3:1) ~-ethylhexyl acrylate/methyl methacrylate (ratio, by weight, 1:3 to 3:1) ethyl acrylate/ethyl methacrylate (ratio, by weight9 1:2 to l:lj 25 vinyl acetate/vinyl propionate vinyl chloride/ ethylene vinyl chloride/ vinyl acetate/ ethylene vinyl chloride/ methyl fumarate A preferred copolymer according to the invention 30 is based on:
A) 9,98 to 55 %, by weight, preferably 20 to 35~ by weight, of an N-vinyl amide of the general formulao Le A 23 271 ~, .
, ~216~
R-c-N-c~I=cH2 R' in which R and R' independently represent Cl-C alkyl groups, preferably methyl groups;
5 B) 90 to 23 ~, by weight, preferably 80 to 33 %~ by weight, of a methycrylic acid ester containing 1 to 8, preferably 1 to 6, C-atoms in the ester moiety, in particular n-butyl and/or isobutyl methacrylate in combination with 0 to 20 %, by weight, of methyl methacrylate and, op-tionally,C) 0 to 30 %, by weight, of one or more olefinically unsa-turated monomers which copolymerize with A) and B).
The copolymers to he used according to the inven-tion must be cross-linked.
Cross-linking can be affected in known manner by radical formers, for example by the action of high energy radiation, for example electron beams, on the finished co-polymer or preferably by using 0.01 to 3 %, by weight, pre-ferably 0.1 to 2 %, by weight, in particular 0.2 to 1 %, by 20 weigth, of cross-linkers containing at least 2 olefinically unsaturated groups in the copolymerization reaction.
Cross-linkers suitable according to the invention are D) (meth)acrylate cross-linkers and/or E) vinyl or allyl cross-linkers. The cross linkers D) are known compounds which, 25 in addition to a (meth)acrylate group, also contain at least one other, identical or different olefinically unsaturated group. Such compounds include acrylates or methacrylates o~ polyfunctional alcohols, such as ethylene glycol dimeth-acrylate, propylene glycol dimethycrylate, die~hylene glycol 30 dimethycrylate, triethylene glycol dimethycrylate, polyethylene glycol methylcrylate, 1,4-butane diol meth~crylatel 1,6-hexane-Le A 23 271 : ~ :
.
...
. . , :
- :
diol dimethycrylate, trimethylolpropane trimethycrylate, pentaeryhtrol tri- and tetra-methycrylate, methyl-1,5-pentane diol dimethycrylate, dihydrodicyclopentadienyl-monomethycrylate, allyl methycrylate, vinyl methycrylate, bisphenol-A-dimethycrylate and the corresponding acrylates.
The cross-linkers E) contain at least two olefinically unsaturated groups (vinyl or allyl groups), but no (meth)-acrylate group. Examples of such known monomers are butane diol divinyl ether, divinylethylene urea, divinylpropylene urea, divinyl adipate, divinyl benzene, divinyl phthalate, triallyl cyanurate, triallyl isocyanurate, diethylene glycol diallyl carbonate, diallyl maleate, diallyl itaconate, tri-methylol propane di and tri-allyl ether, triallyl trimellitate, N,N-diallyl melamines, etc.
lSBoth cross-linker D) and cross-l`inker E) are preferably used in the copolymerisation in a ratio, by weight, OL 1: 3 to 3:1, preferably 1:2 to 2:1, in particular approximately 1:1. The combination of the two types of cross-linker is advantageous to the transparency and radius stability of the lenses and caps made from the copolymer and means that th~ materials contain only very small amounts (<0.5%, by weight) of water-extractable components.
The N-methyl N-vinyl amides oS acetic acid, propionic acid and butyric acid are preferably used as component Aj in the above-mentioned preferred copolymers according to the invention. N-methyl N-vinyl acetamide is particularly preferred.
- Aliphatic, cycloaliphatic, aromatic and araliphatic methycrylates, preferably methyl; ethyl; n-, i and t-butyl; cyclohexyl, phenyl and benzyl methcrylate can be used as component ~) of the preferred copolymers according to the invention. N-butyl and isobutyl methacrylate, op-tionally in combination with methyl methacrylate, are par-ticularly preferred.Le A 23 271 :: :
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7 _ Up to 30 %l by weight, of other monomers C) which copolymerize with ~) and B) may be used (preferably instead of a part of ~)) in the production of the above-described, preferred copolymers according to the invention. These monomers C) are especially inter alia, Cl~Cl2alkyl or cycloalkyl esters of acrylic or methycrylic acid; meth-acrylic acid; acrylic acid; vinyl pyrrolidone; monohydroxy or dihydroxy C2-C6-alkyl esters of (meth)acrylic esters there-of, such as, for example, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2,3-dihydroxypropyl methacrylate, 1,4-butane diol monoacrylate, 2-ethoxyethyl methycrylate; gly-cidyl methycrylate; vinyl acetate, vinyl laurate, vinyl propionate and vinyl versate. The molar ratio of B) to C) should not exceed 1:0.5. Preferred monomers are vinyl ace-tate, vinyl laurate, vinyl propionate, vinyl versate (versaticacid vinyl ester) and 2-oxyethyl ethyl methacrylate.
Accordingly, particularly preferred copolymers according to the invention have the following composition:
A) 9.98 to 35 %, by weight, of N-methyl vinyl acetamide, B) 90 to 33 ~, by weight, of n-butyl methacrvlat2 and/or isobutyl methacrylate or a mixture with 0 to 20 %, by weight, of methyl methacrylate, C) 0 to 30 ~, by weight, of one or more olefinically unsa-turated monomers which copolymerize with A) and B), D) 0.01 to l %, by weight, of a polyfunctional (meth)-acrylate cross-linker, E) from 0.01 to l ~, by weight, of a polyfunctional vinyl or allyl cross-linker.
The sum of the percentages by weight beiny in each case 100.
The water-absorbing capacity of these preferred copolymers is about 4~to 50 %, by weigth, preferably 5 to 20 %, by weight, based on the hydrated state, and ~he glass ; ~ transition temperatures~of the dry copolymers are 25 to 55C.
~fter hydration to equilibrium moisture, the glass transi-tion temperatures thereof are 20 to 35C. The materials are Le A 23 271 :, ..
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3l9~
characterized by the sudden transition from the glassy to the rubber-elastic state which may be demonstrated by thermo-mechanical differential analysis.
The cross~linking copolymerisation of the olefi-nically unsaturated monomers may be carried out by conven-tional radical polymerizat~on techniques, for example ini-tiated by heat, light of radical-forming initiators. It is preferably carried out by photopolymerization, as described in detail in DE-OS 3,300~345 and Int. Chim. 1983, No. 242, pp 121-126. The pol~meri~ation may be carried out as so-called block polymerization in plate chambers or even in glass tubes or plastic cups. A preferred embodiment comprises polymeri-zing the consituents in plastic cups of polyolefins, such as polyethylene, polypropylene, polymethyl-1-pentene, poly-amides or polyacetals. The caps may be shaped appropriatelyfor a blank or even for the finished lens. The polymerization may also be carried out in the presence of ethylene glycol which is subsequetnly washed out with water.
The described material is eminently suitable for - 20 the production of thin to very thin PWT lenses. By virtue of the low absorption of water, there is only a slight in-crease in thickness during hydration. Thin to very thin lenses are to be understood to be lenses having a thickness at the centre thereof of from 0.04 to 0.15 mm when designed for minus lenses (to correct short~sightedness) or from 0.08 to 0.3 mm for plus lenses (to correct long-sightedness) and from 0.1 to 0.4 mm for aphacia lenses (to correct the ab-sence of a lens). By appropriate geometry of the inner side (aspherical construction), it is possible to obtain an increased ex-change of lacrimal fluid, as is already prior art nowadaysin the case of hard lenses, and thus to increase the tolerance on the eye.
Compared with conventional lenses having a thick-~- ness at the centre of greater than 0.15 mm, the thin to ~35 very thin lenses show increased permeability to oxygen which Le A 23 271 :
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is an advantage, particularly for prolonged wearing of contact lenses.
The novel aspect of the lenses according to the invention is that they can be turned, milled and polished in the dry state at xoom temperature and, after hydration on the eye, change into a soft material which does not im-pose mechanical strain, without undergoing a significant increase in thickness or losing stability. Accordingly, the lenses according to the invention represent a novel and advanced combination of the hitherto known hard and soft lenses~
Examples Monomer mixtures having the composition indicated in Table 1 below were irradiated in cups of poly-4-methyl-l-pentene which had a diameter of 12 mm and a depth of 4 m~
for 6 days at room temperature using a UV fluorescent lamp.
The buttons (blanks) obtained were then tempered for 6 hours at 80C and for 2 hours at 120C. Contact lensQs were pro-duced from the buttons by turning and polishing.
Table 1 Composition in %, by weight A B C D E
n-butyl methacrylate 78.99 - 53.99 73.99 iso-butyl methacrylate - 71.99 - - 68.99 25 methyl methacryIate - - 15 N-methyl vinyl acetamide 20 25 30 20 30 vinyl versate - 2 2-oxyethyl ethyl methacrylate - - - 5 ethylene glyccl dimethacrylate 0.5 0.5 0.5 0.5 0.5 30 triallyl cyanurate 0.5 - 0.5 0.5 0.5 divinylpropylene urea - 0.5 - - ~
az ~ isobutyrid acid dinitrile 0.01 0.01 0.01 0.01 0.01 The lenses produced from materials A to E were treated Le A 23 27I
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"' ' ~2~0~g~
Ior 6 hours at room temper~ture in 5 % by weight H202 solution and then dialyzed for 6 days with ion exchange water. The hydrated lenses did not show streaks, clouding or light scattering e~fects under a slit lamp.The properties of the lenses are shown in Table 2 :
Table 2 Lens material _ A _ B C D E
Glass transition temperature in the dry state (C) 35 30 40 25 28 Glass transition temperature in the hydrated state (C) 22 23 25 15 22 Water-absorbing capacity, based on the hydrated ~tate (~, by weight) 5 8 10 8 10 Increase in thickness on hydra~ion (%) 2 3.5 3.5 3.54 Animal testing of the lenses on rabbit's eyes revealed good biocompatibility of the material, even after 21 days' con-tinuous wearing.
To determine the increase in thickness finished lace cutted, dry lenses were stored for 6 days in physiological sodium chloride solution at 20~C. To determine the extrac.
table contents, the lenses were washed after storage, dried for 24 hours at 80C and reweighed. In every case, the 2S weight loss was less than 0.1 ~, by weight.
The radius stability amounted to approx. 0.05 mm and the permeability to light for a layer thickness of 4.5 mm to approx. 90 %; this includes the liqht loss due to total reflection.
he A 23_271 . J~
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A) 9,98 to 55 %, by weight, preferably 20 to 35~ by weight, of an N-vinyl amide of the general formulao Le A 23 271 ~, .
, ~216~
R-c-N-c~I=cH2 R' in which R and R' independently represent Cl-C alkyl groups, preferably methyl groups;
5 B) 90 to 23 ~, by weight, preferably 80 to 33 %~ by weight, of a methycrylic acid ester containing 1 to 8, preferably 1 to 6, C-atoms in the ester moiety, in particular n-butyl and/or isobutyl methacrylate in combination with 0 to 20 %, by weight, of methyl methacrylate and, op-tionally,C) 0 to 30 %, by weight, of one or more olefinically unsa-turated monomers which copolymerize with A) and B).
The copolymers to he used according to the inven-tion must be cross-linked.
Cross-linking can be affected in known manner by radical formers, for example by the action of high energy radiation, for example electron beams, on the finished co-polymer or preferably by using 0.01 to 3 %, by weight, pre-ferably 0.1 to 2 %, by weight, in particular 0.2 to 1 %, by 20 weigth, of cross-linkers containing at least 2 olefinically unsaturated groups in the copolymerization reaction.
Cross-linkers suitable according to the invention are D) (meth)acrylate cross-linkers and/or E) vinyl or allyl cross-linkers. The cross linkers D) are known compounds which, 25 in addition to a (meth)acrylate group, also contain at least one other, identical or different olefinically unsaturated group. Such compounds include acrylates or methacrylates o~ polyfunctional alcohols, such as ethylene glycol dimeth-acrylate, propylene glycol dimethycrylate, die~hylene glycol 30 dimethycrylate, triethylene glycol dimethycrylate, polyethylene glycol methylcrylate, 1,4-butane diol meth~crylatel 1,6-hexane-Le A 23 271 : ~ :
.
...
. . , :
- :
diol dimethycrylate, trimethylolpropane trimethycrylate, pentaeryhtrol tri- and tetra-methycrylate, methyl-1,5-pentane diol dimethycrylate, dihydrodicyclopentadienyl-monomethycrylate, allyl methycrylate, vinyl methycrylate, bisphenol-A-dimethycrylate and the corresponding acrylates.
The cross-linkers E) contain at least two olefinically unsaturated groups (vinyl or allyl groups), but no (meth)-acrylate group. Examples of such known monomers are butane diol divinyl ether, divinylethylene urea, divinylpropylene urea, divinyl adipate, divinyl benzene, divinyl phthalate, triallyl cyanurate, triallyl isocyanurate, diethylene glycol diallyl carbonate, diallyl maleate, diallyl itaconate, tri-methylol propane di and tri-allyl ether, triallyl trimellitate, N,N-diallyl melamines, etc.
lSBoth cross-linker D) and cross-l`inker E) are preferably used in the copolymerisation in a ratio, by weight, OL 1: 3 to 3:1, preferably 1:2 to 2:1, in particular approximately 1:1. The combination of the two types of cross-linker is advantageous to the transparency and radius stability of the lenses and caps made from the copolymer and means that th~ materials contain only very small amounts (<0.5%, by weight) of water-extractable components.
The N-methyl N-vinyl amides oS acetic acid, propionic acid and butyric acid are preferably used as component Aj in the above-mentioned preferred copolymers according to the invention. N-methyl N-vinyl acetamide is particularly preferred.
- Aliphatic, cycloaliphatic, aromatic and araliphatic methycrylates, preferably methyl; ethyl; n-, i and t-butyl; cyclohexyl, phenyl and benzyl methcrylate can be used as component ~) of the preferred copolymers according to the invention. N-butyl and isobutyl methacrylate, op-tionally in combination with methyl methacrylate, are par-ticularly preferred.Le A 23 271 :: :
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, ~
` .
7 _ Up to 30 %l by weight, of other monomers C) which copolymerize with ~) and B) may be used (preferably instead of a part of ~)) in the production of the above-described, preferred copolymers according to the invention. These monomers C) are especially inter alia, Cl~Cl2alkyl or cycloalkyl esters of acrylic or methycrylic acid; meth-acrylic acid; acrylic acid; vinyl pyrrolidone; monohydroxy or dihydroxy C2-C6-alkyl esters of (meth)acrylic esters there-of, such as, for example, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2,3-dihydroxypropyl methacrylate, 1,4-butane diol monoacrylate, 2-ethoxyethyl methycrylate; gly-cidyl methycrylate; vinyl acetate, vinyl laurate, vinyl propionate and vinyl versate. The molar ratio of B) to C) should not exceed 1:0.5. Preferred monomers are vinyl ace-tate, vinyl laurate, vinyl propionate, vinyl versate (versaticacid vinyl ester) and 2-oxyethyl ethyl methacrylate.
Accordingly, particularly preferred copolymers according to the invention have the following composition:
A) 9.98 to 35 %, by weight, of N-methyl vinyl acetamide, B) 90 to 33 ~, by weight, of n-butyl methacrvlat2 and/or isobutyl methacrylate or a mixture with 0 to 20 %, by weight, of methyl methacrylate, C) 0 to 30 ~, by weight, of one or more olefinically unsa-turated monomers which copolymerize with A) and B), D) 0.01 to l %, by weight, of a polyfunctional (meth)-acrylate cross-linker, E) from 0.01 to l ~, by weight, of a polyfunctional vinyl or allyl cross-linker.
The sum of the percentages by weight beiny in each case 100.
The water-absorbing capacity of these preferred copolymers is about 4~to 50 %, by weigth, preferably 5 to 20 %, by weight, based on the hydrated state, and ~he glass ; ~ transition temperatures~of the dry copolymers are 25 to 55C.
~fter hydration to equilibrium moisture, the glass transi-tion temperatures thereof are 20 to 35C. The materials are Le A 23 271 :, ..
.. ,` .' ~, ;
3l9~
characterized by the sudden transition from the glassy to the rubber-elastic state which may be demonstrated by thermo-mechanical differential analysis.
The cross~linking copolymerisation of the olefi-nically unsaturated monomers may be carried out by conven-tional radical polymerizat~on techniques, for example ini-tiated by heat, light of radical-forming initiators. It is preferably carried out by photopolymerization, as described in detail in DE-OS 3,300~345 and Int. Chim. 1983, No. 242, pp 121-126. The pol~meri~ation may be carried out as so-called block polymerization in plate chambers or even in glass tubes or plastic cups. A preferred embodiment comprises polymeri-zing the consituents in plastic cups of polyolefins, such as polyethylene, polypropylene, polymethyl-1-pentene, poly-amides or polyacetals. The caps may be shaped appropriatelyfor a blank or even for the finished lens. The polymerization may also be carried out in the presence of ethylene glycol which is subsequetnly washed out with water.
The described material is eminently suitable for - 20 the production of thin to very thin PWT lenses. By virtue of the low absorption of water, there is only a slight in-crease in thickness during hydration. Thin to very thin lenses are to be understood to be lenses having a thickness at the centre thereof of from 0.04 to 0.15 mm when designed for minus lenses (to correct short~sightedness) or from 0.08 to 0.3 mm for plus lenses (to correct long-sightedness) and from 0.1 to 0.4 mm for aphacia lenses (to correct the ab-sence of a lens). By appropriate geometry of the inner side (aspherical construction), it is possible to obtain an increased ex-change of lacrimal fluid, as is already prior art nowadaysin the case of hard lenses, and thus to increase the tolerance on the eye.
Compared with conventional lenses having a thick-~- ness at the centre of greater than 0.15 mm, the thin to ~35 very thin lenses show increased permeability to oxygen which Le A 23 271 :
~!
.
. . . : ~ ' " ' ` '' . `
'' ,~ .
.. '.''` ` ~`~
9~
is an advantage, particularly for prolonged wearing of contact lenses.
The novel aspect of the lenses according to the invention is that they can be turned, milled and polished in the dry state at xoom temperature and, after hydration on the eye, change into a soft material which does not im-pose mechanical strain, without undergoing a significant increase in thickness or losing stability. Accordingly, the lenses according to the invention represent a novel and advanced combination of the hitherto known hard and soft lenses~
Examples Monomer mixtures having the composition indicated in Table 1 below were irradiated in cups of poly-4-methyl-l-pentene which had a diameter of 12 mm and a depth of 4 m~
for 6 days at room temperature using a UV fluorescent lamp.
The buttons (blanks) obtained were then tempered for 6 hours at 80C and for 2 hours at 120C. Contact lensQs were pro-duced from the buttons by turning and polishing.
Table 1 Composition in %, by weight A B C D E
n-butyl methacrylate 78.99 - 53.99 73.99 iso-butyl methacrylate - 71.99 - - 68.99 25 methyl methacryIate - - 15 N-methyl vinyl acetamide 20 25 30 20 30 vinyl versate - 2 2-oxyethyl ethyl methacrylate - - - 5 ethylene glyccl dimethacrylate 0.5 0.5 0.5 0.5 0.5 30 triallyl cyanurate 0.5 - 0.5 0.5 0.5 divinylpropylene urea - 0.5 - - ~
az ~ isobutyrid acid dinitrile 0.01 0.01 0.01 0.01 0.01 The lenses produced from materials A to E were treated Le A 23 27I
~. .
, . . .. .
: ,.~. , :
"' ' ~2~0~g~
Ior 6 hours at room temper~ture in 5 % by weight H202 solution and then dialyzed for 6 days with ion exchange water. The hydrated lenses did not show streaks, clouding or light scattering e~fects under a slit lamp.The properties of the lenses are shown in Table 2 :
Table 2 Lens material _ A _ B C D E
Glass transition temperature in the dry state (C) 35 30 40 25 28 Glass transition temperature in the hydrated state (C) 22 23 25 15 22 Water-absorbing capacity, based on the hydrated ~tate (~, by weight) 5 8 10 8 10 Increase in thickness on hydra~ion (%) 2 3.5 3.5 3.54 Animal testing of the lenses on rabbit's eyes revealed good biocompatibility of the material, even after 21 days' con-tinuous wearing.
To determine the increase in thickness finished lace cutted, dry lenses were stored for 6 days in physiological sodium chloride solution at 20~C. To determine the extrac.
table contents, the lenses were washed after storage, dried for 24 hours at 80C and reweighed. In every case, the 2S weight loss was less than 0.1 ~, by weight.
The radius stability amounted to approx. 0.05 mm and the permeability to light for a layer thickness of 4.5 mm to approx. 90 %; this includes the liqht loss due to total reflection.
he A 23_271 . J~
'' ~' . ~'` . ' .
~" .".,.
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A scleral lens comprising a water-absorbing, cross-linked copolymer of an olefinically unsaturated monomer having a softening point in the hydrated state below 35°C, characterized in that the copolymer has;
(a) a water-absorbing capacity of 25°C of 4 to 50%, by weight, based on the hydrated state and (b) a glass transition temperature in the dry state of 25 to 55°C.
(a) a water-absorbing capacity of 25°C of 4 to 50%, by weight, based on the hydrated state and (b) a glass transition temperature in the dry state of 25 to 55°C.
2. A lens according to claim 1 wherein the copolymer has a water-absorbing capacity of 5 to 35%, by weight.
3. A lens according to claim 1, wherein the copolymer has a water-absorbing capacity of 5 to 20% by weight.
4. A lens according to claim 1, 2 or 3 wherein the copolymer has a glass transition temperature in the dry state of 28 to 45°C.
5. A lens according to claim 1, 2 or 3, wherein the copolymer has a glass transition temperature in the hydrated state of 20 to 35°C.
6. A lens according to claim 1, 2 or 3, wherein the article exhibits an increase in thickness on hydration of 2-20%.
7. A lens according to claim 1, 2 or 3, wherein the copolymer includes 0.01 to 3%, by weight, of a cross-linker containing at least two olefinically unsaturated groups.
8. A lens according to claim 1, 2 or 3, wherein the copolymer includes 0.01 to 3% by weight of a cross-linker containing at least two olefinically unsaturated groups and the cross-linker is a combination of (meth) acrylate cross-linker and vinyl or allyl cross-linker.
9. A lens according to claim 1, 2 or 3 wherein the copolymer includes 0.2 to 1% by weight of a cross-linker containing at least two olefinically unsaturated groups and the cross-linker is a combination of (meth) acrylate cross-linker and vinyl or allyl cross-linker.
10. A lens according to claim 1 wherein the copolymer comprises:
A) 9.98 to 55%, by weight, of an N-vinyl amide of the general formula in which and R1 independently represent C1-C4 alkyl groups B) 90 to 23%, by weight, of a methacrylate containing 1 to 8 C-atoms in the ester moiety, C) 0 to 30%, by weight, of an olefinically unsaturated monomer which copolymerizes with A) or B), and D) 0.01 to 1%, by weight, of a polyfunctional (meth)-acrylate cross-linker and/or E) from 0.01 to 1%, by weight, of a polyfunctional vinyl or allyl cross-linker, the sum of the percentages, by weight, being 100.
A) 9.98 to 55%, by weight, of an N-vinyl amide of the general formula in which and R1 independently represent C1-C4 alkyl groups B) 90 to 23%, by weight, of a methacrylate containing 1 to 8 C-atoms in the ester moiety, C) 0 to 30%, by weight, of an olefinically unsaturated monomer which copolymerizes with A) or B), and D) 0.01 to 1%, by weight, of a polyfunctional (meth)-acrylate cross-linker and/or E) from 0.01 to 1%, by weight, of a polyfunctional vinyl or allyl cross-linker, the sum of the percentages, by weight, being 100.
11. A lens according to claim 10 wherein, in component A), R
and R1 are methyl groups and in component B) the methacrylate is n-butyl or iso-butyl methacrylate.
and R1 are methyl groups and in component B) the methacrylate is n-butyl or iso-butyl methacrylate.
12. A lens according to claim 10 or 11, wherein the proportion of component A) is 9.98 to 35%, by weight.
13. A lens according to claim 10 or 11, wherein the proportion of component B) is 90 to 35%, by weight.
14. A lens according to claim 10 or 11 wherein the proportion of component A) is 9.98 to 35% by weight and the proportion of component B) is 90 to 33%, by weight.
15. A process for preparing a scleral lens, comprising polymerizing two or more olefinically unsaturated monomers, wherein the monomers and their ratio by weight are selected to provide a copolymer having a glass transition temperature in the dry state of 25 to 55°C and a transparency of > 95%.
16. A process according to claim 15 wherein said two or more olefinically unsaturated monomers comprises:
A) 9.98 to 55%, by weight, of an N-vinyl amide of the general formula in which R and R1 independently represent C1-C4-alkyl groups, B) 90 to 23%, by weight, of a methacrylic acid ester containing 1 to 8 C-atoms in the ester moiety, and C) 0 to 30% by weight of an olefinically unsaturated monomer which copolymerizes with A) or B3, and the polymerization is effected in contact with a radical former.
A) 9.98 to 55%, by weight, of an N-vinyl amide of the general formula in which R and R1 independently represent C1-C4-alkyl groups, B) 90 to 23%, by weight, of a methacrylic acid ester containing 1 to 8 C-atoms in the ester moiety, and C) 0 to 30% by weight of an olefinically unsaturated monomer which copolymerizes with A) or B3, and the polymerization is effected in contact with a radical former.
17. A process according to claim 16 wherein said monomers include 20 to 35% of component A) and 80 to 33% of component B).
18. A process according to claim 16 or 17 wherein in component A) R and R1 are each methyl groups and component B) is n-butyl or iso-butyl methacrylate in combination with 0 to 20% by weight of a methyl methacrylate.
19. A process according to claim 16 or 17 wherein component B) is a methacrylic acid ester containing 1 to 6 C-atoms in the ester moiety.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3445092.0 | 1984-12-11 | ||
| DE19843445092 DE3445092A1 (en) | 1984-12-11 | 1984-12-11 | SOFT, LESS HYDROPHILE CONTACT OPTICAL ITEMS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1260196A true CA1260196A (en) | 1989-09-26 |
Family
ID=6252443
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000497138A Expired CA1260196A (en) | 1984-12-11 | 1985-12-09 | Soft, with a low hydrophility contactoptical articles |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0184727B1 (en) |
| JP (1) | JPS61144622A (en) |
| AT (1) | ATE49061T1 (en) |
| CA (1) | CA1260196A (en) |
| DE (2) | DE3445092A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3708308A1 (en) * | 1986-04-10 | 1987-10-22 | Bayer Ag | CONTACT OPTICAL ITEMS |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1394056A (en) * | 1971-07-21 | 1975-05-14 | Nat Res Dev | Contact lenses |
| US4182802A (en) * | 1977-12-27 | 1980-01-08 | Samuel Loshaek | Hydrophilic polymers and contact lenses of high water content |
| JPS59195621A (en) * | 1983-04-22 | 1984-11-06 | Toyo Contact Lens Co Ltd | Soft contact lens |
-
1984
- 1984-12-11 DE DE19843445092 patent/DE3445092A1/en not_active Withdrawn
-
1985
- 1985-11-29 DE DE8585115137T patent/DE3575024D1/en not_active Expired - Lifetime
- 1985-11-29 AT AT85115137T patent/ATE49061T1/en not_active IP Right Cessation
- 1985-11-29 EP EP85115137A patent/EP0184727B1/en not_active Expired
- 1985-12-09 CA CA000497138A patent/CA1260196A/en not_active Expired
- 1985-12-11 JP JP60277092A patent/JPS61144622A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0184727A2 (en) | 1986-06-18 |
| EP0184727B1 (en) | 1989-12-27 |
| JPS61144622A (en) | 1986-07-02 |
| DE3575024D1 (en) | 1990-02-01 |
| EP0184727A3 (en) | 1987-09-23 |
| DE3445092A1 (en) | 1986-06-19 |
| ATE49061T1 (en) | 1990-01-15 |
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