Note: Descriptions are shown in the official language in which they were submitted.
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Sof~ co~t~ct-eptical ~bjects
Thi~ invenLion relates to soft contact-optical
~ouldin~ , in ~articular contact len~es and scleral
lense~, from cross-li~kin~, hydrophilic copolymers of
olefi~ic un~aturated compou~d~, which contain N-alkvl-N-
vinyl carboxylic acidamides as hydrophilic monomar
component in addition to the monomers kno~n ~ sa fro~
contact optic~ The mouldings accordin~ to the invention
have a lower water absorption capacity tha~ convantional
~oft lense~, better compatibility over long p~riods of
wear and ~how no tendency towards the migration of low
molecular wei~ht constituents.
Soft hydrophilic contact lenses of hydroxyethyl
2~ methacr~lat~ ~HEMA) were developed in the vears 1963 to
1965 ~espe~iallv in the USSR~. This typ~ of lens was very
quickly accepted by contact l~s wQarers owin~ to th~ir
comfort. Th~ mechanical stress on Lhe corneal tissu~ i5
lo~er with soft lenses than ~ith hard lenses; moreoverJ
the metabolism of the cornea is influenced to a lesser
~ extent.
: ~ : Simple ad~u~tm~nt, short acclim~tization and ~ood
: wear;n~ comfort were decisive fàctor~ in making soft
hydrophilic lens~s capture a ~ubstantial proportion of th~
: ~o mark~t within a short time~
~ : A~ter over a decade of experience with HEMA lenses,
: . disa~vanta~ffs havs, however, al50 become known in this
;: ~ro~ of materials. Thus, the compatibility i8 impaired
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aft~r wearinq soft hydrophilic HEMA lenses for a
r01ativelv lon~ time. The ca~ses of this li~ especially
in preservative3 contained in caring a~ents, caring a~ents
in conjunction with tha len~ material and d~maging effects
of the mat2rial itself. HEMA material6 can cau3e toxic
dama~e to ~he eye. In the clinical picture, such dama~3
in addition ~o ~he complaints ~ujecti~ely mado by contact
le~s wearer~, can be recognized from hypere~ia in the
limbus region and broadeninas of the border tachyphagia
ves~al network with more or less substantially formsd
corneal vascularizationc. The lstter ar0 ;rraYersable and
occur not seldom without sujective complaint~. Re~idual
monomers and cros~-linkin~ aqents contributa to thisO
Their influenc~ on the biological compatibility is
demonstrable.
Similar manifestations can al o be detacted when
wearing contact lenfia~ from copolvmer~ of HEMA.
"HEMA-free" pol~ars or copolymers, such as polvvinyl
pyrrolidone or vinyl pyrrolidonelmethyl methacryla~e
copolymers have been used for some time for highly
hydrophilic contact lenseQJ they should have a be~ter eya
compatibili~y than HEMA lenæes. These so-called hydrogel
lenses are hydrophilic polymer networks based on water-
soluble monomers, which are capable of absorbing from 25
to over 70% by weight of wat~r, bas~d on the hydrated
form, and whi~h soften as a resul~ of absorbing water. The
~ N-vinyl lac~am~ in co~bination with polvallyl cross-
lin~ing agents have achieved an important role among the
watar-soluble monomers. US Pa~en~ 4 158 089 and ~uro~ean
Pa~ent~ 79 720, 79 721, 106 650 a~ well as Sh~ll PD1Vm,
7 ~1983) 9 no. 3 p~ 69-71 are mentioned, for example, as
3~
Le A Z3 47?
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prior art. Soft hydrogel lenses initially have high
wearing comfort owing to their ~oftness and moulding
abili~y compared with lenses from hard and semi-hard
materials with low water absorption capacity, for example
polymethyl methacrylate, polysilyl methacrylatesJ
cellulose ace~obutya~e among others, but suffer from the
disadvantage ~hat they can easily be mechanically
damaged. To increase tensil0 strength, it was thus
proposed to add from 0.9 to 5% by weight of methacrylic
acid to the monomer mixture ~see European Patent no.
106 650). Rasidual monomeric methacrylic acid, however,
has a high toxic e~fect in contact lens materials, so that
a method must be sought for achieving a high mechanical
strength without addi~ion of methacrylic acid.
With lenses Df N-vinyl lactam monOmQr-containing
polymers, i~ i5 often observed that a slight clouding and
brown colouring occurs aftar a relatively long wearing
time. Hydrogel lenses, moreover, suffer from tha
disadvantage that they can be easily damaged, require
intensive care and can store and absorb metabolic
products, caring agenta as well as bacteria.
In recent years, new lenses have been developed from
hard and semi-hard materials, for example polysilyl
mothacrylates, cellulose acetobutyrate among others, with
low water absorption capacity9 which in the meantime have
captured a considerable proportion of the market
Good compatibili~y, simple care and good optical
properties of ~hs ma~erial are hereby decisive factors.
Al~hough the development of these lens ma~erials can
be evaluated positively, the desire for a soft, rubber-
elastic materia~l with low water absorption, par~icularly
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for exte~ded wear lensas, ha~ existed for a lon~ time.
This desire could be partiallv met by lenses of ilicon~
rubber. With th~ silicone lens, however, problems occur
with ~he ~ettabilitv~ Furthermor~, they have ~o be cast
in a special production process. Tha cheaper rotating
procsss cannot be appliad in the case of silicone rubber.
la An obi~ct of tha invention was to find a new ma~erial
which combines ~he advantages of Lhe hard materials~ such
as good optical proper~ies, relatively low water
absorption capacity, low care expenditure and
productability of thin lenses a~ a result of tha
mechanical stability of the material, with the advantages
of soft9 rubber-elastic materials, such as low mechanical
stress on th2 eye ti sue, high wearing comfort etc.
It was fourd that ~h~ ob~ect can be achieved when
in the production of the cross-linking copolymer an N-al-
kyl-N-vinyl carboxylic acid amide ars simultaneou~ly used
as hydrophilic monomar, optionally in addition to other
hydrophilic monomers.
The present invsntion provides contac~-optical
mo~ldings, in particular contact lenses ard scleral
2~ lensest from water-absorbing, cross-linking copolv~ers Df
olefinic unsatura~ed monomers, characterised in that ths
copolymer contain~ polvmerised from 5 to 55% by weight,
preferably from 8 to 40% by weiyht, particularly
prefarably from 10 to ~5% by weight of an N-vinyl amide
of the general formula
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R-C-~-CH=CH2
~5 R
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231~9 6137
wherein
R and R' represent, independently ~rom each other, C1-C4-alkyl
yroups, preferably methyl, with the proviso that R and R' cannot
both be methyl.
The N-methyl-N-vinyl amides of acetic acid, propionio
acid and butyric acid are preferred accordlng to the lnvention.
In additlon to the monomer components which are
important for the invention, monomers known per se from contact
optics can be used in the production of the copolymer, whereby
aliphatic, cycloallphatic, aromatic and araliphatic methacrylic
acid esters having ~orm 1 to 8 carbon atoms in the ester part are
preferred. ~xamples o~ these are methyl-, ethyl-, n-, i- and t-
butyl, cyclohexyl-benzyl- and phenyl methacrylate, in part~cular
methyl ~ethacrylate and the butyl methacrylates. A further
preferred class of monomers are the above-mentloned vinyl lactams,
ln particular ~-vinyl pyrrolidone.
Examples of further monomers known per se are generally
the C1-C12-alkyl- or cycloalkyl esters o~ acrylic acid or
methacrylic acid; methacrylic acid; acrylic acid; monohydroxy- or
dihydroxy-C2-C6-alkyl esters of (meth)acrylate acid as well as the
alkyl ethers thereof such as 2-hydroxyethyl methacrylate, 2-
hydroxy-ethyl acrylate, 2,3-dihydroxypropyl methacrylate, 1,4
butandiol-monoacrylate, 2-ethoxye~hyl methacrylate; glycidyl
~ethacrylate; vinyl acetate, vinyl laurate, vinyl propionate,
vinyl versate, as well as methacrylic acid-2- oxyethyl ethyl
esters.
~; The oopolymers to be used accor~ing to the invention
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mUc~ be cross-linked.
The cross-linking can bs carried out in a known
manner, for example by ~he influence of high-energv
radiation~ for exampla elactron radia~iont on the finished
copolvmer or by the ~imul~aneous U5e of from 0.01 to 3%
by wei~h~, preferably from 0.1 to 2% by waight, in
particular from 0.2 to l'X. by wei~ht, of at least two
olefinicallv unsaturated ~roup-containin~ cro~s-linking
agents during copolymerisation.
Cross-linking agents which are suitable according to
the invention are A) (meth)acrylic ester cros~-linking
a~ents and/or B) vinyl or allyl cross-linkin~ agents. The
cross-linking agents A) are compounds known per se, which
in addition to a ~meth)acrylic ester ~roup have at least
one further ol;finically ~nsaturated group of the same
kind or diff~rent. Amon~ these are acrvlic acid or
methacrvlic acid esters of polyfunctional alcoh~ls, for
example ethvlene glycol dimethacrylate, propylene glycol
diethyl acrvlate, diethvlane glycol dimethacrylate
triethylene glysol dimethacrvlat~, polyethylene glycol
dimethacrylate, 1,4-~utandiol dimethacrylats, 1,6-
hexandiol dimethacrylate, trimethylol propane trime~h-
acrylate, pentaerythrita-tri- and tetramatha~rylata,
methyl-lt5 pentandiol-dim~thacrylate, dih~drodicyclo-
pentadianyl monomethacrylate, allyl methacrylate, vinyl
methacrylate, bisphenol-A-dimathacrylata, as well as the
correspondin~ acrylic acid esters.
The cross-linking agents B) have at least two
olefinically unsaturated groups ~vinyl or allyl ~roups),
howevar, n~ ~m~th~acrylic ester groupin~. Examples of
tho_a monomers known 0r se are butandiol-divinyl ether~
:~ LQ A_ 23 477
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divinvl e~hvlene urea, divenyl propolylene ur~a, divinyl
adipate, divenvl benzene, divinyl phthalate, triallvl
cyanurate, triallyl isocyanurate, diethyl2ne glycol
diallyl carbonate, diallyl maleate, diallyl i~aconate,
trimethylol propane-di- and triallyl other, triallyl
trimellita~e, N,N-diallyl mel2mines etc.
The cross-linkin~a aaents D) and cross-linkin~ a~ents
E) in a weiaht ratio of from 1:3 ~o 3:1, preferably frDm
1:2 to 2:1, in particular about 1:1, are preferably used
in the copolvmerisation. The combination of the ~wo typas
of cross-linking a~ent is advanta~eous for the transparen-
cv and radii st~bilitv of the lenses and shells producedfro~ ths copolvmer and results in the matarials continaing
only verv low proportions (<0.5% by weight) of water-
extractable portions.
Tha cross-linked copolv~ersiation of th2 olefinicallv
~ unsaturated monomer~ can take place accordin~ to the con-
ventional ~achniques of rad;cal polymeri~ation, for
xamplo initiated by heat, li~ht or by initiators
decompnsin~ in radicals. The li~ht polymerisation is
preferred, as described in detail in DE-05 ~ 300 ~45 and
Int. Chim. 198~, no. 242, p. 121-1~6~ The polymerisation
can ~herebv be carried out as so-called block polymeri-
sation in plate chambers, glass tubes or plastics material
cups. A preferrèd embodiment is the polymerisation of the
constituents in plastic~ material cups of polyolefins~
such a= polvethylene ? polypropylene, polymethyl pen~ene-1 ?
polyamides or polvacetalene. The cups can have a corres-
~ondin~ shape for an unfinished product or also for the
.
finished lens. The polymerisation
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can also take place with addition of ethylene glycol which
i5 later washed out with water.
Depending on the quanti~y of hydrophilic monomer
components in the copolymer, the water absorpt;on capacity
thereof is variable within wide lirnits, for e~ample
between 6 and 70%, by weight, based on the hydrated
condition. Compared with conventional soft lenses, the
products accDrding to the invention have the advantage,
however, that they can be adapted to a lower water
absorption capacity, and in spite of this have the sought
af~er wearing comfort on the eye of a soft lens.
The mat3rial to be used according to the invention
is outstandingly suitable for the production of thin to
very thin extended wear lenses. Owing to the low water
absorption, only a slight increase in thickness takes
place during hydration. By thin to very thin lenses, are
to be understood those lenses with an average thickne s
of from 0~04 to 0.15 mm by design for minus lenses (for
correcting short-sightedness), or from 0.08 ~o 0.4 mm with
plus lenses tcorrection long-sightedness) and from 0.1 to
8~4 mm in the case of aphacia lenses (for correcting
aphacia). By corresponding interior geometry (aspherical
constructi-on), an increased diffu~ion of lacrimal fluid
can be produced as is already the state of the art
nowadays with hard lenses, and thus the compatibility on
the eye can be increased.
The thin to very thin lenses have an increased
permeability to oxygen compared with conventional lenses
with an average thickness, of greater than 0~15 mm, which
is shown to be preferable, in particular for the extended
wear of contact lenses.
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A further advantage of the soft lenses according to
the invention is ~hat they do not become cloudy on the
eye, even after a relatively long wearing time, ~hey do
not turn brown and in addition to outstanding
compatibility on the eye, have particularly good radii
stability and optical stability.
In con~rast to commercial hydrophilic contac~ lenses
based on N-vinyl pyrrolidone, lenses according to
inven~ion contain no notable portions which can be
extracted with water ~preferably)<0.1% by weight).
The block polymerisation in plate chambers, described
in ~he following examples, firstly enables the biolocical
charge testing of soft lens materials, since relatively
large homogeneous plates ~preferably with a surface area
greater than 1 m2) can be produced in a preparation, from
which a large number tfor example more than 1000) of
finished products with identical chemical composition can
be pressed.
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Example 1
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Monomer mi~tures of ~he composition lis~ad in ~ha
following Table 1 are exposed to radia~ion with a UV
fluorescent lamp in cylindrical cups of poly-4-methyl
1~ pen~-1-ene wi~h a deameter of 12 mm and a height of 4 mm,
for 6 days a~ room tempera~ure, The blanks obtained are
~hen annealed for 6 hours at 80C and for 2 hours at
120C. Contas~ lenses are produced from ~he blanks by
rotating and polishing.
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Th~ lenses produced from the materials A to E are treat~d
for 6 hours at room temperature in a 5% H~02 solution and
then dialyzed for 6 days with ion exchange water. No
streaks, cloudiness or light scatter can be observed on
the hydrated lenses w;th the slit lamp. The properties of
the lenses are set out in Table 2:
lS
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The ~estin~ of the lenses in an ani~al experiment on
the eve of a rabbit re ~lts in a~ood bioco~patibility of
the material, even after 21 day~ of ~ninterrupt~d wear.
For determining ~he in~rease in thi~kne~s, dry
l~nses, rotated to completion, are stor~d for 6 days in
a phvsiolo~ic~l salt solution at 20C. For determining the
axtractable portions, the lense3 are washed after storage~
dried for 24 hours at 80C and rewei~hed~ In each case,
tha wei~ht 10s5 is less than 0.1% by weight. The radii
~tability i5 about 0005 mm, the li~ht transmission with
a layer thickness of 4.5 mm i5 about 90%.
Example 2
Monomer mix~ures of the ~ompositions listed in the
follGwin~ Table 3 are filed into glass plate chambers with
the measurements Z50 x 250 x 5 mm, provided with a sealin~
cord, under N2 after careful de~assing under vacuum, and
exposed to radiation with a UV fluorescent lamp for 6
: 25 days. The plat~s are annealed for 24 hours at 80C and
then for 2 hours at 14~ C. Unfinish~d product with a
diameter of i2.5 m~ ar~ cut from ths plate6, which have
b0en dialyzed for 6 days in deionized water. After drying
ths unfinished products, contact lenses Df varyin~
thickness are produced therefrom by rotatin~ and
polishin~.
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The measurement of the inner radii with average
thickne~ses up to 0.08 mm r2sults in good raddi
stabili~ies tvariations 0.1 mm). No streaks or cloudiness
~an be found during testing with the slit lamp. Light
transmission 90% with a layer thickness of 4.7 mm. The
portion which can be extracted with water is in all cases
less than 0.1~/. by weight.
The animal experiment on ~he eye of a rabbit resul~
in good biological compatibility of the material with the
eye, e~en after 21 day~ of uninterrup~ed ~ear.
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