CA1330951C - Synthetic polymer for endocapsular lens replacement - Google Patents

Abstract

SYNTHETIC POLYMER FOR ENDOCAPSULAR LENS REPLACEMENT

ABSTRACT OF THE DISCLOSURE
A synthetic polymer (24) is provided for endocapsular lens (18) replacement in an eye (10). The polymer, which is injected into the lens capsule (16) after removal of the lens, comprises an oxygen-stabilized photosensitive prepolymer. An example of such a prepolymer comprises polyether with urethane linkages with one or both ends capped with a functional group containing at least one double bond, such as an acrylate, a methacrylate, or a styrene.

The polymerization reaction is initiated with a pho-toinitiator such as dimethoxyphenylacetophenone and is quenched in the presence of oxygen. Contrary to the prior art polymers, the time of curing is on the order of only a minute or so. The viscosity and thickness of the polymer formed may be tailored to achieve a desired index of re-fraction of between about 1.3. and 1.6.

Description

~ `:` 1 1 330951 .... .
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CIT-~88~

SYNT~TIC PO~YME~ FOR ~NDO~APSUI.AR ~NS RE~AC~M~NT ~-.
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T~CNNICAI. FIIU.D

The present lnvention relates to treatment~ ol~ de~ect~
;~ ~ ln the eye, ~nd, a~ore partlcularly, to the roplacement of di~eased or otherwlse ~efoctlve eye len~e~
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- ~,, ACKGROUND ART

Sur~ery on the ~ye l~:b~co~ing Dore co~monplace und 10 sophistlcated ~B new technlgues and devlc~ are :;~eveloped .
to :co~bat i~palred~si~ht or even blin~n~s. ;~One ~uch ; field of ~urgery i8 the:replace~ent of the lens ln th~ eye whlch~can be necessitated~,:for:exa~ple, by ca~aract devel~
op~ent, wh~oh:opaclfl~s the lens. :~
15: ~ Procedures have be~n d~veloped~for removal of th~
len~ Early procedures have~1nvolvèd:th~ re~oval of the ens~:and~l-ns~cap-ule (transpar-nt~ ~bran- onc-psulatlng : ~.
the lens) by ~eans of forceps~or suction.~ More recently, less~ trau~atlc aeans have been devoloped: ouch ~ean~:;ln~
20~ volve ~partloul~tlng ~the l-n-, an exa~pl~ ~of ~hlch ~ 18 : called onlcatlon, ~hlch lnvolve~ ultr~oonlc di~inte~ra~
tion of the len~ by.appllcatlon of hl~h frQquency vlbra- ~a~
tlQn8 thereto. The lens fra~ent~ ar~ then r~oved ~y pir~tion. :~
25:~ ~ ~Replac~nt of the l~ns to:~vold r~quirln~ the pa~
~:;tlent to ~ear ~pectaclc~ ~ith ~a~lv-~ -nRe3 has ~been '~ ''.'t~
inve~tl~ated. So~e 801UtloD~ hav~ lnoludo~ in~actln~ a ,. ~ 2 1330~51 vi~couo liquld or a sillcone into the ~acant l~ns cap~ule.
Implantation of lntraocular lenses has also been done, but the l~plant i8 rl~ld and not ~ocu~able and 18 oaslly dls~
lod~ed by shock or vibratlon.

More recently, G. M. Wr1~ht ~nd T. D. Talcott ln U.S.
Patent~ 3~,943; 4,642,~42; and 4,G08,050 have dlsclosed ln~ectlon by n~edle of a poly~erlc lomposition into the lens capsule. The poly~eric composl~ion comprl~es a slli~
cone prepolymer, a croos-llnker and a platlnum-based cata-10 lyst. The composltlon cures ln thle l~n8 capoule to an -:~:
optically clear, ~el-ll~e ~at~rial whlch may accommodate, or focus, through action of the eye lans mu3cle~.
However, a proble~ with the polymeric composltion disclosed 18 that a ~eparate h~ating step is required to ;~
15 permit removal of the needle fro~ the eye to lnltiate :~:
polymerlzatlon at the ln~cctlon slte and thus prevent 108s of polymer therefrom. Further, the tlme of lnltlal cross- :
linking i8 on the order o~ ~everal hour8, whlch lnvolves lengthy immobillzatlon of the eye to per~lt co~plete cur-ing.
Thus, what i8 reqUirQd i8 a poly~eric compofiitlon providlng the advantayes of the prior art while avoidlng ~ost, lf not all, the problem~ assoclated wlth the prlor ~
art approache~. :
:
DISCLOSURE OF INVENTION

In accordance wlth the lnventlon, a ~ynthetlc polymer is provided for endocapsular lens replac~3ent. The poly-ner, which is ln~ect~d into the lens capsule after rc~ovalof the l-n~s, co~prlses an oxy~en-stabill~od photocon~ltlve prepolymer. An 2xa~ple of ~uch a prepolymer comprises a polyether with urethane llnkages wlth one or both ~nds capped with a ~unctlonal yroup containin~ at l~a~t one ' ~

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double bond, such as an acrylate, methacrylate, or a sty~
rene.
The polymerization reaction is initiated by light using a photoinitiator such as dimethoxyphenylacetophen~
one and other aryl ketones and is ~uenched in the presence of oxygen. Contrary to the prior art polymers, the time of curing is on the order of only a minute or so. The viscosity and thickness of the polymer formed may be tailored to achieve a desired index of refraction.
In accordance with a first aspect of the present invention there is provided a method of endocapsular lens replacement by forming a synthetic polymer in the lens capsule of an eye after removal of the lens comprising: (a~ injecting a polymer composition comprising a photo-sensitive prepolymer and a photoinitiator into the lens capsule in the absence of oxygen; (b) exposing the composition to light to form the synthetic polymer; and (c) curing the polymer within several minutes.
', ~: ~',.' BRIEF DESCRIPTION OF THE DRAWINGS ~ ;

Figs. 1-5 are diagrammatic views of a portion of an eye, showing the procedure of lens removal, followed by injection of the polymer used in the method of the invention.
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BEST_MODES FOR CARRYING OUT THE INVENTION

Referring now to the drawings, wherein like numerals designate like elements throughout, a portion of an eye 10 is shown, with a probe 12 inserted through the cornea 14 and the lens capsule 16 into the lens 18.
As shown in FIG. 1, the probe, which advantageously comprises means for emitting high frequency vibrations, ~:~
has caused ultrasonic disintegration of the lens 18 by a 10 process known as sonication. In FIG. 2, the probe 12, :~
which also includes aspiration means 12', has begun . :~
removal of the denatured protein of the lens, or lens fragments, 18. In FIG. 3, the process is complete, leaving behind the empty lens capsule 16. The 15 particular method of disintegrating the lens and e removing it is immaterial to the practice of the ~ ~:
invention, and thus forms no part of this invention~ :-n FIG. 4, a needle 20 is inserted into the same incisions 22a and 22b by the probe 12 and is used to inject a : ,..

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: , 1 poly~er co~posltlon 2~ lnto the lonl c~p~ull 16. Th~
polymer 18 d~oxy~enated prlor to inJectlon.
Th~ needle 20 18 ~radually wlthdr~wn a~ the polymer flll~ the capsule 16 and the lncislon 22a throu~h the cornea 14 18 ~ur~lcally clo~ed. Since the polymer cures to lt~ S~nal ~tatQ wlthin ~ ~attor of ~lnutos u~in~ ht, no heatlng ot~p 18 r~qulrQd to cure the poly~cr around the lnci~lon 22b ln the l~ns capBule 16 to per~lt removal of the needle 20. The co~pletely filled lens c~p~ule 16 18 depicted ln FIG. 5.
The poly~er composltlon 2~ 1B lnJected lnto the lens capsule 16 throu~h 31it 22b, ~h~ch 18 typlcally no larger than 3 ~, and i8 ~ntended to cro~s-link rapldly ~o that the compositlon, which la lnJectod in a llquid ctate, wlll not squlrt out the sllt when th~ needle 20 1B with~r~wn.
The poly~er compo3it~0n us~d ln the practlc~ of the invention co~prises (a) a prepoly~er and (b) a photoinitl-ator. The prepoly~er 18 preferably one that 18 ~ubstan-tially llnear, with one, znd preferably both, onds capped with a functional group h2vin~ at least one olefinlc bond.~amples of ~uch ~unctional yroups lnclude acrylates, ~ethacrylates, ~nd styren-s.
It 15 pre~erred that both ~nds be capped, ln order to for~ a ~ore ho~ogeneous poly~er. The pre~ence of ~he double bond p~rmlts olofinlc-type cro~s-llnkln~.
Exa~ples Or ~ultable prspoly~-rs include polypropyl~
~ne ~lycols, polypropylene ~lyC018 wlth polyethylene ~ly-col unlts, polybutylene ~lycols wlth pcly~thylene ~lycol unlts, urethanes, and ~llloones such as dl~ethyl sllicone and ethyl slllcone. The ~olecular wel~ht o~ the prepoly~
~er ~dvantay~ously ranges from about 2,000 to 8,000, al-thou~h lower or hl~h~r ~olecular wei~ht ~aterlal ~y b~
e~ployed The photoinitlator co~prises a co~po~ltlon ~hlch inltlatos poly~erlzation o~ ol~flnlc ~nd ~roups ~n the ..

~``` 1 33()~5i 1 vi~lblo-to-near- W r~on. ~xa~plas oS such photolnltla-tors, partlcularly sultcd Por c~usin~' cro~s-llnklng of acrylat~ ~roups, lnclude ac~tophenon2 d~rlvatlvo~, ~uch ~8 ~l~ethoxyphenylac~tophenone.
The procodure ~or for~ation ~ld re~oval Or l~n3 ~ra~-~ents 18 lnvolv~ tho u~e Or a alcro~copa and a l~mp ror lllumlnatlon of the eye. ~hen lnJectlng the poly~er co~-posltlon 2~ lnto the lon~ capsulc 16, th~ cros~-llnklng procedure ~ay be perfor~ed u~ln~ the same la~p ~mployed ln con~unctlon wlth tho ~lcroscope ~ d by the ~ur~on to r~move the lens fr~y~ents 18. Thl~ lamp i8 0~ th~ appro-prlatc wavelen~th and i~ of ~uffic:lent ~nt~nsity to actl-vate the photolnitiator and b~ln the proces~ of cross-llnking. The concentratlon of photolnitiator ~8 nor~ally about 0.25 to 2 wt%.
The time ~or reaction 1~ ordin~rlly 1~8~ than about five ~lnutes. The obs~rvable physlcal properties do not seem to chan~e aftcr the ~lrst ~everal ~lnu~ of cross-l$nklng.
The photoinltiator i8 quenched by the presence Or oxygen, ~nd ~ccordin~ly, the operation ~ay be done by contlnuously ~lushln~ the eye wlth an lnert gas, such as nltrogen or arqon, or wlth saline untll th~ reaction i~
~ubstanti~lly co~plete.
The prepoly~er 18 ~tabil~z~d wlth oxyg~ durln~ stor~
in~ and sample pr~par~tion and do~a~ed in the dark before ln~ectlon, ~uch ~a wlth a vacuum pU~p, ~nd back-fllled w1th the lnert ga~. Normal ~t~osphere i8 ~ufflclent to stablllze the propoly~er durlng ~a~dlln~ and stora~e.
It ~ well-~nown that the eye len~ i8 layerod, llke that of an onlon, wlth ~ch l~y-r h~vln~ a ~lff~rent re-fractlve lndex. Th~ poly~erized co~posltlon ~8 ~8~0ntlal-ly ho~o~en~ou~. ~owever, th~ viscoslty and rofractlv~
lndex o~ the co~positlon i8 a ~unction o~ th~ uncapped . ~ ~ . . - .. . : . . .............................. . - -. ..
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~:~` 6 1 330~51 : ~
1 portlon o~ ~he pr~poly~r, and aay b0 csn~gNr~d to pro~
vlde a refractive lndex b~tweon about l.S and 1.6.
Slnce the poly~erlzed composi~ion 24 18 ~n ~ to~er, th~ ~uscles of the eye 10 ~ay otill p~rfor~ their nor~al 6 ~unction of acco~oda~ion. Further, the ~billty to tallor the poly~-rlz~d oo~ool~ion ln tor~s Or Qlastici~y, vi~-co~ity and refractlve lndex ~eans that the lons for~atlon, when done ln co~Junction wlth the l~onication len~ r~oval, ~ay be perfor~ed ~arly ln the process of cataract for~a-tlo~.

RXAMPL~S

Polyether ~lycols o~ avera~e ~ol~cular ~l~hts bc-tween 1,000 and 4,000 were combined throu~h ur~thane llnk-age~ u~ing dllsocyanates ~uch as lsophorone diisocyanate (~luka Che~ical Corp., Hauppau~e, NY) or ~ethylene bis (4-cyclohexyldilsocyanate) (Mobay Ch~tcal Corp., ~itt~bur~h, PA). The ends were then capped wlth a co~pound contalnin~
a tor~lnal alke~e such as lsocyanatoethyl ~ethacrylate (Dow Che~ical Co., Mldland, MI) or 2-hydroxyethyl sethac-rylate (Aldrlch Che~lcal Co., Mllwaukee, WI). Reaction were catalyzed by a tin co~pound ~uch as ~tannou~ dioctan~
oate.
The resultant pr~polymer ~as a colorless liguid with vioco~ity ~u~ficie~tly low ~o that lt could be lnJected by ~yrin~e through a 20 gauge nsedle. The ~at~rl~l coul~ be purified, if nocessary, throu~h various ~nown chro~ato-~raphic ~thod~. BHT (25 to 100 pp~) ~y b~ added to ~tabillze the poly~er.
She ~oly~er was thorou~hly ~ixed with tb~ ~pproprl~t~
quantity o~ photolnltiator, ~uch ~ 2,2-dl~ethoxy-2 phenyl acetoph~none ~Aldrlch Che~lcal Co.), tra~s~erred to ~yrln0~, then pumped in vacuo, pro~ct~d ~ro~ llght, gor : ~, '~ ~. :' . . -, 1 330q5 1 ::
1 at least 24 hrs. The polymer-filled syringc was ~tored, protected f rom l~ght, under an lnert atmosphere.
The Table below liQt~ various polymer ~ormulations :
prepared pursuant to the foregoing teachlngs.
: 5 Table.

No. Polyether Dii~ocyanate Cata- End cap; Photoln-alYcol ~ a linker: a l~st q itiator; X
; ~ 10 1 Voranol* IPDI 0.76 Sn(Oc)2 I~M; 0.29 DMPA; 0.3 (lg65); 8.8 .~
: 2 Voranol* IPDI; 0.96 -do- I~M; 0.28DMPA; 0.25 ::
(1965); 10.7 15 3 Voranol* IPDI; 0.58 -do- I~M; 0.~3 DMPA; 0.3 : (3829); 20.1 4 Voranol* IPDI; 1.1 -do- ~A; 0.69 DMPA; 1.2 (3829); 10.0 ~ :
: 5 PPG-4000~ De ~; 1.~ -do- H~M; 0.75 DMPA; 1.0 11.6 6 PPG-4000~ DeQW; 1.4 -do- HEA; 0.67 -do-11.6 : 7 PPG-4000~ IPDI; 0.93 -do- HEA; 0.50 -do-8.9 :~
25 8 PPG-3000;*~: IPDI 1.0 -do- ~EM; 0.31 -do~
9 . 0 ,-~
9 PPG-3000* IPDI; l.0 -do- HEA; 0.27 -do-9,O ~ -10 Terethane --- -do- I~M; 7.1 -do-. 30 (650); 15.0 L~end~
;~ Voranol (1965) - Polypropylene ~lycol ¢nd capped with ; 12X ethylene oxlde; M~ = 1,965 ~ :

* - Trade-marks ~-"~'~. ':, ` .~

_ 8 l 330951 , 1 Voranol ~3829) - Polypropylene ~lycol end capped with 22% ethylene oxlde; MW = 3,829 PPG-4000 - Polypropylene glycol; MW = ~,000 PPG-3000 - Polypropyl~ne glycol; MW = 3,000 Tcrethane (650) - Polytetramethylene ~lycol; MW = 650 IPDI - Ioophorono dllsocyanate DesW - Desmodur*W tmethylene bis(4-cyclohexylisocyan-ate)] .
Sn(Oc)2 - Stannous dloctanoate IEM - I~ocyanatoethyl ~ethacrylate r' ~:
HEA - 2-Hydroxyethyl acrylate ;
HEM - 2-Hydroxyethyl methacrylate DMPA - 2,2-Dimethoxy-2-phenylacetophenone ' Several of the foregolng polymers (Nos. 1, 2, 5, 6, ~) were in~ected into len6 capsules of rabbit;s. Photo ;~
; cross-linking was promoted by the visible light used to ~; illuminate the surgical procedure. The poly~er was -~; stabilized ln the lens shape within ~ to 2 ~inutes and reaction wa~ complete withln 5 minutes.
The ~echanism for the photoinitiation apparently lnvolves homolytic cleavage of the initiator to give two radicals, which then lnltiate the cross-linking reaction.
Because molecular oxygen reacts with radlcals, deoxy~ena-tlon of the ~onomer allow~ for rapid cross-linklng.
The re~ultant in situ cross-linked polymer was a transparent plastlc with variable elasticity, depending on the degree of cross-link~ng and chemlcal compositlon. ;
Thus, a ~ethod of endocapsular lens replacement by ~`
30 forming a synthetic polymer in the lens capsule of an eye -~
after removal of the len~ has been disclo~ed. The ~ethod compri~es in~ecting a photosensitlve prepolymer into the --lens capsule ln the absence of oxygen. It will be clear to one of ordinary skill in the art that various changes and modifications of an obvious nature ~ay be ~ade without ''''' " "' . :
*- Trade-mark ,~ 9 1 330q51 . ;. , d~partln~ ~ro~ the splrlt o~ the lnv~ntlon, ~nd ~ uch chan~os ~nd l~odl~lcation~ ~re con~lder-d to b~ ~ithln th~
~cop~ o~ the lnvontion, ~ de~inod by the~ ~ppend-d c:lal~.

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Claims (34)

1. Use of a cured synthetic polymer as the replacement for a lens which has been removed from a lens capsule of an eye, said polymer being the product of in vivo exposure to light and curing within several minutes of a deoxygenated polymer composition comprising a photo-sensitive prepolymer and a photoinitiator provided within said lens capsule.

2. Use of a cured synthetic polymer as the replacement for a lens which has been removed from a lens capsule of an eye, said polymer being the product of in vivo exposure to light and during within several minutes at ambient temperature of a deoxygenated polymer composition comprising a photo-sensitive prepolymer and a photoinitiator provided within said lens capsule.

3. Use of a cured synthetic polymer as claimed in claim 1 or 2 wherein said photoinitiator comprises an acetophenone derivative.

4. Use of a cured synthetic polymer as claimed in claim 3 wherein said photoinitiator comprises dimethoxyphenylacetophenone.

5. Use of a cured synthetic polymer as claimed in claim 1 or 2 wherein said photoinitiator is present in an amount ranging from about 0.25 to 2 wt%.

6. Use of a cured synthetic polymer as claimed in claim 1 or 2 wherein said light is visible-to-near-UV radiation.

7. Use of a cured synthetic polymer as claimed in claim 1 or 2 wherein said prepolymer has been stabilized against polymerization with oxygen.

8. Use of a cured synthetic polymer as claimed in claim 1 or 2 wherein said prepolymer is substantially linear, with at least one end capped with a functional group having at least one olefinic bond.

9. Use of a cured synthetic polymer as claimed in claim 8 wherein said functional group is one selected from the group consisting of acrylates, methacrylates, and styrenes.

10. Use of a cured synthetic polymer as claimed in claim 9 wherein said functional group comprises a methacrylate.

11. Use of a cured synthetic polymer as claimed in claim 8 wherein said prepolymer comprises a composition selected from the group consisting of urethanes, polypropylene glycols, polypropylene glycols with polyethylene glycol units, polybutylene glycols with polyethylene glycol units, and silicones.

12. Use of a cured synthetic polymer as the replacement for a lens which has been removed from a lens capsule of an eye, said polymer being the product of in vivo exposure to light and curing within about five minutes of a deoxygenated polymer composition comprising a photo-sensitive prepolymer and a photoinitiator comprising an acetophenone provided within said lens capsule, said prepolymer comprising a polyether having both ends capped with an acrylate group and stabilized against polymerization with oxygen.

13. Use of a cured synthetic polymer as the replacement for a lens which has been removed from a lens capsule of an eye, said polymer being the product of in vivo exposure to light and curing at ambient temperature within about five minutes of a deoxygenated polymer composition comprising a photo-sensitive prepolymer and a photoinitiator comprising an acetophenone provided within said lens capsule, said prepolymer comprising a polyether having both ends capped with an acrylate group and having been stabilized against polymerization with oxygen.

14. Use of a cured synthetic polymer as claimed in claim 12 or 13 wherein said photoinitiator comprises dimethoxyphenylacetophenone.

15. Use of a cured synthetic polymer as defined in claim 14 wherein said photoinitiator is present in an amount ranging from about 0.25 to 2 wt%.

16. Use of a cured synthetic polymer as defined in claim 14 wherein said light is visible-to-near-UV radiation.

17. Use of a cured synthetic polymer as defined in claim 12 or 13 wherein said acrylate group comprises a methacrylate.

18. Use of a deoxygenated polymer composition for forming a polymeric endocapsular lens replacement in the lens capsule of an eye from which the lens has been removed by providing said composition in the lens capsule and forming the replacement lens by in vivo exposure of said composition to light and curing said composition within several minutes, said composition comprising a photo-sensitive prepolymer and a photoinitiator.

19. Use of a deoxygenated polymer composition for forming a polymeric endocapsular lens replacement in the lens capsule of an eye from which the lens has been removed by providing said composition in the lens capsule and forming the replacement lens by in vivo exposure of said composition to light and curing said composition within several minutes at ambient temperature, said composition comprising a photo-sensitive prepolymer and a photoinitiator.

20. Use of a deoxygenated polymer composition as claimed in claim 18 or 19 wherein said photoinitiator comprises an acetophenone derivative.

21. Use of a deoxygenated polymer composition as claimed in claim 20 wherein said photoinitiator comprises dimethoxyphenylacetophenone.

22. Use of a deoxygenated polymer composition as claimed in claim 18 or 19 wherein said photoinitiator is present in an amount ranging from about 0.25 to 2 wt%.

23. Use of a deoxygenated polymer composition as claimed in claim 18 or 19 wherein said light is visible-to-near-UV radiation.

24. Use of a deoxygenated polymer composition as claimed in claim 18 or 19 wherein said prepolymer has been stabilized against polymerization with oxygen.

25. Use of a deoxygenated polymer composition as claimed in claim 18 or 19 wherein said prepolymer is substantially linear, with at least one end capped with a functional group having at least one olefinic bond.

26. Use of a deoxygenated polymer composition as claimed in claim 25 wherein said functional group 18 one selected from the group consisting of acrylates, methacrylates, and styrenes.

27. Use of a deoxygenated polymer composition as claimed in claim 26 wherein said functional group comprises a methacrylate.

28. Use of a deoxygenated polymer composition as claimed in claim 25 wherein said prepolymer comprises a composition selected from the group consisting of urethanes, polypropylene glycols, polypropylene glycols with polyethylene glycol units, polybutylene glycols with polyethylene glycol units, and silicones.

29. Use of a deoxygenated polymer composition for forming a polymeric endocapsular lens replacement in the lens capsule of an eye from which the lens has been removed by providing said composition in the lens capsule and forming the replacement lens by in vivo exposure of said composition to light and curing said composition within about five minutes, said composition comprising a photo-sensitive prepolymer and a photoinitiator comprising an acetophenone, said prepolymer comprising a polyether having both ends capped with an acrylate group and stabilized against polymerization with oxygen.

30. Use of a deoxygenated polymer composition for forming a polymeric endocapsular lens replacement in the lens capsule of an eye from which the lens has been removed by providing said composition in the lens capsule and forming the replacement lens by in vivo exposure of said composition to light and curing said composition within about five minutes at ambient temperature, said composition comprising a photo-sensitive prepolymer and a photoinitiator comprising an acetophenone, said prepolymer comprising a polyether having both ends capped with an acrylate group and having been stabilized against polymerization with oxygen.

31. Use of a deoxygenated polymer composition as claimed in claim 29 or 30 wherein said photoinitiator comprises dimethoxyphenylacetophenone.

32. Use of a deoxygenated polymer composition as claimed in claim 31 wherein said photoinitiator is present in an amount ranging from about 0.25 to 2 wt%.

33. Use of a deoxygenated polymer composition as claimed in claim 31 wherein said light is visible-to-near-UV
radiation.

34. Use of a deoxygenated polymer composition as claimed in claim 29 or 30 wherein said acrylate group comprises a methacrylate.