Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Intraocular lens
Reexamination Certificate
1998-10-16
2001-08-21
Nguyen, Dinh X. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Intraocular lens
C623S006400
Reexamination Certificate
active
06277147
ABSTRACT:
Intraocular lenses made from silicone polymeric materials are usually deformable, so that for implantation a smaller incision needs to be surgically cut in the eye than for the implantation of “hard” intraocular lenses. In this respect, the size and mechanical characteristics of the silicone polymeric Intraocular lenses play an important role. As it will be well understood by those skilled in the art, for successful implantation the lens must have sufficient structural integrity, elasticity and small enough size to permit the folding for insertion through a small incision. After insertion, the lens must, of course, regain its original molded shape.
It will be further understood by those skilled in the art that the thinner is the lens, the easier is the surgical insertion procedure. On the other hand, in order to function as an intraocular lens, the lens material must have sufficient optical refractory power. Consequently, the higher in the optical refractive index of the silicone material, the thinner can be the lens to obtain the same optical refractory power.
Some silicone polymeric materials described in the prior art contain a silica reinforcer finely distributed in the polymeric silicone resin. Usually such reinforcement of the silicone polymeric material with silica in necessary for the polymeric material to attain adequate structural strength to be used as a foldable intraocular lens. Such silica reinforced polymeric silicone resins suitable for use as soft contact or intraocular lenses are described in U.S. Pat. No. 3,996,187; 4,615,702; 3,996,189. Additional disclosures relating to polymeric silicone materials or silica reinforcers, which comprise the background of the present invention can be found in U.S. Pat. No. 3,341,490; 3,284,406; 3,457,214; and in European Patent Application No. 0110537 filed on Oct. 18, 1983.
Additional disclosures relating to intraocular lenses can be found in U.S. Pat. No. 4,573,998, published UK Patent Application GB 2114315, and in co-pending application for U.S. Pat. Ser. No. 946,703 filed on Dec. 24, 1986 by Reich et al. The latter U.S. Patent application is assigned to one of the co-assignees of the present application.
The prior art intraocular lenses made of silica reinforced silicone copolymers still do not fully satisfy the need for high enough optical refractory power to permit sufficiently lens size which in turn would make it possible to surgically implant the lens through a desirably small incision in the eye. In other words, there is still need in the art for reinforced silicone polymeric materials which have sufficiently high optical clarity, refractive index, durometer hardness, tensile strength and related mechanical properties to permit construction of thin foldable intraocular lenses. The present invention satisfies this need.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide optically clear reinforced silicone polymeric materials of a refractive index of at least 1.44 coupled with sufficient durometer hardness, tensile strength and other mechanical properties to permit forming of thin intraocular lenses through final cross-linking of the polymeric material into desired lens shape.
It is another object of the present invention to provide a thin intraocular lens body from a reinforced silicone polymeric material, wherein the lens body has an optical refractive index of at least 1.44 and sufficient mechanical properties to permit implantation through a small incision in this eye.
The foregoing objects and advantages are attained by an optically clear, reinforced cross-linked silicone elastomer which includes a polymer containing 12 to 18 mol percent of aryl substituted siloxane units of the formula R
4
R
5
-SiO. In the formula R
4
and R
5
are identical with one another or are different from one another and represent phenyl, or mono- lower alkyl substituted phenyl groups, or di- lower alkyl substituted phenyl groups. Preferably both R
4
and R
5
are phenyl.
The polymer has end blockers containing siloxane units of the formula R
1
R
2
R
3
-Si-O.5 wherein R
1
and R
2
are alkyl, aryl or substituted alkyl or substituted aryl groups, and R
1
and R
2
may be identical or different from one another. The R
3
group of the end blocking siloxane units in an alkenyl group. Preferably, the end blocker is a dimethylvinyl siloxane unit.
The balance of the polymer consists of dialkyl siloxane units of the formula R
6
R
7
-SiO wherein R
6
and R
7
are identical with one another or are different from one another and are methyl or ethyl groups, and the polymer has a degree of polymerization approximately between 100 to 2000. Preferably, the R
6
and R
7
units are both methyl, and the degree of polymerization is approximately 250.
A trimethyl silyl treated silica reinforcer is finely dispersed in the polymer, in a weight ratio of approximately 15 to 45 parts of the reinforcer to 100 parts of the polymer. Preferably, there is approximately 27 parts of reinforcer to 100 parts of the copolymer.
The polymer when cured by cross-linking in a mold forms the body of an intraocular lens of the invention, and has the properties of an optical refractive index which is at least 1.44, a type A durometer hardness value of at least 35, a tensile strength of at least 500 psi, and a tear strength of at least 20 pli.
Further objects and advantages of the present invention will become readily apparent from the ensuing description wherein the specific embodiments are described as follows.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
Reinforced elastomeric polysiloxane copolymer compositions are provided in accordance with the present invention, which after appropriate curing by cross-linking, are eminently suitable to serve as the body of foldable “soft” intraocular lenses capable of implantation through a small incision in the eye.
More particularly, the reinforced elastomeric composition of the present invention has the chemical composition of a cross-linked copolymer including approximately 12 to 18 mol per cent of aryl substituted siloxane units of the formula R
4
R
5
-SiO where the aryl substituents (R
4
and R
5
groups) can be phenyl groups, mono- lower alkyl substituted phenyl groups, or di- lower alkyl substituted phenyl groups, and can be identical with one another or different from one another. Preferably, both aryl groups are simple phenyl, and the resulting diphenyl siloxane unit is present in the copolymer in a ratio of approximately 14 to 16 mol per cent. In the hereinafter described specific example, the diphenyl siloxane unit content of the copolymer is approximately 15 mol per cent.
It is noted in connection with the diaryl, preferably simple diphenyl substituted siloxane units, that the presence of the aryl groups tends to increase the optical refractive index of the copolymer.
The copolymer is end blocked with trisubstituted (monofunctional) siloxane units, an important feature of which is that at least one substituent of the end blocking group contains an olefenic bond. Thus, the general formula of the end blocking group incorporated in the copolymer of the invention is R
1
R
2
R
3
-SiO
.5
where the nature of the R
1
and R
2
is not critical, and they may be, for example, alkyl, aryl, or substituted alkyl or substituted aryl groups. R
1
and R
2
may be identical to one another, and may also be different from one another. The nature of the R
3
group in important in that R
3
contains an olefenic bond. Thus, R
3
is an alkenyl group, preferably a vinyl group. In the preferred embodiment of the invention the end blocking group is a dimethyl, vinyl siloxane unit. The role of the olefenic (vinyl) group, is to enable curing or cross-linking of the polymer an well as covalently linking, in accordance with another feature, certain ultraviolet light absorbing compounds to tho cross-linked copolymer matrix of an intraocular lens made in accordance with the invention.
The balance of the siloxane building blocks of the copolymer are dialkyl siloxane units wherein the two alkyl substituents are either ethyl or methyl. In
Christ Richard
Nash Brian Allen
Petraitis Del Joseph
Allergan
Nguyen Dinh X.
Stout, Uxa Buyan & Mullins, LLP
Uxa Frank J.
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