Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-03-28
2002-10-15
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S320000, C526S328500, C623S006120, C351S16000R, C524S359000, C524S558000
Reexamination Certificate
active
06465588
ABSTRACT:
TECHNICAL FIELD
This invention relates to a hydrophilic copolymer, or hydrogel, which is suitable for the production of ocular lens such as intraocular lens, contact lens or the like, and is particularly suitable for foldable intraocular lens (foldable IOL).
BACKGROUND ART
Intraocular lens (IOL) has been used to replace crystalline lens in cataract surgery. Since IOL was first used in implanting in 1949, various researches have been carried out on IOL materials. With the great evolution of operation methods and advancement of operation methods, demands on the characteristic features of IOL have also changed a lot. Recently, with the popularity of phacoemulsification techniques and the like, it is possible to open a very small incision to remove the opaque crystalline lens, and thus the demands on the characteristic features of implanted IOL have changed gradually. For example, in order to implant IOL through a small incision, the IOL should be in a folded form when implanted and returned to an expanding state in lens capsule, this is the characteristics of the so-called foldable IOL. Herein, various researches have been carried out on IOL materials. Polymethyl methacrylate (PMMA), silicone, acrylic resin and the like have been widely used as IOL materials, while silicone and acrylic acid resin can be used as foldable IOL materials. Recently, copolymers of hydroxyethyl methacrylate, methyl methacrylate and the like have also been used as foldable IOL materials. Moreover, besides the studies on these IOL materials, the following techniques have been adopted in the practical use: an ultra-violet (UV) light absorber such as hydroxybenzophenone or hydroxyphenyl benzotriazole has been added to the IOL materials to avoid the effect of UV light on retina; polysaccharide such as heparin is coated on IOL surface to improve biocompatibility and to avoid cell deposition and the like.
One characteristic of the copolymer according to the present invention is that it contains acrylic monomer having a pyrrolidone group as its structural unit. There have been reports on this kind of polymer, especially those used in ocular lens, such as copolymer of methacryloyl-oxyethyl-2-pyrrolidone and acrylic acid and the like (JP Laid-Open 28705/1992); polymer prepared from monomer which is formed from amidation of acrylic acid and pyrrolidone (JP Laid-Open 43208/1990); polymer of polyoxyalkylene skeleton having a pyrrolidone group (JP Laid-Open 8218/1990) and so on. In particular, as for copolymers prepared from three components or more, only the following several kinds have been disclosed: copolymers prepared from vinyl pyrrolidone and hydroxyethyl methacrylate or methyl methacrylate (JP Laid-Open 105250/1978); copolymer prepared from methacryloyloxyethyl-2-pyrrolidone, alkyl methacrylate and fluoroalkyl methacrylate (JP Laid-Open 150197/1993) and so on. However, these materials were studied mainly for the applications in soft contact lens and not in IOL, the possibility of application in foldable IOL as described in this invention has totally not been suggested.
It is an object of the present invention to provide a kind of ocular lens such as intraocular lens, contact lens and the like, to say in more detail, it is used mainly as foldable intraocular lens (foldable IOL). For the study of foldable IOL materials, their properties including refractive index, surface strength, tensile strength, recovering speed, transparency and the like should be considered. For example:
1) if the refractive index of IOL is too low, the thickness of IOL would increase too much, thus contraction difference of periphery would become over large. So it is necessary for IOL to have a proper refractive index. Specifically, the preferable range of refractive index is 1.4-1.6.
2) because tweezers are used to implant foldable IOL, surface strength and tensile strength of IOL bearing the operation is needed.
3) after foldable IOL is implanted, it must be returned to its original form in lens capsule. Recovering speed can be varied with the difference of habit and ability among operators. In general, the possibility of mechanical invasion of peripheral tissue increases with the increase of recovering speed. On the other hand, with the slowdown of recovering speed, the operation in turn gets longer, the possibility of bad effects on peripheral tissue also increases. Accordingly, suitable recovering speed is needed for foldable IOL.
Moreover, the material should be easily shaped into IOL. Only when the above requirements are satisfied can different kinds of foldable IOLs find practical use, and more preferable material be developed. For example, though the commercially available silicone foldable IOL has suitable refractive index, its recovering speed is too fast; when acrylic foldable IOL is implanted with tweezers, compressive mark or scar may possibly form. The operators must be very skillful when using these two IOLS. In addition, silicone foldable IOL can not resist to damage from laser, is easy to chap and pit, and has the possibility to form white turbidness.
Furthermore, to avoid the effect of UV light on retina, a more preferable material can be obtained if an UV absorber is added, so it is expected to develop a kind of excellent material with both the above mentioned properties and at the same time having the ability to absorb UV light.
The present inventors, with the consideration to solve the above problems, have investigated the more applicable foldable IOL materials, and have found that a four component copolymer prepared from acrylic derivatives having pyrrolidone groups could be used as a kind of particularly excellent IOL material.
DISCLOSURE OF THE INVENTION
The present invention relates to a novel copolymer prepared from the copolymerization of the following monomers a), b), c) and d), to the process for preparing the copolymer, and to the ocular lens thereof.
a)
[wherein R
1
represents hydrogen or a lower alkyl group; R
2
represents a lower alkylene group, which can be replaced by a hydroxyl group, and there can be oxygen in the alkylene group chain. The followings are same.]
b)
[wherein R
3
represents hydrogen or a lower alkyl group; R
4
represents the following radicals or a single bond,
R
5
, R
6
, R
7
and R
8
represent hydrogen or a lower alkyl group, respectively. m, n, p and q are integers of 1 to 4. The followings are same.]
c)
[wherein R
9
represents hydrogen or a lower alkyl group; R
10
represents a lower alkyl group. The followings are same.]
d)
[wherein R
11
represents hydrogen or a lower alkyl group; R
12
represents a phenyl lower alkyl group, a naphthyl lower alkyl group, a pyrimidyl group, or a pyrimidyl piperazinyl group. The phenyl ring of the phenyl lower alkyl group and naphthyl ring of the naphthyl lower alkyl group can also be replaced by a lower alkyl group, a lower alkoxy group or a halogen atom. X represents —O—, —NH— or a single bond. The followings are same.]
When structural units are used to represent the copolymers, the copolymers are composed of the following four components: [I], [II], [III] and [IV], wherein the weight ratios are 40-80 for [I], 5-30 for [II], 5-20 for [III] and 5-30 for [IV], respectively.
The preferred weight ratios of the said components in copolymers according to the present invention are 50-70 for [I], 10-25 for [II], 5-15 for [III] and 5-20 for [IV].
The said weight ratio of the component is based on the total weight of the copolymer, which is obtained by mixing and polymerizing the described weight of the respective components (monomers).
Following is the detailed description of the above-mentioned groups. The said lower alkyl group is straight or branched chain alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl and the like; lower alkoxy group is straight or branched chain alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethox
Cheung William K
Santen Pharmaceutical Co. Ltd.
Wu David W.
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