Compositions capable of forming hydrogels in the eye

Details Compositions capable of forming hydrogels in the eye Compositions capable of forming hydrogels in the eye

2002-07-16

2004-06-08

Sastri, Satya (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S563000, C524S560000, C524S501000, C623S005110, C623S006110, C623S006130, C526S264000, C526S330000, C522S034000, C522S035000, C522S064000, C522S111000, C522S112000, C522S904000

Reexamination Certificate

active

06747090

ABSTRACT:

FIELD OF INVENTION
The present invention refers to aqueous solutions of reactive polymers suitable for the production of hydrogel materials upon irradiation with blue light. The hydrogels are especially useful for production-of intraocular lenses, which can be formed in-situ in the capsular bag in an eye having undergone surgical excision of a natural lens.
BACKGROUND OF THE INVENTION
The natural lens of the human eye is a precisely formed structure of fibre cells containing about 65 percent water and 35 percent organic material, chiefly structural proteins. The proteins are responsible for the relatively high refractive index of 1.42 of the lens and are structured in such a way that there are negligible local variations in their density, resulting in a transparent lens. Aging or large stresses can change the morphology of the proteins causing a progressive loss of transparency. This is termed cataract formation and is irreversible and can eventually result in blindness.
Implantation of an intraocular lens (IOL) following cataract surgery is performed to replace the optical function of the natural lens. In order to remove the natural, cataractous lens, as well as to prepare for the introduction of the IOL, an incision is made into the eye. For many years most IOLs were made of poly(methylmethacrylate), a material with good optical characteristics and compatibility with the tissues of the eye. A disadvantage of PMMA is, however, that it is a very rigid material and the incision must be made large enough, at least 5-6 mm, for implantation of the IOL. With improved devices for less traumatic removal of the natural lens by phacoemulsification, requiring only a rather small, there was a need for lenses with deformable optics. In such small incision surgery an opening of only 3 mm, or less is required. Various silicone, acrylate and hydrogel lenses have been commercialized.
All incisions in the eye are accompanied by trauma, and so, although foldable lenses have been a great improvement, there is still a need for lenses than can be placed through an even smaller incision. A lens can be implanted through a 1.2 mm opening by injecting the lens material into the capsular bag as a fluid, followed by formation of a solid full size lens in-situ in the eye. An additional advantage of this technique is that, due to the formation of a fill sized lens, complications of conventional IOL implantation namely decentration and posterior capsular opacification may be overcome. Full sized lenses show excellent centration and there is evidence that they may prevent posterior opacification (PCO). Hydrogels are a class of materials that are very interesting for an injectable lens because they have the added advantage is that their aqueous composition approximates to that of the natural lens.
Hydrogels can be made by crosslinking aqueous polymer or monomer/crosslinker solutions. Since monomers are often toxic, the use of polymers is preferred for applications in the eye. Polymers to which a reactive group is attached, for example, an acrylate group, can be polymerized in the presence of water and form a hydrogel. This is a process of crosslinking polymer or prepolymer solutions have been described before. In U.S. Pat. No. 5,665,840 crosslinkable water-soluble prepolymers based on copolymers of vinylalcohol and vinyllactams are claimed for contact lens application. Several other publications also disclose the production of hydrogels after crosslinking crosslinkable water-soluble (pre)polymers. The crosslinkable water-soluble (pre)polymers are designed to polymerize in a mould yield hydrogel. However, in-situ in the eye, water is present which demands certain specific requirements of the crosslinkable water-soluble prepolymers not described in any of these publications.
It is evident that the coherence of the aqueous solution during injection and prior to crosslinking is very important. This coherence prevents, or limits, the water in the eye from interfering with the solution before crosslinking. Without it, the carefully regulated hydrogel composition, required for generating an IOL of precise refractive index, may be diluted or altered and it is also needed to prevent leakage of polymer from the capsular bag before the polymer is crosslinked.
In addition, all hydrogels have an equilibrium water content, which is controlled both by the structure of the hydrogel and its crosslink density. Water-soluble polymers, when crosslinked, have a tendency to swell in water. For this invention it is important that after injecting the aqueous hydrogel solution into the eye, and crosslinking it, the amount of water that it takes up afterwards, the additional swelling, is limited, that is to say that the solution concentration of water in the injected hydrogel solution is equal to, or very close to, the equilibrium water concentration of the crosslinked hydrogel formed in the eye. Any additional swelling will decrease the refractive index of the lens and in more severe cases will cause collapsing of the capsular bag or even damage the eye.
A few publications and patents describe the design of injectable and crosslinkable water-soluble (pre)polymers and some polymerizations, which form hydrogels in-situ in the eye.
Ravi et al. reported in Polymer Preprints, 1999, 40, 630 on an injectable hydrogel material made by thermally curing poly(ethylenglycol) monoacrylates and diacrylates (PEGMA and PEGDA, respectively). They, were, however, not studied for possible lens refilling material but as potential probes to study the accommodation mechanism. The polymer content and, therefore, the refractive indices of the materials were very low (<1.36) and the materials showed severe swelling after curing.
In the International Patent Application WO 93/02639 an injectable collagen-based intraocular hydrogel lens is described. The concentration collagen was very low which resulted in a low refractive index of the intraocular lens (1.363). It was claimed that high refractive lenses could also be made. To achieve re-active indices closer to that of the natural lens much higher collagen concentrations are needed, than those reported in the patent, and this will increase the problem of swelling, post-injection.
In the International Patent Application WO 01/08604 it was claimed that with aqueous solutions of modified linear polymers, accommodative lenses could be prepared in-situ. The water-soluble polymers were modified to low degrees, to obtain lightly crosslinked hydrogels in order to keep the elasticity modulus of the hydrogel lenses low. The moduli of the hydrogels were measured directly after crosslinking the aqueous polymer solution. The hydrogel were, however, after crosslinking not subjected to an aqueous environment. If these materials would be made in the eye in the presence of an excess natural aqueous fluid, densities they may be expected to swell significantly due to their low crosslink density. Such swelling is to the detriment of the refractive indices of the lenses they form.
In the International Patent Application WO 00/47185, a method of producing an injectable hydrogel intraocular lens is described. The hydrogel lens materials are based on macromolecular particles. However, !the problems of obatining a suffcient coherence and avoiding additional swelling are not addressed in this disclosure.
It can be concluded that the specific requirements regarding coherence and prevention of additional swelling for injectable hydrogel lenses still needs attention if a clinically acceptable surgical process is to be attained.
DESCRIPTION OF THE INVENTION.
An object of the present invention is to provide an aqueous composition of a water soluble linear polymer that can fill the capsular bag of the eye and upon a crosslinking reaction by means of irradiation with light in the visible range can form a hydrogel intraocular lens implant of a predetermined refractive index.
It also an object of the present invention to provide an aqueous composition of a linear water soluble which has suitable coherence to avoid leaking from the cap

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