Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2001-11-09
2004-05-11
Schwartz, Jordan M. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S177000
Reexamination Certificate
active
06733123
ABSTRACT:
The invention relates to a hydrogel contact lens of high oxygen permeability, to a polymer material suitable for this purpose and to the use of the latter for producing such lenses.
BACKGROUND OF THE INVENTION
On its inner side, the natural cornea of the eye has a layer of endothelial cells, which are supplied through the cornea with oxygen from the surrounding air. In order to make this possible, the cornea must therefore have a high oxygen permeability. However, permanent exposure of the cornea to the surrounding air would cause the cornea to dry out. In order to avoid this, the cornea, by blinking of the eye, is permanently wetted with a liquid, which is referred to as tears, and contains proteins, lipoproteins, lipids and mucins in solution. Because this liquid is constantly replenished and evaporates on the surface of the eyes, the materials dissolved in the tear liquid would have to be deposited on the cornea, making it cloudy. So that this does not happen, nature has developed a protective mechanism for which, however, there is not yet a complete explanation.
There is therefore a need for a contact lens which has a high oxygen permeability and a good compatibility and which imitates the properties of the cornea.
The water content of the cornea usually is about 65% to 75% by weight. The cornea itself has an exceptionally high water-retention capability. By these means, an excessive decrease in the moisture content of the cornea surface is avoided, even in dry air, such as cold, polar air, and in air-conditioned spaces, such as aircraft, in which water evaporation is particularly strong. This high water-retention capability also prevents the concentration of the tear liquid increasing to such an extent that the materials dissolved in the liquid crystallize out.
In this connection, it is known that sulfo compounds, especially keratan sulfates and chondroitin sulfates, play a role in the water-retention capability of the natural cornea.
It is furthermore known that, in nature, the deposition of the above-mentioned substances on the surface of the cornea is avoided by a betaine structure within the collagen. Moreover, the collagen of the cornea contains glycine, proline, glutamine, alanine, arginine, asparagines, lysine, leucine, serine, isoleucine, etc. as amino acids.
The U.S. Pat. No. 5,311,223 discloses a hydrogel contact lens, the polymer composition of which consists of a reaction product of hydrophilic methacrylamide as well as an acrylic monomer, which in a preferred embodiment contains a zwitterionic monomer, such as a sulfobetaine, for example, N-(3-sulfopropyl)-N-methacryloxyethyl-N,N-dimethylammonium betaine (SPE), in order to improve the water-retention capability. Moreover, U.S. Pat. No. 4,663,409 discloses that the water-retention capability is improved by polymerizing amino acid monomers into the matrix of a hydrogel contact lens. In many cases, however, the water-retention capability is still not yet satisfactory.
The refractive index is a further, important property of hydrogel contact lenses. The natural cornea has a refractive index of 1.37 and the whole lens of the eye has an overall refractive index of 1.42. The refractive index of the contact lens should therefore approximate that of the cornea, without, however, reducing its water-retention capability.
It is therefore an object of the invention to provide a hydrogel contact lens which exhibits exceptionally high oxygen permeability and a water-retention capability and refractive index which approximate that of the natural cornea.
BRIEF DESCRIPTION OF THE INVENTION
Pursuant to the invention, this objective is accomplished by a hydrogel contact lens, the base or basic material of which contains monomers, which are modified with amino acids, and zwitterionic monomers, which are modified with betaine. Moreover, the modified monomers preferably are polymerized randomly distributed in the basic material.
Surprisingly, it was found pursuant to the invention that not only does this copolymer have a particularly pronounced water retention capability, but also that a refractive index can be set with it which comes very close to that of the natural cornea of 1.37.
The water content also corresponds to that of the natural cornea. In the swollen state, the contact lens material contains 55% to 60% water. The water content can be adjusted relatively accurately by an appropriate use of the betaines or amino acids, so that lenses with a higher or somewhat lower water content and, with that, also different swelling capabilities, can be obtained, as desired.
Pursuant to the invention, the amino acids are polymerized directly into the polymer. For this purpose, they are preferably tied into a monomer, which can be linked to the polymer chain. Pursuant to the invention, preferred monomers are those which can be co-polymerized directly with the basic lens material, that is, incorporated directly into the polymer chain. Pursuant to the invention, &agr;, &bgr; unsaturated carbonyl compounds (carbonyl modified), are particularly preferred. In this way, the modified amino acids, used for the copolymerization, are obtained. The betaimes, which are used pursuant to the invention are also co-polymerized in this manner in the polymer matrix.
Preferably, the amino acids are those which occur in the natural collagen of the cornea, such as those named above, or a mixture thereof, glycine being preferred. Basically, all natural or synthetic amino acids, such as &bgr;-alanine, &ggr;-aminobutyric acid, &ohgr;-aminocapronic acid, &ohgr;-aminododecanoic acid, &bgr;-cyanalanine, &egr;-methylhistidine, canavanine, djencolic acid, 1-azaserine, &ggr;-methyleneglutamic acid, N-methyltyrosine, glycine, alanine, serine, cystine, cysteine, lanthoinine, phenylalanine, tyrosine, diiodotyrosine, tryptophane, histidine, aminobutyric acid, methionine, valine, norvaline, leucine, isoleucine, norleucine, arginine, ornithine, lysine, aspartic acid, glutamic acid, threonine, hydroxyglutamic acid, proline, hydroxyproline, asparagine, glutamine, desmosine, isodesmosine and 5-hydroxylysine can be used.
Acrylic acid, crotonic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and their functional derivatives, such as acid chlorides, anhydrides, amides and esters are &agr;,&bgr;-unsaturated carbonyl modifiers for the modified amino acids.
Preferably, the amino acid, polymerized into the basic material of the contact lens, is present as methacryloyl amino acid. Preferably, the amino acid monomer and the betaine monomer are co polymerized with a main chain and/or a side chain of the matrix material.
The percentage of amino acid in the polymer, preferred with respect to the water-retention capability and the refractive index, is 0.5% to 25% by weight, preferably 0.5% to 10% by weight and particularly about 3% by weight.
The betaine, polymerized in the matrix, preferably is present as sulfobetaine, especially as N-(3-sulfopropyl)-N-methacrylxoyethyl-N,N-dimethylammonium betaine (SPE) and/or as carboxybetaine, which forms a block-free copolymer in the basic material.
The percentage of betaine in the polymer, preferred with respect to the water retention capability and the refractive index, is 0.5% to 22% by weight, preferably 0.5% to 10% by weight and especially about 3% by weight.
All transparent polymers are suitable as basic material for the inventive contact lens. Appropriate polymers are, for example, acrylates and/or polyvinyl polymers, especially polyvinylpyrrolidone.
Hydroxyethyl methacrylate (HEMA) and/or hydroxypropyl methacrylate (HPMA), as well as vinylpyrrolidone (VP) or a mixture thereof are particularly preferred basic materials for the contact lens. Acrylamide derivatives, preferably dimethyl acrylamide derivatives, can also be used as the basic material.
Preferably, the percentage of base material in the polymer is 53% to 99% by weight, especially 80% to 99% by weight and particularly about 94% by weight.
The refractive index of the contact lens material does not deviate by more than 10% and preferably not by more 4% from 1.37, that
Fromme Roland
Haase Lothar
Herter K
Kollosche Birgit
Polzhofer Kurt
Schwartz Jordan M.
Schweitzer Cornman Gross & Bondell LLP
Stultz Jessica
Wohlk Contact-Linsen GmbH
LandOfFree
Hydrogel contact lenses of high biocompatibility does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydrogel contact lenses of high biocompatibility, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydrogel contact lenses of high biocompatibility will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3234909