Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1992-04-13
1995-05-23
Zitomer, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
351160R, 351160H, 523106, 5253274, 5253276, 5253282, 5253288, 5253295, 5253297, 5253299, 5253305, 525374, 525430, C08J 712, C08F 832
Patent
active
054182956
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the treatment of sight correction devices to reduce protein deposition and improve compatibility with the eye.
Synthetic polymers are widely employed in sight correction devices, including soft, rigid gas permeable and hard contact lenses and intra-ocular lenses. However, it is now well recognised that the performance of commonly employed polymer compositions can be hindered by the absorption of tear proteins (such as lysozyme) at polymer interfaces. A variety of problems can then result such as a reduction in gas permeability of the lens, discomfort to the patient and loss of visual acuity. Complete rejection of the lens is not uncommon.
The present invention relates to contact lens coating treatments which are convenient and use economical and readily available materials. The coatings produced have good oxygen permeability and resistance to protein binding.
The invention therefore provides a process for treating polymeric contact lenses comprising the steps of: R are the same or different and
The group X which must react with the polymer surface may be, for example, selected from: an epoxy group or function convertible thereto; a group ZC(O)O-- in which Z is a heterocyclic ring, for example benzotriazole or an imidazole ring or a group Z'OC(O)-- in which Z' is a succinimido or pentafluorophenyl group.
The epoxy group and the group ZC(O)O-- are most preferred as groups X.
The counterion A.sup..crclbar. is present such that the compounds are neutral salts. When the compounds are used to coat lenses, the counterion may be exchanged with ions in the tears or in a washing solution applied to the lens, thus the specific nature of the counterion is of little relevance in the present invention. However, physiologically acceptable counterions are preferred. Suitable counterions therefore include halide ions, especially chloride, bromide or fluoride ions, and acetate, citrate, lactate and the like.
The group Y may be any straight or branched C.sub.1-6 alkylene although straight chain alkylenes are preferred and methylene is most preferred.
The groups R may be the same or different and each may be straight or branched C.sub.1-4 alkyl. Preferred groups R are methyl, ethyl, n-propyl, and n-butyl. The most preferred group R is methyl.
Preferably all groups R are the same and most preferably they are all methyl.
The preferred compounds of formula (I) are glycidyltrimethylammonium halides and N-(trimethylammonium ethyloxycarbonyl) imidazole chloride (choline imidazolide, also referred to as "CDI-choline").
The most preferred compound of formula (I) is glycidyltrimethylammonium chloride ("choline epoxide").
In the process of the invention, step (a) may be omitted where the surface of the contact lens has sufficient free hydroxyl, carboxyl or primary or secondary amino groups for reaction with the compounds of formula (I). Typical of such contact lenses having adequate surface free reactive groups are those made from polyHEMA (poly 2-hydroxyethyl methacrylate), including both low and high water-content polyHEMA lenses, and lenses made from mixtures of polyHEMA with other methacrylic acid polymers.
With soft contact lenses (high or low water content) the refractive index is mainly dependent on the water content of the lens material. Many surface treatments which rely on reaction with surface hydroxyl or carboxyl groups result in the derivatisation of such groups which affects the water content and may lead to a change in refractive index. This is clearly disadvantageous in the manufacture of lenses. In contrast, by using the compounds of formula (I) although the surface hydroxyl groups are derivatised, new hydrophilic groups are introduced onto the surface of the lens by means of the reaction. The effect of the present surface treatment on refractive index is therefore minimal.
For contact lenses made of other materials which do not have surface hydroxyl, carboxyl or amino groups, such as polymethyl methacrylate, it is necessary to activate the surface before treatment with the compounds of
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Bowers Roderick W. J.
Driver Michael J.
Jones Stephen A.
Straford Peter W.
Biocompatibles Limited
Zitomer Fred
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