GB2221688A

GB2221688A - Contact lenses

Info

Publication number: GB2221688A
Application number: GB8917447A
Authority: GB
Inventors: Terrence Geoffrey Croucher
Original assignee: Polymer Laboratories Ltd
Current assignee: Polymer Laboratories Ltd
Priority date: 1988-07-30
Filing date: 1989-07-31
Publication date: 1990-02-14
Also published as: GB8917447D0; GB8818217D0

Abstract

A contact lens is made from a material comprising poly-1-trimethylsilyl-1-propyne (poly-TMSP) or a blend of poly-TMSP in a polymeric matrix. Alternatively it is made from a material comprising a co-polymer of 1- trimethylsilyl-1-propyne (TMSP) and at least one other monomer such as methyl methacrylate or cyclohexyl methacrylate. The presence of poly-TMSP or TMSP leads to or enhances the oxygen-permeability of the lens.

Description

CONTACT LENSES This invention relates to contact lenses.

It is desirable for contact lenses to be made from a material that is permeable to oxygen, and an aim of the present invention is to provide a material having that property and that is suitable for the manufacture of contact lenses, and to provide contact lenses made from that material. Another aim is to provide bodies of that material, of dimensions making them suitable for the manufacture of contact lenses, and to provide contact lenses made from those bodies.

From a first aspect the present invention consists in a solid transparent material from which contact lenses can be made and comprising poly-1-trimethylsilyl-1-propyne or a blend of poly-l-trimethylsilyl-1-propyne in a polymeric matrix, or comprising a co-polymer incorporating l-trimethylsilyl-l-propyne as a constituent monomer.

From a second aspect the present invention consists in a body of a material in accordance with the first aspect of the present invention, the body being of such dimensions that it constitutes a blank or can be formed into at least one blank from which a contact lens can be machined.

From a third aspect the present invention consists in a contact lens made from a material in accordance with the first aspect of the present invention or from a body in accordance with the second aspect of the present invention.

The body referred to above preferably comprises a disk that constitutes a blank, or a rod of such a diameter that that disks constituting blanks can be severed from it, or a sheet of material of a thickness such that disks constituting blanks can be cut from it. In each instance the blank is of standard dimensions enabling it to be readily machined to form a contact lens.

The invention stems from the observation that poly-1-trimethylsilyl-l-propyne (herein referred to for convenience as poly-TMSP) is highly permeable to oxygen and that co-polymers made from monomers including 1-trimethylsilyl-l-propyne (herein referred to for convenience as TMSP) are also, in general, more highly oxygen permeable than polymers or co-polymers that differ from them only in the omission of TMSP.

Poly-TMSP appears to be a polymer consisting principally of unbranched chains, those chains being of unusually bent, angular shape. It is thought that it is this configuration of the polymer chains that leads to the polymer being so highly permeable to oxygen.

At present poly-TMSP is made only in the form of a powder. Nevertheless it may become possible to fabricate poly-TMSP into a solid body suitable for the manufacture of contact lenses. Moreover it is likely that it is possible to mould the powdered polymer to form a solid body by using a thermal technique to melt it and cause it to agglomerate into a solid body. A body or a contact lens made from poly-TMSP will normally contain one or more minor ingredients such as wetting agents and cross-linking agents.

Poly-TMSP can be blended with other polymers or co-polymers to form suitable solids. In each such instance the poly-TMSP is embedded in a polymeric matrix. One suitable polymer for use in the formation of such a matrix is poly-methyl-methacrylate, a particular advantage of that polymer being that it is already widely used as a material from which contact lenses are made. Another suitable polymer is polystyrene. Even a small proportion of poly-TMSP in the matrix polymer may well lead to a significant increase in the permeability to oxygen of the resultant material; the proportion of poly-TMSP in the material may be about 10% by weight, though the proportion may be less than that if desired and may be no more than about 1% by weight or even less.

Other polymers or co-polymers may be used as polymeric matrices in which poly-TMSP is embedded.

Monomers that may be used in forming suitable polymeric matrices include C1 to C20 alkyl and cycloalkyl esters of acrylic or methacrylic acid, including the following: methyl acrylate and methyl methacrylate, ethyl acrylate and ethyl methacrylate, propyl acrylate and propyl methacrylate, isopropyl acrylate and isopropyl methacrylate, butyl acrylate and butyl methacrylate, amyl acrylate and amyl methacrylate, hexyl acrylate and hexyl methacrylate, heptyl acrylate and heptyl methacrylate, octyl acrylate and octyl methacrylate, 2-ethylhexyl and 2-ethylhexyl methacrylate, nonyl acrylate and nonyl methacrylate, decyl acrylate and decyl methacrylate, undecyl acrylate and undecyl methacrylate, lauryl acrylate and lauryl methacrylate, cetyl acrylate and cetyl methacrylate, octadecyl acrylate and octadecyl methacrylate, and cyclohexyl acrylate and cyclohexyl methacrylate.Other vinyl monomers which can readily co-polymize with methy-lmethacrylate may be used in place of part or all of the preferred acrylates or methacrylates listed above, suitable replacement vinyl monomers including: styrene, a-methylstyrene, alkylated styrenes, diethyl itaconate, perfluorylethyl vinyl ether, isoprene, isobutylene, 4-methyl-1-pentene and chlorotrifluoro ethylene. Preferably any such monomer has a molecular weight of less than 300.

In a preferred method of manufacture, pre-formed poly-TMSP is dissolved in a liquid comprising an unpolymerised or only partially polymerised substance which is then fully polymerised to form a polymer matrix of the kind described above. Thus, poly-TMSP may be dissolved in a monomer or a mixture of monomers from which poly-methyl-methacrylate or other polymers or co-polymers can be polymerised. The liquid solution of poly-TMSP is preferably polymerised in a mould so shaped that the resultant solid material is in the shape of a disk, or a rod, or a sheet of such dimensions as to make it suitable for use as a blank or for the manufacture of contact lenses, as outlined above, by the machining techniques commonly employed.

An alternative form of material comprises a co-polymer made from monomers including TMSP. In addition to TMSP there may be a single type of monomer or there may be two or more types of monomer. One particular type of monomer that may be employed, either alone or in combination with one or more other types of monomer, is methyl-methacrylate. Another monomer that may be employed is cyclohexyl-methacrylate. Other monomers that may be employed are the same as those listed above as being suitable for use in forming polymeric matrices. The TMSP content of the material may be about 30% by weight.

In one method of making poly-TMSP, TMSP is dissolved in toluene at 800C, and to this is added a solution of tantalum pentachloride, also at 800C. This initiates polymerisation, which is completed in less than 24 hours. The resultant polymer is dissolved in toluene and is poured into methanol, whereupon the polymer is precipitated as a powder. This is then purified. In order to incorporate this in a poly-methyl-methacrylate matrix, the purified powder is dissolved in methylmethacrylate which is itself caused to polymerise in the usual way. Polymerisation is caused to occur in moulds so shaped that the resultant material is shaped as disks, or as rods of circular cross-section or as sheets, of appropriate dimensions, which are used for the manufacture of contact lenses in a manner similar to any of those outlined above. The material contains about 1% of poly-TMSP by weight.

Claims

1. A solid transparent material from which contact lenses can be made and comprising poly-TMSP (that is poly-l-trimethylsilyl-l-propyne) or a blend of poly-TMSP in a polymeric matrix, or comprising a co-polymer incorporating TMSP (that is l-trimethylsilyl-1-propyne) as a constituent monomer.

2. A material according to claim 1 which comprises a blend of poly-TMSP in a polymeric matrix, that matrix being formed from one or more monomers selected from C1 to C20 alkyl and cycloalkyl esters of acrylic acid and of methyacrylic acid.

3. A material according to claim 2 in which said monomer or one of said monomers comprises methyl-methacrylate.

4. A material according to claim 2 modified in that for a part or all of the monomer or at least one of the monomers there is substituted another vinyl monomer which can readily co-polymerize with methyl methylacrylate.

5. A material according to claim 4 in which said other vinyl monomer is styrene.

6. A material according to any one of claims 2 to 5 in which the proportion of poly-TMSP in the material is no more than about 10% by weight.

7. A material according to claim 6 in which the proportion of poly-TMSP in the material is no more than about 1% by weight.

8. A method of making a material according to claim 1 in which poly-TMSP is dissolved in a liquid comprising an unpolymerised or only partially polymerised substance which is then fully polymerised to form a polymeric matrix in which the poly-TMSP is embedded.

9. A material according to claim 1 which comprises a co-polymer made from TMSP and one or more other monomers selected from C1 to C2 alkyl and cycloalkyl esters of acrylic acid and < of methacrylic acid and other vinyl monomers which can readily co-polymerize with methyl methacrylate.

10. A material according to claim 9 which comprises a co-polymer made from TMSP and methyl methacrylate with or without one or more other monomers.

11. A material according to claim 9 which comprises a co-polymer made from TMSP and cyclohexyl methacrylate with or without one or more other monomers.

12. A material according to any of of claims 9 to 11 in which the TMSP content of the material is about 30% by weight.

13. A blank for a contact lens comprising a material in accordance with any one of claims 1 to 7 or 9 to 12.

14. A contact lens made from a blank in accordance with claim 13.