METHOD FOR THE PRODUCTION OF OPTHALMIC DEVICES

Abstract: The present invention provides a method of spin casting an opthalmic device the method comprising: i) polymerising one or more monomers in a spin casting mould to form the opthalmic device; and ii) sealing the opthalmic device in the spin casting mould to provide a package.

Description: METHOD FOR THE PRODUCTION OF OPTHALMIC DEVICES The present invention relates to a method of spin casting an ophthalmic device. In particular the present invention relates to a method in which one or more monomers are polymerised in a spin casting mould to form the ophthalmic device, and the ophthalmic device is subsequently sealed in the spin casting mould to provide a package. The unit costs for the production of ophthalmic devices, in particular contact lenses, have typically been low with respect to the period over which the device may be used. However, as with all products there has been a desire to reduce the unit cost. In the field of ophthalmic devices this desire has been increased by the provision of disposable contact lenses, such as monthly and daily disposable lenses. GB-A-2237241 teaches that during the preparation and processing of an ophthalmic device such as a contact lens, a cost and quality advantage may be achieved by carrying out inspection, power measurement, extraction, and hydration in the cast mould in which a lens is formed. The disclosed method comprises polymerising a monomer in a mould cavity between a male mould surface in a first mould part and a female mould surface in a second mould part, opening the mould to expose the cast lens, and sealing the lens in a package. GB-A-2237241 teaches that the disclosed advantages may be achieved by opening the cast mould to expose the cast lens while supported on the male mould surface, and sealing the lens in a package by sealing a cover member on to said mould part. The male portion is that which presents the lens to the user convex surface uppermost. According to GB-A-2237241 such a presentation is an advantageous for the user and is necessary for many post-polymerisation treatments. The cost and quality implications of transferring lenses after polymerisation has also been addressed in the art by the provision of release agents, see for example WO 95/1 1789 which discloses a release solution comprising isopropanol. In a first aspect the present invention provides a method of spin casting an ophthalmic device the method comprising, (i) polymerising one or more monomers by spin casting in a spin casting mould to form the ophthalmic device, and (ii) sealing the ophthalmic device in the spin casting mould to provide a package. The present invention is advantageous as it provides a simple method for manufacture and packaging of ophthalmic devices. The present invention provides for a one piece mould and container which carries the device throughout the manufacturing process. The present invention does not require the complex apparatus of cast moulding methods. Yet further because a one piece mould is utilised the present invention does not require the complex control which is required in cast moulding to ensure that the ophthalmic device is held on the required portion of the two piece mould. Spin casting is a process known in the art. for example in US-A-4516924, US-A- 4517138. US-A-4517140, US-A-4551086, US-A-4534723, US-A-4584148, US-A- 5076683, US-A-5260001, and US-A-4719248. The process provides a concave mould comprising a single portion into which monomer in dosed. The mould is spun at high speed and the monomer is cured. Polymerisation is typically initiated by UV irradiation. It will be appreciated therefore, that the spin casting process/package of the present invention is utilises a single mould portion. The lens is presented in the mould concave side upper most. Preferably the polymerisation of the monomer of the present invention is initiated by UV irradiation. Once the ophthalmic device has been formed the treatment(s) necessary to prepare a device suitable for wear is/are performed on the device whilst present in the mould. For example, the device may be hydrated and/or tinted. Thus in a preferred aspect the method of the present invention comprises the further step of hydrating the polymerised monomer prior to the sealing of the spin casting mould to provide a package. Preferably the hydration is performed by contacting the polymerised monomer with a hydration solution containing a surfactant. The presence of a surfactant in the hydration solution will assist in the prevention and/or inhibition of differential hydration of the polymer. After polymerisation, the polymer will be adhered to the spin casting mould. On hydration. the polymer will separate from the mould. Differential hydration may lead to areas of the device which have different thicknesses to each other separating from the mould at different rates. This may lead to stresses in the device which damage the optical surface of the device. Such damage may lead to a hazy appearance on the surface of the device. The one or more monomers of the present invention are selected to provide a device having the desired final properties. Suitable monomers include one of: (alkyl and cycloalkyl) acrylates; (alkyl and cycloalkyl) methacrylates; free-radical polymerisable olefinic acids. including alkoxy-, alkylphenoxy-, alkylphenoxy-(polyethyleneoxide)-, vinyl ester-, amine substituted (including quaternary ammonium salts thereof), nitrile-, halo-, hydroxy-, and acid substituted (for example phospho- or sulpho-) derivatives thereof; and other suitable ethylenically unsaturated polymerisable moieties; including combinations thereof. Preferably the alkyl and cycloalkyl groups contain up to 20 carbon atoms, e.g. (Cι-C 2 o alkyl and C 1 -C 20 cycloalkyl) acrylates. and (C 1 -C 20 alkyl and C 1 -C 20 cycloalkyl) methacrylates. In more detail, typical monomers include any one of methyl acrylate. ethyl acrylate. n- propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, isobornyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, iso-octyl acrylate, nonyl acrylate, lauryl acrylate. stearyl acrylate, eicosyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, cycloheptyl acrylate, methyl methacrylate, ethyl methacrylate. hydroxymethylacrylate. hydroxymethylmethacrylate, propyl methacrylate, n-butyl methacrylate. t-butyl methacrylate. isobutyl methacrylate. pentyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, heptyl methacrylate, cycloheptyl methacrylate, octyl methacrylate, iso-octyl methacrylate, nonyl methacrylate. decyl methacrylate, lauryl methacrylate, eicosyl methacrylate, dodecyl acrylate, pentadecyl acrylate, cetyl acrylate, stearyl acrylate, eicosyl acrylate, isodecyl acrylate, vinyl stearate, nonylphenoxy-(ethyleneoxide)ι. 2 o acrylate, octadecene, hexadecene, tetradecene, dodecene, dodecyl methacrylate, pentadecyl methacrylate, cetyl methacrylate, stearyl methacrylate. eicosyl methacrylate, isodecyl methacrylate. nonylphenoxy- (ethyleneoxide)ι- 20 methacrylate, acrylic acid, methacrylic acid, fumaric acid, crotonic acid, itaconic acid, fumaric anhydride, crotonic anhydride, itaconic anhydride, maleic acid, maleic anhydride, styrene, alpha-methyl styrene, vinyl toluene, acrylonitrile, methacrylonitrile, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylamide. methacrylamide. methacrylamide 2-cyanoethyl acrylate, 2-cyanoethyl methacrylate. dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylate t-butylaminoethyl methacrylate. glycidyl acrylate, glycidyl methacrylate. glyceryl acrylate. glyceryl methacrylate. benzyl acrylate. benzyl methacrylate. phenyl acrylate, phenyl methacrylate. vinyl pyridine, vinyl pyrrolidine, siloxanes, silanes and mixtures thereof. Other polymerisable monomers are disclosed in US-A-2879178. US-A-3037006. US-A-3502627, US-A-3037969 and US-A-3497485. Preferred monomers include any one of glyceryl methacrylate (GMA), (2,2 dimethyl- 1.3-dioxolan-4-yl) methyl methacrylate (GMAK), hydroxy ethyl methacrylate (HEMA), methacrylic acid, acrylic acid, GYMA. N-vinyl pyrrolidone, alkyl methacrylates (such as C i- 2 0 alkyl methacrylates. more preferably C M S alkyl methacrylates, more preferably C M O alkyl methacrylates. more preferably Ci-s alkyl methacrylates, such as methyl methacrylate), alkyl acrylates (such as C ι- 2 o alkyl acrylates, more preferably C M alkyl acrylates. more preferably C 0 alkyl acrylates, more preferably C |- 5 alkyl acrylates. such as methyl acrylate), aryl methacrylates, aryl acrylates, diacetone acrylamide, acrylamide. methacrylamide. N-alkyl acrylamides (such as Ci- 20 N-alkyl acrylamides. more preferably C ι-t 5 N-alkyl acry lamides. more preferably C M O N-alkyl acrylamides. more preferably C 1 - 5 N-alkyl acrylamides. such as methyl acrylamide), N-alkyl methacrylamides (such as Ci- 20 N-alkyl methacrylamides, more preferably C M . N-alkyl methacrylamides. more preferably C O N-alkyl methacrylamides. more preferably C \ . $ N-alkyl methacrylamides. such as methyl methacrylamide), vinyl acetate, vinyl esters, styrene, other substituted olefms. N- dialkyl acrylamides (such as Ci- 20 N-dialkyl acrylamides. more preferably C M N-dialkyl acrylamides. more preferably C M O N-dialkyl acrylamides, more preferably C|-s N-dialkyl acrylamides. such as N N dimethyl acrylamide), N-dialkyl methacrylamides (such as C 1 . 20 N-dialkyl methacrylamides. more preferably C M 5 N-dialkyl methacrylamides, more preferably C M 0 N-dialkyl methacrylamides, more preferably .s N-dialkyl methacrylamides. such as N N dimethyl methacrylamide), 3-methacryloxypropyl tris (trimethysilyl siloxy) silane (TRIS monomer), fluoro substituted alkyl and aryl acrylates and methacrylates (preferably wherein the alkyl is Cι- 20 alkyl, more preferably C M 5 alkyl, more preferably C MO alkyl. more preferably C 1 . 5 alkyl), and combinations thereof. More preferred monomers include any one of glyceryl methacrylate (GMA), (2,2 dimethyl- l,3-dioxolan-4-yl) methyl methacrylate (GMAK). 2-hydroxy ethyl methacrylate (2- HEMA), methacrylic acid, acrylic acid and glycidyl methacrylate. or combinations thereof. The lists of monomers also include substituted derivatives of those monomers, such as halogenated monomers, especially fluorinated monomer derivatives, and acetal and ketal derivatives. In a preferred aspect the one or more monomers are selected from glyceryl methacrylate (GMA), 2-hydroxy ethyl methacrylate (2-HEMA). and mixtures thereof. Preferably the one or more monomers are selected from a mixture of 2-HEMA and GMA. Preferably the one or more monomers consist essentially of 2-HEMA and or GMA. Preferably the one or more monomers consist essentially of a mixture of 2-HEMA and GMA. In this aspect the monomers may be the monomers disclosed in US-A-4038264. In a further preferred aspect the mould are configured such that they are stackable. In this aspect the present invention is further advantageous. Use of a single mould portion during formation of the device allows one to design the mould to be stackable with similar moulds. When a two part mould system is used, as is required by cast moulding, the mould configuration is determined by its relationship would the other mould portion. Thus the present invention may further provided a plurality of packages which are stacked together. Preferably, the stackable packages are as described in WO 99/11529. The present invention provides a packaged ophthalmic device prepared in accordance with a method described herein. Yet further the present invention provides an article comprising a spin casting mould containing an ophthalmic device, wherein the ophthalmic device is ready for wear and is sealed in the spin casting mould As described above, the articles may be stacked. Thus the present invention further provides a plurality of articles as described herein wherein the articles are in a stacked configuration. The material from which the spin casting mould and hence final packaging is formed may be selected depending on the properties required during production, storage and/or use. In the process of the present invention the material is preferably selected such that the spin casting mould is transparent or translucent. A transparent or translucent mould allows for inspection of lens whilst located in mould and thereby allows automatic inspection of the lens. Moreover inspection of the lens without the need to remove the same from the mould packaging avoids the risks of contamination and/or damage. Thus in a further preferred aspect the method of the present invention comrpises the further step of inspecting the opthalmic device whilst in the spin casting mould. Suitable materials for the formation of the spin casting mould include polyvinyl chloride, polypropylene, derivatives and mixtures thereof. The spin casting process of the present invention is yet further advantageous as it allows for the preparation of a toric ophthalmic device having the advantages described above. Spin casting is particularly employed for the preparation of toric devices. Thus the prior art processes using for example cast moulding have not been able to provide a satisfactory toric device. Preferably the ophthalmic device of the present invention has a toric configuration. EXAMPLE A contact lens was prepared by spin casting in accordance with the following procedure Spin casting moulds were provided formed from polypropylene. The moulds were translucent. The amount of initiated monomer (a mixture of 2-HEMA and GMA in a ratio of 1 : 1) required in the casts for the power of lens required was identified from tabulated fabrication data. The monomer was dispensed into the casts using a Hamilton volumetric syringe. The filled cats were transferred to a wetting apparatus for no more than 30 minutes A spin casting machine available from Concept Design and Engineering, Gosport (UK) was started up in accordance with standard procedure. The required spin speed was ascertained in the fabrication data for the power of lens required an was set and checked with a tachometer. The cycle time was set for 30 seconds ± 2 seconds. Filled casts were removed from the wetting apparatus and were placed in the loading mechanism. The spinning motor was switched on and the cycle started. The lenses were cured during spinning by UV irradiation. The spun and cured lenses were hydrated with a packaging solution consisting of a phosphate buffered saline solution. The lenses were allowed to stand in the solution until they had hydrated and released from the mould. The solution was removed and a further portion of the solution was added to the mould. The moulds were then forwarded to a packaging line. On the packaging line a foil/polymer laminate film was adhered to the outer rim of each mould. The film was trimmed and the lenses forwarded for inspection. The translucency of the mould allowed for inspection through the '"bottom portion" of the mould. All publications mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described methods and system of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in chemistry or related fields are intended to be within the scope of the following claims.

Claims: CLAIMS 1. A method of spin casting an ophthalmic device the method comprising, (i) polymerising one or more monomers in a spin casting mould to form the ophthalmic device, and (ii) sealing the ophthalmic device in the spin casting mould to provide a package. 2. A method according to claim 1 wherein the method comprises the further step of inspecting the ophthalmic device whilst in the spin casting mould. 3. A method according to claim 1 or 2 wherein the polymerised monomer is hydrated prior to the sealing of the spin casting mould to provide a package. 4. A method according to claim 3 wherein the hydration is performed by contacting the polymerised monomer with a hydration solution containing a surfactant. 5. A method according to any one of claims 1 to 4 wherein the polymerisation of the monomer is initiated by UV irradiation. 6. A method according to any one of claims 1 to 5 wherein the one or more monomers are selected from HEMA, GMA and mixtures thereof. 7. A method according to any one of claims 1 to 6 wherein a plurality of packages are provided and subsequently stacked together. 8. A packaged ophthalmic device prepared in accordance with the method of any one of claims 1 to 7. 9. An article comprising a spin casting mould containing an ophthalmic device, wherein the ophthalmic device is ready for wear and is sealed in the spin casting mould 10. A plurality of articles as defined in claim 9 wherein the articles are in stacked configuration. 1 1. The invention of any one of claims 1 to 10 wherein the spin casting mould is transparent or translucent. 12. The invention of any one of claims 1 to 1 1 wherein the spin casting mould is formed from a material selected from polyvinyl chloride, polypropylene, derivatives and mixtures thereof. 13. The invention of any one of claims 1 to 12 wherein the ophthalmic device has a toric configuration. 14. A method of spin casting an ophthalmic device as substantially described herein with reference to the Example. 15. A packaged ophthalmic device as substantially described herein with reference to the Example. 16. An article comprising a spin casting mould containing an ophthalmic device as substantially described herein with reference to the Example.

Inventors: SUTTON HOWARD STEPHEN, TIPTON WADE MARCEL, SUTTON, HOWARD, STEPHEN, TIPTON, WADE, MARCEL
Applicants: HYDRON LTD, SUTTON HOWARD STEPHEN, TIPTON WADE MARCEL, HYDRON LIMITED, SUTTON, HOWARD, STEPHEN, TIPTON, WADE, MARCEL
Application year: 2000
Main classification: B29D11
IPC codes: B29C35, B29C41, B29D11