EP2807198A1 - Silicone hydrogels and methods for manufacture - Google Patents

Abstract

Silicone hydrogels, ophthalmic lenses made therefrom, and methods of making the same are described. Fully hydrated silicone hydrogels have relatively high water content and oxygen permeability, along with relatively low modulus of elasticity. Embodiments of the silicone hydrogels in substantially dehydrated condition are adapted to lathe cutting at or above room temperature. The silicone hydrogels include silicon-containing monomers in an amount 10% by weight or greater than, such as greater 25% by weight, a hydrophilic substituted N-vinyl acetamide monomer in an amount greater than 30% by weight, and a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N- vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1.

Description

Silicone Hydrogels and fVtethods of Manufacture

The present application claims priority to US 13/360,568 filed on 27 January 2012, the contents of which are hereby incorporated by reference in their entirety.

Background

Materials must meet demanding criteria in order to function effectively in a biocompatible role, where sustained intimate contact with the internal or external tissues of a living organism is required. Contact lenses for ophthalmic applications must meet particularly demanding criteria, and materials from which lenses are made must therefore also possess a demanding combination of properties. A lens material must be sufficiently oxygen permeable to allow adequate oxygen to permeate through it so as to sustain the corneal health of the wearer. Lenses must be sufficiently physically robust to retain their integrity while being worn in the wearer's eye, as well as during handling, insertion, and removal. During wear, lens surfaces must be wettable and lubricious, while concomitantly resisting deposition of proteins, lipids, and other biochemical compounds. Lens material must also be highly transparent, and lenses that are soft and highly pliable are generally more comfortable to wear.

Some of the above characteristics are difficult to achieve concomitantly. Rigid ophthalmic lenses have good visual clarity and are generally sufficiently physically robust, but their lack of pliability, among other factors, can make them uncomfortable for some users to wear.

Soft contact lenses have a lower tensile modulus that makes them more comfortable to wear, but decreased modulus often comes at the expense of decreased tear strength.

Moreover, soft ophthalmic lenses typically cover a larger area and conform closely to the contour of the surface of an eye than rigid ophthalmic lenses. Accordingly, soft ophthalmic lenses typically need to have sufficient oxygen permeability to avoid corneal hypoxia.

Ophthalmic lenses made of non-silicone hydrogels typically have moderate to high water content (38-75%) and, provided the lens is sufficiently thin, can be fabricated to exhibit viable oxygen permeability with a satisfactory level of wettability. However, elevated oxygen permeability characteristics are difficult to attain with non-silicone hydrogels, and high water content hydrogels can be physically unstable, having a tendency to reduce in size with increases in temperature. In addition, thin lenses made from materials with high water content are also prone to dehydrate on the eye, which can result in lower on-eye oxygen permeability and which can in some instances lead to serious clinical complications. For lathe cut lenses, which often have increased thickness compared to cast-molded lenses, oxygen transmissibility levels can approach undesirably low values.

Silicone hydroge!s generally have higher oxygen permeability than non-siiicone hydrogels, but high silicone content can result in increased modulus and low surface energy properties that lead to poor wettability and to deposition of biological materials, especially lipids, on lens surfaces. High silicone content material also tends to be difficult or impossible to lathe at or above room temperature, thereby making manufacture of ophthalmic lenses by lathing silicone hydrogel material impractical. Silicone hydrogei material that has a T_g at or near room temperature may nonetheless be difficult or impossible to lathe at room temperature because cutting the silicone hydrogel with a lathe leads to the warming of the material being cut. Lowering silicone content typically results in decreased oxygen permeability where equilibrium water content remains constant.

Ophthalmic lenses made from silicone hydrogels can achieve an adequate, albeit not optimal, balance of surface wettability and resistance to deposition, modulus of elasticity, tear resistance, and oxygen permeability. However, manufacturing silicone hydrogel polymers and lenses therefrom introduces problems that are difficult and/or expensive to overcome. Moreover, it can be difficult to simultaneously achieve high oxygen permeability, low modulus and a viable level of wettability in silicone hydrogels, and conversely it can be difficult to attain high water content silicone hydrogels that possess sufficient silicone content to exhibit desirable oxygen permeability characteristics. An additional complication is that lenses comprising high water content silicone hydrogels including abundant N,N-dimethyl acry!amide and N-vinyi pyrroiidone tend to swell incrementally when stored in water or aqueous buffer for extended periods, limiting the shelf life of such lenses. Finally, silicone hydrogel lenses that have high water content tend to suffer from high water loss rates that result in undesirable dehydration of both lenses and wearers' eyes.

Silicon-containing monomers and hydrophilic monomers, from which silicone hydrogels are typically formulated, tend to resist amalgamation and instead form separate phases in polymerization reaction mixtures comprising relatively high concentrations of the hydrophilic and silicon-containing monomers. Manufacture of silicone hydrogels is thus complicated by the tendency of polymerization reaction mixtures to segregate into predominantly hydrophilic and hydrophobic phases, which can negatively impact both the course of the polymerization and the silicone hydrogel polymer thus formed. Silicon-containing monomers are often chemically modified to form prepolymers or macromonomers with relatively hydrophilic substituents that can be used in higher proportions than monomers containing exclusively silicone functionalities. Such silicon-containing prepolymers and macromonomers can be mixed more readily with hydrophilic monomers, helping to avoid phase segregation in polymerization reaction mixtures comprising relatively high concentrations of these silicon- containing species.

US 4,71 1 ,943 (the Harvey patent) discloses silicone hydrogels comprising modified silicon- containing monomers, the modified silicon-containing monomers comprising a urethane linkage. Harvey discloses silicone hydrogels having exceptional putative physical properties. One example of silicone hydrogels disclosed in Harvey purportedly has a fully hydrated water content of 50.3%, oxygen permeability of 43 Barrers, and an exceptionally low modulus of elasticity of 1 .6 ^χ 10^"6 dynes/cm² (1 .6 ^χ 1 0 ¹³ MPa; see Sample A, Harvey Table XI !). However, this modulus value is not credible. Persons of ordinary skill in the art recognize that 1 .6 x 1 0 ^s dynes/cm² is an unfeasibly low modulus value, approximately 1 2 to 14 orders of magnitude below a sensible number. Accordingly, it is tempting to suggest that the author(s) of the Harvey patent were confused about the sign on the exponent, and the modulus value should be a more reasonable 1 .6 ^χ 10^s dynes/cm². However, 1 .6 ^χ 10⁶ dynes/cm² (0.16 MPa) remains a very low modulus value for a silicone hydrogel, especially one comprising 43.38% N-[tris(trimethylsi!oxy)siiylpropy!]methacrylamide (TSMAA), leading persons of ordinary skill to reasonably surmise that the absolute value of the modulus exponent is incorrect as well as the sign.

Further evidence that modulus values disclosed in the Harvey patent are unfounded is shown in many other tables, and particularly in Table XIX, where modulus values of about 1 .9 1 0^~10 dynes/cm² (1 ,9 ^χ 10^"17 MPa) are disclosed in silicone compositions containing 35% to 40% TSMAA. Such values are inconceivably low.

in summary, the Harvey patent discloses modulus values that defy credibility by persons of ordinary skill in the art. Accordingly, modulus figures disclosed in Harvey are not convincing. Nevertheless, Harvey discloses a silicone hydrogel embodiment with fully hydrated water content of 58.2% and oxygen permeability (Dk) of 35.2 Barrers, and another silicone hydrogel embodiment with oxygen permeability (Dk) of 58 Barrers and water content of

37.6%. These water content and oxygen permeability values are fully plausible in that the Dk values are elevated above what would be predicted exclusively on the basis of the equilibrium water contents (EWC) of these polymers using the Benjamin and Young 'Dk- EWC correlation [iog(Dk) = 0.01754 (%GEWC) + 0.3897] (see Young et ai. Eye & Contact Lens: Science & Clinical Practice: 2003 , 29, 1 26-133), where %GEWC is the gravimetric EWC, for which a conventional 35.2% (EWC) polymer would be predicted to exhibit a Dk of 1 0.2 Barrers and a 37.6% (EWC) polymer a Dk of 1 1 .2 Barrers.

US 5,486,579 (the Lai patent) discloses silicone hydrogel compositions comprising silicon- containing monomers with urethane linkages. The silicone hydrogels disclosed in Lai have varied water content and modulus of elasticity that are adjusted by varying abundance of hydrophilic monomers, including N-vinyl pyrrolidone (NVP) and Ν,Ν-dimethy! acrylamide (DMA). Lai discloses silicone hydrogels with modulus values as low as 0.62 MP a (6.2 ^χ 10⁶ dynes/cm²) at 37% fully hydrated water content (Table 1 ), but does not disclose any fully hydrated water content above about 46% (Table 1 ), and no modulus below 0.62 MPa.

interestingly, the Lai patent claims modulus values as low as 0.05 MPa (5.0 ^χ 10⁵ dynes/cm² in claim 5 and 15), an exceptionally low but not inconceivable value. However, Lai does not disclose how a person of ordinary skill in the art might achieve such low modulus in silicone hydrogels. Moreover, it is not implicit that silicone hydrogel formulations such as those disclosed in Lai could achieve modulus values lower than those of the specific examples disclosed.

Conversely, the Lai patent suggests that silicone hydrogels preferably have oxygen permeability of Dk > 60 Barrers (Lai column 8, lines 58 - 59). A person of ordinary skill in the art would recognize that Dk > 60 Barrers is possibly an inherent quality in a silicone hydrogel composition such as disclosed in Lai, examples of which contain about 30% - 47% TRIS (Lai columns 9 and 10) and an equilibrium water content <46%. Lai does not, however, explicitly enable a person of ordinary skill in the art to make a silicone hydrogel with oxygen permeability > 80 Barrers.

in summary, the Lai patent discloses silicone hydrogels with fully hydrated water content around 25% to 46% that also have modulus values of 0.62 MPa to 0.85 MPa (6.3 ^χ 10⁶ dynes/cm² to 8.5 ^χ 10⁶ dynes/cm*). Lai does not disclose how a person of ordinary skill in the art can make a silicone hydrogel with a modulus below 0.62MPa, and embodiments of hydrogels and processes for making hydrogels exemplified in Lai do not implicitly achieve the low modulus claimed in Lai claims 5 and 15.

US 6,649,722 (the Rosenzweig patent) discloses silicone hydrogel compositions that achieve relatively high oxygen permeability (Dk = 1 17 Barrers) at moderately low water content (32%), and lower oxygen permeability (88 Barrers) at higher water content (48%). Rosenzweig discloses silicone hydrogels with water content as high as 53%, but does not disclose a Dk value for 53% water content silicone hydrogel. The Rosenzweig disclosure shows a loose inverse correlation between water content and oxygen permeability in the Rosenzweig silicone hydrogels. Rosenzweig also discloses numerous silicone hydrogels that comprise styrene or substituted styrene.

US 2006/0004165 (the Phelan application) discloses silicone hydrogel compositions that are prepared from reaction mixtures comprising urethane macromonomers and styrene or substituted styrene monomers. Examples of silicone hydrogel material disclosed in Phelan have oxygen permeability > 65 Barrers and glass transition temperatures (T_g) in a 60 - 68 °C range. Interestingly, Phelan discloses room temperature iathability and associated property T_g of 60° to 68° in silicone hydrogels comprising styrene or substituted styrenes that are remarkably similar to silicone hydrogels comprising styrene or substituted styrene disclosed in Rosenzweig.

US 7,939,579 describes earlier work by the present inventors in preparing hydrogel material having relatively high water content and oxygen permeability, along with relatively low modulus of elasticity. The silicone hydrogel material typically comprises a high weight content of Ν,Ν-dimethyi acrylamide (DMA) and/or N-vinyl pyrro!idone (NVP). For example Ν,Ν-dimethy! acrylamide may be present (without N-vinyl pyrrolidone) at levels above 24 wt %, and as much as 84 wt % (see Table 1 ). For example N-vinyl pyrrolidone and

Ν,Ν-dimethy! acrylamide may be present together at levels above 60 wt %, typically around 64 wt % (see Table 2). it has been found that hydrogel materials comprising N,N-di methyl acrylamide and N-vinyl pyrrolidone are susceptible to change, such as swelling, under simulated aging conditions. Where a hydrogel material is to be used in a lens product, it is preferable that the lens diameter remains substantially constant in a simulated aging test.

Summary of the Invention

in a general aspect there is provided a silicone hydrogel material including a copolymer comprising a silicone-containing monomer, hydrophilic substituted N-vinyl acetamide monomer and a hydrophilic non-acetamide monomer. Also provided is the ophthalmic lens obtainable from the silicone hydrogel material, including a contact lens. Polymerisabie compositions for the preparation of the silicone hydrogel material are also provided.

The silicon-containing monomer may be present in an amount 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25 % by weight or more. The silicon- containing monomer may be present in an amount greater than 25% by weight.

The hydrophilic substituted N-vinyl acetamide monomer may be present in an amount 20% by weight or more, 25% by weight or more, 30% by weight or more. The hydrophilic substituted N-vinyl acetamide monomer may be present in an amount greater than 30% by weight. The hydrophilic non-acetamide monomer may be present in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1 .

The silicone hydrogel material of the invention minimizes the use of Ν,Ν-dimethyl acrylamide (and related monomers) in the hydrogel material. Such monomers tend to provide a material that will swell incrementally when stored in water or aqueous buffer for extended periods, limiting the shelf life of the downstream hydrogel products, such as lenses. The silicone hydrogels provided herein have excellent oxygen permeability levels, low on-eye water loss levels, and suitable modulus of elasticity, hydrated water content, hardness and Tg values to allow a hydrogel material to be machined and used as a lens material, and particularly a contact lens. Importantly, a lens prepared from N-vinyl acetamide monomer-containing material does not increase in dimensions (swell) when tested under simulated aging conditions, as shown herein.

Ν,Ν-dimethyl acrylamide monomer may be present as a hydrophilic substituted N-vinyi acetamide monomer in an amount 20% by weight or less; 15% by weight or less, or 14% by weight or less.

In a first aspect of the invention there is provided a silicone hydrogel material having an oxygen permeability greater than 45 Barrers, a water content greater than 60% by weight, and a modulus less than 1 .0 MPa, and including a copolymer comprising:

a silicon-containing monomer in an amount 10% by weight or more, such as greater than 25% by weight;

a hydrophilic substituted N-vinyl acetamide monomer in an amount greater than 30% by weight; and

a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1 .

in a second aspect of the invention there is provided a method of making an ophthalmic lens comprising lathe cutting a silicone hydrogel material of the first aspect of the invention. The ophthalmic lens may be a contact lens.

Also provided is an ophthalmic lens obtained or obtainable from a silicone hydrogel of the first aspect of the invention.

The present invention also provides a poiymerisabie composition comprising:

a silicon-containing monomer in an amount 10% by weight or more, such as greater than 25% by weight;

a hydrophilic substituted N-vinyl acetamide monomer in an amount greater than 30% by weight: and

a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1 .

in a further aspect there is provided a silicone hydrogel material obtained or obtainable from the poiymerisabie composition of the invention. in a further aspect there is provide a method of preparing a silicone hydrogel material, wherein the method comprises the step of polymerizing the po!ymerisable composition of the invention.

in one aspect of the invention there is provided a method of forming a blank for an ophthalmic lens, the method comprising the steps of:

(a) polymerizing a polymerisable composition of the invention in a rod-shaped mould thereby to form a polymer rod; and

(b) working the polymer rod into a plurality of blanks.

A further aspect of the invention provides a method of forming a blank for an ophthalmic lens, the method comprising the step of polymerizing a polymerisable composition of the invention in a button mould thereby to form a lens blank.

The invention also provides a method for forming an ophthalmic lens, the method comprising the steps of:

(a) providing a blank according to the invention; and

(b) working the blank to form an ophthalmic lens.

in a another aspect, there is provided a method for forming an ophthalmic lens, the method comprising the step polymerizing a polymerisable composition of the invention in a mould thereby to form an ophthalmic lens, wherein the mould is shaped so as to provide an ophthalmic lens having anterior and/or posterior portions.

Deta ed Description

Embodiments of the present invention comprise biocompatible material adapted to be in relatively sustained, intimate, contact with sensitive tissues of living organisms.

Embodiments of silicone hydroge!s have properties including oxygen permeability (Dk) greater than 45 Barrers, such as greater than 55 Barrers, modulus of elasticity less than 1 .0 MPa, such as less than 0.79 MPa, such as less than 0.70 MPa, such as less than 0.60 MPa, sessile contact angle (a measure of wettability) of less than 1 15°, such as less than 1 10 °, and fully hydrated water content greater than 60% by weight. The hydroge!s show increasing oxygen permeability with increasing abundance of a silicon-containing monomer at a constant level of equilibrium water content.

Some silicone hydrogels are sufficiently rigid in a substantially dehydrated state to be lathabie at or above room temperature. Embodiments include hydrogels with a Shore D hardness of 70 or greater at 21 °C, or with T_g at or above room temperature, such as greater than 27°C. Variations of ophthalmic lenses made from silicone hydrogel embodiments have on-eye water loss of less than 3%. On-eye water loss refers to a decrease in water content of an ophthalmic lens that occurs when the ophthalmic lens is worn on a user's eye during an interval of 8 hours or more.

Embodiments of hydrogels contemplated in the present invention comprise silicone hydroge! copolymers. Silicone hydrogels typically contain one or more silicon-containing monomers in addition to one or more hydrophilic monomer components, and may optionally contain other components to further modify or enhance the physicochemical properties of the polymer. These other components include, but are not limited, to fluorine-containing monomers, cross-linking monomers, and structural (strengthening) monomers. Additional variants of hydrogels comprise compounds employed to change or enhance the color of ophthalmic lenses or other hydrogel products, and some embodiments comprise compounds employed for their UV absorbing properties.

Embodiments of silicone hydrogels and contact lenses disclosed and claimed herein do not require surface treatment in order to achieve the disclosed or claimed physical properties such as modulus, oxygen permeability, oxygen transmissibi!ity, water content, lubricity or surface hydrophi!icity.

Embodiments of silicone hydrogels further comprise a first polymer comprising a silicon- containing monomer, the first polymer being in molecular entanglement with a second polymer. The second polymer may or may not comprise a silicon-containing monomer. The first polymer is typically in molecular entanglement with a second polymer through formation of an interpenetrating network (IPN). The iPN may be formed through sequential IPN, simultaneous IPN, or other IPN techniques.

Embodiments of silicone hydrogels further comprise polymerization reaction products of a reaction mixture, the reaction mixture comprising both a silicon-containing monomer and a hydrophilic monomer, together with a cross-linking monomer and a suitable polymerization imitator, and then optionally further including components such as a fluorine-containing monomer. Reaction mixtures may comprise two or more different species of hydrophilic monomer. Silicone hydrogel polymerization reaction mixtures typically comprise monomers that have a po!ymerizable reactive functional group, such as a vinyl, acrylate, or

methacrylate group.

Some embodiments of silicone hydrogel reaction mixtures are substantially free of silicon- containing pre-polymers or silicon-containing macromonomers, and some variations are substantially free of end-capped or other derivatized monomers. Monomers that have not participated in a polymerization or pre-polymerization reaction, and therefore have not been transformed into prepoiymers or macromonomers, are referred to here as true monomers. Embodiments of siiicon-containing monomers include, but are not limited to, bulky siiy! monomers. For the purposes of this application, bulky silyl monomers consist of compounds having the following general formula [I],

[I]

where W¹ is CH₃ or H; W² is CH₃ or H; / is 0 where Y is O (oxygen) and / is 1 where Y is N (nitrogen); m is Q or 1 ; n is an integer from 1 to 6, inclusive; A¹ , and A² are the same or are different and are selected from the group consisting of triaikyl siloxy and lower alkyl functional groups; B is the same as or is different from A¹ or A² and is selected from the group consisting of the following formula [II],

[I I]

where Z¹ , Z², and Z³ are the same or are different and are selected from the group consisting of phenyl, benzyl, triaikyl siloxy, and lower alkyl functional groups; Y is O or N; and X is selected from the group consisting of the following formulas [ill] and [IV], C— O— CH₂

O

CH₃

-C— O— CH₂— CH₂-NH—

O

OH

C O CH^ CH CH

11 ^*~

o

[IV]

where W³ is H or an a!ky! functional group.

Silicon-containing monomers further comprise monomers having one or more aikyi siioxy functional groups. Examples of silicon-containing monomers having one or more a!ky! si!oxy functional group include 3~(tns(trimetbyisiloxy)sily1)propyi methacrylate (TRIS), having the following formula [V]:

[VI

and (3~methyiacryioxy-2-hydroxypropoxy)propylbis(trimethylsiioxy)methylsiiane (SiGMA), having the formula [VI]:

VI]

SiGMA is also used to designate a minor isomer, (2-metbylaeryioxy-3- hydroxypropoxy)propyib!S{trimethyisiloxy)methyisiiane_! having the formula [VI

[VII]

For the purposes of this specification and appended claims, the term SiGMA refers to a composition comprising either or both of the isomers represented in formulas [VI] and [VI!].

Bulky siiyl monomers can have one or more alky! si!oxy functional groups. However, SiGMA is an example of a silicon-containing monomer having one or more alkyl siloxy functional groups, but that is not a bulky silyi monomer.

Other silicon-containing monomers include, but are not limited to:

0-[3-(tris(trimethylsi!oxy)silyi)propyi]-N-[2'-(methacry!oyloxy)ethyi]carbamate;

0- [2-(methacryloyloxy)ethyi]-N-[3'-(tris(trimethyisiioxy)silyl)propyl]carbamate;

N-(3-((trimethyls!ioxy)silyl)propyl)methacrylamide; 1 ,3-bis(3^!-methacrylarnidopropyl)-1 , 1 ,3,3- tetrakis(trimethylsiioxy)disi!oxane; 1 -(3'-methacryloyioxypropy!)-1 ,1 ,3,3,3- pentamethy!disi!oxane; 1 ,3-bis(3^:-methacry!oyioxypropy!)-1 ,1 ,3,3-tetramethyidisiioxane;

1 - (3'-methacry!oyloxypropy1)polydimethylsi!oxane; and

1 -(3'-acryloyloxypropyl)poiydimethylsiloxane. Embodiments of silicon-containing monomers include true monomers and other monomers.

As described herein, a silicone hydrogel of the invention may comprise a silicon-containing monomer in an amount of 25% weight or more, more preferably between 25% and 40% weight, still more preferably about 32.75% weight, and most preferably approximately 32.75% weight.

Hydrophi!ic monomers include, but are not limited to, Ν,Ν-dimethyl acrylamide (DMA), having the following formula [VIII],

fV

2-hydroxyethyl methacrylate (HEMA), having the following formula

[IX]

N-methyi-N-vinylacetamide (MVAc), having the following formula [X],

[X]

2-hydroxyethyl acryiate, 3-hydroxypropyl acryiate, 3-hydroxypropyi methaerylate, N-vinyi-2- pyrroiidone (NVP), glycerol meihacryiate, acrylic acid, acrylamide, methacrylic acid, and other hydrophi!ic monomers. MVAc is sometimes referred to as N-vinyi-N-methylacetamide, and can be abbreviated VMAc.

MVAc is a member of a group of compounds referred to as hydrophilic substituted N-vinyl acetamide monomers, having the general formula [XI],

;xi]

where R¹ and R^ are the same or are different, R¹ is an alkyl functional group, and R² is selected from the group consisting of H and an alkyl functional group. Alkyl functional groups include C C₃ linear and cyclo-a!ky! functional groups. In a subset of hydrophilic substituted N-vinyl-acetamide monomers, which includes MVAc, R² is a methyl group.

As described herein, a silicone hydrogel of the invention may comprise a hydrophilic substituted N-vinyl acetamide monomer in an amount 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25 % by weight or more.

The hydrophilic substituted N-vinyl acetamide monomer may be present at an amount of 55% by weight or less, 50% by weight or less, 45% by weight or less, or 40% by weight or less.

The hydrophilic substituted N-vinyl acetamide monomer may be present at an amount selected from a range, where the lower and upper amounts are selected from the values above. For example, the hydrophilic substituted N-vinyl acetamide monomer may be present at an amount in the range from 10 to 40% by weight.

The silicone hydrogel of the invention may comprise a hydrophilic substituted N-vinyi acetamide monomer in an amount of 30% by weight or more, more preferably between 34% and 55% by weight; still more preferably about 44.8% by weight, and most preferably approximately 44.8% by weight.

In one embodiment, Ν,Ν-dimethyl acrylamide monomer may be present as a hydrophilic substituted N-vinyl acetamide monomer in an amount 20% by weight or less; 15% by weight or less, or 14% by weight or less.

In one embodiment, Ν,Ν-dimethyl acrylamide monomer may be present as a hydrophilic substituted N-vinyl acetamide monomer in an amount 1 % by weight or more, 2% by weight or more, 5% by weight or more, or 10% by weight or more.

Ν,Ν-dimethy! acrylamide monomer may be present as a hydrophilic substituted N-vinyi acetamide monomer in an amount from a range, where the lower and upper amounts are selected from the values above. For example, Ν,Ν-dimethyl acrylamide monomer may be present as a hydrophilic substituted N-vinyi acetamide monomer in an amount in the range 5 to 15% by weight.

Hydrophilic monomers that do not fit within the definition of hydrophilic substituted N-vinyl- acetamide monomers provided above can be referred to as hydrophilic non-acetamide monomers.

As described herein, a silicone hydrogel of the invention may comprise a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight ratio preferably greater than 2.1 :1 and most preferably in a range between 3:1 and 7:1 .

The total hydrophilic monomer content of a silicone hydrogel of the invention is preferably 44% weight or more, more preferably between 49.7% and 69.7%, and most preferably approximately 56%.

in one embodiment, the silicone hydrogel of the invention does not comprise an N-vinyl pyrrolidone monomer.

Hydrophilic substituted N-vinyl acetamide monomers contain a reactive or polymerized vinyiic group positioned β to the carbony! moiety. Conversely, DMA and HEMA are examples of carbony!-containing hydrophilic monomers having a vinyiic group positioned a to the carbonyl. Polymerized or copolymerized MVAc is more hydrophilic than polymerized or copolymerized DMA, probably because β positioning of the polymerized vinyiic group of MVAc results in less steric shielding of its carbonyi functionality by the polyvinyiic chain to which it is associated. Accordingly, the MVAc carbonyi oxygen is more accessible for hydrogen bonding and dipolar attraction to water, resulting in greater hydrophilicity compared to pDMA, where the polymerized viny!ic group at an a position likely causes steric shielding of the DMA carbonyi oxygen by its associated polyvinyiic chain, which is further compounded by the shielding effecting of the two amido-methyl groups on the converse side of this carbonyi functionality. It is understood that a polymerized vinylic group no longer contains its carbon to carbon double bond, and is thus no longer literally vinylic in character.

Vinylic groups positioned a to a carbonyi carbon in DMA and β to a carbonyi carbon in a generic hydrophiiic substituted N-viny! acetamide monomer are shown in the following formulas [XII].

Fluorine-containing monomers include, but are not limited to, 1 ,1 ,1 ,3,3,3-hexafluoroisopropy! methacry!ate (HFPM), having the following formula [XIII],

2,2,2-trifluoroethyl methacrylate, , 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,3,3- pentafluoropenty! acrylate, 1 , ,1 ,3,3,3-hexafluoroisopropy! acrylate, and other f!uorinated monomers.

Cross-linking monomers include, but are not limited to, 1 ,6-hexanediol diacrylate (HDDA), having the following formula [XIV],

[XIV]

1 ,2-Ethy!ene glycol dimethacrylate, diallylrnaieate, triethyleneglycol dimethacrylate

(TGDMA), ally! methacrylate (AMA), and other cross-linking monomers. Cross-linking monomers can also be referred to as cross-linkers or cross-linker monomers.

initiators include thermal initiators such as, but not limited to, 2,2^!-azobisisobutyronitrile (AIBN), shown in the following formula [XV],

[XV]

benzoyl peroxide, and 2_!2^!-azobis(2,4-dimethyi)vale!Onitriie, and UV initiators such as, but not limited to, 2-hydroxy-2-methy!-1 -phenyl-1 -propanone and phenylbis(2,4,6- trimethy!benzoy!)-phosphine oxide.

Embodiments may also comprise strengthening monomers, such as, but not limited to, methyl methacrylate (MMA), ethyl methacrylate, cyclohexyl methacrylate, other

methacrylates, and other strengthening monomers. Addition or incorporation of

strengthening monomers into a polymer or copolymer usually reinforces the polymeric material to increase mechanical properties such as tensile strength and tensile modulus.

Embodiments can also include softening monomers such as, but not limited to, hexyl methacrylate, 2-ethoxyethyl methacrylate (EEMA), 2-(2'-ethoxyethoxy)ethyi acrylate, poly(ethyienegiycol)-methacryiate and other alkoxyaikyi and alkyloxya!ky!oxyalkyl type methacrylates and acryiates. Softening monomers can reduce the modulus of polymers or copolymers into which the softening monomers are incorporated, or of lenses made therefrom.

it has been observed that contact lenses comprising high water content silicone hydrogel formulations containing DMA-NVP-TRiS monomer combinations with EWC values in excess of 70% have a tendency to exhibit compromised shelf-life. Such lenses tend to gradually increase in size upon prolonged storage in buffered and unbuffered saline, although the phenomenon is appreciably less pronounced in the latter medium. Meticulous investigations have correlated the magnitude of this temporal swelling effect to both the EWC of the DMA-NVP-TRIS polymer and the proportion of DMA within its constituent formulation. The phenomenon is greatly diminished at lower water contents and DMA levels. Hence silicone hydrogel formulations containing minimized DMA contents in relation to the primary hydrophilic NVP/MVAc components and preferentially demonstrating lower EWC values would typically be expected to exhibit greater shelf-life.

A limiting factor in reducing DMA content in a TR!S-DMA-MVAc/NVP containing silicone hydrogel polymer is clarity (haze) of the resulting polymer, since DMA can act as a reactive diluent, amalgamating the hydrophobic TRIS and the hydrophilic MVAc/NVP from the initial admixing of these monomeric components through to their final co-polymerized form. If the DMA level is too diminished within a TRIS-DMA-MVAc/NVP containing formulation, haze considerations can become significant and limit utility of the polymer for ophthalmic applications.

SiGMA contains a po!ymerisab!e methacrylate functionality, a 'MD^RM'-type siioxane moiety [R = (2-methyiacryloxy-3-hydroxypropoxy)propyi], and a hydroxy! group that introduces both an additional dipole into this molecule and a hydrogen bond donor. Presence of the hydroxy! mediated dipole in combination with the hydroxyl's hydrogen bonding capability enhances SiGMA's compatibility with hydrophilic monomers such as MVAc, NVP, DMA, and HEMA, in contrast to TRIS, which does not possess a hydroxy! or similarly polar functional group. SiGMA's enhanced compatibility with hydrophilic monomers, as compared to TRIS, potentially permits diminution in the amount of DMA required to yield transparent, haze-free ophthalmica!iy viable polymers in DMA-VMAc-SiGMA or DMA-NVP-SiGMA type

formulations, in such SiGMA-containing formulations, increased ratios of more hydrophilic monomers such as MVAc or NVP, to less hydrophilic DMA, permits development of lower EWC polymers while maintaining acceptably wettabie, iubricious surface properties in the resultant polymeric materials.

Embodiments of the present invention comprise methods of preparing silicone hydrogels including both solvated and non-solvated polymerization reactions. Variations of solvated polymerization reactions include reaction mixtures comprising a non-participating solvent. A non-participating solvent serves at least in part to solvate other reaction mixture

components, such as monomers, cross-linkers, and initiators, which might not be completely miscible in bulk form in the absence of solvent. However, non-participating solvent molecules are not incorporated into the resultant polymer. A non-participating solvent may act as a hydrogen donor or acceptor. Variations of ophthalmic lenses are produced by casting silicone hydrogels in molds, and some ophthalmic lenses are lathed from silicone hydrogel material cast in bulk shapes such as, but not limited to, buttons, bonnets, pseudo bonnets, rods, cylinders, or semi-finished lenses. Contact lenses and other ophthalmic lenses are frequently, but not necessarily, lathed at ambient room temperature. However, temperature of the silicone hydrogel material itself may be increased above room temperature during ambient room temperature lathing, and the T_g of a silicone hydrogel represents a temperature ceiling for !athability of the material. Thus a silicone hydrogel may require a T_g above room temperature in order to be lathabie in a room temperature environment.

Lathabie bulk silicone hydrogel material is typically, but not necessarily, produced from a polymerization reaction mixture that is substantially free of non-participating diluent solvent, in contrast, cast-molded lenses are typically, but not necessarily produced from a solvated polymerization reaction mixture. A solvated polymerization reaction mixture comprises a non-participating solvent, the non-participating solvent being present in the reaction mixture, at least in part to facilitate dissolution of other reaction mixture components, but not becoming a constituent in a polymer product.

in a further aspect of the invention there is provided a poiymerisabie composition

comprising:

a silicon-containing monomer in an amount greater than 10% by weight;

a hydrophilic substituted N-vinyl acetamide monomer in an amount greater than 30% by weight; and

a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1 .

The silicone hydrogel material of the invention is obtained or obtainable from the

poiymerisabie composition. Thus, a silicone hydrogel may be obtained by polymerization of the poiymerisabie composition, for example by free radical polymerization. The silicone hydrogel material may be characterized by the methods described herein, including, for example, as modulus, Shore D hardness, sessile contact angle and so on.

The present invention also provides an ophthalmic lens obtainable or obtained by the methods of preparation described herein.

Terminology

The terms and phrases as indicated in quotation marks (" "} in this section are intended to have the meaning ascribed to them in this Terminology section applied to them throughout this document, including in the claims, unless clearly indicated otherwise in context. Further, as applicable, the stated definitions are to apply, regardless of the word or phrase's case, to the singular and plural variations of the defined word or phrase.

The term "or" as used in this specification and the appended claims is not meant to be exclusive; rather the term is inclusive, meaning "either or both."

References in the specification to "one embodiment", "an embodiment", "another

embodiment, "a preferred embodiment", "an alternative embodiment", "one variation", "a variation" and similar phrases mean that a particular feature, structure, or characteristic described in connection with the embodiment or variation, is included in at least an embodiment or variation of the invention. The phrase "in one embodiment", "in one variation" or similar phrases, as used in various places in the specification, are not necessarily meant to refer to the same embodiment or the same variation.

The term "couple" or "coupled" as used in this specification and appended claims refers to an indirect or direct connection between the identified elements, components, or objects. Often the manner of the coupling will be related specifically to the manner in which the two coupled elements interact.

The term "hydrogei," as used in this specification and appended claims, refers to a polymerization product of one or more hydrophilic monomers, the polymerization product being adapted to comprise at least 10% by weight water when fully hydrated.

The term "silicone hydrogei," as used in this specification and appended claims, refers to a hydrogei that is the polymerization product of one or more silicon-containing monomers, a proportion of the silicone hydrogei comprising the silicon-containing monomer being at least 0.5% by weight.

The terms "alky! siloxy functional group" or "aikyi siioxy group," as used in this specification and appended claims, refer to a substituent comprising a silicone atom directly bonded to at least one oxygen atom and at least one aikyi group, the aikyi group having the general formula C_nH₂n-_i ; . Examples of alkyl siloxy functional groups include, but are not limited to, the following formulas [XVI].

f- C— Si— O

[XVI] CH₃

Si— O

CH_,3

C Hg CH2

— Si— o—

CH3

The terms "alkyl group" or "alky! functional group," as used in this specification and appended claims, refer to a functional group having the genera! formula C_nH_2n+i. Where n is an integer from 1 to 6, inclusive, the alkyl group or alkyl functional group is a lower alkyl group" or lower alkyl functional group."

The term "substantially free," as used in this specification and appended claims, refers to a reaction mixture or polymer composition that comprises less than 2% by weight of the component to which the term "substantially free" refers. For instance, a reaction mixture that is substantially free of silicon-containing prepolymers comprises less than 2% by weight silicon-containing prepolymers; that is, silicon-containing prepolymers contribute less than 2% to the weight of the reaction mixture. Similarly, a reaction mixture that is substantially free of non-participating solvent comprises less than 2% by weight non-participating solvent; that is, non-participating solvent contributes less than 2% to the weight of the reaction mixture. As used herein, substantially free does not apply to cross-linking agents or initiators because those reaction mixture components are routinely used in reiatively small quantities. Thus a reaction mixture that comprises 0.10% AIBN (a thermal initiator) and 0.75% HDDA (a cross-linker) are not substantially free of AIBN or HDDA.

The term "ophthalmic lens," as used in this specification and appended claims, refers to a lens adapted to be placed or worn in intimate contact with a user's eye. Some ophthalmic lenses, such as contact lenses, reside in intimate contact with a tear film or other liquid film that usually resides between the contact lens and a users eye. Examples of ophthalmic lenses include, but are not limited to, contact lenses in all their variants, therapeutic lenses, protective lenses, cosmetic lenses, drug delivery devices, and intraocular lenses.

Ophthalmic lenses as defined herein may also include 'hybrid devices' lying in the interzone between fully implantable ophthalmic devices such as intraocular lenses and fully externalized devices such as contact lenses; these 'hybrid devices' may include but are not limited to corneal inserts, corneal rings, corneal inlays and corneal onlays.

The term "fully hydrated," as used in this specification and appended claims, refers to compositions that are substantially in equilibrium with water, a buffered solution that approximates physiological pH and ionic strength, a buffered solution that approximates a human ocular environment, or a human ocular environment. Thus, where modulus of elasticity or oxygen permeability is measured, a fully hydrated hydrogel material is equilibrated with water or the appropriate aqueous solution. Ophthalmic lenses comprising hydrogel material are typically stored in buffered aqueous saline solution, pH about 7.4, or in 0.9% NaCi aqueous solution.

The term "substantially dehydrated," as used in this specification and appended claims, refers to hydrogel compositions within which less than 1 % water by weight resides. As used in this application, T_g, Shore D hardness, and lathabiiity apply to hydrogel material that is substantially dehydrated, unless otherwise specified.

The term "true monomer," as used in this specification and appended claims, refers to monomers that have not been polymerized or pre-polymerized. True monomers are not part of a polymer, prepo!ymer, or macromonomer. For the purposes of this specification and appended claims, molecules with molecular weights greater than 1000 are considered polymers, prepolymers, or macromonomers, and are therefore not "true monomers." True monomers contain less than 10 repeating subunits. Some embodiments of true monomers contain preferably less than 8 repeating subunits, and most preferably less than 6 repeating subunits.

The term "monomer," as used in this specification and appended claims, refers to a compound adapted to polymerize (or copolymerize with other monomers), under

polymerization reaction conditions. As used in this application, the term monomer includes end-capped and other derivatized monomers, prepolymers, and macromonomers. After incorporation into a polymer, a monomer is still referred to as a monomer. Persons of ordinary skill in the art recognize that a monomer that is incorporated into a polymer or prepolymer is chemically modified by incorporation, such that the incorporated monomer is not identical to the unincorporated monomer.

The terms "hydrophiiic monomer," "hydrophilic substituted N-vinyl acetamide monomer," and "hydrophilic non-acetamide monomer," as used in this specification and appended claims, refer to monomers that upon homopoiymerisation in the presence of a small amount of cross-linking agent, form homopo!ymers that are at least 20% by weight water when fully hydrated. Variations of hydrophilic monomers form homopoiymers that are 38% or greater by weight water when fully hydrated. For instance, it is believed that fully hydrated poly- HEMA is approximately 38% by weight water, fully hydrated poly-NVP is approximately 90% by weight water; fully hydrated poly-MVAc is approximately 95% by weight water; and fully hydrated poly-DMA is approximately 81 % by weight water. Accordingly, hydrophilic monomers form homopoiymers that, when fully hydrated, are preferably at least 20% water by weight, more preferably at least 40% water by weight, and most preferably at least 50% water by weight.

The terms "reaction mixture," or "polymerization reaction mixture," as used in this

specification and appended claims, refers to any combination of polymerization reaction components, including, but not limited to, monomers and other reactants, solvents, catalysts, initiators, cross-linkers, color additives, or UV absorbers that are combined, mixed, or blended under conditions that result in a polymerization reaction. The reaction mixture may comprise a solution, heterogeneous mixture, homogeneous mixture, emulsion, suspension, other composition, or mixtures thereof.

The term "approximately," as used in this specification and appended claims, refers to plus or minus 10% of the value given. For example: "approximately 25.0% NVP" means a range of NVP content from 22.5% to 27.5%; "approximately 0.010% component X" means a range of compound X from 0.009% to 0.01 1 %; and "approximately 50 g" means a range from 45 g to 55 g.

The term "about," as used in this specification and appended claims, refers to plus or minus 20% of the value given.

The term lathable," as used in this specification and appended claims, refers to a

composition that is adapted to be cut with a lathe to produce a serviceable ophthalmic lens, or to generate a product that can be polished to produce a serviceable ophthalmic lens. Thus a lathable silicone hydrogei blank can be cut with a lathe to produce an ophthalmic lens without substantial burns or surface rips, and that has at most only minor surface imperfections that can be substantially removed by polishing. In order to be serviceable, a lathed contact lens must have substantially high quality optics. Unless otherwise specified, lathability refers to hydrogei material that is substantially dehydrated. A composition that is lathable at or above room temperature is adapted to be cut with a lathe in an environment with ambient temperature at 20 °C to 23.5 °C (room temperature) or above 23.5 °G (above room temperature). It is appreciated by a person of ordinary skill in the art that hydrogei material being cut with a lathe typically gets hotter than ambient temperature, especially proximate the interface between a cutting edge and the hydrogei material. Thus temperature of a silicone hydrogei material being cut with a lathe in an environment with an ambient temperature of 23,5 °C will typically be greater than 23,5 Ό at the cutting edge interface, and potentially higher than 40 °C. A hydrogei material that is lath able at or above room temperature can be lathed without additional environmental protocols such as refrigeration or employment of chilled tooling or chilled chucks.

The terms "polymer" and "copolymer" are used interchangeably in this specification and appended claims, and refer to a polymer comprising one or more species of monomer. As used here, polymers and copolymers are molecules comprising repeating structural units that are linked by covalent bonds, the repeating structural units being monomers.

The term "modulus of elasticity" or "modulus," as used in this specification and appended claims, refers to Young's modulus of elasticity (also referred to as tensile modulus of elasticity), which is a standard measure of elasticity known to persons skilled in the art. The unit for expressing "modulus" or "modulus of elasticity" is the pascal (Pa), a unit known to persons of ordinary skill in the art (1 pascal = 1 N/m², where N = Newton and m = meter). A practical unit used in this application is the megapascai ( Pa; 1 MPa = 1 x 1 Q⁶ Pa). 1 MPa is approximately equal to 1 Q2g/mrn² or 1 x 10'^' dynes/cm². As it pertains to this application, modulus is measured and expressed for fully hydrated hydrogei material, unless otherwise specified.

The term "sessile contact angle," as used in this specification and appended claims, refers to an index of surface wetting known to persons of ordinary skill in the art. As it pertains to this application, sessile contact angle is measured and expressed for fully hydrated hydrogei material, unless otherwise specified.

The term "oxygen permeability," as used in this specification and appended claims, is abbreviated Dk, and is expressed in Barrers (1 Barrer = 10 ¹¹ cm²- mL 0₂ / cm^3■ second^■ mmHg. As it pertains to this application, oxygen permeability is measured and expressed for fully hydrated hydrogei material, unless otherwise specified.

The term "oxygen transmissibiiity,^" as used in this specification and appended claims, is abbreviated Dk/t, where t is a thickness of a hydrogei film or ophthalmic lens. Dk/t is expressed x 1 Q^~9 cm-mL0₂ / cm^3,second-mmHg. Thus a lens made of material with an oxygen permeability of 80 Barrers and a thickness of .008 cm has oxygen transmissibiiity of 60 x 10^"" (cm²- mL 0₂ / cm^3■ second^■ mmHg) / .008 cm = 75 x 10^"9 cm-mL0₂ /

cm³-second-mmHg. Because Dk/t is expressed x 1 Q^~9 crn-rnL0₂ / cmS-second-mmHg. Dk/t for the aforementioned lens is 75.

The term "room temperature," as used in this specification and appended claims, refers to a temperature range of 20 °C to 23.5 °C. Above room temperature is therefore above 23.5 °C. The term "interpenetrating network," "interpenetrating networks," "!PN," and "IPNs," as used in this specification and appended claims, refers to a combination of two or more polymers in network form, at least one of which is polymerized or cross-linked in the immediate presence of the other.

Throughout this specification and appended claims, per cent (%) composition is by weight, except where clearly indicated otherwise in context.

ANALYTICAL METHODS

Analytical methods for assessing properties of hydrogel materials and ophthalmic lenses are described below.

Mechanical Properties

Modulus of elasticity, tensile strength, and elongation to break are determined by tensile testing of material using a Zwick Z0.5 tensiometer equipped with a KAD-Z 100N load cell. The jaws of the tensiometer are set to 5-10 mm separation depending on the dimensions of the material being tested, and test speed is set to 10 mm/min.

Test strips are prepared by first machining flat disks with a constant thickness of typically 0.20mm from standard contact lens blanks. The disks are hydrated in buffered saline and autoclaved. Strips with a typical width of 2.0mm are cut from the hydrated disks and individually mounted between the jaws of the tensiometer. The strip being tested is held under tension, and applied force is gradually increased until the sample breaks. The modulus of elasticity is determined from a graphical plot of stress vs. strain over the elastic region of the curve. The tensile strength is the stress required to break the sample. The elongation to break is the strain on the sample expressed as a percentage of unstretched sample. For each material a minimum of 5 strips are tested, and the results averaged.

Water Content

Water content by weight is determined using a procedure based upon guidance specified in the following standard. ISO 18369-4:2006 Ophthalmic Optics - Contact lenses - Part 4: Physicochemica! properties of contact lens materials. Specifically, this corresponds to section 4.6.2 Gravimetric determination of water content of hydrogel lens by loss on drying using an oven. After accurate weighing of the finished contact lens, the hydrated lenses are dried to constant mass in an oven and weighed again. The equilibrium water content (EVVC) is expressed as: EVVC = Weight of water in hydrated gel x 100

Total weight of hydrated gel

Equilibrium water content is synonymous with fully hydrated water content for the purposes of this specification and appended claims.

Oxygen Permeability

Oxygen permeability is measured in fully hydrated hydrogel material in a water saturated air environment at 35 °C. The oxygen permeability is measured using the procedure outlined in the following standard. ISO 18369-4:2006 Ophthalmic Optics - Contact lenses - Part 4: Physicochemical properties of contact lens materials. This corresponds to section 4.4 Oxygen Permeability and more specifically section 4.4.3 Poiarographic method. Measurements were made using an 0₂ Permeometer Model 201 T supplied by the Rehder Development Company, California, USA.

For each material to be measured a minimum of 4 piano contact lenses with different centre thicknesses (t) ranging from 0.10 to 0.30 mm are prepared following normal lens

manufacturing methods. Designs of the fully hydrated lenses are such that their central regions, from where oxygen flux measurements are taken, are of constant thickness. For each lens an initial oxygen transmissibility (Dk/t) measurement is determined, and then corrected for edge effects by application of a numerical method described in ISO 18369- 2004. To correct for boundary effects, the reciprocal of the corrected oxygen

transmissibilities of each of the lenses is plotted against time, t. The inverse of the gradient of the least squares best fit of the line is equal to the corrected Oxygen Permeability (Dk) of the material. Piano is a lens with zero power and as such does not provide any visual correction. Dk measurements are performed on piano lenses because the front and back surfaces are parallel to each other. Consequently, the lens is of constant thickness over the area the measurement is being taken from.

As described by ISO 18389-2004 the equipment is calibrated using reference materials obtained from the Oxygen Permeability Reference Material Repository at the University of Alabama, Birmingham, USA. The corrected Dk of 4 reference materials with Oxygen Permeability in the range of 26-130 Barrers are determined by the method described above, and then used to construct a calibration curve from which a linear regression is derived.

The calibrated and corrected Dk of an unknown sample can then be derived by

application of the linear regression to the corrected Dk initially measured. Shore D Hardness

Shore D Hardness is measured using a calibrated Shore Scale Durometer Hardness Tester supplied by Bowers Metrology, UK. A trimmed blank of material is placed in line with the needle on the durometer. The blank is moved up as quickly as possible without shock towards the needle on the durometer, raising the weight until the needle on the dial will not move any further. The handle is held in this position for one second and the reading recorded. A minimum of 4 measurements are taken for each material and averaged.

Sessile Contact Angle

Sessile contact angle is determined using the sessile drop technique using the Kruss EasyDrop Drop Shape Analysis System. A hydrogei lens to be measured is placed on a dome support and the front surface lightly blotted dry with a lint free tissue. A 2.0 μί. drop of distilled water is placed on the surface of the material being measured, and a digital image of the drop is captured. The sessile contact angle is then measured from the image and is the angle that the drop of water makes with the surface. The angle at both sides of the drop is measured and averaged.

Qn-Eye Water Loss

Water loss during wear is determined using an Atago handheld refractometer, model CL-1 . The refractometer is calibrated at using saturated salt solution. The plate of the refractometer is opened and a drop of solution placed on the prism. The plate is then closed so that the standard solution covers the whole prism. The eyepiece is focused to produce a crisp image, and the position of the interface between the white and blue portions in the field of view adjusted to the S20 position.

Water content of an ophthalmic lens is measured by opening the plate and placing the lens convex side down on the prism. The plate is carefully closed, flattening the lens onto the prism. Light pressure is applied and water content of the lens is read from the scale viewed through the eyepiece.

Water loss during wear is determined by first taking a base water content measurement from a fully hydrated lens, fresh from its vial at room temperature (20 °C to 23.5 °C). The lens is then worn for a minimum of 8 hours. Immediately following removal of the lens from the eye, water content is measured again, and the difference between the two measurements provides an estimate of water loss from the lens during wear. The on-eye water loss measuring method reported here utilizes baseline water content measurement at room temperature, and final, after-wear water content measurement at higher temperature, the after-wear measurement being made on a lens that is heated to about 35 °C during wear. Because water content of a hydrogei lens at 35 °C is less than room temperature, this on-eye water loss measuring method overestimates on-eye water loss.

On-eye water loss data reported here was collected over a period of 1 month in a variety of environments, and the values measured were averaged. Ambient temperatures were 15- 22 °C and relative humidity was approximately 60%.

Glass Transition Temperature (T_g)

Differential Scanning Calorimetry (DSC) analysis technique familiar to persons of ordinary skill in the art is performed using a DSC2920 (TA Instruments) to measure the thermal properties of the samples. The samples are sealed in aluminum pans, heated to 130 °C, and maintained at that temperature for SOmins to ensure complete dehydration. The

temperature is then ramped from 30°C to 25 °C in order to determine the T_g. T_g is the onset of the glass transition determined during an initial sample heating cycle. T_g is determined from the extrapolated onset of glass transition for the first heating cycle, not the mid-point of glass transition during the first heating cycle.

Method for Preparing a Hydrogei

An exemplary method for preparing a silicone hydrogei of the invention includes the step of making a reaction mixture, which may be referred to as a po!ymerisabie composition, by combining the following components:

* a silicon-containing monomer in an amount preferably 10 g or more, preferably 15 g or more, preferably 20 g or more, preferably greater than 25 g, more preferably between 25 g and 40 g, still more preferably about 32.75 g, and most preferably approximately 32.75 g; and

* a hydrophiiic substituted N-vinyi acetamide monomer in an amount preferably 20 g or more, preferably 25 g or more, preferably greater than 30 g, more preferably between 34 g and 55 g; still more preferably about 44.8 g, and most preferably approximately 44.8 g; and » a hydrophi!ic non-acetamide monomer in an amount resulting in a hydrophi!ic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight ratio preferably greater than 2.1 :1 and most preferably in a range between 3:1 and 7:1 ; and

* a total hydrophilic monomer content preferably greater than 44 g, more preferably

between 49.7 g and 69.7 g, and most preferably approximately 56 g; and

* a fluorine-containing monomer in an amount preferably 0 g to 10 g, more preferably 2.0 g to 8.0 g, and most preferably 4.0 g to 6.0 g; and

» a first cross-linker in an amount preferably between 0 g and 3.75 g, more preferably 0.10 g to 2.0 g, and most preferably 0.20 g to 1 .0 g; and

* a second cross-linker in an amount preferably 0 g to 3.75 g, more preferably 0.20 g to 2.0 g, and most preferably 0.30 g to 1 .0 g; and

* an initiator in an amount preferably between 0 g and 1 .0 g, more preferably between 0 g and 0.50 g, and most preferably between 0 g and 0.20 g; and

* a strengthening monomer in an amount preferably 0 g to 20 g, more preferably 0 g to 15 g, and most preferably about 10 g.

The reaction mixture may be substantially free of non-participating solvent.

Other methods of making silicone hydrogels comprise making a reaction mixture consisting of or consisting essentially of some or ail of the ingredients listed above in the first method of making a silicone hydrogel. Some methods of making silicone hydrogels use reaction mixtures comprising initiators other than thermal initiators, the other initiators including, but not limited to, UV initiators or other free-radical initiators. The other initiators can be used in addition to or in place of a thermal initiator. Some methods of making silicone hydrogels use reaction mixtures comprising non-participating solvents.

The reaction mixture of the third method is mixed and dispensed into molds, which are incubated at elevated temperature. Incubation is typically, but not necessarily, between 37°C and 75 °C for at least 2 hours, whereupon the resulting silicone hydrogel is removed from the molds. The resulting silicone hydrogel is removed from the molds and annealed by- heating in a fan oven under atmospheric pressure for at least 90 minutes at an oven temperature of 127°C. Some embodiments of silicone hydrogels are annealed at other temperatures, including a range of temperatures that are typically, but not necessarily, above 100 °C. Variations are annealed at reduced pressure.

Variations of silicone hydrogels made by the third method have a T_g preferably at or above room temperature, more preferably above 25 °C, even more preferably above 27°C, even more preferably still above 40 "C, and most preferably above 45 °C. Some variations of silicone hydroge!s made by the third method have Shore D hardness preferably greater than 70 at 21 °C, more preferably greater than 75 at 21 °G, and most preferably greater than 80 at 21 °C.

Some ophthalmic lenses, including but not limited to contact lenses, are made by casting the silicone hydrogels directly in lens molds. Variations of ophthalmic lenses are made by casting silicone hydrogels into bulk shapes or blanks, from which contact lenses are formed through cutting such as lathe cutting. Typically, but not necessarily, bulk or blank hydrogei material from which lenses are cut or lathed is prepared from reaction mixtures that are substantially free of non-participating solvent. Other methods of making silicone hydrogei embodiments use reaction mixtures comprising appreciable levels of non-participating solvents.

Reference Examples

The present inventors have previously described the preparation of a silicone hydrogei material comprising a high weight content of Ν,Ν-dimethy! acrylamide and/or N-vinyl pyrroiidone.

Thus, for reference, the contents of US 7,939,579 are hereby incorporated by reference in their entirety, including, in particular, the worked examples set out from column 13, line 28 to column 17, line 45, such as worked examples 1 to 19 (see Tables 1 and 2)..

Example Method 1

A silicone hydrogei was prepared from a reaction mixture by combining the following reactants: 29.8 g TRIS; 9.9 g MM A; 14.2 g DMA; 45.4 g MVAc; 0.25 g AMA; 0.45 g

TGDMA; and 0.16 g AIBN. Other examples of making a silicone hydrogei include making a reaction mixture consisting of, or consisting essentially of, some or all of the reactants listed above.

The reaction mixture is thoroughly mixed and subsequently dispensed into cylindrical molds, which are sealed and placed in a water bath at approximately 60 °G for approximately 24 hours. The resulting silicone hydrogei is removed from the molds and annealed by heating in a fan oven under atmospheric pressure for at least 90 minutes at an oven temperature of 127°C. This method of making a silicone hydrogei produces Example Hydrogei 1 (see Table 1 ). Silicone Hydrogel

An exemplary silicone hydrogel comprises a copolymer including the following:

» a silicon-containing monomer in an amount preferably 10% or more, preferably 15% or more, preferably 20% or more, preferably greater than 25%, more preferably between 25% and 40%, still more preferably about 32.75%, and most preferably approximately 32.75%; and

» a hydrophilic substituted N-vinyi acetamide monomer in an amount preferably 20% or more, preferably 25% or more, preferably greater than 30%, more preferably between 34% and 55%; still more preferably about 44.8%, and most preferably approximately 44.8%; and

» a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyi acetamide monomer to hydrophilic non-acetamide monomer weight ratio preferably greater than 2.1 :1 and most preferably in a range between 3:1 and 7:1 ; and

® a total hydrophilic monomer content preferably greater than 44%, more preferably

between 49.7% and 69.7%, and most preferably approximately 56%; and

• a fluorine-containing monomer in an amount preferably 0% to 10%, more preferably 2.0% to 8.0%, and most preferably 4.0% to 6.0%; and

• a first cross-linker in an amount preferably between 0% and 3.75%, more preferably 0.20% to 2.0%, and most preferably 0.30% to 1 .0%; and

» a second cross-linker in an amount preferably 0% to 3.75%, more preferably 0.20% to 2.0%, and most preferably 0.30% to 1 .0%; and

® an initiator in an amount preferably 0% to .0%, more preferably 0% to 0.50%, and most preferably 0% to 0.20%; and

• a strengthening monomer in an amount preferably 0% to 20%, more preferably 0% to 15%, and most preferably about 10%.

Other silicone hydrogeis of the invention include silicone hydrogels consisting of, or consisting essentially of, some or all of the silicone hydrogei components listed above. The silicone hydrogel is prepared by the method of making a silicone hydrogel described above.

In substantially dehydrated condition, the silicone hydrogels are !athable at ambient temperatures at or above room temperature. During lathing, the silicone hydrogel material itself is preferably at or above room temperature, more preferably at temperatures above 25°C, even more preferably at temperatures above 27 °C, and most preferably at temperatures between 27° and 58 °C. The silicone hydroge!s may have a T_g preferably at or above room temperature, more preferably above 25°C, even more preferably above 27°C, even more preferably still above 40 °C, and most preferably above 45 °C. The silicone hydrogels may have Shore D hardness that is preferably greater than 70 at 21 °C, more preferably greater than 75 at 21 °G, and most preferably greater than 80 at 21 °C.

Fully hydrated silicone hydrogels have oxygen permeability preferably greater than 45 Barrers and most preferably greater than 55 Barrers, The silicone hydrogels may have a sessile contact angle preferably less than 1 15 ° and most preferably less than 1 10 °, and fully hydrated water content preferably greater than 60% and most preferably greater than 65%. The silicone hydrogels may have a modulus preferably less than 1 .0 MPa, more preferably less than 0.79 MPa, still more preferably less than 0.70 MPa, and most preferably less than 0.60 MPa.

Example Silicone Hydrogei 2

Example 2 is a silicone hydrogei comprising the following proportions of components: 35.0% SiGMA; 8.45% MMA; 7.6% DMA; 48.1 % MVAc; 0.25% AMA; 0.60% TGDMA; and 0.10% AIBN. Some examples of silicone hydrogels contemplated within the scope of the present invention consist of, or consist essentially of, some or ail of the Example 2 components listed above. The silicone hydrogei of Example 2 is typically prepared using Example Method 1 .

Example 2 includes a hydrophilic substituted N-vinyl acetamide monomer (MVAc) in an amount of 48.1 % and a hydrophilic non-acetamide monomer (DMA) in an amount of 7.6%. Accordingly, Example 2 embodies a total hydrophilic monomer content of 55.7% and a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of 6.3 to 1 .

When stored in water, aqueous buffer, or aqueous saline solution, ophthalmic lenses made from the silicone hydrogei of Example 2 typically exhibit longer shelf lives compared to previous high water content silicone hydrogei lenses comprising both NVP and DMA as predominant hydrophilic monomers. The previous lenses tend to swell when stored fully hydrated over relatively long time intervals.

The Example 2 silicone hydrogei in a substantially dehydrated condition is iathable at an ambient temperature at or above room temperature, having a Shore D hardness of 83.0 at 21 °G. Fully hydrated, the Example 2 silicone hydrogei has a water content of 65.6%, an oxygen permeability of 57.4 Barrers, a sessile contact angle of 105 °, and a modulus of 0.54 MPa. Example Silicone Hydrogei 3

Example 3 is a silicone hydrogei that exemplifies the third embodiment silicone hydrogei copolymer and comprises the following proportions of components: 29.8% TRIS; 7.45% MM A; 4.5% EMMA; 13.7% DMA; 43.9% MVAc; 0.25 % AMA; 0.45% TGDMA; and

0.16% AIBN.

The Example 3 silicone hydrogei in a substantially dehydrated condition is lathable at an ambient temperature at or above room temperature, having a Shore D hardness of 84.5 at 21 °C. The silicone hydrogei of Example 3 has a fully hydrated water content of 86.7%, an oxygen permeability of 55.2 Barrers, a sessile contact angle of 107° and a modulus of 0.51 MPa.

Table 1 displays compositions and physical properties of numerous examples of silicone hydrogels of the invention, including Example 3. Each of the examples presented in Table 1 has an oxygen permeability greater than 55 barrers, a fully hydrated water content greater than 60%, and a modulus of elasticity less than 0.58 MPa. Examples 6, 7, and 1 -3 each have a sessile contact angle less than 1 10°, and moreover exhibit relative resistance to swelling when stored in aqueous media, resulting in increased shelf life compared to prior art high water content lenses.

TABLE 1

Component {%} Ex. 1 _E,₂ ΕΞ ιι 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7

TRIS 29.8 - 29.8 29.8 34.8 29.8 31 .8

SiGMA 35.0 - MMA 9.9 8.45 7.45 9.9 7.4 7.45

EEMA - - 4.5 - 14.9 4.5 2.5

DMA 14.2 7.6 13.7 14.2 14.9 13.7 1 3.7

MVAc 45.4 48.1 43.9 45.4 34.8 43.9 43.9

AMA 0.25 0.25 0.25 0.20 0.20 0.20 0.25

TGDMA 0.45 0.60 0.45 0.40 0.40 0.40 0.45

AIBN 0.16 0.10 0.1 6 0.16 0.16 0.16 0.16

Property

Dk (Barrers) 59.0 57.4 55.2 56.5 63.0 58.6 59.1

Water Content^' 67.3 65.6 66.7 67.6 62.0 65.7 65.8

C.A.^" 106 105 107 ND 1 14 107 107 Component (%) Ex. 1 E 3 Ex. 4 Ex. 5 Ex. 6

Modulus (MPa) 0.57 0.54 0.51 0.55 0.45 0.48 0.49

Shore D hardness 84.3 83.0 84.5 ND ND ND ND

50.3 45.3 49.9 ND ND ND ND

Elongation to Break 278 206 268 303 223 261 260

MVAc / DMA**^* 3.2 6.3 3.2 3.2 2.3 3.2 3.2 water by weight

** sessile contact angle, in degrees

*^** weight to weight ratio of MVAc, a hydrophilic substituted N-vinyl acetamide monomer, to DMA, a hydrophilic non-acetamide monomer

ND = not determined

Method of Preparing an Ophthalmic Lens

A method of making an ophthalmic lens comprises machining blanks from the silicone hydrogei material of the invention. Lens shapes are cut from blanks with a lathe at an ambient temperature at or above room temperature, and are subsequently hydrated and sterilized. Lathe cutting is performed at ambient temperatures at or above room

temperature. Lenses include, but are not limited to, contact lenses.

Example Method 2

Example Method 2 is a method of making an ophthalmic lens. In Example Method 2, cylinders of Example 2 Silicone Hydrogei are machined into blanks that are 12.7 mm diameter by 5.0 mm thick. The dry lens shapes are formed from the Example 2 cylinders using conventional lathe cutting techniques performed at room temperature. The lenses are eluted and hydrated in borate buffered saline for 1 8 hours, transferred to fresh borate buffered saline, and then thermally sterilized. Lenses made by the Example 2 Method include, but are not limited to, contact lenses.

Ophthalmic Lenses

An ophthalmic lens of the invention comprises silicone hydrogei, and may be prepared by the method of making an ophthalmic lens described above. The lens has oxygen transmissibiiity (DK/t) preferably greater than 55, more preferably greater than 69, and most preferably greater than 72. Variations of the iens are adapted to have on-eye water loss preferably less than 4%, more preferably less than 3%, and most preferably less than 2%.

Example Silicone Hydrogel 8

Example 8 exemplifies further ophthalmic lens of the invention and is prepared by Example Method 2 of making an ophthalmic iens. The ophthalmic lens of Example 8 is a contact lens with an average center thickness of 0.08 mm and an oxygen transmissibiiity (Dk/t) of approximately 74, It is adapted to have an on-eye water loss of 4% or less.

Table 2 displays compositions and physical properties of numerous examples of further silicone hydrogeis. Each of the examples presented in Table 2 has an oxygen permeability greater than 52 barrers, a fully hydrated water content of 62% or greater, and a modulus of elasticity less than 0.79 MPa.

TABLE 2

Component (%) Ex. 8 Ex, 9 Ex, 10 Ex. 11 ΕΞχ« i 3 Ex. 14

TRIS 29.9 29.8 22.5 15.0 7.5 29.8 29.8

SiGMA - - 7.5 15.0 22.5 - -

MMA 10.0 9.9 10.0 10.0 10.0 5.0 -

HFPM - - - - - 5.0 9.9

DMA 14.9 9.9 14.3 14.3 14.3 14.2 14.2

MVAc 44.8 49.7 45.7 45.7 45.7 45.4 45.4

A A 0.20 0.20 0.20 0.20 0.20 0.25 0.25

TGDMA 0.30 0.40 0.45 0.45 0.45 0.45 0.45

AIBN 0.16 0.16 0.10 0.10 0.10 0.16 0.16

Property

Dk (Barrers) 53 60 57.0 54.0 55.6 56.2 58.9

Water Content^' 68.0 69.5 67.3 68.1 69.0 66.8 65.7

C.A.^" 101 104 107 107 106 108 108

Modulus (MPa) 0.48 0.58 0.43 0.36 0.35 0.50 0.77

T_g ND ND ND ND ND 49.3 51 .0

Elongation to break 316 236 283 274 264 223 224

MVAc / DMA^*** 3.0 5.0 3.2 3.2 3.2 3.2 3.2

% water by weight

*^* sessile contact angle, in degrees ^*** weight to weight ratio of MVAc, a hydrophilic substituted N-viny! acetamide monomer, to DMA, a hydrophilic non-acetamide monomer

ND = not determined Simulated Aging Study

Lens prepared from hydrogels of the invention were evaluated in an accelerated aging test alongside a lens prepared from a hydrogei containing_N-vinyi pyrrolidone. The lenses were prepared from polymerisable compositions set out in Table 3 below.

TABLE 3

WP-Containing

Component (%) T86 T67

Hydrogei

TRIS 30.00 30.00 12.00

MM A 7.50 10.00 2.50

ET A 4.50

DMA 13.80 14.30 54.60

HFPM 5.00

MVAc 44.20 45.70

AMA 0.25 0.25

NVP 25.00

HEMA 0.50

TGDMA 0.45 0.45

HDDA 0.40

AIBN 0.16 0.16 0.10

Properties

Dk (Barrers) 59.4 57.1

Water Content^' 68.90 67.69

C.A. 107.5 108.9

Modulus (MPa) 0.46 0.55

Prepared lenses were treated with borate-buffered saline (BBS) at 45°C and the lens diameter was measured periodically over time.

The diameter of fully hydrated piano lenses was measured using an Optimec JCF with a wet ceil maintained at 21 "C. The lenses were then transferred into individual glass vials containing 5 mL of borate buffered saline. The vials were placed into a GenLab incubator maintained at 45 °G, at periodic intervals the vials were removed from the incubator and allowed 3 hours to re-equilibrate to room temperature prior to re-measurement of lens diameter. As recommended in ISO 1 1987:1997 first order kinetics were assumed and each 10°C increase in temperature above normal storage temperature was taken to

approximately double the degradation rate of the synthetic polymer. Consequently storage at 45 °C accelerated the ageing of the lenses by a factor of four when extrapolated to 25 "C, such that 3 months storage at 45 °C was equivalent to 12 months at 25 °C.

The diameter measurements for three lenses are shown in the table below, where the time has been converted to an equivalent aging time for a lens stored at 25°C over a period of months (as noted above, in reference to ISO 1 987:1997).

Figure 1 shows the change in lens diameter over time, where 4 is the NVP hydrogei material, as is the MVAc-containing hydrogei material T68, and is the VAc-containing hydrogei material T67 Alternative Embodiments and Variations

The various embodiments, examples, and variations thereof, described above, are merely exemplary, and are not meant to limit the scope of the invention, it is to be appreciated that numerous other variations of the invention have been contemplated, as would be obvious to one of ordinary skill in the art, given the benefit of this disclosure. All variations of the invention that read upon appended claims are intended and contemplated to be within the scope of the invention.

Claims

Claims

1 . A silicone hydrogel material having an oxygen permeability greater than 45 Barrers, a water content greater than 80% by weight, and a modulus less than 1 ,0 MPa. and including a copolymer comprising :

a silicon-containing monomer in an amount at 10% by weight or more;

a hydrophilic substituted N-vinyl acetamide monomer in an amount greater than 30% by weight; and

a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1 ,

2. The silicone hydrogel material of claim 1 . further having a sessile contact angle less than 1 15°.

3. The silicone hydrogel material of claim 1 or claim 2, further having a Shore D hardness of 70 or greater at 21 °C.

4. The silicone hydrogel material of any one of claims 1 to 3, wherein the silicon- containing monomer is present in an amount between 10% and 40% by weight.

5. The silicone hydrogel material of any one of claims 1 to 3, wherein the copolymer comprises the silicon-containing monomer in an amount greater than 25% by weight.

6. The silicone hydrogel material of any one of claims 1 to 5, wherein the silicon- containing monomer is selected from the group consisting of bulky silyi monomers;

(3-methylacryloxy-2-hydroxypropoxy)propylbis(trimethoxy)methylsilane; and

(2-methylacryioxy-3-hydroxypropoxy)propyibis(trimethoxy)methy!silane.

7. The silicone hydrogel material of any one of claims 1 to 5, wherein the silicon-containing monomer is selected from the group consisting of:

3-{tris(trimethy!siloxy)sily!)propyi methacrylate (TRIS);

(3-methylacry!oxy-2-hydroxypropoxy)propylbis(trimethoxy)methy!silane;

(2-methylacry!oxy-3-hydroxypropoxy)propylbis(trimethoxy)methyisilane;

0-[3-(tris(trimethylsiloxy)siiyl)propyl]-N-[2'-(methacryloyloxy)ethyi]carbamate;

0-[2-(methacryioyloxy)ethyl]-N-[3'-(tris(trimethylsiloxy)siiyi)propyi]carbamate;

N-(3-((trimethylsi!oxy)siiyl)propyI)methacry!amide; 1 ,3-bis(3'-methacrylamidopropy!)-1 ,1 ,3,3-tetrakis(trimethyisiloxy)disiioxane;

1 -{3'~methacryioyloxypropyl)-1 ,1 ,3,3,3-pentamethyidisilQxane;

1 ,3-bis(3'-rnethacryloyloxypropyl)-1 ,1 ,3,3-tetramethyidisiloxane;

1 -(3'-methacryioylQxypropyl)polydimethylsiloxane; and

1 -(3'-acry1oyiQxypropyl)poiydirnethylsiloxane.

8. The silicone hydrogei material of any one of claim 1 to 5, wherein the silicon- containing monomer is selected from the group consisting of:

TRIS;

(3-methylacryloxy-2-hydroxypropoxy)propyibis{trimethoxy)meihyisiiane; and

(2-methylacryloxy-3-hydroxypropoxy)propyibis(trimethoxy)methyisilane.

9. The silicone hydrogei material of any one of claim 1 to 8, wherein the copolymer has a sessile contact angle less than 1 10 °.

10. The silicone hydrogei material of any one of claims 1 to 9, wherein the modulus is 0.79 MPa or less.

1 1 . The silicone hydrogei material of claim 10, wherein the modulus is 0.70 MPa or less.

12. The silicone hydrogei material of any one of claims 1 to 1 1 , wherein the oxygen permeability is 55 barrers or more.

13 The silicone hydrogei material of any one of claims 1 to 12, wherein the silicone hydrogei material has a Tg of 27 ^<Ό or more.

14. The silicone hydrogei material of any one of claims 1 to 13, wherein the copolymer comprises the hydrophilic substituted N-vinyi acetamide monomer in an amount between 34% and 55% by weight.

15. The silicone hydrogei material of any one of claims 1 to 14, wherein the copolymer further comprises a hydrophilic substituted N-vinyi acetamide monomer to hydrophilic non- acetamide monomer weight to weight ratio between 3:1 and 7:1 .

16. The silicone hydrogei material of claim 15, wherein the hydrophilic substituted N-vinyl acetamide monomer has a methyl group at the R² position, and the hydrophilic non- acetamide monomer is selected from the group consisting of: N.N-dimethyl acry!amide (DMA); 2-hydroxyethyl methacrylate (HEMA); 2-hydroxyethyl acrylate; hydroxypropy! acrylate; hydroxypropy! methacrylate; N-viny!-2-pyrrolidone (NVP); glycerol methacrylate; acrylic acid; acryiamide; and methacrylic acid.

17. The silicone hydrogel material of any one of claims 1 to 16, wherein the copolymer comprises less than 5% by weight styrene monomer or substituted styrene monomer.

18. The silicone hydrogel material of claim 1 , wherein the silicone hydrogel material has an oxygen permeability greater than 55 Barrers, a water content greater than 60% by weight, and a modulus less than 0.60 MPa, and including a copolymer comprising:

a silicon-containing monomer in an amount of about 32.75% by weight, the silicone monomer being selected from the group consisting of:

3-(tris(trimethy!siloxy)sily!)propyi methacryiate (TRIS);

(3-methylac!y!oxy-2-hydroxypropoxy)propy!bis(trimethoxy)methyisilane;

(2-methylacryloxy-3-hydiOxypropoxy)propylbis(trimethoxy)methy!siiane;

0-[3-(tris(trimethylsiioxy)silyi)propyl]-N-[2^!-(methacryloyioxy)ethyl]carbamate;

0- [2-(methacryloyloxy)ethyl]-N-[3^,-(tris(trimethyisiloxy)silyl)propyl]carbamate; N-(3-((trimethylsiioxy)si!yl)propyi)methacry!amide;

,3-bis(3'-methacrylamidopropy!)-1 , ,3,3-tetrakis(trimethy!siloxy)disi!oxane; 1 -(3^!-methacryloyioxypropyl)-1 ,1 ,3,3,3-pentamethy!disiloxane;

1 ,3-bis(3'-methacryloyloxypropyl)-1 , 1 ,3,3-tetramethy!disiloxane; 1 ~(3^:-methacryloyioxypropy!)poiydimethylsi!oxane; and

1 - (3'-aciy!oyloxypropy!)polydimethy!si!oxane;

a hydrophilic substituted N-vinyl acetamide monomer in an amount of about 44.8% by weight; and

a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of between 3:1 and 7:1 .

19. A method of making an ophthalmic lens comprising lathe cutting a silicone hydrogel of any one of claims 1 to 18.

20. The method of claim 19, wherein the hydrogel is lathe cut at ambient temperature or above.

21 . The method of claim 19, wherein the silicone hydrogel resides at a temperature of 20 °C or more.

22. The method of any one of claims 19 to 21 , wherein the ophthalmic lens is a contact lens.

23. An ophthalmic lens obtainable by the method of any one of claims 19 to 22.

24. A polymerizable composition for a silicone hydrogel material, wherein the

po!ymerizable composition comprises:

a silicon-containing monomer in an amount greater than 10% by weight;

a hydrophilic substituted N-vinyl acetamide monomer in an amount greater than 30% by weight; and

a hydrophilic non-acetamide monomer in an amount resulting in a hydrophilic substituted N-vinyl acetamide monomer to hydrophilic non-acetamide monomer weight to weight ratio of greater than 2.1 to 1 .

25. A silicone hydrogel material obtained or obtainable from the polymerisable composition of claim 24.

26. An ophthalmic lens formed from the silicone hydrogel material according to claim 25.

27. A method of preparing a silicone hydrogel material, wherein the method comprises the step of polymerizing the polymerisable composition of claim 24.

28. A method of forming a blank for an ophthalmic lens, the method comprising the steps of:

(a) polymerizing the polymerisable composition of claim 24 in a rod-shaped mould thereby to form a polymer rod; and

(b) working the polymer rod into a plurality of blanks.

29. A method of forming a blank for an ophthalmic lens, the method comprising the step of polymerizing the polymerisable composition of claim 24 in a button mould thereby to form a lens blank.

30. A method for forming an ophthalmic lens, the method comprising the steps of:

(a) providing a blank according to claim 28 or claim 29; and

(b) working the blank to form an ophthalmic lens.

31 . A method for forming an ophthalmic lens, the method comprising the step of polymerizing the po!ymerisabie composition of claim 24 in a mould thereby to form an ophthalmic lens, wherein the mould is shaped so as to provide an ophthalmic lens having anterior and/or posterior portions.