Process of producing intraocular lens

Abstract: A process of producing an intraocular lens (28) of a one-piece type in which the lens includes an optical portion (24) and at least one support portion (26) produced integrally with each other, the process being characterized by including the steps of (a) forming a first polymerized material into a lens blank (10), the lens blank including a convex portion (12) providing the optical portion of the intraocular lens, and a flange portion (14) surrounding the convex portion, (b) applying, to one (15) of opposite surfaces of the flange portion (14) on a side of a convex surface (13) of the convex portion (13), a monomer composition which is polymerizable to produce a second polymerized material (22) different from the first polymerized material, the monomer composition including at least one polymerizable monomer, (c) polymerizing the monomer composition on the flange portion (14) to provide a double-layer portion (14, 22) having the flange portion (14) and the second polymerized material (22) produced integrally with the lens blank from the monomer composition, and (d) forming the convex portion (12) and double-layer portion (14, 22) of the lens blank, into the optical portion (24) and at least one support portion (26) of the intraocular lens, respectively.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a process of producing an intraocular lens of a one-piece type in which an optical portion and a support portion of the lens are produced integrally with each other, and simultaneously of a type which the optical and support portions are formed of different materials. Related Art Statement An intraocular lens includes an optical portion serving as an optical lens, and a support portion for attaching the optical portion to a suitable site in an eye of a patient. Conventionally, there are known an intraocular lens of a two- or three-piece type in which an optical portion and a support portion are produced separately from each other and subsequently the support portion is fixed to the optical portion, and an intraocular lens of a one-piece type in which an optical portion and a support portion are produced integrally with each other. In addition, there is well known in the art an intraocular lens of a type in which an optical portion and a support portion are formed of different materials. For example, the optical and support portions are produced by polymerization of different monomer compositions including different polymerizable monomers, different compounding agents and/or additive agents, or different amounts of those agents. More specifically, the optical portion may be formed of a colorless, transparent polymerizable material and simultaneously the support portion may be formed of a polymerizable material containing a coloring agent, so that the support portion can easily be identified when the intraocular lens is inserted to patient's eye. In addition, it has been practiced to add different amounts of crosslinking agent to respective materials for optical and support portions of an intraocular lens, for the purpose of providing the two portions with different degrees of flexibility. In this way, the intraocular lens is produced such that the optical and support portions thereof possess different optical or physical properties required thereto. EP-A-331 457 discloses a process of producing an intraocular lens of the one piece-type and of the type in which the optical and support portions thereof are formed of different materials. More specifically, this document teaches a process of producing an intraocular lens in which only the support portion thereof is colored. In the disclosed process, first, a colorless, transparent plastic material is used to provide a central portion for a lens blank. Subsequently a liquid, colored plastic material is located around the central colorless portion, and then is polymerized to harden the outer colored portion. Thus, a lens blank is produced in which the central colorless portion and the outer colored portion are integrally combined with each other. An alternative process disclosed by the document is that a colored material first is formed into an outer portion for a lens blank and subsequently a colorless transparent material is poured into a central hole of the colored portion and then polymerized, so as to produce a lens blank similar to the above-indicated first lens blank, that is, lens blank in which the colorless central and colored outer portions thereof are integrally connected with each other. A desired intraocular lens is obtained by forming the colorless central and colored outer portions of the lens blank into the optical and support portions of the lens, respectively. However, the above-indicated second process, in which the central portion of a lens blank is formed within a central hole in the colored outer portion, may suffer from a problem that distortion occurs to the central portion thus formed. That is, the optical properties of an intraocular lens as an end product may adversely be affected. Meanwhile, the above-indicated first process, in which the colored outer portion of a lens blank is formed by polymerization around the colorless central portion, may suffer from a problem that it is extremely difficult to align the center of the colorless central portion with the center of the lens blank as a whole. This problem causes the "color misalignment" problem that an intraocular lens as an end product has a colored part in the optical portion thereof or has a colorless part in the support portion thereof, because the lens blank therefor is worked or machined into the lens by employing the center of the lens blank as a whole as the center for the shape working. Another process of producing a one piece-type intraocular lens whose support portion is colored, is disclosed in JP-A-62-161360. In the disclosed process, a colored plastic material is located around an optical member formed of a colorless transparent plastic material, and subsequently heat is applied to fuse the optical member and the plastic material into an integral member, that is, a lens blank. An intended lens is obtained from this lens blank. This process may suffer from the problem that it is very difficult to align the center of the optical member with the center of the lens blank as a whole, that is, the above-identified "color misalignment" problem. As is understood from the foregoing description, the known processes have the problem that the optical properties of an intraocular lens produced thereby are deteriorated due to distortion occurring to the optical portion of the lens, or invasion of the material for the support portion of the lens into that for the optical portion thereof. In addition, the known processes suffer from the problem that the support portion of an intraocular lens fails to have satisfactory physical properties due to invasion of the material for the optical portion of the lens into that for the support portion. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process of producing an intraocular lens of the one-piece type and of the type in which the optical and support portions thereof are formed of different materials, which process is free from the problems of distortion of the optical portion, misalignment of the center of the optical portion, or "color misalignment". The present invention provides a process of producing an intraocular lens of a one-piece type as set out in claim 1. In the intraocular lens producing process arranged as described above, an unreacted polymerizable material is applied to the flange portion of the lens blank formed of the first polymerized material, and subsequently is polymerized on the flange portion to produce a second polymerized material. Consequently, a layer of the second polymerized material superposed on the flange portion is integrally combined with the outer periphery of the convex portion of the lens blank. According to the present invention, the first portion providing the optical portion of an intraocular lens is polymerized first. Therefore, the present process does not suffer from the problem of distortion of the optical portion of the lens. Therefore, an intraocular lens produced by the present process enjoy stable optical properties. In the present producing process, the lens blank includes the flange portion surrounding the first portion such that the flange and first portions are integral with each other, and therefore the position of the first portion relative to the flange portion cannot be changed. On the flange portion, a superposed layer is formed of the second polymerized material. Thus, the center of the first portion cannot be changed relative to the center of the lens blank as a whole, between before and after the formation of the superposed layer on the flange portion. Thus, the present process is free from the problem of misalignment of the center of the optical portion of the lens. That is, the present process insures that the center of working or machining of a lens blank into a lens product is easily specified on the blank even after the second polymerized material has been formed on the flange portion. Therefore, the first portion of the first polymerized material is accurately formed into the optical portion of the lens product, while the superposed layer of the second polymerized material on the flange portion is accurately formed into the support portion of the lens. Consequently, the present process does not suffer from the problem of invasion of the colored material for the support portion into the colorless material for the optical portion, or invasion of the colorless material for the optical portion into the colored material for the support portion, and therefore is free from the conventionally encountered "color misalignment" problem. BRIEF DESCRIPTION OF THE DRAWINGS The above and optional objects, features and advantages of the present invention will be better understood by reading the following detailed description of the present preferred embodiments of the invention when considered in conjunction with the accompanying drawings, in which: Fig. 1A is a plan view of a lens blank; Fig. 1B is a cross-sectional view taken along line 1B-1B of Fig. 1A, of the lens blank of Fig. 1A; Fig. 2 is a cross-sectional view corresponding to Fig. 1B, of another lens blank; Fig. 3 is a cross-sectional view corresponding to Fig. 1B, of yet another lens blank; Fig. 4 is a cross-sectional view corresponding to Fig. 1B, of a different lens blank; Fig. 5 is a cross-sectional view showing a superposed layer formed on a flange portion of the lens blank of Fig. 3; Fig. 6 is a plan view of an intraocular lens produced by the process according to the present invention; Fig. 7 is a view for explaining the configuration and dimensions of a lens blank as Invention Example 1 or Invention Example 2; Fig. 8 is a view for explaining the configuration and dimensions of a lens blank as Invention Example 3; and Fig. 9 is a view for explaining the configuration and dimensions of a lens blank as Invention Example 4. DETAILED DESCRIPTION OF THE INVENTION In the present invention, the first and second polymerized materials used for a lens blank and a superposed layer on the flange portion of the lens blank, respectively, are formed of different monomer compositions containing different polymerizable monomers, different sorts of compounding agents and/or additive agents, or different amounts (or contents) of those agents. Therefore, the first and second polymerized materials have different optical or physical properties. It is preferred that the first polymerized material be formed of a polymerizable composition suitable for the optical portion of an intraocular lens while the second polymerized material be formed of a polymerizable composition suitable for the support portion of the lens. In this preferred case, is obtained an excellent intraocular lens whose optical and support portions have good optical or physical properties. For example, the first polymerized material may be a colorless, transparent material formed of a polymerizable composition without a coloring agent, while the second polymerized material may be a colored material formed of a polymerizable composition containing a coloring agent. In this case, is produced an intraocular lens whose optical portion is colorless and transparent and whose support portion is colored. The first or second polymerized material may be formed of various polymerizable compositions which conventionally have been used for providing hard or soft materials for intraocular lenses. For example, a suitable hard or soft material may be obtained by polymerizing one or more of the following polymerizable monomers (hereinafter, regarding the expression of an acrylate or an acryl derivative, the term "(meth)acrylate" or "(meth)acryl-" is used to indicate two sorts of acrylates, i.e., acrylate and methacrylate, or two sorts of groups, i.e., acryl- and methacryl-, respectively): straight chain, branched chain, or cycloalkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, tert-pentyl (meth)acrylate, hexyl (meth)acrylate, 2-methylbutyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate; fluorine-containing (meth)acrylate derivatives; silicon-containing (meth)acrylate derivatives; styrene and its derivatives; fluorine-containing styrene derivatives; N-vinyllactam and its derivatives; hydroxyl group-containing (meth)acrylate derivatives such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, dihydroxypropyl (meth)acrylate, dihydroxybutyl (meth)acrylate, diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, and dipropylene glycol mono(meth)acrylate; (meth)acrylamide and its derivatives such as (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N, N-diethyl(meth)acrylamide, and N-ethylaminoethyl(meth)acrylamide. From the above-indicated monomers, one or more sorts of monomers may be selected and used. Alternatively, it is possible to obtain a "macromonomer" by polymerization of one or more monomers and use the macromonomer as a constituent of a polymerizable composition for the first or second polymerized material. Depending upon desired properties of the first or second polymerized material, a suitable monomer or monomers and, if appropriate, suitable proportions of the monomers may be selected and specified. A commonly used polymerizable ultraviolet absorbing agent and/or a polymerizable dye may be used as a polymerizable constituent or constituents of a polymerizable composition for the first or second polymerized material. Although according to the principle of the present invention it is possible to use as the first or second polymerized material a polymerized material without having crosslinking structure therein, it is preferred from the standpoint of shape stability to use, in particular as the second polymerized material providing the optical portion of the intraocular lens, a polymerized material which has crosslinking structure therein. The following crosslinking agents are preferably added to the polymerizable composition for the first or second polymerized material: 4-vinylbenzyl (meth)acrylate, 3-vinylbenzyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, allyl (meth)acrylate, and vinyl (meth)acrylate. From these agents, one or more sorts of crosslinking agents may be selected and used. It is possible to use, as a crosslinking agent, a macromonomer containing two or more polymerizable groups in the molecule thereof. It is preferred that the polymerizable composition for the first or second polymerized material contains 0.5 to 15 parts by weight, more preferably, 1 to 10 parts by weight, of the crosslinking agent per 100 parts by weight of all the polymerizable constituents of the composition. If the content of the crosslinking agent is higher than the upper limit, 15 parts by weight, the polymerized material produced suffers from brittleness and therefore weakness against stress caused by mechanical shock applied thereto. Meanwhile, if the content of the crosslinking agent is lower than the lower limit, 0.5 part by weight, the crosslinking agent fails to exhibit satisfactory crosslinking effect. In addition to the crosslinking agent, one or more sorts of known compounding agents and/or additive agents may be added to the polymerizable composition for the first or second polymerized material. Different polymerizable compositions for producing the first and second polymerized materials are produced by uniformly mixing one or more polymerizable monomers, crosslinking agent, compounding agent, and/or additive agent. The coloring agent added to the polymerizable composition for the first or second polymerized material may be a well known additive agent. A coloring agent is commonly added to the polymerizable composition for the second polymerized material, so as to allow a doctor to easily recognize the support portion of an intraocular lens to be implanted in patient's eye. According to the present invention, coloring agents are not limited to specific ones, although the coloring agents are required to have sufficient safety to human living. Any known dye or pigment may be used as a coloring agent. Preferable coloring agents are as follows: coloring matters used in the field of food and medicine, such as C.I. Acid Red 26 and C.I. Food Blue 2; direct dyes such as C.I. Direct Blue 237 and C.I. Direct Yellow 8; acid dyes such as C.I. Acid Blue 29 and C.I. Acid Black 2; basic dyes such as C.I. Basic Blue 5 and C.I. Basic Violet 1; vat dyes such as C.I. Vat Blue 18 and SOLUBILIZED C.I. Vat Blue 1; solvent dyes such as C.I. Solvent Violet 13 and C.I. Solvent Green 3; and disperse dyes such as C.I. Pigment Blue 15. In particular, the polymerizable dyes disclosed in Japanese Patent Application laid open under Publication No. 1-299560 are suitable for an intraocular lens, because those dyes are securely combined with the polymerized material. From the above indicated coloring agents, one or more are selected and added to the polymerizable composition for the first or second polymerized material. It is preferred that the polymerizable composition contain 0.01 to 30 parts by weight of the coloring agent. If the content of the coloring agent is below the lower limit, 0.01 parts by weight, the color produced thereby becomes too light. Meanwhile, if the content of the coloring agent exceeds the upper limit, 30 parts by weight, the coloring effect provided thereby saturates. In the latter case, the coloring agent may come out of the lens to the patient's tissue. In the case where a coloring agent which is hardly soluble or disperseable to the polymerizable composition, it is possible to additionally use a surface active agent and/or dispersing agent for promoting the solution or dispersion. Furthermore, a suitable polymerization initiator is added to the polymerizable composition thus prepared for the first or second polymerized material. Conventional polymerization processes may be employed for polymerizing the polymerizable composition. For example, it is possible to employ a thermal or heat polymerization process in which a radical polymerization initiator such as azobisisobutyronitrile or azobisdimethylvaleronitrile is mixed with the polymerizable composition and subsequently the composition is gradually heated from room temperature to about 130 o C in ten and several hours, so as to effect polymerization of the composition. In addition, a photopolymerization process may be used in which a photopolymerization initiator such as benzoin or methylorthobenzoyl benzoate is added to the polymerizable composition and then the composition is irradiated by light having wavelengths corresponding to the absorption band of the initiator, so as to polymerize the composition. Alternatively, it is possible to combine the thermal polymerization and photopolymerization techniques to polymerize the polymerization composition for the first or second polymerized material. Out of commonly used polymerization initiators, one or more sorts of initiators is/are selected and used. It is preferred that the polymerizable composition contain 0.001 to 5 parts by weight, more preferably 0.01 to 2 parts by weight, of the polymerization initiator per 100 parts by weight of all the polymerizable constituents of the composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the process according to the present invention, first, the polymerizable composition for the first polymerized material is polymerized into the first polymerized material. The first polymerized is then formed into a lens blank which includes a first portion providing the optical portion of an intraocular lens, and a flange portion surrounding the convex portion. Therefore, the intraocular lens as an end product has the optical portion which is free from distortion and accordingly possesses excellent optical properties. The lens blank may be formed into a variety of configurations or shapes depending upon desired shapes of intended lens products (i.e., intraocular lenses). For example, a lens blank 10 shown in Figs. 1A and 1B has a generally disc-like configuration. The lens blank 10 includes a convex portion 12 in a central portion thereof such that the convex portion 12 is concentric with the blank disc 10. The convex portion 12 has a partial spherical surface 13. The lens blank 10 further includes an annular flange portion 14 surrounding the outer periphery of the convex portion 12. Reference numeral 16 designates a continuous thick portion protruding from the outer periphery of the flange portion 14. The convex portion 12 and the continuous thick portion 16 cooperate with each other to define a generally annular groove 17 on the side of the part-spherical surface 13 of the convex portion 12. When the polymerizable composition for the second polymerized material is poured into the annular groove 17, the continuous thick portion 16 effectively prevents the composition from overflowing from the groove 17, thereby facilitating the pouring operation. The convex portion 12 of the lens blank 10 may have a cylindrical shape with a circular plane surface as shown in Fig. 2, or a generally cylindrical shape with a partial spherical surface as shown in Fig. 3. Alternatively, the convex portion 12 may have a prismatic shape. The flange portion 14 is not required to have the annular configuration as shown in Fig. 1A. The flange portion 14 may be provided at only a location or locations along the outer periphery of the convex portion 12 where a support portion or portions 26 (Fig. 6) of the intraocular lens is/are to be formed. The continuous thick portion 16 may be omitted as shown in Fig. 2 or 3. In this case, as shown in Fig. 4, a continuous frame member 20 may be applied to the outer periphery of the flange portion 14 of the lens blank 10, so that the convex portion 12 and the frame member 20 cooperate with each other to define a generally annular hollow space 21 on the side of the convex surface of the convex portion 12. This arrangement contributes to facilitating the application to the flange portion 14 of the polymerizable composition for the second polymerized material. Furthermore, as shown in Fig. 9, it is possible to form a lens blank including a plurality of convex portions 12 each of which provides an optical portion of an intraocular lens, and a plurality of flange portions 14 each of which surrounds a corresponding one of the convex portions 12. In this case, the polymerizable composition for the second polymerized material is applied onto the continuous flange portions 14 all at once, so that the second polymerized material is integrally combined with the lens blank 10. Before final shape working or machining (i.e., finishing), the convex portions 12 are separated from each other by cutting the continuous flange portions 14, so as to provide the independent convex portions 12, each of which subsequently is subjected to the finishing. The lens blank 10, as shown in Figs. 1 through 4, has dimensions slightly greater than those of an intraocular lens as an end product. If the dimensions of the lens blank 10 are excessively great, it takes much time and labor to remove unnecessary portions from the lens blank 10. It is therefore preferred that the convex portion 12 have a diameter or length of about 5 to 15 mm, that the lens blank 10 including the convex and flange portions 12, 14 except for the thick portion 16 have a diameter or length of about 10 to 20 mm, and that the height of the convex portion 12 as measured from the flange portion 14 be about 1 to 15 mm. The polymerizable composition for the second polymerized material is applied to one of opposite surfaces of the flange portion 14, that is, annular groove 17 (Fig. 1B) or annular hollow space 21 (Fig. 4). The surface 15 of the flange portion 14 is located on the side of the convex surface of the convex portion 12. The applied composition is polymerized by a suitable process to produce the second polymerized material, that is, a superposed layer 22 as shown in Fig. 5. The superposed layer 22 and the underlying flange portion 14 cooperate with each other to provide a double-layer portion. Since the applied composition is polymerized after partially having been impregnated into the convex portion 12 (and the flange portion 14), the superposed layer 22 is combined strongly with the convex portion 12, so that the superposed layer 22 is produced integrally with the convex portion 12. Since the convex portion 12 is stationary or fixed in position relative to the flange portion 14, the lens blank 10 is free from the problem of misalignment between before and after the polymerization of the applied composition to the superposed layer 22. Preferably, the composition for the second polymerized material is applied onto the flange portion 14 such that at least the top of the convex portion 12 is not covered by the applied composition or superposed layer 22, as shown in Fig. 5. In this situation, the convex portion 12 is easily distinguished from the superposed layer 22, and the center of working or machining of the lens blank 10 is easily found or specified based on the convex portion 12. In this case, the superposed layer 22 is formed such that the thickness of the layer 22 is smaller than the height of the convex portion 12. Usually, the thickness of the superposed layer 22 is selected at about 0.2 to 10.0 mm. After the superposed layer 22 has been formed as described above, the lens blank 22 is subjected to shape working including cutting and polishing to provide an intraocular lens as an end product as indicated in broken line shown in Fig. 5. Since the convex portion 12 is stationary in position relative to the lens blank 10 as a whole, as described above, the center of working is easily identified on the convex portion 14 by grasping the outer periphery of the lens blank 10, that is, outer periphery of the flange portion 14 or thick portion 16. The center of working coincides with the center of the convex portion 12. In the case where the superposed layer 22 is formed with the top of the convex portion 12 being left exposed, the center of working is easily specified by grasping the convex portion 12. The convex portion 12 and flange portion 14 of the lens blank 10 are respectively formed into an optical portion 24 and a pair of support portions 26 of an intraocular lens 28 as shown in Fig. 6. Each support portion 26 takes the form of a J-shaped hook. The shape working of the lens blank 10 is effected by using a precision instrument such as a commonly used fraise or milling machine. As emerges from the foregoing description, in the intraocular lens producing process according to the present invention, the convex portion 12 corresponding to the optical portion of an intraocular lens, is securely connected with the superposed layer 22 corresponding to the support portion of the lens 28. Thus, the present process enables production of an excellent intraocular lens of a one-piece type in which the optical and support portions thereof are securely combined with each other, notwithstanding that the optical and support portions are formed of different materials. In addition, since the convex portion 12 cannot be displaced relative to the lens blank 10 as a whole when the superposed layer 22 is formed on the lens blank 10, the lens blank 10 thus obtained does not suffer from the problem of misalignment of the center of the convex portion 12 with respect to the outer periphery of the lens blank 10. Therefore, based on the outer periphery of the lens blank 10 or, if appropriate, the convex portion 12, the center of working for forming the lens blank 10 into the end product 28, is easily identified. Thus, the present process is immune to the problem of "color misalignment" which has conventionally been encountered in the art. Example 1 97 Parts by weight of methyl methacrylate and 3 parts by weight of diethylene glycol dimethacrylate are mixed with each other, and then are polymerized to produce a crosslinked polymethyl methacrylate as the first polymerized material. The polymerized material is formed into a disc-like plate having a 20 mm diameter. With the outer periphery of the plate (i.e., outer periphery of protruding portion 16 thereof) being grasped, the plate is formed into a disc-like lens blank having dimensions (unit : mm) as indicated in Fig. 7. Meanwhile, 0.1 % of C.I. Solvent Violet 13 (coloring agent) and 0.2 % azobisisobutyronitrile (polymerization initiator) are added to methyl methacryate to thereby prepare a polymerizable composition for the second polymerized material. The composition is poured into an annular groove provided on flange portion 14 of the lens blank. The annular groove is covered with polyethylene film, and is kept at 50 o C for four hours. Thereafter, the temperature is raised from 50 o C to 110 o C in eight hours, so as to polymerize the composition and thereby form superposed layer 22 on the lens blank. Subsequently, the center of the lens blank is identified based on the outer periphery of protruding portion 16, and this center is used as the center of working by a fraise. Thus, an intraocular lens including colored support portions is produced. Example 2 A lens blank is formed of the same first polymerized material as that used in Example 1. Meanwhile, 54 g of methyl methacrylate, 45 g of trifluoroethyl methacrylate, 1 g of ethylene glycol dimethacrylate (crosslinking agent), and 0.1 g of azobisisobutyronitrile (polymerization initiator) are mixed with each other to thereby prepare a polymerizable composition for the second polymerized material. The thus prepared composition is poured into an annular groove provided on flange portion 14 of the lens blank. The annular groove is covered with polyethylene film, and is kept at 35 o C for 16 hours and then at 50 o C for six hours. Thereafter, the temperature is raised from 50 o C to 130 o C in 12 hours, so as to polymerize the composition. Subsequently, the center of the lens blank is identified based on the outer periphery of convex portion 12, and this center is used as the center of working by a fraise. Thus, an intraocular lens including optical and support portions formed of different materials is produced. Example 3 A disc-like lens blank having dimensions (unit : mm) indicated in Fig. 8 is formed of the same first polymerized material as that used in Example 1. Subsequently, a cylindrical frame member (not shown) having an inner diameter of 20 mm and an axial length of 4 mm is located around the outer periphery of flange portion 14 of the lens blank, so that an annular groove is defined between convex portion 12 and the cylindrical frame member. Meanwhile, 5 % of C.I. Pigment Blue 15 (coloring agent; disperse dye) and 0.2 % azobisisobutyronitrile (polymerization initiator) are added to methyl methacryate to prepare a polymerizable composition for the second polymerised material. The composition is poured into the annular groove provided on flange portion 14 of the lens blank. The lens blank is heated from 50 o C to 110 o C in eight hours, so as to polymerize the composition and thereby form a superposed layer on the lens blank. Subsequently, the center of the lens blank is identified based on the outer periphery of convex portion 12, and this center is used as the center of working by a fraise. Thus, an intraocular lens including colored support portions is produced. Example 4 A rectangular lens blank having dimensions (unit : mm) indicated in Fig. 9 and including four convex portions 12, is formed of the same first polymerized material as that used in Example 1. Meanwhile, 0.1 % of C.I. Solvent Green 3 (coloring agent) and 0.2 % azobisisobutyronitrile (polymerization initiator) are added to methyl methacryate to prepare a polymerizable composition for the second polymerized material. The composition is poured into an annular groove provided on flange portion 14 of the lens blank. The annular groove is covered with polyethylene film, and is kept at 50 o C for four hours. Thereafter, the temperature is raised from 50 o C to 110 o C in eight hours, so as to polymerize the composition and thereby form a superposed layer on the lens blank. From the rectangular lens blank, four disc-like lens blanks having a diameter of 20 mm are cut out such that each of the four lens blanks includes a convex portion 12 at a central part thereof and a double-layer portion surrounding the convex portion 12. The double layer portion consists of the flange portion 14 and the superposed layer formed of the second polymerised material. Subsequently, the center of each lens blank is identified based on the outer periphery of convex portion 12, and this center is used as the center of working by a fraise. Thus, an intraocular lens including colored support portions is obtained. Example 5 A lens blank similar to that used in Example 1 is formed of the same first polymerized material as that used in Invention Example 1. Meanwhile, 0.1 % of C.I. Solvent Violet 13 (coloring agent) and 0.8 % of 2-methyl-2-hydroxy-1-phenylpropane-1-one (photopolymerization initiator) are added to methyl methacryate to prepare a polymerizable composition for the second polymerized material. The thus prepared composition is poured into an annular groove provided on flange portion 14 of the lens blank. The annular groove is covered with polyethylene film, and is kept at a 20 cm distance under a 15W ultraviolet (UV) lamp for eight hours, so as to polymerize the composition and thereby form on the lens blank a superposed layer of the second polymerized material. Subsequently, the center of the lens blank is identified based on the outer periphery of protruding portion 16, and this center is used as the center of working by a fraise. Thus, an intraocular lens including colored support portions is produced. While the present invention has been described in detailed with respect to the presently preferred embodiments, it is to be understood that the present invention is by no means limited to the detailed particulars of the illustrated embodiments

Claims: A process of producing an intraocular lens (28) of a one-piece type in which the lens includes an optical portion (24) and at least one support portion (26) produced integrally with each other, the process being characterized by including the steps of: forming a first polymerized material into a lens blank (10), said lens blank including a first portion (12) for subsequently providing said optical portion of the intraocular lens, and a flange portion (14) surrounding said first portion, said first portion projecting upwardly from one surface of said flange portion; applying, to said surface of said flange portion (14) from which said first portion (12) projects, a monomer composition which is polymerizable to produce a second polymerized material (22) different from said first polymerized material, said monomer composition including at least one polymerizable monomer; polymerizing said monomer composition on said flange portion (14) to provide said lens blank with a double-layer portion (14, 22) having said flange portion (14) and said second polymerized material (22) produced from said monomer composition; and forming said first portion (12) and said double-layer portion (14, 22) of the lens blank, into said optical portion (24) and at least one support portion (26) of the intraocular lens, respectively. The process as set forth in claim 1, wherein said monomer composition comprises a coloring agent. The process as set forth in claim 1 or claim 2, wherein said monomer composition comprises a dye which is polymerizable with said at least one monomer. The process as set forth in any one of claims 1 through 3, wherein said monomer composition comprises a crosslinking agent. The process as set forth in any one of claims 1 through 4, wherein said lens blank (10) includes a continuous thick portion (16) protruding from an outer periphery of said flange portion (14) of the lens blank, said first portion (12) and said continuous thick portion cooperating with each other to define a generally annular groove (17) on the side of said one surface (15) of said flange portion. The process as set forth in any one of claims 1 through 5, wherein said lens blank (10) has a circular configuration. The process as set forth in any one of claims 1 through 5, wherein said lens blank (10) has a rectangular configuration. The process as set forth in any one of claims 1 through 7, wherein said first portion (12) of said lens blank has a partial spherical surface as an upper convex surface thereof. The process as set forth in any one of claims 1 through 7, wherein said first portion (12) of said lens blank has a cylindrical shape with a circular plane surface as an upper surface thereof. The process as set forth in any one of claims 1 through 7, wherein said first portion (12) of said lens blank has a cylindrical shape configuration with a partial spherical surface as an upper surface thereof. The process as set forth in any one of claims 1 through 4, further comprising the step of applying a continuous frame member (20) to an outer periphery of said flange portion (14) of said lens blank, said convex portion (12) and said frame member cooperating with each other to define a generally annular hollow space (21) on the side of said one surface (15) of said flange portion. The process as set forth in any one of claims 1 through 11, wherein the step of forming said lens blank comprises forming said lens blank including a plurality of said first portions (12) each of which respectively provides one said optical portion of the intraocular lens, and a plurality of flange portions (14) each of which surrounds a corresponding one of said convex portions; the step of applying said monomer composition comprises applying said monomer composition to said surface of said each flange portion from which said first portion projects;and the step of polymerizing said monomer composition comprises polymerizing said monomer composition on said surface of said each flange portion to provide said double-layer portion having said each flange portion (14) and said second polymerized material. The process as set forth in claim 12, further comprising the step of separating said plurality of first portions (12) from each other, so that the separate first portions are surrounded by the corresponding double-layer portions. The process as set forth in any one of claims 1 through 13, wherein the step of forming said at least one support portion (26) comprises forming said second polymerized material (22) as a layer of said double-layer portion (14, 22), into said at least one support portion. The process as set forth in any one of claims 1 through 14, wherein said at least one support portion of the intraocular lens (28) comprises a pair of J-shaped hooks (26) which are opposite to each other with respect to said optical portion (24).

Inventors: ICHIKAWA MAKOTO, IKEDA YOSHIYUKI, NAKADA KAZUHIKO, ICHIKAWA, MAKOTO, IKEDA, YOSHIYUKI, NAKADA, KAZUHIKO., Ichikawa, Makoto, c/o Menicon Co., Ltd., Ikeda, Yoshiyuki, c/o Menicon Co., Ltd., NAKADA, KAZUHIKO, C/O MENICON CO., LTD.
Applicants: MENICON CO LTD, MENICON CO., LTD.
Application year: 1992
Main classification: A61F2
IPC codes: B29D11, A61F2