BRIEF SUMMARY OF THE INVENTION
The present invention is directed to customized lenses and a method for making them. In one embodiment, lenses are provided whose optical properties can be customized through the use of external stimuli such as light or other radiation.
BACKGROUND OF THE INVENTION
The most common method for correcting vision is through the use of corrective lenses, e.g., spectacles, contact lenses, and intraocular lenses. In the case of each of these lenses, the lenses are prefabricated with a specific set of optical properties, mostly optical power.
In some cases, the lenses are capable of some post-fabrication modification (e.g., grinding of lenses). In many cases, the lenses must be prefabricated to a specific power or diopter. In still other instances, the desired optical properties must be estimated and the lenses specifically fabricated. The latter process can be time-consuming and inexact.
The typical solution to this problem has been the maintenance of an inventory of lenses with a wide assortment of optical powers. For example, an optometrist often maintains a large inventory of contact lenses having different diopter values so that prescriptions can be quickly filled. When a lens is out of stock or when a patient requires a custom lens, special orders must be made, causing delays in dispensing the lens.
Thus, there exists a need for lenses which can be readily customized to fit the patient's needs. In this manner, precise correction of the patient's vision can be performed without significant delay or expense.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
SUMMARY OF THE INVENTION
Customizable lenses are provided whose optical properties can be adjusted post-manufacture without the addition or removal of material from the lens. The lenses are self-contained units having dispersed therein a modifying composition (“MC”) which, when exposed to an external stimulus, changes the optical properties of the lens.
As used herein, the term “self-contained” means that the lenses are self supporting and contain all the elements necessary to affect the change in optical properties without the addition or removal of modifying compositions. For example, in the preferred embodiment, the lenses comprise a fully or partially cross-linked polymer matrix having MCs dispersed throughout the matrix. Only the exposure of a portion of the MC to an external stimulus followed by the polymerization of the MC within the matrix in the said portion is required to affect the changes in optical properties. No modifying composition is added or removed from the lens to induce the change in properties.
A method for preparing customized lenses is also provided. In the method, the correction requirements of the patient is determined. A lens containing a modifying composition is selected. The lens is then exposed to an external stimulus in a manner that the optical properties of the lens are changed so as to provide the desired vision correction. The lenses are then dispensed to the patient. Adjustments can be made without adding or removing modifying composition.
DETAILED DESCRIPTION OF THE INVENTION
Corrective lenses are provided which can be customized, post-manufacture, to suit the specific needs of the user. The optical properties of the lenses can be modified without the addition or removal of materials from the lens.
The lenses contain a MC dispersed throughout the lens. The MC is capable of stimulus-induced polymerization and can freely diffuse or migrate within the lens.
In one embodiment, the lens is formed from a first polymer matrix which has the MC dispersed throughout. The first polymer matrix gives the lens its basic shape as well as its physical properties, such as hardness, clarity, flexibility and the like.
The nature of the first polymer matrix and the MC will vary depending upon the end use contemplated for the optical element. However, as a general rule, the first polymer matrix and the MC are selected such that the components that comprise the MC are capable of diffusion within the first polymer matrix. Put another way, a loose first polymer matrix will tend to be paired with larger MC components and a tight first polymer matrix will tend to be paired with smaller MC components. While the FPM generally comprises a crosslinked matrix, the FPM need not be fully crosslinked, but may be partially crosslinked. The only requirement is that the FPM be self suupportive and allow the diffusion of the MC within the FPM and allow the crosslinking of MC upon exposure to the appropriate stimulus.
Upon exposure to an appropriate energy (e.g., heat or light), the MC typically forms a second polymer matrix in the exposed region of the optical element. The presence of the second polymer matrix changes the material characteristics of this portion of the optical element to modulate its refraction capabilities. In general, the formation of the second polymer matrix typically increases the refractive index of the affected portion of the optical element. After exposure, the MC in the unexposed region will migrate into the exposed region over time. The amount of MC migration into the exposed region is time dependent and may be precisely controlled. If enough time is permitted, the MC components will re-equilibrate and redistribute throughout optical element (i.e., the first polymer matrix, including the exposed region). When the region is re-exposed to the energy source, the MC that has since migrated into the region (which may be less than if the MC were allowed to re-equilibrate) polymerizes to further increase the formation of the second polymer matrix. This process (exposure followed by an appropriate time interval to allow for diffusion) may be repeated until the exposed region of the optical element has reached the desired property (e.g., power, refractive index, or shape).
The first polymer matrix is a covalently or physically linked structure that functions as an optical element and is formed from a first polymer matrix composition (“FPMC”). In general, the first polymer matrix composition comprises one or more monomers that upon polymerization will form the first polymer matrix. The first polymer matrix composition optionally may include any number of formulation auxiliaries that modulate the polymerization reaction or improve any property of the optical element. Illustrative examples of suitable FPMC monomers include acrylics, methacrylates, phosphazenes, siloxanes, vinyls, homopolymers and copolymers thereof. As used herein, a “monomer” refers to any unit (which may itself either be a homopolymer or copolymer) which may be linked together to form a polymer containing repeating units of the same. If the FPMC monomer is a copolymer, it may be comprised of the same type of monomers (e.g., two different siloxanes) or it may be comprised of different types of monomers (e.g., a siloxane and an acrylic).
In one embodiment, the one or more monomers that form the first polymer matrix are polymerized and cross-linked in the presence of the MC. In another embodiment, polymeric starting material that forms the first polymer matrix is cross-linked in the presence of the MC. Under either scenario, the MC components must be compatible with and not appreciably interfere with the formation of the first polymer matrix. Similarly, the formation of the second polymer matrix should also be compatible with the existing first polymer matrix. Put another way, the first polymer matrix and the second polymer matrix should not phase separate and light transmission by the optical element should be unaffected.
As described previously, the MC may be a single component or multiple components so long as: (i) it is compatible with the formation of the first polymer matrix; (ii) it remains capable of stimulus-induced polymerization after the formation of the first polymer matrix: and (iii) it is freely diffusable within the first polymer matrix. In preferred embodiments, the stimulus-induced polymerization is photoinduced polymerization.
The inventive lenses comprises a first polymer matrix and a MC dispersed therein. The first polymer matrix and the MC are as described above with the additional requirement that the resulting lens be biocompatible.
Illustrative examples of a suitable first polymer matrix include: polyacrylates such as polyalkyl acrylates and polyhydroxyalkyl acrylates; polymethacrylates such as polymethyl methacrylate (“PMMA”), a polyhydroxyethyl methacrylate (“PHEMA”), and polyhydroxypropyl methacrylate (“HPMA”); polyvinyls such as polystyrene and polyvinylpyrrolidone (“NVP”); polyvinyl alcohols with polymerizable end groups such as methacrylate side groups; polysiloxanes such as polydimethylsiloxane; polyphosphazenes, and copolymers thereof. U.S. Pat. No. 4,260,725 and patents and references cited therein (which are all incorporated herein by reference) provide more specific examples of suitable polymers that may be used to form the first polymer matrix.
In embodiments where flexibility is desired (e.g., contact lenses), the first polymer matrix generally possesses a relatively low glass transition temperature (“Tg”) such that the resulting lens tends to exhibit fluid-like and/or elastomeric behavior, and is typically formed by cross-linking one or more polymeric starting materials wherein each polymeric starting material includes at least one cross-linkable group. In other embodiments, flexibility is less important (e.g., spectacle lenses). In this case, the monomers are such that the finished lens has a Tg of >25° C. In another embodiment, the FPM and MC are dissolved in a suitable medium. The solution is then exposed to an external stimulus causing the crosslinking of the FPM and some of the MC to form a self supporting structure being MC dispersed therein. The optical properties of the lens are then modified by the re-exposing the lens to the external stimulus. This causes further polymizeration of the full MC and inducing changes in the lens with manner described above. Alternatively, if the MC has already been crosslinked, if there are additional reactive groups present, further crosslinking can occur inducing additional changes in optical properties.
Illustrative examples of suitable cross-linkable groups include but are not limited to hydride, acrylate, methacrylate, acetoxy, alkoxy, amino, anhydride, aryloxy, carboxy, enoxy, epoxy, halide, isocyano, olefinic, and oxine. In one preferred embodiments, each polymeric starting material includes terminal monomers (also referred to as endcaps) that are either the same or different from the one or more monomers that comprise the polymeric starting materials but include at least one cross-linkable group. In other words, the terminal monomers begin and end the polymeric starting material and include at least one cross-linkable group as part of their structure. In second preferred emodiments, each polymeric starting material has crosslinkable groups present either at the terminal ends or side groups or both which can crosslink to form the network (e.g. CIBA's patents—crosslinking occurs via the reactive side grouips along the polymer backbone. In one preferred embodiment, the mechanism for cross-linking the polymeric starting material preferably is different than the mechanism for the stimulus-induced polymerization of the components that comprise the MC. For example, if the MC is polymerized by photoinduced polymerization, then it is preferred that the polymeric starting materials have cross-linkable groups that are polymerized by any mechanism other than photoinduced polymerization.
In an alternative embodiment, the polymerization mechanism for the MC and the starting materials for the first polymer matrix can be the same, but the rates of polymerization must be different such that the first polymer matrix is substantially complete before significant amounts of MC have been polymerized. For example, where photopolymerization is used to form the first polymer matrix and to polymerize the MC, the starting material for the first polymer matrix may contain reactive methacrylate groups as the polymerizable moiety whereras the MC may contain reactive acrylate groups. These groups photopolymerize at significantly different rates allowing the formation of the first polymer matrix before significant amounts of the MC have polymerized.
An especially preferred class of polymeric starting materials for the formation of the first polymer matrix is polysiloxanes (also known as “silicones”) endcapped with a terminal monomer which includes a cross-linkable group selected from the group consisting of acetoxy, amino, alkoxy, halide, hydroxy, and mercapto. Because silicone IOLS tend to be flexible and foldable, generally smaller incisions may be used during the IOL implantation procedure. An example of an especially preferred polymeric starting material is bis(diacetoxymethylsilyl)-polydimethysiloxane (which is polydimethylsiloxane that is endcapped with a diacetoxymethylsilyl terminal monomer).
Another class of materials that may be useful in forming the lenses of the invention are acetal derivatives of polyvinyl alcohols PVAs having crosslinkable end groups such as methacrylate groups along the backbone of the PVA. Illustrative examples of such materials are described in U.S. Pat. No. 5,508,317, the teachings of which are incorporated by reference. The derivatized PVA should have a molecular weight of at least 10,000.
Still another class of materials that may be useful in the practice of the invention are polyhydroxymethacrylates (poly(HEMA)) having polymerizable groups such as those described in U.S. Pat. Nos. 4,495,313 and 4,680,336, the teachings of which are hereby incorporated by reference. The (poly(HEMA)s) should have a molecular weight of at least 10,000.
The MC that is used in fabricating IOLs is as described above except that it has the additional requirement of biocompatibility. The MC is capable of stimulus-induced polymerization and may be a single component or multiple components so long as: (i) it is compatible with the formation of the first polymer matrix; (ii) it remains dispersed in the FPM and is capable of stimulus-induced polymerization after the formation of the first polymer matrix; and (iii) it is freely diffusable within the first polymer matrix. In general, the same type of monomers that are used to form the first polymer matrix may be used as components of the MC. However, because of the requirement that the MC monomers must be diffusable within the first polymer matrix, the MC monomers generally tend to be smaller (i.e., have lower molecular weights) than the monomers which form the first polymer matrix. In addition to the one or more monomers, the MC may include other components such as initiators and sensitizers that facilitate the formation of the second polymer matrix.
Because of the preference for flexible and foldable IOLs and flexible contact lenses, an especially preferred class of MC monomers is polysiloxanes endcapped with a terminal siloxane moiety that includes a photopolymerizable group. An illustrative representation of such a monomer is:
wherein Y is a siloxane which may be a monomer, a homopolymer or a copolymer formed from any number of siloxane units, and X and X1
may be the same or different and each contain a moiety that includes a photopolymerizable group. Illustrative examples of Y include:
wherein: m and n are independently each an integer and R1, R2, R3, and R4, are independently each hydrogen, alkyl (primary, secondary, tertiary, cyclo), aryl, or heteroaryl. In preferred embodiments, R1, R2, R3, and R4, is a Cl-C10 alkyl or phenyl. Because MC monomers with a relatively high aryl content have been found to produce larger changes in the refractive index of the inventive lens, it is generally preferred that at least one of R1, R2, R3, and R4 is an aryl, particularly phenyl. In more preferred embodiments. R1, R2, R3 are the same and are methyl, ethyl or propyl and R4 is phenyl.
Illustrative examples of X and X1
and X depending on how the MC polymer is depicted) are
R5 and R6 are independently each hydrogen, alkyl, aryl, or heteroaryl; and
Z is a photopolymerizable group.
In preferred embodiments R1 and R6 are independently each a C1 and C10 alkyl or phenyl and Z is a photopolymerizable group that includes a moiety selected from the group consisting of acrylate, allyloxy, cinnamoyl, methacrylate, stibenyl, and vinyl. In more preferred embodiments, R5 and R6 is methyl, ethyl, or propyl and Z is a photopolymerizable group that includes an acrylate or methacrylate moiety.
In addition to the silicone-based MCs described above, acrylate-based MC can also be used in the practice of the invention. The acrylate-based macromers of the invention have the general structure
X-An-A1 m-Q-A1 m-An-X1
wherein Q is an acrylate moiety capable of acting as an initiator for Atom Transfer Radical Polymerization (“ATRP”), A and A1
have the general structure:
wherein R7 is selected from the group comprising alkyls, halogenated alkyls, aryls and halogenated aryls, and R8 equals H, CH3, alkyl, and fluoroalkyl, and X and X1 are groups containing photopolymerizable moieties and m and n are integers.
In one embodiment the acrylate based MC has the formula
wherein R9 is selected from the group comprising alkyls and halogenated alkyls R10 and R11 are different and are selected from the group consisting of alkyls, halogenated alkyls, aryls and halogenated aryls, x and x1 are as defined above and is either zero or an interger.
In especially preferred embodiments, an MC monomer is of the following formula:
wherein x and x1
are the same and R1
, and R4
are as defined previously. Illustrative examples of such MC monomers include dimethylsiloxane-diphenylsiloxane copolymer endcapped with a vinyl dimethylsilane group; dimethylsiloxane-methylphenylsiloxane copolymer endcapped with a methacryloxypropyl dimethylsilane group; and dimethylsiloxane endcapped with a methacryloxypropyldimethylsilane group. Although any suitable method may be used, a ring-opening reaction of one of more cyclic siloxanes in the presence of triflic acid has been found to be a particularly efficient method of making one class of inventive MC monomers. Briefly, the method comprises contacting a cyclic siloxane with a compound of the formula:
in the presence of triflic acid wherein R5, R6, and Z are as defined previously. The cyclic siloxane may be a cyclic siloxane monomer, homopolymer, or copolymer. Alternatively, more than one cyclic siloxane may be used. For example, a cyclic dimethylsiloxane tetramer and a cyclic methyl-phenylsiloxane trimer are contacted with bismethacryloxypropyltetramethyldisiloxane in the presence of triflic acid to form a dimethyl-siloxane methyl-phenylsiloxane copolymer that is endcapped with a methacryloxylpropyl-dimethylsilane group, an especially preferred MC monomer.
In another embodiment, where the first polymer matrix is formed from derivatized PVAs of from (poly(HEMA)s with reactive groups, the MC may be formed from the same compositions, but with significantly lower molecular weights (i.e. ˜1,000) and with reactive groups which polymerize via a different mechanism, or at a substantially different rate. In one embodiment, the first polymer matrix is formed by the photopolymerization of an acetal derivatized PVA having reactive methacrylate side groups. The derivaized PVA has a molecular weight of about 10,000. In this case, the MC may comprise a similar derivatized PVA with a lower molecular weight (˜1,000) and having reactive acrylate side groups. Upon exposure to photoradiation, the higher molecular weight derivatized PVA will polymerize faster than the MC forming the polymer matrix before significant amounts of the MC have been polymerized. This creates a polymer matrix with free MC dispersed therein. The free MC is then available for further polymerization as part of the customization process. Similar results may be achieved using high and low molecular weight (poly(HEMA)s with different polymerizable side groups.
As discussed above, the stimulus-induced polymerization requires the presence of an initiator. The initiator is such that upon exposure to a specific stimuli, it induces or initiates the polymerization of the MC. In the preferred embodiment, the initiator is a photoinitiator. The photoinitiator may also be associated with a sensitizer. Examples of photoinitiators suitable for use in the practice of the invention are acetophenones (e.g., substituted haloaceto phenones and diethoxyacetophenone); 2,4-dichloromethyl-1,3,5-triazines; benzoin methyl ether; and O-benzoyl oximino ketone.
Suitable sensitizers include p-(dialkylamino aldehyde); n-alkylindolylidene; and bis [p-(dialkyl amino) benzylidene] ketone.
In practice of the invention, lenses are prefabricated in the manner described above. These lenses are then modified based on the patient's specific needs in the following manner.
First, the patient is examined to determine the individual's specific optical needs. This examination is the same as routinely conducted by ophthalmologists and optometrists. It may involve autorefraction, wavefront based aberrometric analysis, surface topography, and the like.
Based on the results of the examination, a prescription is developed, specifying the desired properties for the lenses. This can include correction for myopia, astigmatism and the like. Once these correction values have been determined, an unmodified lens is then exposed to an external stimulus in a pattern and at sufficient intensity to induce the desired changes in the lenses. Once the desired properties have been achieved, the lenses are dispersed to the patient.
The lens is modified by exposing the lens to an external stimulus in a pattern to modify the optical properties of the lens to correct the vision of the patient. This is accomplished by either altering the refraction index of the lens or by changes in the shape of the lens, or both. In the preferred embodiment, the change in refraction is caused by polymerization of MC in at least a portion of the lens coupled with migration of unpolymerized MC within the lens to reestablish a uniform concentration of MC throughout the lens. Polymerization of the MC causes the creation of a second polymer matrix in the exposed region. This second polymer matrix causes a change in the optical properties of the lens in the exposed region. The migration of unpolymerized MC causes swelling of the lens in the exposed region. This in turn alters the shape of the element, again changing the optical properties. When the UV source is removed, the unpolymerized MC in the unexposed lens will migrate within the lens to reestablish equilibrium. This in turn can cause a change in the shape of the lens. This change in shape causes further changes in the optical properties of the lens. Whether a change in shape occurs depends, in part, on the flexibility of the lens, which in turn depends in part on the Tg of the polymer used to form the first polymer matrix or due to the plasticization of the FPM by a medium or a plasticizer or MC. If the polymer has a low Tg, then the lens will be flexible and a more pronounced shape change will occur. If the polymer has a high Tg, then the lens will be less flexible and less shape change will occur. When no shape change occurs, the change in optical properties will occur strictly based on the change in refractive index caused by the localized polymerization of the MC. The changes occur in specific regions within the lens allowing for the creation of customized lenses, including multifocal lenses.
In a preferred embodiment, the MC with a photopolymerizable group is associated with a polymerization initiator which responds to ultraviolet light. In this case, the lens blank is exposed to ultraviolet light in a pattern to achieve the desired changes in optical properties of the lens.
The lenses of the invention are preferably formed by forming the first polymer matrix in a predetermined form in the presence of the MC. In this embodiment, the starting materials for the first polymer matrix and the MC as well as any necessary adjuvants and catalysts or initiators are combined in a mold in the shape of the desired lens or element. The first polymer matrix is then formed by polymerizing the starting materials. As discussed above, the mechanism used to polymerize the starting material must be such that it does not cause significant polymerization of the MC. While some polymerization of the MC may occur, it should not deplete the amount of free MC in the lens to a level where no change of optical properties can be accomplished through the polymerization of the remaining MC. For this reason, the mechanism used to polymerized the starting materials for the first polymer matrix should be different that that used to polymerize the MC or the polymerization rate for the starting materials should be significantly greater for the starting materials than for the MC.
Polymerization of the starting materials continues until the supply of starting materials is exhausted or the first polymer matrix is such that it forms a self-contained, self supporting structure. By forming the matrix in the presence of the MC, the MC becomes dispersed within the matrix. The lens is then removed from the mold and is ready for further customization. This is accomplished by exposing the lens to external stimuli as described above.
The following is an example of a method that can be used to form the adjustable lenses useful in the practice of the invention. Silicone based first polymer matrix starting materials comprising a vinyl endcapped silicone macromers and hydroxyl endcapped organosilicon compounds are combined in a mold with a silicone based MC such as those described above. A photoinitiator and a catalyst are also added to the composition as well as any required adjuvants such as UV absorbers and the like. Upon addition of the catalyst, the silicone based starting materials polymerize to form the first polymer matrix leaving the MC, photoinitiator and other components unaffected and dispersed within the matrix. The MC can then be exposed to a suitable light source and polymerized causing he desired change in optical properties.
In an alternative embodiment, an aqueous solution of high molecular weight (>10,000) derivatized PVA (dPVA) with reactive methacrylate side groups and low molecular weight (˜1,000) dPVA with reactive acrylate side groups and a photoinitiator is place in a mold. The low molecular weight dPVA is the MC in this embodiment. The solution is than exposed to ultraviolet light such that the high molecular weight dPVA polymerizes to form the first polymer matrix. While some of the low molecular weight dPVA may also polymerize, a significant portion remains unpolymerized when the matrix is formed along with some of the free methacrylate groups on the high DPVA may remain free. This unpolymerized low molecular weight dPVA is the free to be polymerized at a later time, thereby causing changes in the optical properties of the lens. In a similar manner, PHEMA abased system can be used where the high molecular weight component has reactive methacrylate groups and the low molecular weight components contain acrylate based groups.
The methods for forming the lenses are illustrative of the techniques that may be used in the practice of the invention. Other methods for forming lenses useful in the practice of the invention are know to those skilled in the art.
The method of the invention can be used to dispense ophthalmic lenses which include corrective spectacles and contact lenses. In this embodiment, the user of the lens is first examined to determine the optical requirements for the lenses. This is done through standard ophthalmologic examination methods such as visual acuity testing, and the like.
Once the optical requirements of the lens are determined, a lens is selected and then exposed to an external stimulus in a pattern and at an intensity so as to produce the desired changes in optical properties. For example, for a patient with hyperopia, the central portion of the lens is exposed to the stimulus or a profiled beam that causes polymerization to occur at a desired depth wise and site specific. In the case of myopia, the outer edges of the lens are exposed or a profiled beam that causes polymerization to occur at a desired depth wise and site specific. Presbyopia can be corrected by exposing the lens in a pattern of concentric rings, thereby creating a multifocal lens. Astigmatism can also be corrected through the use of the appropriate pattern along a certain meridian.
In one embodiment, the customization of the lenses is accomplished at a central facility or distribution point. In this embodiment, the lens requirements are transmitted to the distribution point, a set of lenses is selected, and each lens is separately exposed to an external stimulus to produce the desired changes in optical properties and the distribution facility then sends the customized lenses to the dispensing location.
In an alternative embodiment, the lenses are customized at the dispensing location. In this instance, once the desired lens properties have been determined, a lens is then modified in the manner described above to create a customized lens that meets the requirements of the patient. This second embodiment allows for more precise customization of the lens. In the case of corrective lenses or contact lenses, it is possible to prepare a customized lens, allow the patient to wear the lens, evaluate the vision correction with the lens and, if necessary, further change the optical properties to optimize the correction of the lenses.