Patent Publication Number: US-2022218522-A1

Title: Amniotic or placental preparation and device for ophthalmic use as dressing to enhance healing

Description:
BACKGROUND OF THE INVENTION 
     Treatment of ocular surface disorders requires medical and surgical intervention, both acutely and in the long term. Regardless of the underlying causes involved, the common goals of management include controlling inflammation and promoting ocular surface healing with maximal visual rehabilitation. Various medical therapies have been used to achieve these objectives, including amniotic membrane transplantation (AMT). [1] 
     Amniotic membrane (AM) graft has been used in ophthalmology for several indications because of its beneficial effects. Amniotic membrane is usually obtained from amniotic tissue derived from mammals, such as humans, pigs, or horses. Amniotic membrane is a biological membrane that lines the inner surface of the amniotic cavity and comprises a simple, cuboidal epithelium, a thick basement membrane, and an avascular mesenchymal layer containing hyaluronic acid. Amniotic membrane is known to reduce inflammation, fibrovascular ingrowth, and to facilitate epithelialization in animal and human models. Amniotic membrane is believed to play a role in the scarless wound healing process [2], [3] 
     Previous studies revealed that early intervention with AMT results in marked reduction of inflammation, rapid restoration of the ocular surface, and improved visual acuities while preventing cicatricial complications. [4] However, surgically performed AMT renders a relatively high cost and potentially unnecessary surgical trauma in such compromised eyes. Furthermore, the membrane patch usually dissolves within several days so that multiple sessions of AMT may be required. Previously, a self-retaining AM mounted on a double ring system has been effectively used to promote healing and reduce corneal scarring in a variety of ocular surface disorders, [5] however, patients experienced ocular discomfort from the ring and incomplete healing. [6] 
     Previous studies have also shown that topical amniotic membrane extract (AME) has comparable effect to AMT in promoting epithelialization, decreasing inflammation, and suppressing corneal neovascularization. [7] However AME lacks the physical characteristics of a bandage and as such it cannot be used as a patch graft. [8] Another previous approach to the use of amniotic proteins to treat ocular disease and injury is the application of amniotic fluid topically delivered to the eye. [9] A related technology are placental extracts that have been shown to have wound healing qualities. [10] 
     A related technology are corneal shields, which have been made from collagen. [11] Collagen corneal shields are a bandage lens device for ocular surface protection following surgery and in traumatic and nontraumatic corneal conditions. They are available with dissolution times up to 72 hours. The use of collagen corneal shields for drug delivery has been disclosed, by soaking the devices in a drug solution prior to application. Prior art collagen corneal shields have not been developed with the degradation times within the scope of this invention, and do not contain a mixture of a biodegradable carrier material as provided herein and an active ingredient comprising an amniotic extract, a placental extract, or a combination thereof. 
     A related technology is the PROKERA® SLIM, which is a self-retaining biologic corneal bandage made with cryopreserved amniotic membrane grafts fastened to an ophthalmic conformer. This product is aseptically processed from donated human placenta tissue. The PROKERA® SLIM is indicated for use in eyes in which ocular surface cells are damaged or underlying the stroma is inflamed or scarred. The PROKERA® SLIM includes a plastic ring that is not resorbable and must be removed. The PROKERA® SLIM can remain inserted in an eye for up to 29 days. Thus, as compared to the invention described herein, the PROKERA® SLIM is not fully resorbable and has non-resorbable parts that must be removed. A further shortcoming is that the amniotic membrane itself is not in the shape of a contact lens. Thus, the contact with the cornea is less than optimum. Moreover, the ring may cause discomfort. 
     None of the treatments or devices discussed above provides an effective, convenient application of amniotic and/or placental extracts to heal surface injuries to the cornea as is provided by the instant invention. 
     SUMMARY OF THE INVENTION 
     The invention described herein is a medical device for the treatment of diseases and injuries to the cornea of an eye, that may include a self-retaining patch that incorporates amniotic extract and/or placental extract preparations that is applied to the ocular surface using non-surgical means, does not require external mechanical support, is well tolerated by patients, and lasts for a controlled period of time to achieve the ultimate goal of using amniotic extract and/or placental extract preparations in treating ocular surface disorders. In an embodiment, the instant invention is fully resorbable and is not removed after insertion. The instant invention can be fabricated in forms that dissolve in a time ranging from 1 day to 30 days. 
     In an embodiment, the invention disclosed herein may be a multi-purpose ophthalmic patch incorporating amniotic extracts and/or placental extracts, mixed with or carried on a biodegradable material. In an embodiment, the amniotic patch is formed in the general shape of a contact lens that can easily be placed on the surface of the eye to act as a bandage and protect and enhance the healing of the ocular surface. In an embodiment, the patch contains an amniotic or placental material as an active ingredient that is released over a period of one to thirty days to effect healing of the cornea. The inventive patch may achieve the known therapeutic benefits of the amniotic membrane without the need for surgery or a retaining ring to eliminate surgery related complication as well as ring related discomfort. Moreover, the patch is designed with controlled rate of degradation, such that the time it is used for different ocular surface disorders can vary according to the desired treatment period. For instance, if long term treatment is desired, then a lens with a slow degradation rate may be utilized, whereas, if more short-term treatment is desired a lens having a faster degradation rate may be utilized. 
     In an embodiment, a method is provided of treating an ocular disease or injury in a patient having an ocular disease or injury, by providing a lens-shaped patch formed of biodegradable carrier material and an active ingredient comprising an amniotic extract and/or placental extract, the lens-shaped patch having a substantially convex exterior surface and a substantially concave interior surface; applying the lens-shaped patch to the patient&#39;s cornea, whereby the interior surface of the lens-shaped patch contacts the cornea; and allowing the lens-shaped patch to dissolve while on the patient&#39;s cornea. 
     In an embodiment, a lens-shaped patch is provided for application to the cornea of an eye for the treatment of diseases and injuries to the cornea of an eye. The patch may be formed into the shape of a contact lens, wherein the patch is a uniform mixture of a biodegradable carrier material comprising collagen from a mammalian source and an active ingredient comprising an amniotic extract, a placental extract, or a combination thereof; wherein an interior surface of the lens-shaped patch conforms to the external surface of the cornea and the lens-shaped patch adheres to the cornea, and wherein the lens-shaped patch degrades and completely dissolves while on the cornea and need not be removed, and wherein the patch treats a medical condition selected from dry eye syndrome, corneal trauma, corneal inflammation, corneal burn injury, or corneal ulcers. 
     The patch may be used to treat human or non-human mammal corneal diseases or injuries. The patch may have a controlled degradation time of between one and thirty days. 
     The lens-shaped patch may have 0.05% to 0.75% (w/w) riboflavin incorporated into the it, and the patch may be exposed to UV radiation to crosslink the riboflavin to adjust the degradation time. 
     In an embodiment, may be formed from a uniform mixture of a biodegradable carrier material comprising a poly (DL-lactide co-glycolide) copolymer carrier and an active ingredient comprising an amniotic extract, a placental extract, or a combination thereof; wherein an interior surface of the lens-shaped patch conforms to the external surface of the cornea and the lens-shaped patch adheres to the cornea, and wherein the lens-shaped patch degrades and completely dissolves while on the cornea and need not be removed, and wherein the patch treats a medical condition selected from dry eye syndrome, corneal trauma, corneal inflammation, corneal burn injury, or corneal ulcers. 
     In an embodiment, the inventive patch has veterinary applications. This patch can be useful in pets, for example dogs or cats that have suffered eye injuries, or in livestock and farm animals, such as horses, bovines, goats, sheep, swine, or camelids that have suffered corneal injuries. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cross-sectional schematic view of a contact lens-shaped patch according to an embodiment of the invention. 
         FIG. 2  is a prospective side view of a contact lens-shaped patch according to an embodiment of the invention. 
         FIG. 3  is a side perspective view of a contact lens-shaped patch positioned for insertion on an ocular surface according to an embodiment of the invention. 
         FIG. 4  is a front schematic view of a lens-shaped patch where the biological curative active ingredient is confined to a peripheral ring. 
         FIG. 5  is a graph of mass changes over time for ˜0.1 mm thick lens-patches containing 15% and 30% placental extract, respectively, and 50:50 PLGA. 
         FIG. 6 . Is a plot of the in vitro release of protein over 14 days from an inventive patch employing collagen as carrier. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The term “amniotic extract” herein means any of various preparations derived from amniotic membrane materials, including preparations derived from amniotic membrane, amniotic stroma and amniotic jelly (e.g. membrane particles obtained or purified via a suitable extraction/purification process such as pulverization or homogenization). Placental extracts of any of various sources may be used in different embodiments of this invention. Placenta extract or placenta membrane may be derived from any of various mammalian sources, including human, sheep, or bovine. Sheep placental extract (SPE) is available commercially. For many uses, human placental extract may be less antigenic for use in humans. The term “placental extract” herein means any of various preparations derived from mammalian, including human, placenta (e.g. placental particles obtained or purified via a suitable extraction/purification process such as pulverization or homogenization). In this invention, amniotic extracts or placental extracts may be used alone or they may be blended. Any of amniotic extract or placental extract, or blend thereof, may be alternatively referred to as the “active ingredient” herein. 
     In an embodiment, this invention provides a multi-purpose lens-shaped patch for application to the cornea of an eye for the treatment of diseases and injuries to the cornea of an eye, comprising. The patch may be “self-retaining” meaning that is adheres to the cornea without the use of external support or glues. The patch may be formed into the shape of a contact lens, wherein the patch is a uniform mixture of a biodegradable carrier material comprising collagen from a mammalian source and an active ingredient comprising an amniotic extract, a placental extract, or a combination thereof. An interior surface of the lens-shaped patch conforms to the external surface of the cornea and the lens-shaped patch adheres to the cornea. The lens-shaped patch degrades and completely dissolves while on the cornea and need not be removed. The patch may treat a number of medical conditions, including dry eye syndrome, corneal trauma, corneal inflammation, corneal burn injury, or corneal ulcers. 
     The lens-shaped patch may be used to treat human or non-human mammal corneal diseases or injuries. 
     The lens-shaped patch may have a controlled degradation time of between one and thirty days, or between three and thirty days, or between eight and thirty days. 
     As used herein, the word “about” means +/−20% of a stated value. 
     Matrix Support 
     In an embodiment of this invention, the active ingredients are supported by or associated with a biodegradable carrier, also termed herein a filler or matrix. In an embodiment, collagen is used as a matrix in this invention. Collagenous materials have sufficient structural strength for this invention to maintain a predefined shape and structural integrity during the use of the product, and active ingredients can be dissolved in a homogenous collagen mixture during manufacture. The biodegradable carrier active ingredient is formable into various shapes and configurations according to different embodiments of the invention. In particular, collagen is biodegradable and can be used as a solution or suspension during manufacture and cured to a sufficiently strong patch for this invention. The lens-shaped patch may be translucent or transparent. 
     This invention does not employ other conventional contact lens polymers, such as non-ionic polymeric materials, low-water ionic polymers, or high-water ionic polymers. None of these materials are resorbable which is a feature of this invention. 
     In an alternative embodiment, the material used as a carrier or matrix may be any of various natural or synthetic biodegradable materials or blends thereof. For instance, in one embodiment of the invention, a lens-shaped patch is formed of placental extract powder that is embedded in or carried on a poly (DL-lactide co-glycolide) copolymer carrier (termed herein PLGA or PLDG). The PLGA copolymer acts as a biodegradable carrier for the active ingredients. 
     In an embodiment of the invention, the biodegradable carrier is formed into substantially the shape and size of a conventional contact lens. A patch formed by combining active ingredients with a synthetic or natural biodegradable and casting the same into the general shape of a conventional contact lens may be referred to as a “lens-shaped patch” or “patch” or “lens patch” herein. The biodegradable carriers provide structural support for the shape and structural integrity of the lens-shaped patch. 
     In an embodiment, a lens-shaped patch for treating diseases and injuries to the cornea is provided, including a biodegradable carrier material and an active ingredient comprising an amniotic extract and/or placental extract, wherein the biodegradable material and amniotic and/or placental extract are combined and formed into the general shape of a contact lens. 
     In an embodiment, the base curvature of the lens-shaped patch is similar to or slightly greater than the curvature of the cornea. As such, the inner surface of the patch substantially conforms to the external surface of the cornea, and it adheres thereto allowing the patch to remain centered on the cornea. 
     In an embodiment of the invention, the inventive lens-shaped patch has a variable thickness and provides no magnification power or vision corrective properties. For example, the patch may have a thickness ranging between 0.040 mm and 0.20 mm and more preferably between 0.04 mm and 0.08 mm. In an embodiment, the lens is approximately 0.05 mm thick. The lens-shaped patch may be made in any of various diameters, preferably in the range of 14-24 mm. In order to conform to a medium-size cornea, the lens patch diameter is most preferably around 14 mm in diameter. The lens patch radius of curvature is within the range of 7.5-9 mm and most preferably a 7.8 mm radius of curvature. For example,  FIG. 1  shows a side cross-sectional view of a lens-shaped patch having a diameter of 14 mm and a 7.8 mm radius of curvature. Lens-shaped patch  10  has a substantially convex outer surface  12  and a substantially concave interior surface  14 .  FIG. 2  shows a perspective view of the lens-shaped patch embodied in  FIG. 1 .  FIG. 3  shows a lens-shaped patch  10  positioned to be inserted over the iris  16  of an eye  18 , so that the lens-shaped patch is in physical contact with cornea  17  on the eye. Lens patch  10  is applied with its inner concave surface  14  contacting the cornea. As shown, the lens patch is appropriately sized and shaped to substantially cover the entire surface of the iris  16 . 
     It will be understood by those of ordinary skill in the art that lens patches of other sizes may be molded to fit other eye geometries. In addition, where a numerical range is provided herein for any parameter, it is understood that all numerical subsets of that numerical range, and all the individual integer values contained therein, are provided as part of the invention. 
     For example, in an embodiment of this invention, a lens-shaped patch may be formed with a hole cut in the center of the lens to increase wearer visibility in that region. Alternatively, a small circular region of PLGA or collagen or other biodegradable polymer with no placental or amniotic extract may be placed in the center of the lens to increase wearer visibility.  FIG. 4  shows a lens-shaped patch  20  having a two regions, an outer peripheral ring region  22 , and an inner central region  24 . Outer peripheral ring  22  may contain active ingredients, whereas inner central region  24  may not. In one embodiment, inner central region  24  is a cutout. In another embodiment, inner central region  24  is carrier material (e.g. PLGA) without active ingredients. In either embodiment, the active ingredient is confined to the peripheral band  22 . 
     In an embodiment, the diameter of lens patch  10  is around 14 mm. The diameter of inner central region may be anywhere between 4 mm to 10 mm that allows sufficient light to pass through for reasonable vision. 
     In use, the lens-shaped patch is applied to a corneal surface like a contact lens and is not implanted or supported by external structures like a supporting ring. 
     In an embodiment, the inventive lens-shaped patch need not be removed. Rather, it may be designed to dissolve in place on a cornea into small bio-acceptable components that may either by absorbed by the body or washed out with the eye&#39;s natural processes. 
     In an embodiment of the invention, a poly(DL-lactide co-glycolide) copolymer is used as a biodegradable structural carrier material for the lens-shaped patch. Poly(DL-lactide co-glycolide) copolymer is an ester-terminated copolymer of lactide and glycolic acid (PLGA). In an embodiment, the ratio of lactide to glycolic acid is 50:50. Poly(DL-lactide co-glycolide) copolymers with different lactide to glycolide ratios may be used in different embodiments of the invention. Moreover, any of various biodegradable polymers may be used as an alternative to PLGA. For example, poly(DL-lactide-co-caprolactone), methoxy (polyethylene glycol)-b-poly(L-lactide), polylactide, polyglycolide, and other biodegradable polymers known in the art may be used in embodiments of the invention. 
     PLGA is commercially available, for example, via LACTEL Absorbable Polymers, Birmingham, Ala. PLGA has been used in medical devices, primarily as sutures or cell growth scaffolds. It should be noted that 50:50 PLGA described above provides an excellent balance of the following material qualities: mechanical modulus at 22° C., mechanical modulus at 37° C., &lt;1 month degradation rate at 37° C. in phosphate buffer, optical transparency, high solubility in common organic solvents, and overall material quality. 
     In addition to, or as an alternative to, synthetic carriers, natural biodegradable carrier materials may be used in different embodiments of the invention. For example, collagen obtained from any of various mammalian sources may be utilized in embodiments of the invention as a biodegradable structural material carrier. In an embodiment, collagen from a bovine flexor tendon is employed. Collagen may have the advantages of superior transparency as compared to PLGA polymers, and better oxygen permeability and higher water content. High water content is desirable in this invention and will cause high water transmission and high oxygen permeability. 
     The active ingredients (amniotic or placental extracts) may be bleached and finely ground to render them transparent or translucent. For example, placental extract may be bleached with a suitable solution, such as a solution of approximately 10% aqueous hydrogen peroxide for a period of about 24 hours. Thereafter, the water is removed (e.g. via freeze drying, vacuum drying, air drying), and the resultant placental extract is ground to a powder preferably with a particle size of less than 5 microns, or more preferably a particle size of less than 1.0 microns, or less than 0.1 microns. The degree of transparency or translucency may depend on several factors, including the degree of bleaching of extract powder and the particle size. 
     Plasticizers and other additives and/or active ingredients may be added in different embodiments of the invention. For example, plasticizers such as triethyl citrate, tributyl acetylacetate, glycerol, or the like may be added. 
     In an embodiment of the invention, a lens-shaped patch is formed of approximately 90% PLGA by weight and approximately 10% active ingredients by weight. In another preferred embodiment of the invention, the patch is formed of approximately 80% PLGA by weight and approximately 20% active ingredients by weight. Any of various plasticizers may be added in the range of 1-20% by weight. 
     The following are non-exhaustive possible ranges of respective biodegradable carrier, active ingredient and plasticizer:
         10-30% bleached, dried active ingredient, micronized to a particle size of about 5 microns to less than 1.0 microns;   50-90% 50:50 poly(DL-lactide co-glycolide) block copolymer (PLGA) or other biodegradable polymer(s);   0-20% other additives such as plasticizers, other active ingredients, etc.       

     In other embodiments of the invention, active ingredients may comprise as much as 50% of the lens-shaped patch by weight. In another embodiment, the biodegradable carrier may comprise more than 90% of the lens-shaped patch by weight. The following are non-limiting examples of such ranges:
         1-50% bleached, dried active ingredients, micronized to a particle size of about 5 microns to less than 1.0 microns;   20-99% 50:50 poly(DL-lactide co-glycolide) copolymer (PLGA) or other biodegradable polymer(s);   0-30% other additives such as plasticizers, other active ingredients, etc.       

     In one embodiment of the invention, the constituents of the lens-shaped patch (e.g. biodegradable polymer, active ingredient and any additives) are associated in a matrix or mixture with no covalent bonding or crosslinking of molecules. In this embodiment, the active ingredient is not chemically bound to the carrier material, active ingredient is not chemically bound to active ingredient, and carrier material is not chemically bound to carrier material. 
     PLGA matrices may have the advantages of scalability, controlled biodegradability based on resin selection, and a proven history of use as implants. However, PLGA may be less transparent and have higher haze, and lower oxygen permeability compared to embodiments with a collagen matrix. PLGA may also be more brittle than collagen lens patches. By contrast collagen carrier materials may have greater transparency than PLGA matrices, collagen may have superior oxygen permeability and a higher water capacity than PLGA, which are both desirable features. 
     Controlled Biodegradability 
     Depending on the nature of the ocular condition being treated, the treatment time will vary from a few days to several weeks. These treatment durations are determined by experienced clinicians. 
     Accordingly, the lens-shaped patches provided herein may be designed to degrade over a specified timeframe. That is, different lens patches may be specifically calibrated to degrade at pre-determined times, ranging from days to several weeks. The degradation time may be as short as one day and extend up to 30 days. In embodiments of this invention, the inventive lens-shaped patches completely dissolve and need not be removed after application. A specific degradation time may be selected, for example, by varying any of the following: the dissolvable polymer, the ratio of polymer to active ingredient, the plasticizer concentration and type, the thickness of lens patches or a combination of the foregoing. Alternatively or additionally, chemical curing processes may be performed, such as, crosslinking by gamma or e-beam sterilization, or a adding a chemical crosslinker. 
     The term degradation (or biodegradation) as used herein means the loss of mechanical integrity of the lens-shape patch, followed by the degraded material breaking into small portions that can either be absorbed by the body or slough off the eye in the form of tears. 
     Many biomedical polymers are sterilized with gamma radiation or e-beam sterilization techniques. In addition to preventing future microbial or viral growth, this sterilization has the effect of partially crosslinking collagen or PLGA polymers. This method may be used on the polymer/active ingredient matrix described herein to decrease the rate of degradation. That is, crosslinking by gamma or e-beam will make the polymer material more resistant to degradation and, as such, it may be extend the degradation time by up to 2-3 times depending on the total radiation level imposed by the gamma radiation or e-beam exposure. However, the dosage of gamma radiation or e-beam used for this purpose must be adjusted to maintain the biological activity of the active ingredients. 
     Additionally or alternatively, a chemical crosslinker could be used in a similar fashion. There are many biologically compatible, bi- and tri-functional chemical crosslinkers that are commercially available. These may include organic molecules terminated with azides, amines, bromides, maleimides, isocyanates, sulfides, and esters. Riboflavin is a crosslinker that can be incorporated into the inventive patch and crosslinked by exposure to UV radiation for several seconds to one hour to adjust the degradation time of the inventive patch. 
     Thickness 
     The patch lens may be formed of different thicknesses and/or geometries in different embodiments of the invention. For example, lenses may be between 0.02 mm and 0.2 mm thick. With thinner layers of the PLGA or collagen-based films, the overall degradation rate should be slightly faster since there is more surface area exposed to the 37° C. physiological environment and because mechanical failure (tearing through the thickness) will occur more quickly. However, degradation does not necessarily scale 1:1 with thickness because water can saturate into the polymer within hours of exposure. The biodegradation rate of a 0.1 mm PLGA patch lens is approximately 18-25 days. A lens patch of approximately 0.05 mm thickness will degrade in approximately 14-21 days. Thus, extending or reducing the degradation period may be achieved by respectively increasing or decreasing the patch lens thickness. 
     Active Ingredient Content 
     In an embodiment, the inventive patch incorporates and amniotic extract or a placental extract or a combination thereof. The weight of the amniotic and or placental extract may vary from 5% to 80% w/w. In an embodiment, the weight of the amniotic extract or a placental extract may be about 30%, about 40%, about 50%, about 60%, or about 70% w/w. 
     Control of degradation rates may also be affected by altering the concentration of active ingredients. For example, in a lens-shaped patch where amniotic and/or placental extract contents are below ˜40% by weight (˜40% by volume), most active ingredient particles will be dispersed and isolated within the biodegradable matrix. In this situation, the degradation rate will be slightly decreased as the active ingredient level goes from 0-40%, since the dissolution of active ingredients into the surrounding water-based region will lead to cavities in the PLGA matrix which will slightly increase degradation rates. However, this acceleration in degradation rate will be small, since the PLGA matrix will remain continuous. 
     For active ingredient contents above ˜50% by weight (˜50% by volume), the active ingredient particles will start to bridge a PLGA matrix, and dissolution of the PE particles will lead to the PLGA matrix to rapidly break down. It may be expected that if 50% or greater PE particles are added, degradation rates of the PE-PLGA film will be very fast, on the order of &lt;1 week. 
     Plasticizer Content 
     Yet another method mechanism of altering degradation rates is through the use of plasticizers. That is, when plasticizers such as triethyl citrate, tributyl acetylacetate, glycerol, etc. may be added to the polymer/active ingredient matrix, the degradation could be significantly accelerated. For example, the 50:50 PLGA has a glass transition temperature of ˜45-50° C. [LACTEL product literature], which is still above the 37° C. use temperature. Addition of a plasticizer will suppress the glass transition temperature to close to or below 37° C., leading to the PLGA being significantly softened and a much faster degradation time. With plasticizer at 1-20% by weight, a 0.1 mm thick PLGA film will degrade at 37° C. in phosphate buffer in 1-7 days. Thus, adding varying concentrations of plasticizers will accordingly allow for producing lens patches of varying degradation rates. 
     Other Features 
     Other additives and active ingredients may be used in different embodiments of the invention. For example, bioactive ingredients (pharmaceuticals or natural ingredients) that are known in the art to assist with healing and limit irritation may be included in addition to the placental or amniotic active ingredients. Biocompatible dyes may also be added to increase the visibility of the lens when being handled, prior to insertion in the eye. Finally, other biocompatible polymers that have a different biodegradation rate than the primary biocompatible polymer may be added. 
     In one embodiment of the invention, placental extract may be encapsulated in biodegradable polymer microcapsules (made of similar biodegradable polymer as discussed above), and then incorporated into an alternate polymer matrix. For example, these microcapsules could be placed in a traditional contact lens hydrogel and the release of placental extract would be dependent on biodegradation of the microcapsule walls, rather than biodegradation of the full bandage lens. 
     In some embodiments of the invention, the lens may incorporate varying thickness to provide a magnification power. Additionally, the lens radius of curvature may be changed to provide more or less centering force on the underlying cornea. The lens diameter may also be varied to fit different corneal sizes or to cover more of the sclera. 
     The inventive lens-shaped patches may be used to maintain the ocular surface health and to promote healing after injury due to inflammation, infection, trauma or surgery. Because the patch contains naturally active ingredients, and it degrades into bio-absorbable molecules, it is an ideal alternative to bandage contact lenses for protecting the eye. 
     Inventive lens-shaped patches also may be designed as a drug delivery system. For example, the lens patch may be impregnated or otherwise provided with drugs such as antibiotics, vitamins or other medicines that are to be applied to the eye. The drugs, as such, are delivered directly to a site where they are needed. As mentioned above, the timing of drug delivery may be manipulated by choosing a patch having a desired degradation rate. 
     Preparation 
     An embodiment of a degradable matrix or carrier material for this invention employs poly(DL-lactide-co-glycolide). 
     For example, PLGA can be dissolved in a suitable solvent (e.g. a blend of 95% acetone and 5% N,N-dimethylacetamide), and bleached sheep placental extract (SPE) (5% to 50% by weight compared to the PLGA) is added to this mixture. The mixture is homogenized, for example by wet ball milling until the mixture is transparent and uniform. This mixture is then cast onto a smooth, low energy surface (e.g., Teflon-coated glass) to produce a film of PLGA+SPE with a dry film thickness of 0.010-0.2 mm. The film is then carefully dried, first under room temperature air, and then under vacuum, until it is stiff and durable. The film is then thermoformed at 40-90° C. into the bandage lens-shaped patch and demolded at 0° C. A concave or convex thermoforming mold may be used. After thermoforming, the bandage lens may be trimmed or punched to the appropriate diameter. This solvent casting and molding process leads to a highly uniform, high optical transparency product. 
     In another embodiment, patch lenses may be produced by compounding the placental extract powder and PLGA at elevated temperatures, followed by hot pressing sheets, and finally, followed by thermoforming to lens shapes. Alternatively, extract powder and PLGA are compounded at elevated temperatures, followed by compression molding to lens shapes. In another alternative, extract powder and PLGA are injection molded at elevated temperatures into a lens cavity. 
     It has been demonstrated that in 37° C. phosphate buffer, a PLGA film containing 0-30% SPE and having a thickness of ˜0.1 mm exhibited significant softening after approximately 18 days. By 25 days, these same films had broken into fragments and with mechanical actions were easily decomposed. Thus, lens patches of ˜0.1 mm in thickness should degrade in the eye at ˜18-25 days. For example,  FIG. 5  shows a graph illustrating mass changes over time for ˜0.1 mm thick lens-patches containing 15% and 30% placental extract, respectively, and 50:50 PLGA. As shown, the mass decreases slightly over the first week, as the PE is leached out of the film and into the buffer solution. The mass then increases with time as the PLGA matrix swells with water as part of the degradation process. Note that this behavior may be modified for other mixtures of biodegradable polymer with the extract. 
     The 50:50 PLGA copolymer is known to degrade faster than other copolymers or homopolymers of lactide and glycolide. Water can diffuse through the matrix, and the PLGA degrades by the action of hydrolysis on the esters in the lactide/glycolide chains. This hydrolysis occurs much faster at 37° C. than at 22° C. 
     Another embodiment of this invention uses collagen as a carrier material. [12] In an embodiment, a form of collagen that is amenable to forming transparent membranes may be used. An embodiment of such a collagen is bovine flexor tendon collagen. [13] This form of collagen is supplied as a powder that can be dissolved in cold water at pH 2-3, and then blended with additional materials. The collagen can be blended with amniotic or placental extracts into a uniform and homogenous mixture and poured into molds and gelled at 5° C. over several hours to give transparent products that are resorbable when applied onto living tissue. 
     The rate of degradability of collagenous matrices can be controlled by the degree of crosslinking. The more highly crosslinked the material, the slower the degradation. The crosslinking can be a factor of the collagen itself, depending on the tissue source and chemical features of the extraction, or it can be adjusted by the use of an additive such as riboflavin and then UV irradiation, which crosslinks the collagen stands and retards the biodegradation. The degradation time can be adjusted to as long as 30 days. The amount of riboflavin can be 0.05% to 0.75% (w/w of the entire patch). The amount of riboflavin can be about 0.3%. 
     Therapeutic Utility 
     The amniotic extract and placental extracts in the lens-shaped patches employed in this invention reduce inflammation, reduce fibrovascular ingrowth, and facilitate epithelialization. These activities will have a healing effect for diseases and injuries to the cornea. This invention provides a method of treating an ocular condition, including providing a lens-shaped patch formed of biodegradable carrier material and an active ingredient comprising an amniotic extract and/or placental extract, where the lens-shaped patch has a substantially convex exterior surface and a substantially concave interior surface. The lens-shaped patch is applied to a patient&#39;s cornea, so that the interior surface of the lens-shaped patch contacts the cornea. The lens-shaped patch may be allowed to dissolve while on the patient&#39;s cornea. 
     The inventive lens-shaped patch may be used to therapeutically treat damaged or diseased cornea, limbus and surrounding conjunctiva, in addition to other wounds and conditions. For example, the patch may be used to promote healing after injury due to inflammation, infection, trauma or surgery and/or to treat dry eye or other ocular conditions. Any treatment and/or benefit imparted to a patient&#39;s cornea, limbus and/or surrounding conjunctiva is alternatively termed “treatment of an ocular condition” herein. 
     The following are non-limiting examples of methods of ocular treatment using the inventive lens-shaped patch: 
     Treatment of Dry Eye Syndrome 
     The inventive lens-shaped patch may be inserted into a patient&#39;s eye to treat ocular surface disorders associated with dry eye condition. With the patch so fitted in the eye, it will provide protection and enhance healing of ocular surface. Depending on the desired treatment duration, the patch will dissolve over time and eventually liquefy to provide additional lubrication to the healed ocular surface. The use of the lens-shaped patch may be repeated as needed to protect and maintain ocular surface health. This will provide a sustained level of treatment and may positively impact the quality of life. 
     Treatment of Ocular Surface Trauma Caused by Chemical or Thermal Injury (Burns) 
     The inventive lens-shaped patch has the potential to enhance healing of the damaged ocular surface. After copious irrigation of the injured surface and removing of any residual chemical particles, the patch will be applied to the ocular surface as a bandage contact lens. Other conventional treatment can be applied while the patch in place. And the size of the patch can be changed depends on the affected surface area. Multiple applications of a rapidly degraded lens can be applied during the acute phase. Slower degrading lens-shaped patches can be used thereafter. As the acute phase of this condition is extremely short, early intervention usually decreases the risk of blindness. 
     Treatment of Non-Healing Corneal Ulceration 
     The lens-shaped patch may be inserted into a patient&#39;s eye to as an adjunct in treating superficial corneal ulcers secondary to trauma, infection, disease of after surgery. Treatment of the underlying cause is recommended. 
     Post-Refractive Treatment 
     Postoperative complications after refractive surgery include pain, epithelial defect, and/or haze. The inventive lens patch may present an effective solution to solve these critical problems when inserted post photorefractive keratectomy (PRK). 
     The inventive method further includes the steps of determining a timeframe required for proper healing and/or treatment of an ocular condition (“heal rate”) and selecting a lens-shaped patch that has an expected degradation timeframe (degradation rate) that is the same as or greater than the expected heal rate. Once the determination of a heal rate is made, a clinician inserts a lens patch having a matching degradation rate or a patch having a degradation rate that is greater than the heal rate into the eye of a patient. The patient is then free to go home wearing the patch, which will dissolve on its own, potential averting the need to return to the doctor for removal, and also dispensing with the need for maintaining rings required in prior art systems. 
     The inventive device and method are also of utility for treating corneal injuries to non-human mammals, including pets and livestock. For example, the method can be used to treat ocular injuries in dogs, cats, horses, cattle, sheep, pigs, etc. 
     EXAMPLES 
     In embodiments of the invention, the inventive lens patches are formed as described below. 
     Example 1. Sheep Placental Extract-PLGA Lens-Shaped Patch 
     PLGA is dissolved in a suitable solvent (e.g. a blend of 95% acetone and 5% N,N-dimethylacetamide), and bleached sheep placental extract (SPE) (20% by weight compared to the PLGA) is added to this mixture and it is wet ball milled until the mixture is transparent. This mixture is then cast onto a smooth, low energy surface (e.g., Teflon-coated glass) to produce a film of PLGA+SPE with a dry film thickness of 0.040-0.050 mm. The film is then carefully dried, first under room temperature air, and then under vacuum, until it is stiff and durable. The film is then thermoformed at 70° C. into the bandage lens-shaped patch and demolded at 0° C. A concave or convex thermoforming mold may be used. After thermoforming, the bandage lens is trimmed or punched to the appropriate diameter. This solvent casting and molding process leads to a highly uniform, high optical transparency product. 
     Example 2. Bovine Collagen-SPE Lens Shaped Patch 
     A patch comprising 72.7% bovine flexor tendon collagen, 22% water, 5% sheep placental extract (SPE), and 0.3% riboflavin (all percentages w/w), was formed by first homogenizing and dissolving lyophilized collagen into a viscous mostly clear suspension in cold 1% acetic acid. The collagen was concentrated to 4% solids at 40-50° C. and filtered through a 25 μm polypropylene filter. SPE was homogenized in water at pH 9.0 with 0.1% poloxamer 407 (a hydrophilic non-ionic surfactant), filtered subsequently through 25 μm, 1 μm and 0.2 μm hydrophilic filters. The SPE content was assayed at about 4.5% solids by thermogravimetric analysis as brownish, clear liquid. Protein content was separately verified to be ˜2.4% per a Pierce BCA protein assay. 
     The collagen mixture, SPE mixture, and riboflavin were blended together into a uniform mixture in a ratio of 100:33:0.2 solids content. The pH was adjusted as needed, and the mixture was poured into two-sided polypropylene molds and refrigerated at 5° C. until gelled, approximately 1 hour. One side of the mold was removed, and the patches were then dried at room temperature for 24 hours. The water content of these patches was approximately 22% as measured by thermogravimetric analysis. The patches were irradiated under a low intensity UV-A lamp for 30 minutes to crosslink the collagen and riboflavin. The objective of this experiment was to make a lens that degraded in about 14 days. 
       FIG. 6  shows a plot of in vitro protein release from the inventive contact lens shaped patch of this example. Fourier Transform Infrared Spectroscopy (FTIR) was performed on dried solids from sheep placenta extract solution. Pierce BCA Protein Assay was performed on sheep placenta extract solution. Original liquid (4.5% solids) was determined to contain 2.4% protein. Based on batch sheets for lens fabrication, each 0.1 mm thick 8.4 mm×15 mm lens (total mass˜29 mg) is calculated to contain ˜0.81 mg sheep placenta protein and ˜27.5 mg collagen (which is itself mostly protein). Protein assay over 14 days is plotted in  FIG. 6 , and shows significant release of protein into solution on day 1, followed by a plateau as time approaches 14 days in PBS buffer at 37° C. There was significant release of protein into solution on day 1, followed by a plateau as time approaches 14 days. At 14 days, 15.7 mg of protein was released from a lens (n=3, average of all data points). Since this exceeds the original quantity of 0.81 mg of SPE, these results suggest that both sheep placenta and collagen protein has been released into the buffer solution. The lens was not completely dissolved at 14 days. However, in clinical practice, there are active mechanisms such as tearing, blinking, and enzymatic activity that can cause a lens such as this to degrade. 
     The patch of this example has a water content of 22% when dried and ready for use. In vitro, this lens had a water content of 77% when soaked in phosphate buffered saline for 1 hour, and 66% when soaked in phosphate buffered saline for 24 hours. 
     For storage, this lens can be frozen or dried to &lt;10% water content. 
     REFERENCES 
     
         
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