WO2014089548A1

WO2014089548A1 - Oculoplasty grafts

Info

Publication number: WO2014089548A1
Application number: PCT/US2013/073809
Authority: WO
Inventors: David Myung; Christopher N. Ta
Original assignee: The Board Of Trustees Of The Leland Stanford Junior University
Priority date: 2012-12-07
Filing date: 2013-12-09
Publication date: 2014-06-12

Abstract

Eye tissue grafts from non-native tissue are disclosed. The eye tissue grafts can be made from dehydrated and cross-linked cartilage, corneal, or scleral tissue. The cartilage, corneal, or scleral tissue can be from the patient receiving the eye graft or from another human or animal source. The eye tissue graft can be a corneal implant, scleral implant, or peripheral chondral implant. The graft can be treated to modify the opacity of the implant. For example, the corneal implant can be dehydrated and cross-linked to increase the transparency of the cartilage, scleral, or corneal tissue. Methods for making the implants are also provided. The methods can include harvesting cartilage, corneal, or scleral tissue, dehydrating the cartilage, corneal, or scleral tissue to make it more light-transmissive, cross-linking the cartilage, corneal, or scleral tissue, and implanting the cartilage, corneal, or scleral tissue in the eye.

Description

OCULOPLASTY GRAFTS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. 1 19 of U.S. Provisional Patent Application No. 61/734,846 filed December 7, 2012, titled "Chondro-Oculoplasty Graft", which is incorporated by reference as if fully set forth herein.

INCORPORATION BY REFERENCE

[0002] All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

FIELD

[0003] This disclosure relates generally to eye tissue grafts and methods for making the same. More specifically, this disclosure relates to implantable eye tissue grafts containing dehydrated and cross-linked cartilaginous, corneal, and scleral tissue, and methods for making and using the described grafts.

BACKGROUND

[0004] For any number of reasons, eye tissue such as the sclera or cornea must be replaced or repaired. For example, corneal damage can arise from diseases such as severe corneal ulcer or keratitis, Stevens Johnson's Syndrome, Cicatrizing Pemphigoid, or a perforating injury.

Likewise, scleral damage can result from disease or damage including perforating trauma, or from surgical procedures such as cataract or glaucoma surgeries.

[0005] For corneal repair alone, over 10 million blind worldwide are in need of a corneal transplant. The cornea is an avascular and optically transparent tissue. In order to effectively refract and filter light, the cornea must maintain an adequate degree of transparency. However, injury, trauma, damage, degeneration, or infection can cause the cornea to opacify. As such, a patient may be severely visually compromised or rendered blind by corneal damage. Similarly, sclera damage can also result in vision impairment or blindness.

[0006] The preferred method for replacing eye tissue has been removing tissue from donor sources such as human cadaver for transplant into patients. For example, corneal and scleral grafts exist today and function well, but are limited in a number of ways. Both full-thickness and stromal corneal grafts for Penetrating Keratoplasty (PK) as well as Descemet's Stripping Endothelial Keratoplasy (DSEK), for instance, are confined to human cadaveric tissue, and are subject to stringent storage requirements as well as limited availability. Used in cases where donor grafts fail, the Boston Keratoprosthesis has undergone a number of significant improvements, but still require the use of precious donor corneal tissue and remain subject to a relatively high rate of complications, including end-stage glaucoma and endophthalmitis due in large part to the biointerface between the rigid optic and the graft. Scleral grafts, such as tutoplast or scleral patches, can be prepared from cadaveric human scleral tissue as well as xenograft tissue such as bovine pericardium.

[0007] Where donor tissue is not available, the OsteoOdonto Keratoprosthesis (OOKP) provides an option for patients with severely damaged ocular surfaces (from Stevens Johnsons Syndrome or Cicatricial Pemphigoid), where autograft tooth and buccal mucosa are used as the biological interface around a hard polymer optic. For example, the procedure for OsteoOdonto Keratoprosthesis includes the steps of removing a portion of oral mucosa from the patient's mouth, grafting the oral mucosa tissue over the cornea. A tooth with bone are then extracted from the patient and used to provide a carrier for an optical cylinder lens that is placed into an opening in the extracted tooth and bone. The carrier with optical lens is then placed into the patient's cornea through an opening in the oral mucosa tissue covering the patient's cornea.

[0008] Current methods of using donor or odontological autograft tissue come with several challenges. In the case of allografts, there are risks of infection transmission as well as graft rejection by the host. Moreover, the need for donor tissue greatly outstrips availability.

Furthermore, the harvest, preparation, storage, and delivery of all types of current ocular graft materials are relatively expensive and challenging. Additionally, as described above, the odontological autograft prosthesis requires a challenging and relatively morbid staged procedure.

[0009] As such, there is a need for an alternative to both cadaveric allograft and

odontological autograft tissue procedures. The devices and methods described herein provide for a cost-effective and/or biologically augmented source of graft tissue that can be used, non- exhaustively, as a peripheral keratoprosthesis carrier (donut-shaped) graft, tectonic graft, tutoplast, scleral patch, keratophakia (intracorneal lens or inlay), epikeratophakia (subepithelial onlay), full-thickness graft, or lamellar corneal graft (if transparent), and can be gamma sterilized, albumin-stored, and lathed to different shapes, autograft, allograft, or xenograft (e.g. bovine).

[00010] In the case of a full-thickness graft, either the entire graft itself or just the central optical portion is made transparent. In the case or a partial thickness graft or lens, the graft is transparent or nearly transparent by virtue of its thinness and/or dehydration level. In the case of a peripheral keratoprosthesis carrier graft, the graft is independent of the choice of material placed in the central hole. In some cases, the graft tissue includes cartilaginous tissue either from a donor source (from another living human or a cadaver, i.e. an allograft, or an animal i.e. a xenograft) or from the patient (as an autograft a.k.a. autologous graft). The cartilaginous graft tissue can be crosslinked or not crosslinked. In other cases, the graft tissue includes crosslinked and processed corneal or scleral graft tissue either from a cadaver (allograft) or an animal (xenograft). The purpose of the crosslinking the corneal or scleral graft tissue is to increase the strength and stiffness, properties which may improve the performance of such materials once implanted.

SUMMARY OF THE DISCLOSURE

[00011] The present invention relates generally to improved ocular implants and methods for producing the same. In some embodiments eye tissue grafts are provided including cross-linked cartilage, corneal, or scleral tissue. In some embodiments the cartilage, corneal, or scleral tissue is dehydrated.

[00012] The eye tissue graft can be used to strengthen the eye tissue. In some embodiments the cross-linked cartilage, corneal, or scleral tissue has a higher elastic modulus than a surrounding eye host tissue.

[00013] In some embodiments the eye grafts are corneal implants. In some embodiments the corneal implant is transparent. In some embodiments the corneal implant is transparent centrally. In some embodiments the corneal implant is donut shaped. In some embodiments the corneal implant is a full thickness or partial thickness implant. In some embodiments the corneal implant supports epithelial overgrowth.

[00014] In some embodiments the eye tissue grafts are scleral implants. In some

embodiments the eye tissue grafts are peripheral implants.

[00015] In some embodiments the dehydrated and cross-linked cartilage, corneal, or scleral tissue exhibits increased optical clarity relative to the tissue prior to dehydration. In some embodiments the cartilage, corneal, or scleral tissue is crosslinked by exposing the tissue to riboflavin-5 -phosphate and UV light.

[00016] In some embodiments the cartilage, corneal, or scleral tissue is reshaped using a microlathe.

[00017] In some embodiments the cartilage, corneal, or scleral tissue is harvested from a user receiving the implant. In some embodiments the cartilage tissue is harvested from the user's joint. In some embodiments the cartilage, corneal, or scleral tissue is harvested from a source other than the user receiving the implant. In some embodiments the cartilage tissue is articular cartilage. [00018] In some embodiments methods of treating an eye are provided. The methods can include harvesting cartilage, corneal, or scleral tissue, dehydrating the cartilage, corneal, or scleral tissue to make it more light-transmissive, cross-linking the cartilage, corneal, or scleral tissue, and implanting the cartilage, corneal, or scleral tissue in the eye.

[00019] In some embodiments the cartilage, corneal, or scleral tissue is harvested from a user receiving the implant. In some embodiments the harvested cartilage, corneal, or scleral tissue is stored in a balanced salt solution. In some embodiments the methods further include harvesting the cartilage tissue and cutting the cartilage tissue to form a disc.

[00020] In some embodiments the methods further include increasing the optical clarity of the harvested cartilage, corneal, or scleral tissue by dehydrating the cartilage, corneal, or scleral tissue. In some embodiments glycerol is used to dehydrate the cartilage, corneal, or scleral tissue.

[00021] In some embodiments the methods further include altering the structure of the harvested cartilage, scleral, or corneal tissue by dehydrating and/or cross-linking the tissue. In some embodiments cross-linking the graft tissue includes exposing the tissue to a photosensitizer and UV light. The photosensitizer can be riboflavin-5-phosphate.

[00022] In some embodiments the methods further include adjusting the degree of increased light transmissivity of the cartilage, corneal, or scleral tissue by controlling the amount of dehydration.

[00023] In some embodiments the methods further include shaping the cartilage or corneal tissue into a corneal implant. In some embodiments the methods further include shaping the cartilage or scleral tissue into a scleral implant. In some embodiments the methods further include shaping the cartilage tissue into a peripheral implant with a central hole. In some embodiments the methods further include inserting a second, transparent, biological material within the central hole.

[00024] In some embodiments methods for treating an eye trauma injury are provided. The methods include replacing at least a portion of a patient's cornea with dehydrated and cross- linked cartilage or corneal tissue and securing the cartilage or corneal tissue to the patient's eye.

[00025] In some embodiments methods for treating eye trauma injury are provided. The methods include replacing at least a portion of a patient's scleral tissue with dehydrated and cross-linked scleral tissue and securing the scleral tissue to the patient's eye.

[00026]

[00027] In some embodiments peripheral chondral grafts are provided. The peripheral chondral grafts are furnished with a central hole. In some embodiments the peripheral chondral graft contains a second, transparent, biological material placed within the central hole. BRIEF DESCRIPTION OF THE DRAWINGS

[00028] The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative

embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

[00029] FIG. 1 is a schematic representation of the corneal stroma.

[00030] FIGS. 2A-2B show cartilage tissue.

[00031] FIG. 3 is a schematic representation of cartilage.

[00032] FIG. 4 shows a method for harvesting cartilage according to some embodiments.

[00033] FIG. 5 shows a peripheral corneal autograft.

[00034] FIG. 6 shows superficial cartilage cut from a cartilage plug.

[00035] FIG. 7 shows the dehydrated cartilage tissue in FIG. 6.

[00036] FIG. 8 shows a dehydration process according to some embodiments.

[00037] FIG. 9 shows a cross-linking process according to some embodiments.

DETAILED DESCRIPTION

[00038] As mentioned, current techniques for corneal replacement include removing the damaged or diseased cornea (or portions of the cornea) and replacing the removed cornea with a donor cornea or an artificial cornea (which may include autografted or allografted tissues). An eye having a damaged opacified cornea may be treated by placing a replacement corneal implant in the eye. The implant may be sutured to the patient's eye. The replacement implant may be, for example, the Boston Keratoprosthesis that has an optically clear core surrounded by a biointegrable skirt.

[00039] To avoid the disadvantages of the current techniques, some embodiments described provide for an eye tissue graft or implant incorporating cartilage, scleral, or corneal tissue. In some cases, the cartilaginous, corneal, or scleral tissue is from a donor source such as a cadaver or other mammalian source. In other cases, the cartilaginous, corneal, or scleral material is harvested directly from the patient receiving the implant. In other words, the described eye tissue grafts may be allografted, xenografted, or autografted implants.

[00040] In some embodiments the cartilage, corneal, or scleral tissue can be dehydrated to modify the properties of the tissue graft. Dehydration can modify optical and other properties of the tissue. For example, dehydration can increase the transparency of the tissue graft. [00041] In some embodiments the cartilage, corneal, or scleral tissue can be cross-linked to modify the properties of the tissue graft. Cross-linking can improve the strength and stiffness of the tissue graft.

[00042] The use of biological graft tissues, such as cartilage, corneal, or scleral tissue offer improved functionality and decreased likelihood of implant rejection in comparison to artificial implants.

[00043] The use of cartilage offers the potential for a new, abundant, and more cost-effective supply of ophthalmic graft tissue, which would be of value not only in developing nations, but also developed nations in this age of major health care reform. Autografting is a technique used routinely in other surgical fields such as ENT, plastic surgery, and orthopaedics due to the relative abundance and accessibility of redundant autograft tissue on most patients, such as skin, tendon, and cartilage. In some embodiments, chondro-ocular autografting would comprise harvesting a patient's own cartilage from, for example, the patient's ear, ribcage, or knee joint, and then suturing it into a damaged part of the eye during a two-stage procedure with the help of the appropriate surgical specialist (ENT, plastic surgery, or orthopaedics). In other

embodiments, chondro-ocular allografts and xenografts, would involve harvesting cadaveric or animal cartilage, processing, and then storing the tissue prior to use.

[00044] Without being bound by any theory, it is believed that cartilaginous tissue advantageously shares many similarities with corneal stroma and sclera. The corneal stroma is an avascular connective tissue comprised of collagen fibrils organized in lamellae, interlaced with glycosaminoglycans, and hydrated to about 70% water. The epithelium is the outermost layer of the cornea and is composed of squamous epithelial cells. The Bowman's layer is an acelluar sheet of collagen separating the epithelium from the stroma. The stroma is located beneath Bowman's layer and is composed of water, collagen, and keratocytes. Descemet's membrane lies under the stroma. Figure 1 shows the various layers of the cornea.

[00045] As shown in Figures 2A-2B, cartilage is a flexible, avascular connective tissue also comprised of organized collagen interlaced with the same glycosaminoglycans present in corneal stroma. It is found in three different forms in many areas of the body, including joint spaces, the rib cage, the ear, the nose, the lungs, and between vertebrae. There are three main types of cartilage in the body: elastic cartilage (found in the ear and nose), hyaline cartilage (found in articulating joints), and fibrocartilage (also found in articulating joints as a buffering structure). The relative concentrations and organization of these constituents varies depending on the type of cartilage and its anatomic location. Shown generally in Figure 3, articular cartilage may include three zones. The superficial tangential zone may make up 10-20% of the cartilage thickness. The middle zone may make up 40-60% of the thickness. And 30% of the cartilage thickness may be in the deep zone. The collagen arrangement in the superficial tangential zone of cartilage is most similar to that found in corneal stroma.

[00046] This compositional variation of cartilage is analogous to the architectural differences between corneal stroma and sclera, where the latter can be seen as a more disorganized (hence the lack of transparency) extension of corneal stroma. Like cartilage, the cornea and sclera are load-bearing tissues, subjected to tensile stress (albeit lower stresses than borne by cartilage) induced by intraocular pressure. It is further believed that: (1) both corneal stroma and articular cartilage are comprised of an interpenetrating network of collagen fibrils and

glycosaminoglycans, (2) the superficial zone of articular cartilage is tangentially oriented, not unlike the lamellar arrangement of corneal stroma, (3) optical clarity and tissue hydration of corneal stroma are inversely proportional, and (4) collagen crosslinking via riboflavin administration followed by UV irradiation is now an established way to stabilize corneal stroma, and similar process can also be used on cartilage tissue.

[00047] In some embodiments, described methods provide for altering the structural, mechanical, and/or optical properties of cartilage, corneal, or scleral tissue to make it suitable as either a corneal or sclera graft material, or both. In some embodiments, cartilaginous, corneal, or scleral tissue is first harvested from the patient or from a donor source. Any suitable method of removing cartilage, corneal, or scleral tissue can be used. For example, procedures used in mosaicplasty or O.A.T.S. (osteochondral autograft transfer system) are suitable to remove plugs of articular cartilage from a source. Figure 4 shows the removal of cartilage plugs from a joint surface. The cartilage plug may be extracted from a knee. In mosaicplasty, the healthy cartilage plugs are typically placed in a damaged area, filling in where cartilage is missing, damaged, or has been removed. With the described embodiments provided herein, the mosaicplasty or OATS technique may be used to remove plugs of healthy cartilage for use in an eye tissue graft or implant.

[00048] In some embodiments, the methods known in the art for making a peripheral chondral autograft may be modified for harvesting cartilaginous tissue suitable for eye tissue grafts. For example, a removed cartilage plug can be used to form a peripheral chondral autograft. In some embodiments, the peripheral chondral autograft can be formed to have an appearance similar to the peripheral corneal graft 24 shown in Figure 5.

[00049] The methods for harvesting the cartilage may be used to harvest cartilage suitable for embodiments described herein. Although described as harvested from a joint, it can be appreciated that the cartilage can be harvested from any location from a donor source or from the patient (e.g. ear, nose, etc.) [00050] In some embodiments, an osteochondral plug may be harvested from a human or animal source (e.g. bovine). The harvested plug may be further cut into discs of cartilage. In some embodiments, the superficial cartilage may be removed from the plug. In some cases, about 0.5mm to about 1.0mm of the superficial cartilage is removed. In some embodiments, the superficial cartilage is keratomed off the surface of the plug to form cartilage discs. Figure 6 shows the removed portion of the superficial cartilage from an osteochrondral plug. The removed cartilage tissue 28 is shown as having a generally opaque or white appearance. In some cases, the cartilage is transparent, semi-transparent, or translucent. In other embodiments, the harvested cartilage is opaque.

[00051] In some embodiments the harvested cartilage tissue is processed to achieve the desired implant shape. The tissue can be mechanically processed to change the shape by cutting or other mechanical methods. For example, reshaping of the graft or implant can be done with a microlathe. Shaping the tissue or implant can be done at any point prior to implantation. For example, shaping can be done after harvesting the cartilage tissue, after cross-linking the cartilage tissue, or after optionally dehydrating the cartilage tissue. Multiple shaping steps can be performed to fine tune the shape of the implant. For example, the tissue can be cut to the desired size after harvesting and later cut or shaved to fine tune the implant shape and size prior to implantation.

[00052] In some embodiments, once the cartilaginous, corneal, or scleral tissue is harvested, the tissue is altered by dehydrating or deturgescing the tissue and cross-linking the dehydrated tissue. For example, Figure 6 shows a relatively opaque harvested cartilage tissue 28. Figure 7 shows the same harvested cartilage tissue after dehydration. The dehydrated cartilage tissue 30 is translucent and transmits more light compared to the original harvested cartilage tissue 28. In some embodiments, degree of transparency, optical clarity, or light transmission of harvested cartilage is increased or improved by dehydrating or deturgescing the harvested material.

Without being bound to any theory, it is believed that dehydrating harvested cartilage (e.g. articular) renders it more optically clear, in a similar way seen with dehydrating edematous corneal stroma with deturgescing agents. Additionally, in some embodiments, dehydrating or deturgescing the cartilage, corneal, or scleral tissue can be used to alter the structural, mechanical, and optical properties of cartilage to make it suitable as an eye tissue graft material such as corneal or sclera graft material, or both. In another embodiment, opaque or semi- transparent cartilage is placed in a patient's cornea, and becomes transparent over time, due to the deturgescing pumping action of the endothelial cells, and/or via remodeling of the cartilage by the host stromal cells. [00053] Techniques for dehydrating or deturgescing cartilage, corneal, or scleral tissue include using any suitable methods or materials. In some embodiments air drying can be used to dehydrate the tissue. In some embodiments heat, mechanical squeezing, wicking with another absorbent material, or combinations of these processes can be used to dehydrate the tissue. In some embodiments alcohols or other solvents can be used to dehydrate the tissue. In one example, cartilage, corneal, or scleral tissue can be dehydrated or deturgesced using glycerol. For example, the tissue may be contacted to or submerged in a volume of glycerol. In some cases, the glycerol is applied for set periods of time. For example, the set periods of time may be 30 min, 2 hours, and/or 8 hours. In some embodiments, the degree of hydration is controlled by glycerol administration. Glycerol can be applied in any number of ways, but most preferably by soaking or serial drop-wise administration. Hypertonic saline or other dehydrating/deturgescing agents may also be used in a similar manner. These agents can come in liquid, viscous gel, or ointment form. In other embodiments, the cartilage, corneal, or scleral tissue is compressed to squeeze out all or the majority of its water, or is dried by allowing the water to evaporate from its surface, either by dry heat, vacuum, or freeze-drying. In other embodiments, the amount of dehydration can be used to control the degree of transparency or light transmissivity of the cartilage, corneal, or scleral material. For example, in some embodiments, a white, opaque graft would be useful as a scleral patch, while a semi- transparent graft could be used as a peripheral tectonic corneal graft or keratoprosthesis peripheral graft, while a fully transparent graft could serve as a complete corneal donor button. Each of these types of grafts can be formed from cartilage tissue, corneal tissue, or scleral tissue. The difference in transparency and light transmission between these different types of grafts can be accomplished by controlling and setting the degree the tissue is dehydrated. Such embodiments provide the ability to tune the structure of cartilage or other tissue to enable the fabrication of a variety of ocular tissue grafts. In some embodiments, the degree of dehydration is controlled by first dehydrating the cartilage, corneal, or scleral tissue such that the tissue provides anywhere between 0-100% light transmission. The amount of dehydration can be determined either by weight measurements (to get the % by weight of water) or by dimensional measurements (volume) to obtain the % by weight of water.

[00054] In further embodiments, the dehydrated cartilage tissue is further treated to fix the level of dehydration. In such cases, the dehydrated cartilage, corneal, or scleral tissue is fixed such that the amount of transparency, light transmissivity, optical clarity, translucence, etc. is substantially set. In some embodiments, the setting step can be accomplished by cross-linking the dehydrated cartilage, corneal, or scleral tissue. This can accomplished, in some

embodiments, by applying a photosensitizer, such as riboflavin-5-phosphate, and UV light. In some embodiments, riboflavin-5-phosphate in dextran can be used for cross-linking. In some cases, the cartilage, corneal, or scleral tissue is exposed to riboflavin for designated time points (both through complete immersion and/or drop-wise administration), and then exposed to UV light for periods of 1, 5, and 15 minutes. In other embodiments the UV exposure time ranges from a few seconds to more than 15 minutes. It is believed that cross-linking can be used in combination with dehydration and deturgescence to lock in or fix a particular hydration and transparency level in harvested cartilage, corneal, or scleral tissue. In some embodiments, cross- linking the cartilage, corneal, or scleral tissue can be used to fix or lock in the structural changes effected by dehydration. Additionally, riboflavin/UV crosslinking can be used in combination with matrix deturgescence to lock in or fix the hydration and transparency level in harvested cartilage, corneal, or scleral tissue.

[00055] In some embodiments the cartilage graft tissue and xenograft corneal and scleral tissue may also be processed to remove antigenic material, such as alpha-gal which can cause inflammation and potentially graft rejection.

[00056] Any of the same processes described herein with respect to cartilage can also be applied to corneal and scleral graft tissue to alter the physical properties of the corneal and scleral graft tissue. Corneal and scleral graft tissue can also be shaped to create lenticules, patch grafts, ring segments, or any other shapes described herein.

[00057] Figure 8 shows a harvested cartilage disc 32 dehydrated to disc 34 by way of glycerol. Once dehydrated, Figure 9 shows the dehydrated disc 34 cross-linked to lock in or set hydration and transparency levels. Disc 36 is the fixed cartilage disc. In some embodiments, the dehydration and/or the cross-linking steps alter the structural, mechanical, and/or optical properties of the harvested cartilage.

[00058] Additional factors can be selected and tuned to change the properties of the cartilage and the implant processed and formed from the cartilage. Additional factors include the thickness of the harvested and processed cartilage, type of cartilage harvested, area and position of harvested cartilage, etc. Different areas of cartilage can have different optical properties. Superficial cartilage can be more transparent than deeper sections of cartilage. Superficial cartilage can also be made more transparent than deeper section of cartilage through the processing methods disclosed herein. For example, it was discovered that superficial hyaline cartilage can be made clearer than deeper hyaline cartilage or elastic cartilage. In some embodiments the harvested cartilage is selected from an area based on the desired properties of the implant.

[00059] The thickness of the cartilage can also affect the properties of the implant. In some cases the transparency of the cartilage can be proportional to the thickness of the cartilage. In some embodiments the thickness of the cartilage is decreased by additional processing steps. For example, dehydration and crosslinking can decrease the thickness of the cartilage. In some experiments crosslinking with riboflavin after dehydration decreased the thickness of the cartilage specimens by up to 20%. In some embodiments the thickness of the harvested cartilage and/or processed cartilage is selected based on the desired properties of the implant.

[00060] In other embodiments where transparency or optical clarity is not required, the harvested cartilage may be prepared by cross-linking the harvested cartilage tissue without prior dehydration. For example, where the cartilage is placed in the cornea off the central axis, such as in a donut or ring configuration, or if applied off to the side of the cornea, transparency or optical clarity of the cartilage is not necessary. In other embodiments, where the transparency or optical clarity of the cartilage is not required, the harvested cartilage may not be further processed by either dehydration or cross-linking prior to transplant. In some embodiments, cross-linking the cartilage can be used to fix or lock in the features of the cartilage tissue to prevent changes in the structural, mechanical, or optical properties.

[00061] The corneal tissue and scleral tissue can also be dehydrated and/or cross-linking to modify the properties of the tissue based on the desired implant properties. For example, dehydration of the corneal tissue can be used to improve the optical clarity and transparency of the resulting corneal implant. Dehydration can also be used to decrease the transparency of scleral tissue for a scleral implant. Dehydration and cross-linking can also be used to change the thickness of the corneal or scleral tissue based on the desired properties of the implant.

[00062] Corneal and scleral tissue grafts can be shaped to the desired implant shape. In some embodiments, crosslinked corneal graft tissue is processed and shaped in a way that makes it useful as an optical (lenticular) implant or as a corneal re-shaping element (such as ring segments) that alter the curvature and in turn the refractive power of the host cornea. An example of an optical implant includes a lenticule with either a convex or concave central curvature to add either plus or minus power to the cornea. A re-shaping element such as a ring segment would change the curvature of the cornea by either steepening or flattening. This would be akin to polymeric ring segments known as "Intacs" which are available on the market today for the same purpose, but would be comprised of purely biological graft material to improve their tolerance and performance in the eye. Reshaping of the graft or implant can be done, for example, with a microlathe.

[00063] In some embodiments, cross-linked corneal, scleral, or cartilage graft tissue is used as an implant to increase the stiffness of one area of the eye. The implanted tissue can have a higher stiffness and elastic modulus than the surrounding eye hose tissue. Increasing the stiffness of an area of the eye can be used to divert the stress concentration away from the optic nerve head, specifically the lamina cribrosa. The optic nerve head is thought to be vulnerable to damage from mechanical stresses from such stress concentrations in glaucoma. By placing stiffer tissue in certain positions within the ocular wall and in specific configurations, it may be possible to reduce stresses that are otherwise concentrated on the optic nerve head. Such grafts could serve as an alternative or adjunct to intra-ocular pressure lowering surgery for the treatment of glaucoma.

[00064] In some embodiments, crosslinked corneal or scleral tissue or cartilage graft (with or without crosslinking) is used as a patch graft in, for example, a tutoplast patch over a glaucoma drainage device.

[00065] Further embodiments provide for methods of treating corneal blindness, ocular trauma, glaucoma, etc. by implanting an eye tissue graft containing cartilage, corneal, or scleral tissue into a patient's eye. In some embodiments, the eye tissue graft contains dehydrated cartilage, corneal, or scleral tissue. In other embodiments, the cartilage, corneal, or scleral tissue is cross-linked. The cartilage, corneal, or scleral tissue may be dehydrated and cross-linked. The eye tissue graft may be secured to the patient's eye by suturing the cartilage, corneal, or scleral graft material to the eye tissue in either full-thickness or partial-thickness form. It can also be positioned within stromal pockets or flaps created manually using surgical instruments or using a laser such as a femto-second laser. It can also be positioned directly under the epithelium to allow overgrowth of the surrounding epithelium.

[00066] EXAMPLE 1

[00067] Bovine cartilage specimens were harvested and deturgesced using glycerol. The fresh specimen is opaque (Figure 6) while the deturgesced specimen became translucent (Figure 7). Preliminary experimental data has demonstrated that dehydrating harvested articular cartilage renders it more optically clear, in a similar way seen with dehydrating edematous corneal stroma with deturgescing agents. The key sub-hypothesis is that riboflavin/UV crosslinking can be used in combination with matrix deturgescence to "lock-in" a particular hydration and transparency level in harvested cartilage. The ability to tune the structure of cartilage would enable the fabrication of a variety of ocular tissue grafts. For instance, a white, opaque graft would be useful as a scleral patch, while a semi- transparent graft could be used as a peripheral tectonic corneal graft or keratoprosthesis peripheral graft, while a fully transparent graft could serve as a complete corneal donor button.

[00068] EXAMPLE 2

[00069] The following methods describe an example of forming viable autograft, allograft, or xenograft for either corneal stroma, sclera, or both from cartilage tissue according to

contemplated embodiments. It is contemplated that in some embodiments, the first steps would be to harvest, deturgesce, and characterize bovine articular cartilage specimens. Any type of cartilage can be obtained and used (e.g. animal or human source). In some cases, fresh bovine articular cartilage is obtained. In other cases, human articular cartilage is obtained either from a cadaver or from living donors. In all cases, osteochondral plug specimens can be retrieved using a circular cutting blade mounted to a drill if the cartilage is obtained from a joint surface such as a knee. Any suitable cutting tool can be used as needed to remove cartilage from a source. For articular cartilage, superficial 0.5 - 1.0 mm of cartilage can be keratomed off the surface to create discs of cartilage, which can be stored in BSS (balanced salt solution). For other types of cartilage (such as from the ear, nose, or ribcage), other suitable tools can be used to harvest and cut the specimens to the desired dimensions. Glycerol (or any other suitable deturgescing or dehydrating agent) can be used to deturgesce the disc specimens for designated time points (30 min, 2 hours, 8 hours). After dehydration, the samples can be cleaned, rinsed quickly and stored in a moist chamber. Weight and dimensions of the samples can be taken both pre and post-dehydration.

[00070] In some embodiments, the samples can be allocated for experiments or processing such as described in EXAMPLE 1. The samples may also be either rehydrated and

weighed/measured, or stored in a humid chamber (at 4 degrees C) to prevent rehydration and to enable their use in EXAMPLE 4 described below. All specimens can be photographed and analyzed using Adobe Photoshop to determine the change in transparency between the dehydrated and hydrated states.

[00071] EXAMPLE 3

[00072] In some embodiments, the samples or specimens developed by previous steps in the above examples may be cross-linked and characterized using UV/riboflavin. These methods may include selecting harvested cartilage specimens (e.g. from EXAMPLES 1-2) and then exposing those specimens to riboflavin-5 -phosphate in dextran based on published corneal crosslinking techniques used in clinical practice. The specimens can be exposed to riboflavin for designated time points (both through complete immersion as well as drop-wise administration), and then exposed to UV light for periods of 1 , 5, and 15 minutes. The samples can then be rinsed and then placed back in BSS to allow for equilibrium swelling. The equilibrated samples can then be removed from solution, weighed, and measured for their diameter and thickness.

[00073] In some cases, crosslinking versus re-swelling can be plotted to determine the relationship between the crosslinking conditions and the final hydrated dimensions of the samples. Optical clarity can also be assessed using Photoshop software applied to digital photographs of the specimens. A subset of specimens can be processed both for frozen and paraffin sections of the deturgesced and crosslinked tissues to histologically evaluate them for changes in collagen morphology and cellularity. The dehydrated cartilage specimens can also be exposed to riboflavin and UV light in sequence to stabilize the collagen and prevent rehydration (and potentially re-opacification).

[00074] EXAMPLE 4

[00075] In some embodiments, cartilage tissue may be implanted into animals such as rabbits for testing. It is contemplated that the methods described can be used for in vivo implantation of chondro-corneal grafts. Methods for in vivo implantation of eye tissue grafts include the steps of implanting harvested and crosslinked specimens in a small number of animals. In some cases, bovine-xenografts can be placed in rabbit corneas. Bovine-xenograft may be used as rabbit cartilage is relatively thin and may not provide sufficiently thick tissue to use as an implantable graft. Alternatively, a staged procedure may be used in which either rabbit ear or knee cartilage is harvested intraoperatively and then sutured into the animal's corneas, with or without dehydration and crosslinking.

[00076] EXAMPLE 5

[00077] In some embodiments, the cartilage graft is gamma irradiated which has the effect of both sterilizing and crosslinking the tissue. The gamma irradiation can be applied to graft tissue that has been dehydrated and crosslinked, crosslinked but not dehydrated, or neither crosslinked or dehydrated. It is known in the art that gamma irradiation can render allograft or xenograft tissue less immunogenic (or non-immunogenic).

[00078] Graft tissue from the present invention can be from any number of cartilage sources in the body, including but not limited to the rib cage, sternum, knee joint, meniscus,

intervertebral discs, intervertebral facets, shoulder, labrum, ear, nose, hands/fingers, feet, ankles or toes. The cartilage can come from animals or humans (either living or cadaveric).

[00079] EXAMPLE 6

[00080] In another embodiment, the graft tissue is an autologous graft harvested from a patient and placed into his or her eye during a staged procedure. Cartilage in this case would be obtained from one or more of the anatomic sources listed above, but preferably the knee joint, ear, ribcage, or sternum, cleaned in the operating room, cut to the desired size and shape, and then placed in the eye (cornea or sclera). In another embodiment, the autograft tissue is dehydrated with a deturgescing agent, and crosslinked using riboflavin and UV light in the operating room, rinsed again and then placed in the eye (cornea or sclera).

[00081] EXAMPLE 7

[00082] In another embodiment, the graft tissue (xenograft, allograft, or autograft) is furnished with a central hole and the hole is filled with a second, transparent biological material that is either press-fit sutured, cauterized, or glued in place with an adhesive. The second biological material may be a single material or a combination of materials, for instance an interpenetrating polymer network (IPN) of collagen and glycosaminoglycans. In one example, an IPN of collagen and hyaluronic acid is placed in the center of the peripheral graft. In another example, the second biological material may be physically and/or chemically adhered to the graft tissue by any suitable method.

[00083] EXAMPLE 8

[00084] In another embodiment, the graft tissue is an allograft or xenograft prepared from corneal tissue. The corneal tissue can be harvested from a patient, cadaver, or animal. The corneal tissue can be dehydrated and cross-linked to modify the stiffness and optical properties of the corneal tissue. After cross-linking the graft can be placed into his or her cornea during a staged procedure. In some embodiments, the allograft or xenograft corneal tissue is dehydrated with a deturgescing agent and crosslinked using riboflavin and UV light in the operating room, rinsed again, and then placed in the cornea.

[00085] EXAMPLE 9

[00086] In another embodiment, the graft tissue is an allograft or xenograft prepared from scleral tissue. The scleral tissue can be harvested from a patient, cadaver, or animal. The scleral tissue can be dehydrated and cross-linked to modify the strength and stiffness of the scleral tissue. After cross-linking the graft can be placed into his or her eye during a staged procedure. In some embodiments, the allograft or xenograft scleral tissue is dehydrated with a deturgescing agent and crosslinked using riboflavin and UV light in the operating room, rinsed again, and then placed in the sclera.

[00087] As for additional details pertinent to the present invention, materials and

manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts commonly or logically employed. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Likewise, reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms "a," "and," "said," and "the" include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only" and the like in connection with the recitation of claim elements, or use of a "negative" limitation. Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not to be limited by the subject specification, but rather only by the plain meaning of the claim terms employed.

Claims

CLAIMS What is claimed is:

1. An eye tissue graft comprising cross-linked cartilage, corneal, or scleral tissue.

2. The graft of claim 1, wherein the cartilage, corneal, or scleral tissue is dehydrated.

3. The graft of claim 1, wherein the cross-linked cartilage, corneal, or scleral tissue has a higher elastic modulus than a surrounding eye host tissue.

4. The graft of claim 1, wherein the graft is a corneal implant.

5. The graft of claim 4, wherein the corneal implant is transparent.

6. The graft of claim 4, wherein the corneal implant is transparent centrally.

7. The graft of claim 4, wherein the corneal implant is donut shaped.

8. The graft of claim 4, wherein the corneal implant is full thickness or partial thickness.

9. The graft of claim 4, wherein the corneal implant supports epithelial overgrowth.

10. The graft of claim 1, wherein the graft is a scleral implant.

1 1. The graft of claim 2, wherein the dehydrated and cross-linked cartilage, corneal, or scleral tissue exhibits increased optical clarity relative to the cartilage, corneal, or scleral tissue prior to dehydration.

12. The graft of claim 1, wherein the cartilage, corneal, or scleral tissue is harvested from a user receiving the implant.

13. The graft of claim 12, wherein the cartilage tissue is harvested from the user's joint.

14. The graft of claim 1, wherein the cartilage, corneal, or scleral tissue is harvested from a source other than the user receiving the implant.

15. The graft of claim 1 , wherein the cartilage tissue is articular cartilage.

16. The graft of claim 1, wherein the cartilage, corneal, or scleral tissue is crosslinked by exposing the tissue to riboflavin-5-phosphate and UV light.

17. The graft of claim 16 wherein the cartilage, corneal, or scleral tissue is reshaped with a microlathe.

18. A method of treating an eye comprising:

harvesting cartilage, corneal, or scleral tissue;

dehydrating the cartilage, corneal, or scleral tissue to make it more light-transmissive; cross-linking the cartilage, corneal, or scleral tissue; and

implanting the cartilage, corneal, or scleral tissue in the eye.

19. The method of claim 18, wherein the cartilage tissue is harvested from a user

receiving the implant.

20. The method of claim 18 further comprising harvesting the cartilage tissue; and cutting the cartilage tissue to form a disc.

21. The method of claim 18, wherein glycerol is used to dehydrate the cartilage, corneal, or scleral tissue.

22. The method of claim 18, wherein cross-linking the cartilage, corneal, or scleral tissue comprising exposing the tissue to a photosensitizer and UV light.

23. The method of claim 22, wherein the photosensitizer is riboflavin-5-phosphate.

24. The method of claim 18, wherein the harvested cartilage, corneal, or scleral tissue is stored in a balanced salt solution.

25. The method of claim 18 further comprising increasing the optical clarity of the

harvested cartilage, corneal, or scleral tissue by dehydrating the cartilage, corneal, or scleral tissue.

26. The method of claim 18 further comprising altering the structure of the harvested cartilage, corneal, or scleral tissue by dehydrating and cross-linking the tissue.

27. The method of claim 18 further comprising adjusting the degree of increased light transmissivity of the cartilage, corneal, or scleral tissue by controlling the amount of dehydration.

28. The method of claim 18 further comprising shaping the cartilage or corneal tissue into a corneal implant.

29. The method of claim 18 further comprising shaping the cartilage or scleral tissue into a scleral implant.

30. The method of claim 18 further comprising shaping the cartilage tissue into a

peripheral implant with a central hole.

31. The method of claim 30 further comprising inserting a second, transparent, biological material within the central hole.

32. A method for treating eye trauma injury comprising:

replacing at least a portion of a patient's cornea with dehydrated and cross-linked cartilage or corneal tissue; and

securing the cartilage or corneal tissue to the patient's eye.

33. A method for treating eye trauma injury comprising:

replacing at least a portion of a patient's scleral tissue with dehydrated and cross-linked scleral tissue; and

securing the scleral tissue to the patient's eye.

34. A peripheral chondral graft wherein the peripheral chondral graft is furnished with a central hole.

35. The peripheral chondral graft of claim 34 wherein the peripheral chondral graft

contains a second, transparent, biological material placed within the central hole.