WO2009046158A1

WO2009046158A1 - Keratoplasty graft deployment devices and methods

Info

Publication number: WO2009046158A1
Application number: PCT/US2008/078526
Authority: WO
Inventors: Joel M. Solano; Keith H. Baratz; Sanjay V. Patel; Leo J. Maguire
Original assignee: Mayo Foundation For Medical Education And Research
Priority date: 2007-10-02
Filing date: 2008-10-02
Publication date: 2009-04-09

Abstract

Devices and methods for performing posterior lamellar keratoplasty. The devices may include an elongated delivery element having a tissue delivery section. The tissue delivery section may include one or more openings that are in fluid communication with a delivery element lumen. In use, a graft is placed on the tissue delivery section (over the one or more openings) with the endothelial side of the graft facing the surface of the tissue delivery section. The tissue delivery section may be located within a sleeve during insertion into the anterior chamber of a recipient eye. Delivery of a fluid through the delivery element lumen after the graft is located within the anterior chamber of the recipient eye causes the graft to deploy from the device.

Description

KERATOPLASTY GRAFT DEPLOYMENT DEVICES AND METHODS

RELATED APPLICATION

[01] This application claims the benefit under 35 U.S.C. § 1 19(e) of U.S.

Provisional Patent Application No. 60/997,307 filed on October 2, 2007 and titled KERATOPLASTY GRAFT DEPLOYMENT DEVICES AND METHODS, which is hereby incorporated by reference in its entirety.

[02] The present invention relates generally to endothelial keratoplasty and, more particularly, to keratoplasty graft deployment devices and methods for performing posterior lamellar keratoplasty.

[03] Penetrating keratoplasty has been the traditional method of transplanting full-thickness corneal tissue, and involves full-thickness replacement of the cornea. Keratoplasty for endothelial dysfunction has evolved toward partial thickness tissue transplantation, specifically transplantation of the inner layers of the cornea or posterior lamellar keratoplasty. Posterior lamellar keratoplasty to treat endothelial dysfunction has gained popularity because of the typically more predictable refractive outcomes with lower astigmatism, and faster visual recovery compared to penetrating keratoplasty. Two techniques for posterior lamellar keratoplasty are Descemet's stripping with endothelial keratoplasty (DSEK) and deep lamellar endothelial keratoplasty (DLEK).

[04] Posterior lamellar keratoplasty can be technically challenging, and delivery of the donor tissue into the recipient can be arduous. For small incision surgery, the current method of graft delivery involves folding the tissue so that the endothelium is folded on itself but is coated with a small amount of viscoelastic for protection. The folded tissue is then inserted into the recipient's anterior chamber using, e.g., a forceps. Air and balanced salt solution are injected into the anterior chamber of the eye to help unfold the donor tissue and hold it against the recipient cornea

[05] The current method of tissue graft delivery in posterior lamellar keratoplasty can suffer from problems. One potential problem is that accurate delivery of the graft is not easily repeatable and reliable. For example, the graft may unfold so that the endothelium is positioned adjacent to the host cornea, which typically leads to graft failure. Another potential problem is that because the endothelium is a monolayer of non-replicating cells, the trauma of folding, inserting, unfolding and manipulating the tissue within the anterior chamber can result in irreversible endothelial cell loss. That cell loss may be problematic because corneal endothelial cells are responsible for corneal deturgescence and, therefore, corneal transparency. As a result, cell loss may result in a less than optimal outcome. In addition, initial endothelial cell densities are the best predictor of long-term graft survival. As a result, reducing endothelial cell loss may be important for preventing graft failure.

SUMMARY OF THE INVENTION

[06] The present invention provides devices and methods for performing posterior lamellar keratoplasty. The keratoplasty graft deployment devices may preferably include an elongated delivery element having a tissue delivery section. The tissue delivery section may preferably include one or more openings that are in fluid communication with a delivery element lumen. In use, a graft is preferably placed on the tissue delivery section (over the one or more openings) with the endothelial side of the graft facing the surface of the tissue delivery section. The graft and/or the surface of the tissue delivery section may preferably be coated with a viscoelastic material.

[07] With the graft in position on the tissue delivery section, the elongated delivery element may preferably be inserted into the anterior chamber of the recipient. It may be preferred that the tissue delivery section (with the graft located thereon) be inserted into the anterior chamber while the tissue delivery section is located within a sleeve to protect the graft located on the tissue delivery section during the insertion process.

[08] Once the tissue delivery section (and the graft located thereon) are in the anterior chamber, the tissue delivery section and the sleeve are manipulated such that the tissue delivery section and graft are exposed within the anterior chamber (which may involve advancing the tissue delivery section out of the sleeve and/or retracting the sleeve relative to the tissue delivery section).

[09] With the graft exposed within the anterior chamber, fluid (e.g., air, etc.) may be delivered through the delivery element lumen to cause the graft to release from the surface of the tissue delivery section. The graft release is preferably caused by the fluid pressure exerted on the graft through the one or more openings. It is preferred that the graft be deployed such that it contacts the host cornea.

[10] One potential advantage of the devices and methods of the present invention is that deployment of the donor graft may be performed in a manner that is more repeatable than the known methods that involve folding and unfolding of the graft tissue. Another potential advantage is that, in the absence of folding, endothelial cell loss is preferably reduced. Both of these potential advantages may improve long-term graft survival.

[11] In one aspect, the present invention provides a keratoplasty graft deployment device that includes a sleeve having a sleeve lumen that extends to a distal end of the sleeve, wherein the sleeve lumen extends along a longitudinal axis that passes through the sleeve; a delivery element having a distal end and a proximal end, wherein the delivery element is sized for advancement along the longitudinal axis through the sleeve lumen to the distal end of the sleeve; and a tissue delivery section at the distal end of the delivery element, wherein the tissue delivery section includes one or more openings in fluid communication with a delivery element lumen that extends through the delivery element along the longitudinal axis. The device may optionally include one or more of the following features: a fluid delivery apparatus in fluid communication with the delivery element lumen, wherein the fluid delivery apparatus is capable of delivering a fluid through the delivery element lumen to the tissue delivery section at the distal end of the delivery element; the delivery element lumen may extend from the proximal end of the tissue delivery element to the tissue delivery section; the tissue delivery section may have an elliptical cross-sectional profile taken perpendicular to the longitudinal axis, wherein the elliptical cross-sectional profile defines two opposing major sides, and wherein the one or more openings are located one or both of the two opposing major sides; the tissue delivery section may be suspended within the sleeve lumen when the tissue delivery section is located within the sleeve lumen, etc.

[12] In still other embodiments, the devices of the present invention may also optionally include one or more of the following features: at least one major side of the two opposing major sides of the tissue delivery section may include two or more openings; the delivery element may include a length along the longitudinal axis that is greater than a length of the sleeve through which the delivery element is advanced; the fluid delivery apparatus may include a plunger; the fluid delivered through the fluid delivery apparatus may include air; the distal end of the sleeve may have a blunt end; the distal end of the sleeve may have a tapered end; the device may include a barrel located proximate the proximal end of the sleeve, wherein the sleeve extends through the barrel; etc.

[13] In another aspect, the present invention may provide a keratoplasty graft deployment device that includes a sleeve having a sleeve lumen that extends to a distal end of the sleeve, wherein the sleeve lumen extends along a longitudinal axis that passes through the sleeve; a delivery element having a distal end and a proximal end, wherein the delivery element is sized for advancement along the longitudinal axis through the sleeve lumen to the distal end of the sleeve; and a tissue delivery section at the distal end of the delivery element, wherein the tissue delivery section includes one or more openings in fluid communication with a delivery element lumen that extends through the delivery element along the longitudinal axis.

[14] In still other embodiments, the devices of the present invention may also optionally include one or more of the following features: the delivery element lumen may extend from the proximal end of the tissue delivery element to the tissue delivery section; the tissue delivery section may have an elliptical cross-sectional profile taken perpendicular to the longitudinal axis, wherein the elliptical cross-sectional profile defines two opposing major sides, and wherein the one or more openings are located one or both of the two opposing major sides; the tissue delivery section may be suspended within the sleeve lumen when the tissue delivery section is located within the sleeve lumen; at least one major side of the two opposing major sides of the tissue delivery section may include two or more openings; the delivery element may have a length along the longitudinal axis that is greater than a length of the sleeve through which the delivery element is advanced; a fluid delivery apparatus may be provided that is in fluid communication with the delivery element lumen, wherein the fluid delivery apparatus is capable of delivering a fluid through the delivery element lumen to the tissue delivery section at the distal end of the delivery element; wherein the fluid delivery apparatus may include a plunger; fluid delivered through the fluid delivery apparatus may include air; the distal end of the sleeve may include a blunt end; the distal end of the sleeve may include a tapered end; a barrel may be located proximate the proximal end of the sleeve, wherein the sleeve extends through the barrel; etc.

[15] In another aspect, the present invention may provide a keratoplasty graft deployment device that includes a sleeve including a sleeve lumen that extends to a distal end of the sleeve, wherein the sleeve lumen extends along a longitudinal axis that passes through the sleeve; a delivery element having a distal end and a proximal end, wherein the delivery element is sized for advancement along the longitudinal axis through the sleeve lumen to the distal end of the sleeve; and a tissue delivery section at the distal end of the delivery element, wherein the tissue delivery section includes one or more openings in fluid communication with a delivery element lumen that extends through the delivery element along the longitudinal axis; wherein the delivery element lumen extends from the proximal end of the tissue delivery element to the tissue delivery section; and wherein the tissue delivery section has an elliptical cross- sectional profile taken perpendicular to the longitudinal axis, wherein the elliptical cross-sectional profile defines two opposing major sides, and wherein the one or more openings are located one or both of the two opposing major sides.

[16] In still other embodiments, the devices of the present invention may also optionally include one or more of the following features: the tissue delivery section may be suspended within the sleeve lumen when the tissue delivery section is located within the sleeve lumen; at least one major side of the two opposing major sides of the tissue delivery section may include two or more openings; the delivery element may include a length along the longitudinal axis that is greater than a length of the sleeve through which the delivery element is advanced; a fluid delivery apparatus may be provided that is in fluid communication with the delivery element lumen, wherein the fluid delivery apparatus is capable of delivering a fluid through the delivery element lumen to the tissue delivery section at the distal end of the delivery element; the distal end of the sleeve may have a blunt end; the distal end of the sleeve may have a tapered end; etc.

[17] In another aspect, the present invention provides a method of delivering a corneal transplant, the method including locating a graft comprising lamellar corneal tissue on the tissue delivery section of a keratoplasty graft deployment device according to the present invention; positioning the distal end of the sleeve into the anterior chamber of an eye; advancing the graft on the tissue delivery device through the sleeve lumen of the sleeve until the graft passes out of the distal end of the sleeve; and delivering fluid through the delivery element lumen, wherein the graft releases from the tissue delivery section within the anterior chamber of the eye. The fluid may, in some embodiments, include air.

[18] In another aspect, the present invention may provide a method of delivering a corneal transplant. The method may include locating a graft having lamellar corneal tissue on the tissue delivery section of a keratoplasty graft deployment device according to the present invention; positioning the distal end of the sleeve into the anterior chamber of an eye; advancing the graft on the tissue delivery device through the sleeve lumen of the sleeve until the graft passes out of the distal end of the sleeve; and delivering a fluid through the delivery element lumen, wherein the graft releases from the tissue delivery section within the anterior chamber of the eye. The fluid delivered through the delivery element lumen may be air.

[19] The words "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[20] As used herein, "a,'^* "an," "the," "at least one," and "one or more" are used interchangeably. Thus, for example, a tissue delivery section may refer to one or more tissue delivery sections.

[21] The term "and/or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[22] The above summary is not intended to describe each embodiment or every implementation of the present invention. Rather, a more complete understanding of the invention will become apparent and appreciated by reference to the following Detailed Description of Exemplary Embodiments and claims in view of the accompanying figures of the drawing.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWING

[23] The present invention will be further described with reference to the views of the drawing, wherein:

[24] FIG. 1 is a perspective view of one exemplary keratoplasty graft deployment device according to the present invention.

[25] FIG. 2 is an exploded view of the keratoplasty graft deployment device of FIG. 1.

[26] FIG. 3 is an enlarged side view of an exemplary tissue delivery section that may be used in connection with the present invention.

[27] FIG. 4 is a cross-sectional view of the tissue delivery section depicted in FIG. 3 taken along line 4-4 in FIG. 3.

[28] FIG. 5 is a cross-sectional view of the tissue delivery section depicted in FIG. 3 taken along line 5-5 in FIG. 3.

[29] FIG. 6 is an enlarged cross-sectional view of the sleeve of FIGS. 1 &

2. [30] FIG. 7 is an end view of the device of FIG. 1 with a graft positioned on the tissue delivery section.

[31] FIG. 8 is a perspective vies of an alternate sleeve for use in connection with the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[32] In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

[33] One exemplary embodiment of a keratoplasty graft deployment device 10 is depicted in FIGS. 1 & 2 (with various components of the device being separated in the exploded view of FIG. 2). The device 10 includes a tissue delivery section 20 located at the distal end 32 of a delivery element 30. The device 10 also includes a sleeve 40 that is sized to receive the tissue delivery section 20 and at least a portion of the delivery element 30. An optional fluid delivery apparatus 50 may be attached to the proximal end 34 of the delivery element 30. These various components are preferably positioned along a longitudinal axis 12.

[34] The delivery element 30 is preferably sized to fit within a lumen (not shown) in the sleeve 40. It may be preferred that the delivery element 30 have a length between its distal end 32 and its proximal end 34 such that the tissue delivery section 20 can be extended outside of the sleeve 40 while the distal end 34 of the delivery element 30 extends proximally past the proximal end of the sleeve 30. In some embodiments, the lumen in the delivery element 30 may terminate short of the proximal end 34 in which case it may be preferred that the fluid delivery apparatus be attached to the lumen in some manner that is capable of delivering fluid to the tissue delivery device 20. [35] The sleeve 40 may preferably include a distal portion 42 extending from a barrel 46. The barrel 46 may preferably be larger than the distal portion 42 to facilitate handling of the sleeve 40 by a user, while the distal portion 42 may be smaller and may include an angled tip 44 to facilitate insertion of the distal portion 42 into the anterior chamber of the eye as discussed herein.

[36] The fluid delivery apparatus 50 depicted in connection with the device 10 is preferably adapted to be operably attached to the proximal end 34 of the delivery element 30. The delivery element 30 also preferably includes a lumen (not shown in FIGS. 1 & 2) that is in fluid communication with the fluid delivery apparatus 50 and the openings 22 in the tissue delivery section 20. As a result, fluid can preferably be delivered from the apparatus 50 at the proximal end 34 of the delivery device 30 to the tissue delivery section 20 through the lumen in the delivery element 30.

[37] The fluid delivery apparatus 50 depicted in FIGS. 1 & 2 includes a barrel 52 into which plunger 54 may be advanced to deliver a fluid located within the volume of the barrel 52 through port 56. In essence, the depicted fluid delivery apparatus is a syringe and any apparatus capable of providing fluid to the lumen in the delivery element 30 (and, thus, to the tissue delivery section 20) may be used in place of the depicted apparatus 50.

[38] The tissue delivery section 20 is depicted in an enlarged view in

FIGS. 3-5 (where FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3 and is a cross-sectional view taken along line 5-5 in FIG. 3). The tissue delivery section 20 includes one or more openings 22 and is attached to the distal end 32 of the delivery element 30. The openings 22 are preferably in fluid communication with the lumen 36 formed in the delivery element 30 such that fluid delivered to the distal end 32 of the delivery element 30 can pass out of the tissue delivery section 20 through the openings 22.

[39] It may be preferred that the tissue delivery section have a non-circular cross-section. The depicted tissue delivery section 20, for example, preferably has an elliptical cross-sectional shape as depicted in FIGS. 4 & 5 (which are cross-sectional views taken along lines that are perpendicular to the longitudinal axis 12), although any suitable shape may be used (e.g., oval, egg-shaped, etc.). [40] The elliptical cross-sectional shape of the tissue delivery section may preferably define two opposing major sides 21 and 23. The openings 22 may be located in one or both of the opposing major sides 21 and 23. It may be preferred that the outermost rows of openings 22 (one of which is intersected by cross-sectional line 4-4 in FIG. 3) include fewer openings while the more centrally located rows of openings (one of which is intersected by cross-sectional line 5-5 in FIG. 3) include more openings 22, with openings on both major sides 21 and 23 of the tissue delivery section 20

[41] The tissue delivery section 20 may preferably include a shoulder 24 that narrows where the tissue delivery section 20 meets the distal end 32 of the delivery element 30. The shoulder 24 may provide one manner in which movement of the tissue delivery section 20 in the proximal direction through the sleeve 40 is constrained.

[42] Referring to FIG. 6, sleeve 40 is depicted in cross-section to show the lumen 48 that extends through the sleeve 40. The lumen 48 is preferably sized to allow passage of the delivery element 30 therethrough. It may be preferred that the portion of the lumen 48 within the distal portion 42 of the sleeve 40 be large enough and/or shaped to receive the tissue delivery section 20 and the delivery element 30 therein, while the lumen within the barrel 46 of the sleeve 40 be smaller such that passage of the tissue delivery section 20 therethrough is prevented.

[43] In particular, it may be preferred that the lumen 48 include a shoulder

49 that prevents proximal movement of the tissue delivery section 20 through the portion of the lumen 48 contained within the barrel 46. In addition, it may be preferred that at least a portion of the lumen 48 be small enough and/or include structures such that the tissue delivery section 20 at the distal end 32 of the delivery element 30 is suspended within the distal portion 42 of the sleeve 40.

[44] FIG. 7 , which is an end view of the device taken along the longitudinal axis 12 with a graft 14 located on the tissue delivery section, depicts suspension of the tissue delivery section 20 within the sleeve lumen 48. Suspension of the tissue delivery section 20 within the distal portion 42 of the sleeve 40 preferably prevents contact between the graft 14 on the outer surface of the tissue delivery section 20 and the interior of the sleeve lumen 48.

[45] Another optional feature depicted in FIG. 7 is that the distal portion of the sleeve 42 may preferably have a shape that is complementary to the shape of the tissue delivery section 20. In other words, in the depicted embodiment, it may be preferred that the lumen 48 in the distal portion 42 of the sleeve have an elliptical shape complementary to the elliptical shape of the tissue delivery section 20.

[46] FIG. 8 depicts an alternate sleeve 140 that, unlike the sleeve 40 of

FIGS. 1, 2 & 6, includes a tip 144 at the end of the distal portion 142 that is not angled, i.e., is blunt.

[47] The various components in the devices of the invention may be constructed of any suitable material or materials. Examples of potentially suitable materials may include medical grade polymers, metals, etc. Methods of using the devices of the present invention may preferably involve coating the grafts and/or the outer surfaces of the tissue delivery sections with a viscoelastic material (e.g., 1% sodium hyalurate, etc.) to reduce the likelihood of damage to the graft during the deployment process.

[48] The complete disclosure of the patents, patent documents, and publications cited in the Background, the Detailed Description of Exemplary Embodiments, and elsewhere herein are incorporated by reference in their entirety as if each were individually incorporated.

[49] Exemplary embodiments of this invention have been discussed and reference has been made to possible variations within the scope of this invention. These and other variations and modifications in the invention will be apparent to those skilled in the art without departing from the scope of the invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein. Accordingly, the invention is to be limited only by the claims provided below and equivalents thereof.

Claims

CLAIMS:

1. A keratoplasty graft deployment device comprising: a sleeve comprising a sleeve lumen that extends to a distal end of the sleeve, wherein the sleeve lumen extends along a longitudinal axis that passes through the sleeve; a delivery element comprising a distal end and a proximal end, wherein the delivery element is sized for advancement along the longitudinal axis through the sleeve lumen to the distal end of the sleeve; and a tissue delivery section at the distal end of the delivery element, wherein the tissue delivery section comprises one or more openings in fluid communication with a delivery element lumen that extends through the delivery element along the longitudinal axis.

2. A keratoplasty graft deployment device according to claim 1, wherein the delivery element lumen extends from the proximal end of the tissue delivery element to the tissue delivery section.

3. A keratoplasty graft deployment device according to claim 1, wherein the tissue delivery section comprises an elliptical cross-sectional profile taken perpendicular to the longitudinal axis, wherein the elliptical cross-sectional profile defines two opposing major sides, and wherein the one or more openings are located one or both of the two opposing major sides.

4. A keratoplasty graft deployment device according to claim 1 , wherein the tissue delivery section is suspended within the sleeve lumen when the tissue delivery section is located within the sleeve lumen.

5. A keratoplasty graft deployment device according to claim 1, wherein at least one major side of the two opposing major sides of the tissue delivery section comprises two or more openings.

6. A keratoplasty graft deployment device according to claim 1, wherein the delivery element comprises a length along the longitudinal axis that is greater than a length of the sleeve through which the delivery element is advanced.

7. A keratoplasty graft deployment device according to claim 1 , the device further comprising a fluid delivery apparatus in fluid communication with the delivery element lumen, wherein the fluid delivery apparatus is capable of delivering a fluid through the delivery element lumen to the tissue delivery section at the distal end of the delivery element.

8. A keratoplasty graft deployment device according to claim 7, wherein the fluid delivery apparatus comprises a plunger.

9. A keratoplasty graft deployment device according to claim 7, wherein the fluid delivered through the fluid delivery apparatus comprises air.

10. A keratoplasty graft deployment device according to claim 1, wherein the distal end of the sleeve comprises a blunt end.

1 1. A keratoplasty graft deployment device according to claim 1, wherein the distal end of the sleeve comprises a tapered end.

12. A keratoplasty graft deployment device according to claim 1, further comprising a barrel located proximate the proximal end of the sleeve, wherein the sleeve extends through the barrel.

13. A keratoplasty graft deployment device comprising: a sleeve comprising a sleeve lumen that extends to a distal end of the sleeve, wherein the sleeve lumen extends along a longitudinal axis that passes through the sleeve; a delivery element comprising a distal end and a proximal end, wherein the delivery element is sized for advancement along the longitudinal axis through the sleeve lumen to the distal end of the sleeve; and a tissue delivery section at the distal end of the delivery element, wherein the tissue delivery section comprises one or more openings in fluid communication with a delivery element lumen that extends through the delivery element along the longitudinal axis; wherein the delivery element lumen extends from the proximal end of the tissue delivery element to the tissue delivery section; and wherein the tissue delivery section comprises an elliptical cross-sectional profile taken perpendicular to the longitudinal axis, wherein the elliptical cross- sectional profile defines two opposing major sides, and wherein the one or more openings are located one or both of the two opposing major sides.

14. A keratoplasty graft deployment device according to claim 13, wherein the tissue delivery section is suspended within the sleeve lumen when the tissue delivery section is located within the sleeve lumen.

15. A keratoplasty graft deployment device according to claim 13, wherein at least one major side of the two opposing major sides of the tissue delivery section comprises two or more openings.

16. A keratoplasty graft deployment device according to claim 13, wherein the delivery element comprises a length along the longitudinal axis that is greater than a length of the sleeve through which the delivery element is advanced.

17. A keratoplasty graft deployment device according to claim 13, the device further comprising a fluid delivery apparatus in fluid communication with the delivery element lumen, wherein the fluid delivery apparatus is capable of delivering a fluid through the delivery element lumen to the tissue delivery section at the distal end of the delivery element.

18. A keratoplasty graft deployment device according to claim 13, wherein the distal end of the sleeve comprises a blunt end.

19. A keratoplasty graft deployment device according to claim 13, wherein the distal end of the sleeve comprises a tapered end.

20. A method of delivering a corneal transplant, the method comprising: locating a graft comprising lamellar corneal tissue on the tissue delivery section of a keratoplasty graft deployment device according to any one of claims 1- 19; positioning the distal end of the sleeve into the anterior chamber of an eye; advancing the graft on the tissue delivery device through the sleeve lumen of the sleeve until the graft passes out of the distal end of the sleeve; and delivering fluid through the delivery element lumen, wherein the graft releases from the tissue delivery section within the anterior chamber of the eye.

21. A method according to claim 20, wherein the fluid comprises air.