A trephine blade for preparation of a donor corneal graft

Abstract

There is described a trephine blade (10, 56) for use in the preparation of a corneal graft for use in endothelial keratoplasty, the blade incorporating an asymmetric cutting formation (20) for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in the endothelial keratoplasty. In embodiments, the cutting formation (20) may protrude from a cutting end of the blade in the longitudinal direction of the blade and is generally defined be a first edge (22) for making an inwardly directed cut in the graft and a further cutting edge (24) for making an outwardly directed cut to form the asymmetric notch in the graft. The inner ends of first edge (22) and the further cutting edge (24) typically meet at a curved trough (26) of the cutting formation (20). In embodiments described, at least one of the opposite ends of the first edge (22) and the further cutting edge (24) of the cutting formation (20) is continuous with a respective curved cutting edge (32, 34) that curves into the cutting formation.

Description

[0001] A TREPHINE BLADE FOR PREPARATION OF

[0002] A DONOR CORNEAL GRAFT

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a trephine blade for preparation of a donor corneal tissue graft for use in eye surgery. Cutting devices including the blade are also provided together with methods for use of the blade.

[0005] BACKGROUND TO THE INVENTION

[0006] Comeal transplantation is a key component in the treatment of comeal blindness and other comeal disease. The first iteration of co meal transplant involved the removal of the full thickness of the host cornea and replacement with a healthy full thickness donor cornea.

[0007] Several comeal surgical techniques have been developed in recent times resulting in significant advances in the treatment of diseases and conditions affecting the endothelium and associated tissues of the cornea, primary examples of which include Fuch’s dystrophy, Posterior Polymorphous Membrane Dystrophy and Pseudophakic Bullous Keratopathy (PBK) amongst others. These techniques involve transplanting endothelial tissue of a donor cornea along with selected attached inner layer(s) of the cornea into the recipient’s eye through a comeal or sclerocorneal incision following dissection of relevant tissue from the recipient eye, and are known as endothelial keratoplasty (EK)

[0008] Deep lamellar endothelial keratoplasty (DLEK) is an early form of EK which involves dissection of the posterior stromal lamella, Descemet’s membrane and endothelium of the eye being treated and inserting a comeal graft comprising donor posterior stroma tissue, Descemet’s membrane and endothelium. Later EK methods include Descemet’s Stripping EK (DSEK) and Descemet’s Membrane EK (DMEK). Descemet’s Stripping Automated EK (DSAEK) is a variation of DSEK in which the donor comeal layers are separated using an automated microkeratome for provision of the graft tissue to improve the graft-host interface, resulting in faster visual recovery, and reduced incidence of patient astigmatism and graft failure.

[0009] However, each of these EK techniques require correct orientation of the comeal graft in the recipient’s eye, namely with the graft endothelial layer facing toward the anterior chamber and iris. The graft tissue is generally inserted into the eye through the comeal or sclerocorneal incision in a folded condition. Once located in the anterior chamber, the graft tissue is unfolded by gentle manipulation. It is possible though for the graft to unfold in an incorrect orientation in which the endothelial side of the graft faces upwards (towards the host cornea) rather than downwards (towards the iris). Incorrect orientation of the graft leads to graft failure if not identified by the comeal surgeon.

[0010] As a means for identifying incorrect orientation of the graft in the eye, different numbers of circular cuts can be individually manually punched into each side of the circumferential perimeter of the graft. However, this results in an undesirable amount of comeal tissue being removed from the graft and an irregular circumference increasing the risk of potential dislocation of the graft from the recipient tissue and / or failure of the graft in those areas. In another method, a dye can be used to mark symbols (e.g., a letter in brail) to indicate graft orientation. The dye though may adversely affect tissue cells in the vicinity of the marked symbols and / or wash or fade from clear view. Each of these methods also involves additional steps in the handling of the graft for transplantation which is undesirable increasing the risk of damage to endothelial cells and other tissues of grafts.

[0011] A trephine blade for use in endothelial keratoplasty is described in WO 2022 / 109678 having an asymmetric notch formed on one side of the blade for cutting a correspondingly shaped notch in the outer perimeter of the donor comeal tissue to indicate correct orientation of the graft in the recipient’s eye.

[0012] Comeal grafts though are at risk of tearing and damage during the preparation of the graft tissue as well as during location in its proper orientation in the eye of the recipient patient, which can potentially lead to adverse outcomes both in terms of the integrity of the graft and the success of the transplant. SUMMARY OF THE INVENTION

[0013] The present invention in one or more forms relates to the provision of a trephine blade for use in endothelial keratoplasty and which is configured to form a correspondingly shaped notch in the outer perimeter of the donor comeal graft for indicating correct orientation of the graft in the recipient’s eye and which provides for reducing the risk of damage and / or tearing of the tissue during the preparation of the comeal graft and / or the surgery. More particularly, in arriving at the present invention the inventor has recognised that the donor comeal tissue can flex and / or move during cutting of the tissue during preparation of the graft which may distort the desired profile of the graft particularly when cutting a notch in the graft for indicating orientation of the graft during surgery and further, that the risk of tearing or unwanted folding of the graft during location or manipulation of the graft in endothelial keratoplasty may be ameliorated.

[0014] More particularly, in one aspect of the present invention there is provided a trephine blade for use in the preparation of a comeal graft for endothelial keratoplasty, the blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, the cutting formation protmding from a cutting end of the blade in the longitudinal direction of the blade.

[0015] Typically, the cutting formation is defined by a longitudinally directed channel provided in a peripheral side wall of the blade.

[0016] Most typically, the channel extends from the cutting end of the blade to an opposite end of the blade.

[0017] Typically, the cutting formation of the blade is configured to cut the asymmetric notch in the donor comeal tissue to a shape for indicating whether the endothelial layer of the comeal graft is facing upwardly or downwardly when the graft is viewed from above.

[0018] Typically, the determination of the whether the endothelial layer of the comeal graft is facing upwardly or downwardly is dependent on the orientation of the notch when viewed from above. Typically, the cutting formation of the trephine blade is defined by a first edge for cutting an inwardly directed cut in the graft and a further cutting edge for making an outwardly directed cut in the graft to form the asymmetric notch in the graft.

[0019] Typically, the first edge and the further cutting edge meet at a curved trough of the notch formation.

[0020] Typically, the curved trough of the notch formation has a radius in a range of from about 0.1mm to about 0.3 mm or greater.

[0021] Typically, at least one of opposite ends of the first edge and the further cutting edge of the cutting formation is continuous with a respective curved cutting edge of the blade that curves into the cutting formation.

[0022] In particularly preferred embodiments, both the first cutting edge and the further cutting edge of the cutting formation are continuous with a respective said curved cutting edge that curves into the cutting formation.

[0023] Typically, the first edge and the further cutting edge are oriented at an acute angle relative to one another. Most usually, the acute angle is in a range of from about 70° to about 80° more preferably, is about 75°.

[0024] Typically, the first edge and the further cutting edge are both at least predominantly straight cutting edges.

[0025] Typically, the further cutting edge is longer in length than the first cutting edge.

[0026] Typically, the first edge is orientated for cutting the graft generally radially with respect to the centre of the graft.

[0027] In particularly preferred embodiments, the cutting formation is continuous with a circular cutting edge of the blade for cutting the outer circumferential perimeter of the graft from donor comeal tissue.

[0028] Typically, the cutting formation is a notch formation.

[0029] Hence, in another aspect of the invention there is provided a trephine blade for use in the preparation of a comeal graft for endothelial keratoplasty, the blade having a circular cutting edge for cutting the comeal graft from donor comeal tissue to form a circumferential perimeter of the graft, the circular cutting edge extending around one end of the blade and incorporating an asymmetric notch formation for cutting a correspondingly shaped asymmetric notch in the circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the notch formation protrudes from the one end of the blade in the longitudinal direction of the blade.

[0030] Typically, an opposite end of at least one of the first inwardly directed cutting edge and the further cutting edge of the notch formation of a trephine blade in accordance with the invention is continuous with a respective curved edge that curves from the circular cutting edge of the blade inwardly into the notch formation.

[0031] In embodiments with a circular such cutting edge, the blade is typically tubular with a constant maximum outer circumferential perimeter and a constant maximum internal diameter from the circular cutting edge of the blade to the opposite end of the blade The trephine blade of such embodiments is therefore generally hollow with a longitudinal passageway extending from one end of the blade to the opposite end of the blade and wherein the notch formation protrudes into the passageway.

[0032] As will be understood, embodiments a trephine blade with a circular cutting edge as described herein may be used to cut the full perimeter of the comeal graft including the asymmetric notch in the one cutting action.

[0033] In other embodiments in accordance with the invention, the cutting formation of the trephine blade is a sideward, outwardly directed prominence of the blade. Such embodiments may be used to cut the asymmetric notch in the comeal graft after the graft has been cut to its maximal diameter such as by a conventional tubular trephine blade and typically, are configured to be hand-held for the cutting of the asymmetric notch in the graft. As with embodiments in which the cutting formation is a notch formation of the blade, in embodiments in which the cutting formation is provided by a sideward, outwardly directed prominence, one or both of the opposite ends of the first and the further cutting edge of the cutting formation may be continuous with a respective curved cutting edge as described herein that curves into the cutting formation.

[0034] Typically, the cutting formation of a trephine blade embodied by the invention has a transverse cross section perpendicular to the longitudinal axis of the blade wherein the cross-section is constant from the cutting end of the blade to the opposite end of the blade.

[0035] Typically, the cutting formation of a trephine blade embodied by the invention is configured to form an asymmetrical notch in the perimeter of the comeal graft that is generally in the shape of the number “7” or a stylised form thereof when the comeal tissue is viewed from above with the endothelium layer of the comeal tissue facing down, i.e., the correct orientation within the eye of the recipient.

[0036] In another aspect of the present invention there is provided a trephine blade as described herein for use in the preparation of a comeal graft for endothelial keratoplasty, the blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the cutting formation has a cutting edge defined by a first edge for cutting an inwardly directed cut in the graft and a further cutting edge for making an outwardly directed cut in the graft to form the asymmetric notch in the graft, the first edge and the further cutting edge meeting at a curved trough of the cutting formation.

[0037] In another aspect of the present invention there is provided a trephine blade as described herein for use in the preparation of a comeal graft for endothelial keratoplasty, the blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the cutting formation is defined by a first edge for cutting an inwardly directed cut in the graft and a further cutting edge for making an outwardly directed cut in the graft to form the asymmetric notch, at least one of the opposite ends of the first cutting edge and the further cutting edge of the cutting formation being continuous with a respective curved cutting edge that curves into the cutting formation.

[0038] In another aspect of the present invention there is provided a trephine blade for use in the preparation of a comeal graft for endothelial keratoplasty, the blade having a circular cutting edge for cutting the comeal graft from donor comeal tissue and extending circumferentially around one end of the blade, the circular cutting edge of the blade incorporating an asymmetric notch formation for cutting a correspondingly shaped notch in the circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the notch formation has a notch cutting edge that is continuous with the circular cutting edge of the blade and is defined by an inwardly directed cutting edge and a further cutting edge extending from an inner end of the inwardly directed cutting edge to the circular cutting edge of the blade, the inwardly directed cutting edge and the further cutting edge meeting at a curved trough of the notch formation.

[0039] In another aspect of the present invention there is provided a trephine blade for use in the preparation of a comeal graft for endothelial keratoplasty, the blade having a circular cutting edge for cutting the comeal graft from donor comeal tissue and extending peripherally around one end of the blade, the circular cutting edge of the blade incorporating an asymmetric notch formation for cutting a correspondingly shaped notch in the circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the notch formation has a notch cutting edge that is continuous with the circular cutting edge of the blade and is defined by an inwardly directed cutting edge and a further cutting edge extending from an inner end of the inwardly directed cutting edge to the circular cutting edge of the blade, an opposite end of at least one of the inwardly directed cutting edge and the further cutting edge of the notch formation being continuous with a respective curved cutting edge that curves from the circular cutting edge of the blade inwardly into the notch formation.

[0040] In another aspect there is provided a cutting device for the preparation of a comeal graft for endothelial keratoplasty, the device incorporating a trephine blade embodied by the invention.

[0041] In another aspect of the present invention there is provided a cutting device for the preparation of a comeal graft for endothelial keratoplasty, the device incorporating a trephine blade having a circular cutting edge for cutting the comeal graft from donor comeal tissue and extending peripherally around one end of the blade, the circular cutting edge of the blade incorporating an asymmetric notch formation for cutting a correspondingly shaped notch in the circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the notch formation protmdes from the one end of the blade in the longitudinal direction of the blade.

[0042] In another aspect of the present invention there is provided a method for preparing a comeal graft from donor comeal tissue for use of the graft in endothelial keratoplasty, comprising the steps of: providing a trephine blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in the perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the cutting formation protrudes from a cutting end of the blade in the longitudinal direction of the blade; and cutting donor comeal tissue with the blade to provide the graft.

[0043] In still another aspect of the invention there is provided a method for preparing a comeal graft from donor comeal tissue for use of the graft in endothelial keratoplasty, comprising the steps of: providing a trephine blade having a circular cutting edge for cutting the comeal graft from donor comeal tissue and extending periphery around one end of the blade, the blade incorporating an asymmetric notch formation for cutting a correspondingly shaped notch in the circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the notch formation protmdes from the one end of the blade in the longitudinal direction of the blade; cutting the donor comeal tissue with the blade; and retrieving the cut comeal tissue.

[0044] In at least some embodiments, a trephine blade of the invention is held by a cutting device in use for the cutting of the donor comeal tissue by the blade, and the device is operated to cut the comeal tissue by the blade.

[0045] Typically, the cutting device for the cutting of the donor tissue is a punch. In preferred embodiments the trephine blade is mounted to or housed within the punch in use of the blade to cut the comeal tissue.

[0046] Typically, the blade is arranged for being driven toward the donor comeal tissue to affect the cutting of the donor tissue by the blade with operation of the punch.

[0047] The formation of the asymmetric notch in the comeal graft ameliorates the risk of the co meal graft being located in the recipient’s eye being located incorrectly with the endothelial layer of the graft facing upwardly rather than downwardly, with the surgeon being able to rapidly determine whether the graft is correctly orientated or not by the surgeon viewing the orientation of the notch cut in the graft.

[0048] Advantageously, as the cutting formation of embodiments described herein protmdes from the cutting edge of the trephine blade can act to “pin” the donor comeal tissue in position or otherwise reduce movement of the donor comeal tissue at least in the vicinity of the tissue in which the notch is to be cut by virtue of contacting the tissue first during the cutting process, and so may restrict distortion of the donor tissue in that area and provide a cleaner cut of the tissue and / or reduce the potential for distortion of the shape of the asymmetrical notch cut in the donor tissue.

[0049] Moreover, the provision of a curved trough in the cutting formation of the trephine blade between the first edge and the further cutting edge of the cutting formation provides a corresponding shaped curve in the notch of the comeal graft, ameliorating the risk of the comeal graft tearing from that location during preparation, handling and placement of the comeal graft in endothelial keratoplasty.

[0050] Further advantageously, the provision of curved edge(s) turning into the first and / or further cutting edge(s) of the cutting formation edge of the trephine plane produce corresponding curve(s) in the profile of the comeal graft. This avoids sharp comer(s) in the graft at these locations and so ameliorates or reduces the potential for the comeal graft to fold under itself at those locations as well as reducing contact points and contact drag at each of those locations during the preparation and handling of the graft, reducing the risk of contact forces being transferred to the trough of the notch formation cut in the graft and so tearing of the graft from the trough.

[0051] The endothelial keratoplasty can, for example, be selected from the group consisting of DSAEK, DMEK, DLEK and DSEK comeal transplant methods.

[0052] Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers, integers or steps.

[0053] Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any, or all, of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed in Australia or elsewhere before the priority date of this application. The features and advantages of the present invention will become further apparent from the following detailed description of exemplary embodiments of the invention together with the accompanying drawings.

[0054] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0055] Figure 1 is a front isometric view of a trephine blade embodied by the invention;

[0056] Figure 2 is a rear isometric view of the trephine blade of Fig. 1;

[0057] Figure 3 is a front view of the trephine blade of Fig. 1 ;

[0058] Figure 4 is a slightly rotated rear view of the trephine blade of Fig. 1 ;

[0059] Figure 5 is a view illustrating the end profde of the cutting end of the trephine blade of Fig. 1;

[0060] Figure 6 is an elevated front view of the trephine blade of Fig. 1 mounted in a partially exploded view of a trephine blade cutting assembly;

[0061] Figure 7 shows the plunger of the trephine blade cutting assembly of Fig. 6 from below;

[0062] Figure 8 shows the plunger of the trephine blade cutting assembly of Fig. 6 from above;

[0063] Figure 9 is an isometric view of the base of the trephine blade cutting assembly of Fig. 6;

[0064] Figure 10 shows the base of the trephine blade cutting assembly of Fig. 6 from below;

[0065] Figure 11 is a front view of a further embodiment of a trephine blade in accordance with the present disclosure in which the asymmetric notch formation of the blade does not protrude from the cutting end of the blade; and

[0066] Figure 12 is a view illustrating the profile of the cutting end of another trephine blade embodied by the invention. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE

[0067] INVENTION

[0068] A trephine blade 10 embodied by the invention is illustrated in Figs. 1-4. The blade is tubular in form with a peripheral side wall 12 surrounding a through passageway 14 which extends from the cutting end 16 of the blade to an opposite end 30 having a circular cutting edge 18 extending circumferentially around the blade. The cutting formation 20 in this embodiment is an inwardly directed asymmetric notch formation defined in the side wall of the blade. As can be seen, the notch formation has a cutting edge that is continuous with the circular cutting edge 18 and which is defined by an inwardly directed first cutting edge 22 and a further cutting edge 24 that extends from the inner end of the inwardly directed cutting edge 22 to the circular peripheral cutting edge 18. The inwardly directed cutting edge and the further cutting edge meet at a curved trough 26 of the notch formation. As also shown, the notch formation protrudes into the through passageway 14 of the blade 10.

[0069] As illustrated in Fig. 1, the notch formation is defined by a longitudinally extending channel 28 formed in the peripheral side wall 12 and which extends the full length of the blade. As further best shown in Figs. 4-5, the channel formation protrudes in the longitudinal direction from the cutting end on which the circular cutting edge is defined, with the end of the curved trough 26 standing slightly proud relative to the entrance to the notch formation, the entrance to the notch formation being indicated by the numeral 27. That is, the cutting / notch formation stands proud of the cutting end of the blade at its greatest extent at the curved trough 26 of the formation. In use, the protruding end of the notch formation may therefore contact and cut into the donor comeal tissue slightly before the adjacent regions of the circular cutting edge 18. This may reduce distortion of the comeal tissue about the notch formation during the cutting of the donor tissue as may occur due to the tissue flexing when the circular cutting edge 18 contacts adjacent tissue or when the tissue is not evenly or correctly seated during the cutting process or moves or slides during the cutting process, providing for a sharper or more distinct shape of the notch cut into the tissue.

[0070] In embodiments, the notch formation may protmde, for instance, about 0.1 mm or more from the cutting end of the blade and generally a distance in a range of from about 0.1 mm to about 2.0 mm or more. For example, in embodiments of the present disclosure the notch formation may protrude a distance of about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm 0.9 mm, 1.0 mm, 1.1 mm 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2.0 mm or more from the end of the blade. Preferably, the notch formation protrudes a distance in a range of from about of about 0.1 mm to about 1.0 mm, more typically, a distance in a range of from about 0.1 mm to about 0.75 mm and most typically, from about 0.1 mm to about 0.5 mm, and all distances in the above ranges are expressly encompassed.

[0071] The shape of the notch formation is best illustrated in the end profde of the trephine blade illustrated in Fig. 5.

[0072] In preferred embodiments, the curved trough of the blade 10 is concave in form with a radius of up to about 2.0 mm or more. Advantageously, the present inventor has recognised that by providing the trephine blade with the cutting edges 22 and 24 of the notch formation meeting in a curved trough rather than a sharp point, force exerted on the corresponding trough cut in the donor tissue as can occur during the preparation, handling and location of the comeal graft during comeal endothelial keratoplasty may be dispersed along the trough cut in the graft, reducing the risk of the graft tearing at that location as compared to the cut tissue edges of the graft notch meeting at a point or sharp angle. Typically, the curved trough has a radius in a range of from about 0.05 mm to about 2.0 mm, e.g., 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0,16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.20 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm,

[0073] 0.28 mm, 0.29 mm, 0.3 mm and so on up to e.g., 1.0 mm, 1.05 mm, 1.1mm, 1.15 mm, 1.20 mm, 1.25 mm, 1.30 mm, 1.35 mm, 1.40 mm, 1.45 mm, 1.50 mm, 1.55 mm, 1.60 mm, 1.65 mm, 1.70 mm, 1.75 mm, 1.80 mm, 1.85 mm, 1.90 mm, 1.95 mm or 2.0 mm or more, and all radii within the above ranges are expressly encompassed. Typically, the curved trough will have a radius of about 0.10 mm to about 0.30 mm and most usually, a radius of about 0.18 mm.

[0074] As also illustrated in Fig. 5, the outer ends of the inwardly directed first cutting edge 22 and the further cutting edge 24 are each continuous with a respective curved edge 32 or 34 that curves inwardly into the notch formation from the circular cutting edge 18, the curved edges 32 and 34 respectively providing a curved cutting edge at the cutting end of the blade that is both continuous with the circular cutting edge and a corresponding one of the inwardly directed first cutting edge 22 and the further cutting edge 24. By providing the curved edges 32 and 34 rather than sharp comers, the risk of those locations in the graft tissue folding under the graft during location of the graft during surgery and thereby causing local graft dehiscence or dislocation, or a source of inflammation in the recipient eye, may be ameliorated. As well, the transmission of tearing or shear force to the trough region of the notch and / or cut edges in the notch of the comeal graft from physical “catching” or contact drag at those locations arising during the preparation, handling or location of the graft during surgery may be reduced, in turn reducing the risk of tearing from the trough or cut edges of the notch in the graft.

[0075] In embodiments, the curved edge 32 of the notch formation will generally be convex in form and typically, will have a radius of about 0.05 mm or greater and more generally, a radius in a range of from about 0.05 mm to about 2.0 mm or more, e.g., e.g., 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0,16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.20 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.30 mm and so on up to e.g., 1.0 mm, 1.05 mm, 1.10 mm, 1.15 mm, 1.20 mm, 1.25 mm, 1.30 mm, 1.35 mm, 1.40 mm, 1.45 mm, 1.50 mm, 1.55 mm, 1.60 mm, 1.65 mm, 1.70 mm, 1.75 mm, 1.80, 1.85 mm, 1.90 mm, 1.95 mm or 2.0 mm or more, and all radii within the above stated ranges are expressly encompassed. Typically, the radius of curved edge 32 will be in a range of from about 0.10 mm, 0.15 mm or 0.20 mm to about 0.30 mm and usually, will be about 0.25 mm.

[0076] In embodiments, the curved edge 34 of the notch formation will also be convex in form and usually, will have a larger radius than that of curved edge 32. In particularly preferred embodiments, the radius of curved edge 34 will also typically be about 0.05 mm or greater and more generally, in a range of from about 0.05 mm to about 2.0 mm or more, e.g., 0.05 mm, 0.1 mm, 0.15 mm, 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.50 mm, 0.55 mm, 0.60 mm, 0.65 mm, 0.70 mm, 0.75 mm, 0.80 mm, 0.85 mm, 0.90 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.10 mm, 1.15 mm, 1.20 mm, 1.25 mm, 1.30 mm, 1.35 mm, 1.40 mm, 1.45 mm, 1.50 mm, 1.55 mm, 1.60 mm, 1.65 mm, 1.70 mm, 1.75 mm, 1.80 mm, 1.85 mm, 1.90 mm, 1.95 mm or 2.0 mm or more, and all radii within the above stated ranges are also expressly encompassed. Typically, the radius of curved edge 34 will have a radius of about 1.0 mm to about 1.40 mm, more usually a radius of about 1.10 mm to about 1.30 mm and most usually, a radius of about 1.23 mm.

[0077] The inwardly directed first cutting edge 22 and the further cutting edge 24 of the notch formation are both at least predominantly straight cutting edges in the embodiment shown though in other embodiments, one or both of those cutting edges may be independently slightly bowed. The bowing may for instance be either concave or convex in profile. Typically, the inwardly directed cutting edge 22 lies generally radially with respect to the longitudinal axis of the blade.

[0078] In some embodiments of a trephine blade as described herein the angle between the inwardly directed first cutting edge 22 and the further cutting edge 24 may be in a range of up to about 150°.

[0079] However, to minimise comeal tissue loss from the comeal graft and for reasons as further set out below, the inwardly directed cutting edge 22 and the further cutting edge 24 are oriented at an acute angle relative to one another. The acute angle is ideally in a range of from about 70° to about 80° and more usually, about 75°. The inclined further cutting edge 24 is therefore longer than the inwardly directed cutting edge 22 and in preferred embodiments, the notch formation is configured to form an asymmetrical notch in the circumferential perimeter of the donor comeal tissue that is generally in the shape of the number “7” when the comeal tissue is viewed from above with the endothelium layer of the comeal tissue facing down. Thus, when the final comeal graft tissue is inserted and properly orientated and located in the anterior chamber of the eye during endothelial keratoplasty (EK), the number “7” shaped notch can be discerned by the surgeon when looking into the recipient eye from the front of the eye. If a number “7” cannot be identified it indicates to the surgeon that the graft is incorrectly orientated and the graft has been flipped over so that the endothelium side of the graft is facing the wrong direction, enabling the surgeon to take immediate corrective action to properly orientate the graft.

[0080] The asymmetric notch formation of the trephine is sized for removal of less than about 3% and usually, about 2.5% or less, about 2% or less, or about 1.5% or less of the surface area of the donor comeal tissue to be used as the comeal graft. That is, in the latter instance, the notch formation 20 is sized whereby 98.5% or more of the surface area of the corneal tissue intended for use as the graft remains for transplantation into the recipient eye. More usually, the notch formation is sized to remove about 1.25% or less of the donor comeal tissue intended for use as the comeal graft, more usually about 1.0% or less, about 0.9% or less, about 0.85% or less, or 0.8% or less and most usually less than about 0.75% of the comeal tissue to be used as the graft.

[0081] In preferred embodiments, the length of the section of the tissue cut by the inwardly directed cutting edge 22 of the blade 10 is about 0.5 mm - 0.75 mm whilst the length of the section of the tissue cut by the further cutting edge 24 of the blade is about 1.5 mm - 2.0 mm, the reflex angle between those edges of the tissue generally being about 280° to 290° and preferably, about 285° as described above.

[0082] The maximal internal diameter 10 of the trephine blade at the cutting-edge end 30 of the blade (i.e., excluding the asymmetrical notch) can be as for conventional tubular trephine blades such as e.g., 6.0 mm, 6.25 mm, 6.5 mm, 6.75 mm, 7.00 mm, 7.25 mm, 7.5 mm, 7.75 mm, 8.0 mm, 8.25 mm, 8.5 mm, 8.75 mm or 9.0 mm or more. A range of trephine blades in accordance with the invention of different sizes may therefore be provided in which the internal diameter of the blades at their cutting-edge end may increase in 0.25 mm or 0.5 mm increments as indicated above. As illustrated in Figs. 1-5, the internal diameter of a trephine blade in accordance with the invention is essentially constant along the entire length of the blade. Likewise, the maximum outer diameter of the blade is also essentially constant along the full length of the blade. The thickness of the peripheral side wall 12 of the blade 10 can be that of conventionally known tubular trephine blades, and the blade may be fabricated from surgical grade stainless steel or other suitable metal or metal alloy.

[0083] The trephine blade 10 is generally mounted in a cutting device such as a punch for cutting of the donor corneal tissue in use of the blade. The cutting block 29 and a plunger assembly 33 respectively comprising the base and plunger of a punch for cutting donor comeal tissue with a blade embodied by the invention is illustrated in Figs. 6 to 10.

[0084] As shown, the cutting block 29 comprises a centrally located concave well 38 and openings 40 spaced apart from one another around the block for respectively receiving a corresponding post 42 of the blade assembly. A through passageway 44 opening to a vacuum chamber generally indicated by the numeral 46 of the cutting block located under the well 38 in the fully assembled device is located centrally at the bottom of the well. Further through passageways 48 which also open to the vacuum chamber are equidistantly spaced apart from one another around the central passageway 44. In use, a spring -loaded syringe is connected to the cutting block via medical grade silicone tubing inserted into a port (not shown) formed in a side of the cutting block for creating suction in the vacuum chamber as further described below. The bottom closure to the cutting block forming the floor of the vacuum chamber 46 is also not shown.

[0085] The plunger assembly 32 includes a plunger body 50 in which is defined a centrally located through passageway 52 in which the end 16 of the trephine blade 10 is received in a sliding fit with the circular cutting edge 18 of the blade exposed in the in- use orientation of the blade. The non-cutting end 16 of the blade is seated on an internal lip defined within the through passageway of the plunger body. As also shown, the metal posts 42 of the plunger body are spaced around the through passageway 52 to align with the openings 40 of the cutting block. The cutting block 29 and the plunger body 50 may be fabricated from a stiff plastics material such as high-density polyethylene (HDPE) or high-density polypropylene though any suitable plastics material can be utilised for the intended purpose.

[0086] In preparation for the cutting of the comeal tissue in the punch, the required tissue layers of a donor corneoscleral button for the proposed EK comeal surgery (e.g., DMEK) are generally partially peeled as a single thickness of tissue from the remaining comeal tissue to greater than about 50% to about 75% of the distance across the cornea to form a comeal flap in the known manner. The comeal flap is then laid back over the exposed comeal tissue layer and the cornea is placed generally centrally within the well of the cutting block with the epithelial side of the cornea in contact with the surface of the cutting block (i.e., endothelial side up).

[0087] Prior to the placement of the comeal button in the cutting block, the spring- loaded syringe is connected to the vacuum chamber of the cutting block via the silicone tubing and the plunger of the syringe is pushed all the way into its barrel and held in that position. After placing the comeal button into the well of the cutting block as above, the button is gently pressed down to centre and seat the button against the floor of the well. Once the comeal button is appropriately seated in the well, the plunger of the syringe is released to create a vacuum in the vacuum chamber of the cutting block and thereby hold the comeal button against the well floor.

[0088] To cut the comeal tissue with the trephine blade 10, the blade assembly is located over the donor comeal tissue and the plunger is gently pressed downwardly for the blade 10 to partially cut through the thickness of comeal tissue to at least the depth of the comeal flap before withdrawing the plunger and removing the plunger assembly including the blade 10 from the cutting block. At this point, the vacuum in the vacuum chamber of the cutting block can be released, the scleral rim trimmed from the donor comeal tissue removed with the use of forceps, and the cut donor cornea tissue removed from the well.

[0089] Cutting devices of the above type which may be used or adapted for use with a trephine blade embodied by the invention include Barron Vacuum Punches™ (Barron Precision Instruments LLC, Grand Blanc, Michigan, USA).

[0090] The cutting of the donor comeal tissue as above can be undertaken at a tissue bank or laboratory by a suitably trained technician or on site by the surgeon. As will be understood, once the comeal tissue has been cut to size with a trephine blade embodied by the invention, the peeling of the comeal tissue can be completed to obtain the final comeal graft for transplantation to the patient.

[0091] As described above, the asymmetric notch cut into comeal graft ideally forms the number “7” when the graft is viewed from above with the endothelial side of the graft facing downwardly. Once inserted into the eye of the recipient, the comeal graft can be moved and located as required using known techniques.

[0092] Thus, when transplanted, the correct orientation of the comeal graft is endothelial side down so as to face the anterior chamber of the eye. In this orientation the asymmetrical notch in the graft forms the number “7” when viewed from the front of the eye, irrespective of the rotational position of the graft. Hence, if the surgeon can discern a number “7” shaped notch in the perimeter of the comeal graft (again irrespective of the rotational orientation of the graft) following insertion of the graft into the eye as described above, the graft has been orientated correctly in the eye. If, however, the number “7” shaped notch cannot be discerned by the surgeon (and instead shows a reverse number “7”), the surgeon will know the graft has been located incorrectly and needs to be flipped within the eye to the correct “endothelial side down” orientation. The identification of the orientation of the notch can be assisted by staining of the corneal tissue or graft with a suitable dye, e.g., trypan blue (0.05% v / v) or Membrane Blue Dual™ (e.g., Trypan blue (0.15% v / v), Brilliant blue (0.025% v / v) and polyethylene glycol (4% v / v); Vision Med Hellas IKE, Melissia, Greece), which normally occurs prior to cutting the donor corneal tissue to size as described above.

[0093] In other embodiments, a trephine blade embodied by the invention may have one or more additional cutting formations respectively circumferentially located around the cutting end of the blade for cutting a corresponding shape on the perimeter of the comeal graft at a predetermined radial angle relative to the above asymmetric notch such as 45°, 90° or 180° etc. to assist the surgeon locating the asymmetrical notch cut by the notch formation of the blade. Respective of the cutting formations can independently be for forming an outpouching projecting from the donor graft or further notch in the circumferential perimeter of the graft though it is preferable that the corresponding shape is a further notch rather than an outpouching to avoid the outpouching folding under the comeal graft during location of the graft in the recipient eye during surgery. The, or each, further cutting formation of the trephine blade will generally be shaped to cut a respective symmetrical shape such as a semicircular or other curve so as to not be confused with the asymmetrical notch for identifying correct orientation of the graft in the eye.

[0094] Each such further cutting formation of the trephine blade may likewise be defined by a respective channel defined in the side wall 12 of the blade that extends from one end of the blade to the opposite end of the blade.

[0095] In still other embodiments, the cutting formation 20 of a trephine blade embodied by the invention and / or a further cutting formation as above described may be defined by inwardly or outwardly directed pouching as applicable in the cutting end of the blade rather than by a respective channel formation extending the full length of the blade.

[0096] It will also be understood that the “circular cutting edge” 18 of a trephine blade embodied by the invention need not extend entirely circumferentially around the cutting end of the blade and may for instance be interrupted by one of more further cutting formation(s) if provided. In such embodiments, the circular cutting edge of the blade may therefore be a discontinuous cutting edge. Further, in the broadest sense, the circular cutting edge of a trephine blade embodied by the invention may only extend circumferentially in regions of the trephine blade proximal to either side of the asymmetric cutting formation 20.

[0097] In at least some embodiments of a cutting device of the type shown in Fig. 6-10 as described herein, the plunger body 50 may be provided with an inwardly directed protrusion (not shown) for reception in the longitudinal channel 28 of the trephine blade of the invention for assisting retention of the blade in the plunger body and / or inhibit rotation of the blade about the longitudinal axis of the blade. In such embodiments, the protrusion may be received in the channel in a sliding fit and typically, be shaped to match the profile of the notch.

[0098] A yet further embodiment of a trephine blade 54 in accordance with the present disclosure with an asymmetrical notch formation 20 as described herein and having an end profile as shown in Fig. 5 is illustrated in Fig. 11. In this embodiment though the trough formation does not protrude longitudinally from the cutting end of the blade and instead, the end of the asymmetric notch is flush with the remainder of that end of the blade as in the embodiment illustrated in Figs. 3-4. The radii of the curved trough 26, curved edge 32 and / or curved edge 34 of the embodiment illustrated in Fig. 11 can be as described herein for the trephine blade 10 illustrated in Figs. 1- 5. Further, an embodiment of type as shown in Fig. 11 can also be used in a punch as illustrated in Figs. 6 to 10 and as described herein.

[0099] In yet further embodiments, rather than cutting the full perimeter of the corneal graft from donor comeal tissue in the one cutting operation utilising a trephine blade as described above, trephine blades in accordance with the invention are provided for cutting the asymmetric notch in the perimeter of the graft after the outer perimeter of the graft has been cut to size such as with a conventional trephine blade with a circular cutting edge as is known in the art. That is, the asymmetric notch can be cut in the perimeter of the comeal graft utilising a trephine blade incorporating a cutting formation as described herein, either manually or utilising a cutting device (e.g., a punch) incorporating the blade. In such embodiments, the cutting formation 20 is in the form of an outwardly directed side prominence of the blade rather than an inwardly directed notch formation as in the embodiments illustrated in Figs. 1 to 5 described above. In preferred embodiments in which the asymmetric cutting formation is a sidewardly directed prominence, the cutting formation is again typically defined by a channel formation that extends essentially the full length of the blade wherein the channel faces inwardly rather than outwardly as in the embodiments illustrated in Figs.

[0100] 1 to 5. Also, as in embodiments described above with an inwardly directed notch formation, in trephine blades with an asymmetric cutting formation in the form of an outwardly directed prominence for cutting a correspondingly shaped asymmetric notch in the comeal graft, the cutting formation may project from the cutting end of the blade in the longitudinal direction of the blade. A trephine blade with such a cutting formation 20 is illustrated in Fig. 12.

[0101] As illustrated, the trephine blade 56 is again tubular with the asymmetric cutting formation 20 defined by a channel formation in the side wall 12 of the blade though as described above, the channel 28 faces into the interior of the blade and the channel formation forms a sideward prominence standing outwardly from the blade. The cutting formation in this embodiment has a reverse profile compared to the notch formation of the embodiments shown in Figs. 1 to 5, but again includes a first cutting edge 22 and a further cutter edge 24 which meet at a curved trough 26 as described above, as well as curved edges 32 and 34 which are continuous with the cutting edges 22 and 24 and respectively curve into the cutting formation 20 for forming rounded comers at the entrance to the correspondingly shaped asymmetric notch when cut in the perimeter of the comeal graft using the blade.

[0102] As will be understood, in use of this form of the trephine blade, the user aligns the trephine blade with the circumferential perimeter of the comeal graft such the curvature of the blade at proximal regions 58 are aligned with the circumferential perimeter of the graft whereby only the cutting formation 20 and curved cutting edges 32 and 34 overlie the graft. The asymmetric notch is then cut in the graft by a downward cutting movement of the blade as described above to cut both the asymmetric notch in the graft and the rounded comers at the entrance to the cut notch at the one time. Alternatively, the asymmetric notch can be cut in the donor graft tissue utilising the trephine blade of the type illustrated in Fig. 12, and the graft then cut to size e.g., utilizing a conventional tubular trephine blade.

[0103] The cutting formation 20 of the trephine blade 56 of Fig. 12 protmdes from the end of the blade in the longitudinal direction of the blade in the same manner as in embodiments described herein in which the cutting formation is a notch formation. In still other embodiments of this type of blade, the cutting formation 20 does not protrude in the longitudinal direction of the blade and instead, is flush with the curved cutting edges 32 and / or 34.

[0104] Although the trephine blade 56 illustrated includes curved cutting edges 32 and 34, other embodiments of this type of trephine blade may be provided which do not have one of both of the curved cutting edges 32 or 34. Also, it is not necessary that a trephine blade of the type shown in Fig. 12 be generally tubular in form. In other embodiments, for instance, opposite sides of the trephine may fold inwardly behind the region of the blade including the cutting formation prominence and curved edges 32 and 34 (when provided) as well as proximal regions 58, and come together in a rearwardly directed finger grip formation for being held between the thumb and index finger of the user in use of the blade for cutting of the asymmetric notch in the perimeter of the corneal graft.

[0105] As such, while trephine blades are conventionally tubular in form with a circular exterior profile, the term “trephine blade” as used herein is not limited thereto and is to be taken in its broadest sense to encompass a cutting blade for the cutting of comeal tissue whether tubular with a circular cutting end or not, and whether or not the blade is for use in a cutting device such as punch or for being hand held in use.

[0106] In still further embodiments, the opposite end to the cutting end of a trephine blade in accordance with the present disclosure may be closed-ended for being manually pressed to drive the blade to cut the donor comeal tissue in use of the blade. In further embodiments, the closed end may form a head portion of the blade for facilitating the manual use of the blade.

[0107] In at least some forms, the side periphery of the non-cutting end or head of the blade may be knurled, grooved or e.g., ribbed for easier handling of the blade.

[0108] Whilst a particular type of punch for the cutting of donor comeal tissue has been described above, a trephine blade embodied by the invention may also be used with other types of punches in which the blade is held, retained and / or housed by or in the punch in use, and which is driven to cut the donor comeal tissue such as by operation of a plunger or otherwise to size and shape the tissue to obtain a comeal graft incorporating a asymmetric notch in its circumferential perimeter as described herein. For example, in some embodiments of cutting devices contemplated herein, the noncutting end of the blade may be held in a holder and a hand-operated wheel or ring rotated to extend or drive the blade to cut the donor comeal tissue, and all such arrangements are expressly provided for. In still other embodiments, the trephine blade may be seated or secured in a holder wherein the holder is manually aligned with the donor comeal tissue and driven down whilst being held to cut the donor tissue to size, though such punch arrangements are preferably used in combination with a guide system for guidance of the holder / blade. Such guide systems may for instance comprise a frame structure that mounts to a base on which the donor comeal tissue is placed in use and wherein the frame stmcture has a centrally located opening disposed for being located over the base to receive the blade whereby the blade is aligned with the comeal tissue. As with the cutting block illustrated in e.g., Fig. 9, the comeal tissue can be positioned in a curved well defined in the upper face of the base for the cutting of the tissue by the blade.

[0109] From the above description, it will be appreciated that embodiments of a trephine blade in accordance with the invention may provide for one or more of the following advantages:

[0110] • By protruding from the cutting end of the trephine blade, the asymmetrical cutting formation can preferentially cut the correspondingly shaped notch in the donor comeal tissue relative to the remainder of the circumference of the graft and in doing so may restrict distortion of the tissue at least in the vicinity of the notch formation during the cutting of the tissue to shape, and so provide a cleaner cut of the asymmetric notch in the tissue and / or reduce the potential for distortion of at least the shape of the notch.

[0111] • The provision of the curved trough in the asymmetric cutting formation of the trephine blade between the inwardly directed cutting edge 22 and the further cutting edge 24 provides a corresponding shaped curve in the notch cut in the comeal graft providing for distribution of forces about the trough in the notch in the comeal graft that may be exerted on that region of the corneal graft during the preparation, handling and placement of the graft during endothelial keratoplasty, ameliorating the risk of the comeal graft tearing from the trough region.

[0112] • The provision of the curved cutting edge(s) curving into the inwardly directed and further cutting edge(s) 22 and / or 24 of the cutting formation produce corresponding curve(s) in the profile of the comeal graft, avoiding sharp comer(s) in the graft and thereby ameliorating the risk of the comeal graft tearing or folding under itself and / or reducing “catch points” and contact drag at those locations during locating of the graft in position the eye. This in turn may facilitate correct placement of the graft during endothelial keratoplasty, and reduce the potential for graft dislocation, eye irritation or possible damage to the graft arising from unwanted folding of the graft as well as the risk of transmission of shear forces to the trough of the notch arising from physical contact with those locations during the preparation, handling and location of the graft in position and thereby, the risk of the graft tearing from the trough of the cut notch.

[0113] • In embodiments, the asymmetric notch can be cut into the donor comeal tissue / comeal graft in a single cutting action at the same time the tissue is cut to size for preparation of the comeal graft for transplantation in the recipient eye.

[0114] • Cutting and sizing the donor comeal tissue in a single step saves time in preparing the comeal graft and reduces the risk of user error;

[0115] • The use of a trephine blade embodied by the invention may reduce potential for comeal endothelial tissue damage through reduced handling of the tissue.

[0116] • The asymmetric notch in the comeal graft provides for rapid identification of the correct orientation of the graft and thereby also correct placement of the graft in the recipient eye, and so acts to aid the correct orientation of the graft in the eye reducing user error and risk of an adverse comeal transplantation outcome. • A comeal graft incorporating an asymmetric notch in accordance with the present disclosure can be used in connection with e.g., DSAEK, DMEK, DLEK and DSEK comeal transplant methods.

[0117] • Once inserted in the recipient eye, the comeal graft behaves as a standard graft and can be manipulated without the need for further training of the comeal surgeon.

[0118] • And further, once the graft is attached in the recipient eye, the asymmetric notch can be identified in the graft may be identifiable in the future so the surgeon or attending ophthalmologist can be confident the comeal graft was inserted in the recipient eye in the correct orientation and in the event the graft were to not take and / or ultimately fail, can determine whether this was due to incorrect orientation of the graft or as a result of primary graft failure. Although a number of embodiments of the invention have been described above it will be understood that various modifications and changes may be made thereto without departing from the invention. The above-described embodiments are therefore only illustrative and are not to be taken as being restrictive.

Claims

CLAIMS1. A trephine blade for use in the preparation of a corneal graft for endothelial keratoplasty, the blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, the cutting formation protruding from a cutting end of the blade in the longitudinal direction of the blade.

2. The trephine blade of claim 1 , wherein the blade has a circular edge for cutting the circumferential perimeter of the graft from donor corneal tissue and the cutting formation is continuous with the circular cutting edge.

3. The trephine blade of claim 1 or 2, wherein the cutting formation is a notch formation.

4. The trephine blade of any one of claims 1 to 3, wherein the blade is tubular.

5. The trephine blade of claim 1, wherein the cutting formation is a sideward, outwardly directed prominence of the blade.

6. The trephine blade of any one of claims 1 to 5, wherein the cutting formation is defined by a longitudinal channel formed in a peripheral side wall of the blade.

7. The trephine blade of claim 6, wherein the channel extends from the cutting end of the blade to an opposite end of the blade.

8. The trephine blade of any one of claims 1 to 7, wherein the cutting formation is configured to cut the notch in the graft to a shape for indicating whether the endothelial layer of the graft is facing upwardly or downwardly when the graft is viewed from above.

9. The trephine blade of any one of claims 1 to 8, wherein the cutting formation is defined by a first edge for making an inwardly directed cut in the graft and a further cutting edge for making an outwardly directed cut to form the asymmetric notch in the graft.

10. The trephine blade of claim 9, wherein the first edge and the further edge of the cutting formation meet at a curved trough of the cutting formation.

11. The trephine blade of claim 10, wherein the curved trough has a radius in a range of about 0.1 mm to about 0.3 nun.

12. The trephine blade of any one of claims 9 to 11, wherein at least one of opposite ends of the first edge and the further cutting edge of the cutting formation is continuous with a respective curved cutting edge that curves into the cutting formation.

13. The trephine blade of claim 12, wherein the opposite end of the first edge is continuous with a said curved cutting edge.

14. The trephine blade of claim 12, wherein the further cutting edge is continuous with a said curved cutting edge.

15. The trephine blade of any one of claims 12 to 14, wherein both the first edge and the further cutting edge of the cutting formation are continuous with a respective said curved cutting edge that curves inwardly into the notch formation.

16. The trephine blade of any one of claims 12 to 15, wherein the curved cutting edge curving into the first edge of the cutting formation has a radius of about 0.05 mm or greater.

17. The trephine blade of claim 16, wherein the curved cutting edge curving into the first edge of the cutting formation has a radius in a range of from about 0.05 mm to about 2.0 mm.

18. The trephine blade of any one of claims 12 to 16, wherein the curved cutting edge curving into the further cutting edge of the cutting formation has a radius of about 0.05 mm or greater.

19. The trephine blade of claim 18, wherein the curved cutting edge curving into the further cutting edge of the cutting formation has a radius in a range of from about 0.05 mm to about 2.0 mm.

20. The trephine blade of any one of claims 9 to 19, wherein the first cutting edge and the further cutting edge are oriented at an acute angle relative to one another.

21. The trephine blade of claim 20, where the acute angle is in a range of from about 70° to about 80°.

22. The trephine blade of claim 21, where the acute angle is about 75°.

23. The trephine blade of any one of claims 9 to 22, wherein the first cutting edge and the further cutting edge are both at least predominantly straight cutting edges.

24. The trephine blade of any one of claims 9 to 23, wherein the further cutting edge is longer in length than the first cutting edge.

25. The trephine blade of any one of claims 9 to 24, wherein the first cutting edge is orientated for cutting the graft generally radially with respect to the centre of the graft.

26. The trephine blade of any one of claims 1 to 25, wherein the cutting formation of the blade is shaped such that the asymmetric notch cut in the graft by the cutting formation is generally in the shape of the number 7 when the donor graft is viewed from above with the endothelium layer of the donor graft facing down.

27. A trephine blade for use in the preparation of a corneal graft for endothelial keratoplasty, the blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the cutting formation has a cutting edge defined by a first edge for cutting an inwardly directed cut in the graft and a further cutting edge for making an outwardly directed cut in the graft to form the asymmetric notch in the graft, the first edge and the further cutting edge meeting at a curved trough of the cutting formation.

28. A trephine blade for use in the preparation of a corneal graft for endothelial keratoplasty, the blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the cutting formation is defined by a first edge for cutting an inwardly directed cut in the graft and a further cutting edge for making an outwardly directed cut in the graft to form the asymmetric notch, at least one of the opposite ends of the first cutting edge and the further cutting edge of the cutting formation being continuous with a respective curved cutting edge that curves into the cutting formation.

29. The trephine blade of claim 28, further comprising a circular cutting edge for cutting the outer circumferential perimeter of the graft from donor corneal tissue and wherein the cutting formation for cutting the asymmetric notch in the graft is continuous with the circular cutting edge.

30. The trephine blade of claim 28 or 29, wherein the first edge and the further cutting edge meet at a curved trough of the cutting formation31. The trephine blade of any one of claims 28 to 30, wherein the opposite end of the first edge is continuous with a said curved cutting edge.

32. The trephine blade of any one of claims 28 to 30, wherein the further cutting edge is continuous with a said curved cutting edge.

33. The trephine blade of any one of claims 28 to 32, wherein both the first edge and the further cutting edge of the cutting formation are continuous with a respective said curved cutting edge that curves inwardly into the notch formation.

34. A cutting device for the preparation of a corneal graft for use in endothelial keratoplasty, the device incorporating a trephine blade as defined in any one of claims 1 to 33.

35. A method for preparing a corneal graft from donor corneal tissue for use of the graft in endothelial keratoplasty, comprising the steps of: providing a trephine blade incorporating an asymmetric cutting formation for cutting a correspondingly shaped asymmetric notch in an outer circumferential perimeter of the graft to indicate correct orientation of the graft in said endothelial keratoplasty, and wherein the cutting formation protrudes from a cutting end of the blade in the longitudinal direction of the blade; and cutting the donor corneal tissue with the blade to provide the graft.

36. The method of claim 35, wherein the blade is held by a device for the cutting of the donor corneal tissue by the blade, and the device is used to cut the donor corneal tissue to provide the graft.

37. The method of claim 36 wherein the device for the cutting of the corneal tissue is a punch.

38. The method of claim 37, wherein the blade is housed within the punch in the use of the punch to cut the corneal tissue with the blade.

39. The method of claim 37 or 38, wherein the blade is arranged in the punch for being driven toward the donor corneal tissue to affect the cutting of the donor tissue by the blade with operation of the punch.

40. The method of any one of claims 35 to 39, wherein the endothelial keratoplasty is selected from the group consisting of DSAEK, DMEK, DLEK and DSEK.

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