Corneal graft retainer ring

Abstract

A corneal graft retainer ring 10 for stabilising a grafted cornea 24 comprises a hoop 12 and a plurality of pins 41-48 which protrude from the hoop. The ring further comprises a plurality of indentati

Description

Field of the Invention The present invention relates generally to corneal transplant or graft surgery and, more particularly, to a corneal graft retainer ring to keep the transplant or graft stable, to prevent it from distorting and prevent it from moving out of position. Background of the Invention The cornea is the clear, front window of the eye. A normal, healthy cornea is transparent and clear which allows light to enter the eyeball unhindered. The light entering the eye passes through the clear cornea and clear crystalline lens to become focused onto the retina at the back of the eye. A clear and regular cornea is therefore essential for one to have good vision. When the cornea gets damaged from injury or disease, it becomes scarred and / or cloudy and / or distorted. This prevents the light from entering the eye and from being focused precisely onto the macula of the retina. As a result, vision becomes blurred, distorted, and patchy. In some cases, this can even lead to complete blindness. Further, damage to the cornea can also cause intense pain and discomfort because the cornea is richly innervated with sensory nerve fibres, including those that transmit the sensation of pain. To address the problem of a damaged or diseased cornea, corneal transplant surgery or corneal graft surgery may be necessary. Corneal transplant surgery or corneal graft surgery is an operation where the diseased or cloudy cornea (usually the central cornea) is removed and replaced with a similar matching button of healthy, clear cornea from a donor eye. The graft is usually held in place by fine sutures which are left in the eye until the cornea is adequately healed. Grafts can be full thickness (where the entire 5 layers of cornea are replaced) or partial thickness / lamellar (where only certain layers are replaced). As stated above, corneal transplant or graft surgery can be full thickness or partial thickness, and corneal transplant or graft surgery is broadly classified into 3 main types of procedures: 1) penetrating keratoplasty (full thickness); 2) lamellar keratoplasty (partial thickness), and 3) endothelial keratoplasty (partial thickness). The first type, penetrating keratoplasty, has been the conventional method of performing a corneal transplant. In penetrating keratoplasty, a round button-shaped full-thickness section of unhealthy corneal tissue is removed from the eye. A similar sized, full thickness, healthy, donor corneal button is then used to cover the resulting defect in the recipient cornea. Penetrating keratoplasty is useful for conditions where the entire corneal thickness has been affected, for example a full thickness corneal scar from whatever aetiology and in penetrating / perforating trauma. The second type, lamellar keratoplasty, includes performing a partial thickness corneal graft where only the diseased layers are replaced, and the healthy layers are left intact. Lamellar keratoplasty is suitable redress for e.g., keratoconus. The third type, endothelial keratoplasty, involves replacing most of the diseased recipient endothelium and Descemet’s membrane with healthy donor endothelium on Descemet’s membrane. As with all types of surgery, a corneal transplant or graft operation also comes with its own set of risks and complications. These include astigmatism (both regular and irregular), cataract, glaucoma, persistent inflammation, graft failure / rejection and rarely, endophthalmitis (severe infection affecting the entire eyeball). Further, most corneal transplant or graft surgeries, even those performed by experienced and dedicated corneal surgeons, cause degrees of distortion resulting in various optical aberrations especially, but not only, astigmatism. Additionally, after a corneal transplant or graft, the donor tissue is not very stable initially and can move out of position and can affect the refractive status of the eye. The present invention is intended to maintain regularity of the donor cornea and to secure it in situ during the operation as well as in the ensuing healing phase. 09 09 24 Summary of the Invention According to the first aspect of the invention, there is a corneal graft retainer ring for stabilizing a grafted cornea comprising: a hoop; a plurality of pins which protrude from a first side of the hoop toward an eye in use; a plurality of indentations into an inner 5 circumference of the hoop between the plurality of the pins suitable to allow the passage of sutures; and a plurality of mounds which protrude from the first side of the hoop a lesser height than the pins. In use the corneal graft retainer ring keeps the periphery of donor tissue stable, such as the grafted cornea stable. The corneal graft retainer ring prevents the donor tissue 10 from moving out of position or from distorting. The corneal graft retainer ring helps to provide the necessary tension to keep the transplant or graft in place, allowing it to heal with minimal distortion. The grafted cornea may be held out over the recipient’s pupil by the corneal graft retainer ring attached by sutures. With use of the corneal graft retainer ring the patient who is the recipient of the donor 15 tissue enjoys better and quicker healing at the interface between the donor tissue and recipient’s own tissue. This is in part because the interface is more regular. The patient may be a human person or an animal such as a dog, cat, horse, pet, working animal, wild animal, or a captive animal. Surgeons appreciate the use of the corneal graft retainer ring because its use helps 20 make the surgeons’ effort to place sutures precisely easier. Both the recipient and the surgeons appreciate the corneal graft retainer ring since they both like the better visual outcomes for the recipient who is expected to be visually rehabilitated sooner. Each pin may be a slender rigid piece. Each pin may be identical in length and / or 25 thickness and / or or material to the others. Each pin may be pointed. Each pin may be a spike that protrudes from the hoop. Each pin may be tapered. The pins may extend substantially parallel to the hoop central axis. The mounds may extend substantially parallel to the hoop central axis. The pins and the mounds may 09 09 24 extend in the same direction from the hoop. Since the mounds protrude on the hoop a lesser height than the pins, the mounds may limit the depth of the pin penetration into tissue. The pins and mounds are disposed on the first side of the hoop that is eye facing in use. Both the pins and mounds may contact the eye and / or transplant or graft cornea in use. The pins may be inclined toward each other. From the incline, the tip of the pin may be radially inwards from the base of the pin. From the incline the tip of the pin may be radially inwards from the center of the base of the pin joined to the hoop. The incline of the pins may help the pins to hold the corneal graft retainer ring in position relative to the recipient’s eye. The radially inward position of the tip may be as a result of inclination of the pin radially inward of the hoop. The pins may be at an inclination from the base of the pin on the hoop to a tip of the pin. The amount of inclination may be between one degree and ten degrees radially inwards of the retainer ring. Inclination may be three degrees, four degrees, five degrees, six degrees, or seven degrees radially inwards of the retainer ring. The inclination helps the pins retain a transplant or graft cornea. The pins may taper from the base at the retainer ring to a tip to penetrate eye tissue. The taper enables the pins to be removed from eye tissue, such as the transplant or graft cornea or surrounding eye cornea without tearing tissue or pulling away tissue. The pins may taper from the base to a point, for example the pins may be conical, to be easily removed from tissue. A base of the pin may be attached to the first side of the retainer ring that is eye facing in use. The pins may have a surface finish to stabilize them in the tissue and / or facilitate removal without tearing undue damage to the recipient’s eye. The pins may have a smooth, roughened / brushed or ridged surface finish. The mounds may be semi-spherical which provides a gentle curve to lift the retainer 09 09 24 ring off transplant or graft cornea without hurt and provides strength to the retainer ring. The mounds may comprise semi-spherical studs. The studs may have a circular base attached to or formed integral with retainer ring. The base may be disposed on the first side, that is an eye facing side in use, of the retainer ring. 5 The mounds may be interspersed on the retainer ring between the pins. The corneal graft retainer ring is ideally provided having a repeating sequence around the retainer ring of a pin, indentation, mound, indentation. Preferably there is alternately and regularly, an indentation equally, evenly spaced on either side from a mound and a pin. Preferably each indention is intermediate a pin and a mound. 10 The corneal graft retainer ring may have a unitary structure including the retainer ring, the pins, and the mounds. The corneal graft retainer ring may be easy to use and position. The unitary structure enables the hoop, pins, indentions, and mounds are positioned together at once by a user. The unitary structure may be formed of one piece comprising the retainer ring, the pins, 15 and the mounds. The unitary structure may be formed of a connected assembly of the retainer, the pins, and the mounds. The hoop may comprise a washer. The washer may comprise two opposite flat faces with a first face directed toward the eye in use as one of the flat faces, wherein the pins rise from the first flat face. Such washers are commonly commercially available. The 20 pins and / or the mounds may be easily connected to the first flat face. The corneal graft retainer ring may comprise one or more biocompatible inert materials. The corneal graft retainer ring may comprise exclusively biocompatible inert materials. These materials allow the corneal graft retainer ring to be sutured to a patient’s eye or grafted cornea and rest there for long enough for the patient’s eye to 25 heal. The hoop may be approximately between 4mm to 10mm outer diameter to fit over a patient’s cornea to be subjected to a transplant or graft. The outer diameter may be 6mm, 7mm, 8mm or a distance between these. The hoop 12 may have a radial width of between 0.5mm to 1mm. The hoop 12 may have a depth (thickness) of between 30 0.15mm to 0.5mm in the direction of an axis circumscribed by the retainer ring. patient to whom it is attached and to be easily manipulated by a surgeon. The biocompatible materials are durable for safe use. The biocompatible inert materials may include but are not limited to PMMA (polymethyl methacrylate), titanium or titanium composite / alloy material, nickel-titanium, tantalum, niobium, cobalt, cobalt-chromium, or ceramic. The elements may be unalloyed or alloyed together or with other materials. The hoop, pins, and / or mounds may all comprise the same biocompatible inert material. The hoop may comprise a biocompatible inert material which is different from the biocompatible inert material which the pins, and / or mounds comprise. Preferably the corneal graft retainer ring is inflexible. The hoop may be inflexible and / or the biocompatible material that the hoop comprises may be stiff to impart inflexibility. The biocompatible inert material(s) may have toughness and strength which impart inflexibility to the hoop, pins, and / or mounds and prevent shattering, splintering, buckling and / or crumbling of the hoop, pins, and / or mounds. The hoop may be otherwise continuous to surround and / or to conform to a transplant or graft cornea over a recipient’s pupil. The hoop may be configured to, in use, surround a region from which unhealthy corneal tissue is removed from the eye. The hoop may be circular. The hoop may be a closed loop to give it strength to stay even with minimal distortion all way around. The corneal graft retainer ring may comprise eight or more pins to keep the transplant or graft stable and fixed. The corneal graft retainer ring may comprise at least eight mounds. The retainer ring may have at least sixteen indentations. The indentations for suture may be semi-circular or triangular shape into the inner circumference of the hoop. The shape of the indentation helps to keep the strength and integrity of hoop intact to withstand the radial and torsional forces that are applied by the surgeon during positioning and suturing. The mounds may be provided to give the inflexible corneal graft retainer ring strength. In use the mounds may provide a space between the retainer ring apart from the transplant or graft. The mounds have a smooth curved surface on the eye facing away from their base. For example, the corneal graft retainer ring may comprise a hoop; plurality of pins divided at equal intervals on the eye facing side of the ring; and plurality of indentations for suture and semi-spherical studs in between the plurality of the pins at equal intervals on the ring. According to a second aspect of the invention there is corneal graft retainer ring assembly comprising the corneal graft retainer ring and a graft cornea circumscribed by the hoop. There may be sutures extending radially outwards from the indentations. The corneal graft retainer ring helps to prevent the transplant or graft from becoming distorted, reduces optical aberrations such as astigmatism and chromatic aberrations as well as higher order aberrations such as coma and therefore allows quicker restoration of good quality vision to the patient. The corneal graft retainer ring keeps the transplant or graft stable. Healing is helped by the stability of the transplant or graft so that it does not move out of position which leads to better refractive status of the eye when healed. The corneal graft retainer ring allows more accurate and even suture placement (full thickness or partial thickness). The accurate and even suture displacement reduces distortion of the transplant or graft and so reducing various optical aberrations especially, but not only, astigmatism. The pins of the corneal graft retainer ring keep the graft stable and prevent it from distorting. The pins penetrate the corneal tissue from the epithelial side of the donor at the time the donor tissue is cut, resulting in negligible damage to the donor cornea. The invention will now be described, by way of example only, with reference to the accompanying figures in which: Brief Description of the Figures Figure 1 illustrates a back perspective view of a corneal graft retainer ring. Figure 2 illustrates a front perspective view of the corneal graft retainer ring; Figure 3 illustrates a back view of the corneal graft retainer ring; Figure 4 illustrates a sectional view “A-A” of the corneal graft retainer ring as shown in Figure 3; Figure 5 illustrates a detailed view “C” of the pin of the corneal graft retainer ring; Figure 6 illustrates another sectional view “B-B” of the corneal graft retainer ring as shown in Figure 3; Figure 7 illustrates a detailed view “D” of a mound in a form of a semi-spherical stud of the corneal graft retainer ring; Figure 8 illustrates a schematic diagram of the operation of the corneal graft retainer ring; and Figure 9 illustrates another schematic diagram of the operation of the corneal graft retainer ring. The object of the invention may be understood in more detail and more particularly the description of the invention briefly summarized above by reference to certain embodiments thereof (which are illustrated in the appended drawings), which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate preferred embodiments of the invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective equivalent embodiments. Detailed Description A corneal graft retainer ring will now be described more fully hereinafter with reference to the accompanying drawings. In the accompanying drawings a particular embodiment of the corneal graft retainer ring is shown. This corneal transplant graft retainer ring may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Figure 1 and Figure 2 illustrate back and front perspective views respectively of a corneal graft retainer ring 10 for allowing transplanted or grafted cornea to heal optimally. The corneal graft retainer ring 10 comprises a hoop 12. The hoop 12 has form of a circular band of stiff material. The use is shown in Figure 8 and Figure 9. The hoop 12 is shown in the particular embodiment of the figures as circular, although other embodiments are possible where the hoop is oval or otherwise not round. The hoop 12 as an inner circumference 30 which is shown in the figures as circular, although circular is not necessary as long as the corneal transplant is surrounded. The hoop 12 is around the recipient pupil 28. The corneal graft retainer ring 10 also comprises a plurality of pins 41, 42, 43, 44, 45, 46, 47, 48. The pins are spikes. In the examples of the figures the pins are identical, although it is not essential that the pins be identical. Hereafter pin 41 refers to all the pins. The pins 41 are equally spaced around the hoop 12 on a first side 36 of the hoop 12. The first side 36 of the hoop 12 is eye facing in use. The pins extend parallel to the hoop 12 central axis. The pins 41 extend in the eye facing direction in use from the first side 36 toward the eye 22. The corneal graft retainer ring 10 also comprises a plurality of indentations 61,62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76 in between the plurality of the pins 41 to allow the passage of sutures through the during implantation. In the examples of the figures the indentations are shown identical, although it is not essential that the indentations be identical. Hereafter a reference to indentation 61 is to refer to all the indentations. The indentations 61 are arcs inwards in the hoop inner circumference 30. There are two indentations 61 between two pins 41 all the way around the hoop 12. The indentations 61 are equally spaced around the hoop 12 on the first side 36 of the hoop 12. The corneal graft retainer ring 10 also comprises a plurality of mounds 51, 52, 53, 54, 55, 56, 57, 58. In the examples of the figures the mounds are shown identical, although it is not essential that the mounds be identical. Hereafter a reference to mound 51 is to refer to all the mounds. The mounds 51 are equally spaced around the hoop 12 on the first side 36 of the hoop 12. In the examples shown in the figures, the mounds 51 have a form of a studs that have a semi-spherical profile which protrudes from the back face, although it is not essential that the mounds have this profile. The profile should be a curve above the first side 36 to avoid harm to the eye where the mounds 51 contact the eye. In the figures there is one mound 51 between two pins 41 all the way around the hoop 12. There is one mound between the two indentions 61 that are between the two pins 41 all the way around the hoop 12. There is a repetitive sequence of pin 41 then indention 61 then mound 51 then indention 61 which repeats all the way around the hoop 12. Other sequences are possible. Figure 3 shows that the indentation 61 for suture is semi-circular into the inner side of the hoop 12 to keep the strength and integrity of hoop 12 intact to withstand the radial and torsional forces. The mounds 51 are provided to boost the hoop 12 strength and to space hoop 12 spaced apart from the transplanted or graft tissue. Figures 1,2, 3, and 4 show the hoop 12 has a form of a washer have a first side 36 that is flat and eye facing in use and an opposite second side 36. The corneal graft retainer ring 10 for stabilizing a grafted cornea 24 is shown comprising the hoop 12. The corneal graft retainer ring 10 comprises the plurality of pins 41 which protrude from the hoop 12 toward an eye in use. The corneal graft retainer ring 10 comprises the plurality of indentations 61 into the inner circumference 30 of the hoop 12 between the plurality of the pins 41 to allow the passage of sutures 81. The plurality of mounds 51 protrude on the hoop 12 a lesser height than the pins 41. The hoop 12 as shown in Figures 1,2, 3, and 4 may be formed in various sizes. It has an outer diameter that is typically a minimum of 4 mm though it may be smaller. It has an outer diameter that is typically a maximum of 10 mm though it may be larger. It has at an outer diameter that is ideally between 6 mm and 8mm. The difference between the outer diameter of the hoop 12 and inner diameter is between 500- 1000 microns. The hoop 12 preferably has a thickness in the direction parallel to the hoop 12 central axis of between 150-500 microns. As illustrated, the corneal halo 10 is designed in a manner such that it will cover a small circumferential area of the eye over the cornea and pupil. Thus the corneal graft retainer ring is not significantly impeding entry of light into the eye through the pupil 28. The hoop 12 has an open interior through which light may pass. Figure 3 illustrates a back view of the corneal halo 10 for allowing the grafted cornea to be minimally distorted and to heal optimally. The corneal halo 10 is a unitary structure made from a tough material. The tough material has toughness which prevents the hoop 12, the pins 41, and the mounds 51 from splintering, crumbling, buckling, or shattering. The corneal graft retainer ring 10 is one-piece, or it is composed of the hoop 12, the pins 41, and the mounds 51 assembled together into the unitary structure. The corneal graft retainer ring 10 can be manufactured using different methods such as, but not limited to moulding, vacuum forming, 3D printing, sintering, cnc machining etc. The corneal graft retainer ring 10 is secured to the epithelial (convex) side of the donor at the time the donor tissue is cut to size using a corneal punch device. A modification may be made to a corneal punch device that is commercially available to adapt it to secure or register the corneal graft retainer ring 10. The maximum diameter or thickness of the pins 41 is equivalent or lesser to the width of the hoop 12. The maximum diameter of the pins 41 is at the base of the pins 41 connected to the first side of the hoop that is eye facing in use. The diameter of the base of the pins 41 connected to the hoop 12 is about equal to the width of the hoop 12 from the inner circumference 30 to the outer circumference 32. Typically, the diameter of the indentations 61 is such that the diameter of the indentations will be at the inner circumference 30 of the width of the hoop 12. The diameter of the indentations 61 may be seen to be on the inner circumference 30 in Figure 3. Typically, the corneal graft retainer ring 10 comprises at least eight pins 41 at 45° intervals on the hoop 12. Typically there are at least sixteen evenly spaced indentations 61 into the inner circumference of the hoop 12 to allow for evenly space placement of sutures around the hoop 12. Typically, the corneal graft retainer ring 10 has at least eight evenly mounds 51 on the eye facing side of the hoop 12. Figure 4 illustrates a sectional view A-A through the hoop 12 as shown in Figure 3 and pins 41. The provided plurality of pins 41 have a precise sharp point at the tip to penetrate the corneal tissue without self-distorting or destruction. The length of each pin 41 can be about 500 microns and have a base diameter equivalent or lesser than the width from the inner circumference 30 to the outer circumference 32 of the hoop 12. Figure 5 illustrates a detailed view “C” of the pin 41 of the corneal halo 10 for allowing the grafted cornea to be minimally distorted and to heal optimally according to the embodiments of the present invention. The pins 41 are at inclinations to the central axis of the hoop 12. The preferred angle of inclination is 5 ° radially inwards towards the centre of the corneal halo 10. The tip of the pin 41 is closer to the central axis of the corneal graft retainer ring 10 than the center of the base of the pin 41 because of the inclination radially inwards. Typically, the angle of inclination is between one degree and ten degrees. Inclination of the pin 09 09 24 center of the base of the pin 41 because of the inclination radially inwards. Typically, the angle of inclination is between one degree and ten degrees. Inclination of the pin is not essential. However, inclination helps stabilize the graft or transplant. Figure 6 illustrates another sectional view “B-B” of the corneal graft retainer ring 10 as 5 shown in Figure 3 for allowing the grafted cornea to be minimally distorted and to heal optimally. The provided plurality of mounds 51 boost the strength of the hoop 12. The tip of the pins 41 is farther than the mounds 51 from the first side 36 of the hoop 12 that is eye facing in use. The mounds 51 space the hoop 12 from the transplant or graft and limit the penetration depth of the pins 41 into the graft or transplant. 10 Figure 7 illustrates a detailed view “D” of mounds 51 of the corneal halo 10 for allowing the grafted cornea to be minimally distorted and to heal optimally. The provided plurality of mounds 51 have a form of studs of uniform semi-spherical structure having diameter lesser or equal than the width of the hoop 12. A curvature of the mounds 51 is ideal over the first side 36 of the hoop 12 that is eye 15 facing in use. The curvature prevents cutting like a sharp angle would into the transplant or graft. It is not essential that the curvature be semi-spherical. A semi-spherical structure for the mounds 51 is not essential. The diameter of the base of the mounds 51 connected to the hoop 12 is about equal to the width of the hoop 12 from the inner circumference 32 to the outer circumference 20 36. Figure 8 and Figure 9 illustrates a schematic diagram of the operation of the corneal graft retainer ring 10 for allowing the grafted cornea 24 to be minimally distorted and to heal optimally. These figures show a grafted cornea 24 from a donor that is transplanted into a recipient eye 22. 25 Figure 8 and Figure 9 illustrate the hoop 12 around a recipient pupil 28 shown as a circular region. Within the circular region of the recipient pupil 28 appears a circular light reflex 34 off the implanted cornea. Neither the recipient pupil 28 nor the implanted cornea are part of the corneal graft retainer ring 10. Treatment of the eye 22 via the corneal graft retainer ring 10 involves surgical removal of the diseased / damaged corneal tissue from the eye. The removal of the diseased / damaged cornea results in a defect in the recipient cornea. This is achieved by means of a trephine or laser. The donor cornea is cut precisely with a corneal punch, trephine, or laser to a specified size to match the defect in the recipient eye. As shown in Figure 8 and Figure 9, the corneal graft retainer ring 10 is transplanted into the defect and secured to the recipient corneal rim with sixteen or more sutures 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96. One of the sutures passes through each one of the indentations 61. Once the cornea heals and the grafted cornea 24 is fully integrated with the recipient, the corneal halo 10 and sutures 81 can be removed. Index of Labelled Features in Figures corneal graft retainer ring ......................................................... 10 eye 22 first side of hoop eye facing in use 36 grafted cornea ................................................................... 24 hoop ............................................................................. 12 hoop inner circumference ....................................................... 30 hoop outer circumference ....................................................... 32 indentation for suture ... 61,62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76 light reflex off the implanted cornea ................................................ 34 mound ............................................. 51,52,53,54,55,56,57,58 pin 41,42,43,44,45,46,47,48 pupil 28 second side of hoop facing away from eye in use ............................ 38 suture ............ 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96 While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of, and not restricted to, the broad invention, and that this invention is not limited to the specific constructions and arrangements shown and described, since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above paragraphs, are possible. Those skilled in the art will appreciate that various adaptations and modifications of the just described embodiments that can be configured without departing materially from the scope and 5 spirit of the invention. The invention has been described by way of examples only. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and 10 described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the claims.

Claims

1. A corneal graft retainer ring 10 for stabilizing a grafted cornea 24 comprising:a hoop 12;a plurality of pins 41 which protrude from a first side 36 of the hoop 12 toward an eye 5 in use;a plurality of indentations 61 into an inner circumference of the hoop 12 between the plurality of the pins 41 suitable to allow passage of sutures 81; anda plurality of mounds 51 which protrude from the first side 36 of the hoop 12 a lesserheight than the pins 41.09 09 242. The corneal graft retainer ring 10 according to claim 1 wherein the pins 41 are at an inclination from a base on the hoop 12 to a tip of the pin 41 of between one degree and ten degrees radially inwards of the hoop 12.15 3. The corneal graft retainer ring 10 according to claim 2 wherein the inclinationis five degrees radially inwards of the hoop 12.

4. The corneal graft retainer ring 10 according to any preceding claim comprises a unitary structure including the hoop 12, the pins 41, and the mounds 51.

5. The corneal graft retainer ring 10 according to any preceding claim comprising a biocompatible, inert material.

6. The corneal graft retainer ring 10 according to claim 5 wherein thebiocompatible inert material comprises PMMA (polymethyl methacrylate), titanium or a titanium alloy.

7. The corneal graft retainer ring 10 according to any preceding claim wherein the 5 hoop 12 is inflexible.

8. The corneal graft retainer ring 10 according to any preceding claim wherein the hoop 12 is circular.10 9. The corneal graft retainer ring 10 according to any preceding claim wherein thehoop 12 comprises a washer.09 09 2410. The corneal graft retainer ring 10 according to claim 8 wherein the washer comprises two opposite flat faces with a first face directed toward the eye in use as 15 one of the flat faces, wherein the pins 41 rise from the first flat face.

11. The corneal graft retainer ring 10 according to any preceding claim wherein the hoop 12 is approximately between 4mm to 10mm outer diameter.20 12. The corneal graft retainer ring 10 according to any preceding claim wherein thehoop 12 has a radial width of between 0.5mm to 1mm.

13. The corneal graft retainer ring 10 according to any preceding claim wherein the hoop 12 has a depth (thickness) of between 0.15mm to 0.5mm in a direction of an axiscircumscribed by the hoop 12.

14. The corneal graft retainer ring 10 according to any preceding claim wherein there are at least eight of the pins 41.

15. The corneal graft retainer ring 10 according to any preceding claim wherein there are at least sixteen of the indentations 61.

16. The corneal graft retainer ring 10 according to any preceding claim wherein10 there are at least eight of the mounds 51.09 09 2417. The corneal graft retainer ring 10 according to any preceding claim wherein the mounds 51 have a semi-spherical form.15 18. The corneal graft retainer ring 10 according to any preceding claim whereineach of the mounds comprises a stud attached to or integral to the hoop 12.

19. The corneal graft retainer ring 10 according to any preceding claim wherein the pins 41 have smooth, roughened / brushed or ridged surface finish.

20. The corneal graft retainer ring 10 according to any preceding claim wherein the pins 41 taper from a base at the hoop 12 to a tip to penetrate eye tissue.

21. The corneal graft retainer ring 10 according to any preceding claim wherein the pins 41 are conical.

22. The corneal graft retainer ring 10 according to any preceding claim having a 5 repeating sequence around the hoop 12 of a pin 41, indentation 61, mound 51, indentation 61.09 09 2423. The corneal graft retainer ring according to any preceding claim wherein the mounds 51 are interspersed on the hoop 12 between the pins 41.1024. A corneal graft retainer ring assembly comprising the corneal graft retainer ring 10 according to any preceding claim and a graft cornea 24 circumscribed by the hoop 12.15 25. The corneal graft retainer ring assembly according to claim 24 with suturesextending radially outwards from the indentations 61.

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