BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, wherein like reference numerals refer to similar components:
FIGS. 1A & 1B illustrates a sectional view of a cornea with incisions made therein for a full thickness corneal tissue transplant;
FIG. 2 illustrates a sectional view of donor tissue grafted into a recipient cornea;
FIG. 3 illustrates a sectional view of incisions made in a cornea for a partial thickness ALK corneal tissue transplant;
FIG. 4 illustrates a sectional view of incisions made in a cornea for a partial thickness PLK corneal tissue transplant; and
FIG. 5 is a schematic view of a system for resecting corneal tissue.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning in detail to the drawings, FIG. 1A illustrates the incisions made in a cornea 11 as part of a full thickness corneal transplant procedure. The same incisions are made in both the recipient cornea and the donor cornea, although the incisions in the donor cornea may be made approximately 1%-5% larger, or more preferably 2%-5% larger, than the incisions in the recipient cornea to account for shrinkage in the donor corneal tissue following resection. As part of the procedure, a contact lens 13 placed against the anterior corneal surface 15. This contact lens 13 deforms the cornea 11, forcing the anterior corneal surface 15 to take on the shape of the contact lens 13. Deformation of the cornea 11 in this manner provides multiple advantages which are well known to skilled artisans. For example, U.S. Pat. No. 5,549,632, which is incorporated herein by reference, describes advantages gained in making laser incisions by deforming the shape of the cornea, particularly by applanation. U.S. Pat. No. 6,863,667 and U.S. patent application Ser. No. 11/258,399, both of which are incorporated herein by reference, describe patient interface devices which may be used to align the surgical laser with the recipient cornea for purposes of making accurate incisions.
Further, deformation of the cornea reduces the amount of physical data which needs to be collected for both the recipient cornea and the donor cornea prior to the transplant procedure. The physical data collected includes thickness measurements of both the recipient and donor corneas. These thickness measurements are used to develop a thickness profile of each cornea. Additional physical data may also be collected for each cornea. This thickness profile, along with any other data needed for the procedure, may be obtained by any one of the many known methods for measuring the physical structure of the eye, with the preferred method being through optical coherence tomography (OCT). Many commercially available OCT scanners are capable of performing such measurements. One example is the Visante™ OCT scanning system, manufactured by Carl Zeiss Meditec, which has an office in Dublin, Calif. One advantage of the Visante™ OCT system is that it does not make contact with the cornea when performing the OCT scan.
Three incisions, an annular incision 19 and two sidecut incisions 21, 23, are made in the cornea 11 to resect the corneal tissue 17. These incisions may be made separately, one at a time, or they may be made concurrently. The combined incisions result in corneal tissue being resected from the recipient cornea, and donor tissue being resected from the donor cornea. All incisions are preferably made using a pulsed laser beam having ultra-short pulses, preferably in the femtosecond range. The laser may be of the type described in U.S. Pat. No. 4,764,930, producing an ultra-short pulsed beam as described in one or both of U.S. Pat. No. 5,984,916 and U.S. Pat. No. RE37,585. The disclosures of the aforementioned patents are incorporated herein by reference in their entirety. Commercial lasers capable of performing the incisions are available from IntraLase Corp. of Irvine, Calif.
The annular incision 19 is located at a predetermined depth from the anterior corneal surface 15. To facilitate the resection and grafting process, the entire annular incision 19 is at a uniform distance from the anterior corneal surface 15, although such uniformity of depth is not required. Further, for simplicity the annular incision 19 is described as being defined by an inner radius and an outer radius, although such is not necessary. It is sufficient for this incision to be formed by an inner perimeter and an outer perimeter, both perimeters being of any desired shape. More complex shapes, however, can add significantly to the complexity of the procedure. Various techniques are known for making the annular incision 19 at a uniform distance from the anterior corneal surface 15. For example, the techniques disclosed in U.S. Pat. No. 5,993,438, U.S. Pat. No. 6,730,074, and U.S. Patent Publication No. 20050245915 may be readily adapted to make the desired annular incision 19. Other techniques known to skilled artisans may also be employed.
The first sidecut incision 21 runs from the outer periphery of the annular incision 19 to the anterior corneal surface 15. An acute angle is formed at the juncture 25 of the first sidecut incision 21 and the annular incision 19. The second sidecut incision 23 runs from the inner periphery of the annular incision 19 to the posterior corneal surface 27. An acute angle is also formed at the juncture 29 of the second sidecut incision 23 and the annular incision 19. Alternatively, the angle between each of the sidecut incisions and the annular incision may be perpendicular or obtuse.
FIG. 1B illustrates an alternative configuration for the sidecut incisions 21′, 23′ made in the cornea 11 with respect to the annular incision 19. Here, the first sidecut incision 21′ runs from the inner perimeter of the annular incision 19 to the anterior corneal surface 15, and the second sidecut incision 23′ runs from the outer perimeter of the annular incision 19 to the posterior corneal surface 27.
The donor tissue 31 is shown grafted into the recipient cornea 33 in FIG. 2. Sutures 35, 37 are placed to secure the donor tissue 31 to the recipient cornea 33. Two different techniques for placement of sutures are shown. The first suture 35 is placed through the sidecut incision 39 which runs between the annular incision 41 and the posterior corneal surface 43. The second suture 37 is placed through the sidecut incision 45 which runs between the annular incision 41 and the anterior corneal surface 47. Both locations of sutures are believed to be equally as effective for securing the donor tissue 31 to the recipient cornea 33. Further, neither location is believed to be more likely than the other to induce astigmatism during the healing process.
FIG. 3 illustrates how the incision configuration described above may be adapted for an ALK procedure. For the ALK process, a resection incision 51 is made in the cornea 53 at a predetermined resection depth, and the annular incision 55 is made at a depth which lies between the resection depth and the anterior corneal surface 57. The first sidecut incision 59 is made in the same manner as is described above. The second sidecut incision 61, however, runs from the annular incision to the resection incision 51. The donor tissue may be secured to the recipient cornea by either of the techniques described above.
FIG. 4 illustrates how the incision configuration described above may be adapted for an PLK procedure. For the PLK process, a resection incision 63 is made in the cornea 65 at a predetermined resection depth, and the annular incision 67 is made at a depth which lies between the resection depth and the posterior corneal surface 69. The first sidecut incision 71 is made in the same manner as is described above. The second sidecut incision 73, however, runs from the annular incision to the resection incision 63. In a PLK procedure, sutures are not necessary to secure the donor tissue to the recipient cornea.
Referring to FIG. 5, a surgical system is shown which may be used to incise both a donor cornea or a recipient cornea. Alternatively, two similarly configured systems may be used to incise each respective cornea. A femtosecond surgical laser 81 generates a pulsed laser beam 83 and directs that beam into the focusing assembly 85, which in turn focuses the pulsed beam 83 into the cornea 87. A contact lens 89 is placed over the cornea to deform the anterior corneal surface as described above. Where different contact lenses are used with the donor cornea and the recipient cornea, the posterior curvature, i.e., the side of the contact lens that is placed against the anterior corneal surface, is the same for each contact lens. The controller 91 is a programmable computer which precisely controls the location of the beam focal point within the cornea 87 according to parameters received from the surgeon interface 93. The interface 93 presents the surgeon with several incision patterns from which the desired sidecut pattern is selected. The selected pattern is received by the controller 91, which uses the pattern to incise both the donor cornea and the recipient cornea, placing the annular region of the selected pattern at a predetermined depth from each respective anterior corneal surface. The contact lenses which are used to deform each of the corneas as part of this procedure preferably have the same curvature on the posterior surface, i.e., the surface placed in contact with the anterior corneal surface.
Thus, a method of transplanting corneal tissue is disclosed. While embodiments of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the following claims.
Patent Application
20080082086
