Ординатура / Офтальмология / Английские материалы / Corneal Endothelial Transplant (DSAEK, DMEK & DLEK)_John_2010

Transplantation of the Donor Tissue

With the microscope in place, the temporary scleral suture of the superior wound is cut (Figure 17-32). The anterior chamber of the patient is then filled completely with BSS (Figure 17-33). The donor tissue is then brought into the field and the Charlie insertion forceps are used to grasp the stromal surface of the donor tissue along the horizontal meridian (Figure 17-34). The Charlie forceps are non-

toothed fine forceps that coapt only at the distal tips. The amount of space that is present along the long axis of the blades prevents crushing of the donor tissue. There is a specially designed stop for this purpose that enables the surgeon to transfer and hold the folded donor disk tissue without crushing it. The folded donor tissue is placed into the anterior chamber in one quick, smooth movement, by inserting the donor tissue with the anterior 60% stromal side facing the recipient bed and the posterior 40% stromal side facing the iris (Figures 17-35A to C). Again, the

Figure 17-32: The temporary suture is cut.

Figure 17-33: AC is filled with BSS.

Figure 17-34: Tissue grasped with Charlie forceps.

A

B

C

Figures 17-35A to C: Insertion of the donor corneal tissue.

endothelial layer remains protected on the inside by Healon. The tissue can be gently manipulated with the forceps along the stromal sides if centration of the tissue within the recipient bed needs to be improved. The tissue gently opens up on its own, with the opening of the taco shape to the surgeon’s left. The 60% stromal side gently adheres to the overlying recipient bed with the 40% stromal edge lying nearly perpendicular to the iris plane.

Three 10-0 nylon sutures are then used to close the scleral wound to secure the anterior chamber (Figure 17-36). A cannula is then placed through the stab incision and the tip placed onto the iris surface, between the donor sides, within the interior of the taco. BSS is then gently injected into the anterior chamber to fill the chamber and deepen it (Figure 17-37). Irrigation with BSS also loosens the Healon from the endothelial surface and helps to gently unfold the tissue. Because the donor tissue was folded into an asymmetric shape, the tissue invariably will spontaneously unfold (Figures 17-38A to D) in the correct orientation (i.e. endothelium down), as long as the chamber is deep enough and there is no impediment. Once the tissue has unfolded,

Figure 17-36: The temporal incision is sutured.

Figure 17-37: BSS is added to deepen the anterior chamber.

then an air bubble is gently injected into the anterior chamber (Figure 17-39) to stabilize the tissue.

The donor disk may not be in perfect centration after insertion. If not, it can be positioned from either the endothelial side or the stromal side. A reverse Sinskey hook (Bausch and Lomb, St. Louis, MO) is used for endothelial side positioning (Figure 17-40). The hook is placed through the stab incision, the peripheral endothelium is engaged, and the tissue moved over to whatever position is desired. Although this maneuver undoubtedly causes endothelial cell damage at that point of peripheral contact, we have not found that the central endothelial cell counts 6 months after surgery to be any worse than after a standard PKP.10,11,14 Care is taken, however, to minimize this maneuver and also to avoid the central posterior striae that can occur and can compromise vision. An alternative technique for positioning can be done from the stromal interface side using a 30-gauge needle tip. A slight “barb” is placed on a standard short 30-gauge needle, and the tip is placed through the superior wound directly into the interface. The barb is rotated posteriorly to engage a few stromal fibers of the donor disk, and this grasp is used to move the tissue over into the proper centration. During both the endothelial and stromal positioning maneuvers, the anterior chamber is filled with air.

Once the tissue is in proper centration, it is critical to make sure that all of the donor edges are anterior to all of the recipient bed edges for 360 degrees (Figure 17-41). Visual inspection is not enough, and manual verification is mandatory. If any portion of the donor tissue edge lies posterior to the recipient rim, then the donor tissue will likely be dislocated the next morning or present with a significant space in the interface (secondary anterior chamber). To accomplish proper donor edge position, the anterior chamber is filled completely with air and a reverse Sinskey hook is placed through a stab incision into the anterior chamber. The tip of the hook is then lifted anteriorly and placed between the edge of the donor and recipient rim. The hook is then rotated to engage the recipient rim posterior stromal edge, and then used to pull the edge posteriorly. With this maneuver, the air bubble in the anterior chamber immediately pushes the donor edge up anteriorly, into the recipient pocket, and upon release of the Sinskey hook, the recipient edge “pops” right up posterior to the donor edge. This “tire iron” maneuver is performed for 360 degrees (Figure 17-41), even when the donor tissue appears already in good position. This is done because even small strands of recipient stromal edge tissue can get caught in the edge interface and prevent adherence of the graft or act as a wick for aqueous into the interface, causing later donor disk dislocation.

Oncesatisfiedthatthedonordiskisinfinalpositionwith good edge position, the surgeon then removes the air in the anterior chamber and replaces it with BSS (Figure 17-42). Careistakentoavoidpupillaryblockbytheairbubbleinthe anteriorchamber,butifitoccurs,simplesuctioningoftheair fromthepupillarysurfaceresolvestheproblem.Occasionally air can get trapped behind the iris, giving the impression of

posteriorpressurewiththeiriscomingforwardtothedonor edges.Again,suctioningwithacannulafromthepupillary surface will resolve this issue. The BSS placed into the anterior chamber creates a normal IOP and the chamber deepens. A small (3 mm wide) air bubble is usually left in place (Figure 17-43) to help further stabilize the donor disk position over the first 24 hours postoperatively.

Figure 17-41: “Running the rim” with reverse Sinskey hook.

Figure 17-42: Replacing the air with BSS.

Figure 17-43: Final view of eye after the triple procedure, namely, phacoemulsification, PC IOL and DLEK.

The suture knots of the scleral incision are cut short, and buried on the scleral side. The wound is checked to be watertight. The conjunctival peritomy is closed according to the surgeon preference. We routinely place on the corneal surface a 24-hour collagen shield soaked in antibiotics and

steroids at the close of surgery in order to deliver medication until the patch is removed the next day; however, each surgeon’s usual routine for antibiotics (subconjunctival or otherwise) is acceptable.

An occlusive patch and shield are routinely placed, and the patient is brought to the recovery room. We usually instruct the nurses to have the patient lie in a supine position for the first few hours as much as possible to allow the retained air bubble to further stabilize the graft position, but this is not critical. The patient is discharged from the recovery room when fully recovered from anesthesia.

Postoperative Course

The patient is seen the next morning and the patch is removed. Most patients will remark that the eye was as comfortable as after a standard cataract surgery and that they did not require any narcotic pain relief during the immediate postoperative period. Once the patch is removed, the vision is usually about 20/400. The vision is unimportant on postoperative day one and the only reason for the visit is to insure that the donor disk is attached and in good position. In our prospective series of over 115 patients (as of July 2004), we have experienced only 5 cases where the donor disk was dislocated on the first postoperative day. All these five cases were easily treated by taking the patient back to surgery and usually under topical anesthesia, another air bubble is placed in the anterior chamber and the disk repositioned as before. This procedure usually takes about 15 minutes. We have been successful with all five re-positionings, resulting in clear corneal grafts.

If the graft is in good position on day one, it will heal in good position and we have had no late graft dislocations. The edges of the graft seal down with significant healing sometime within the first 3 months. The overlying cornea has a variable rate of clearing, but some patients are able to see as well as 20/25, only one week after DLEK surgery, with a crystal clear central cornea. The usual visual progression postoperatively of patients with minimal or no macular disease, however, is the following: One day: 20/400, one week: 20/100, one month: 20/60, three months: 20/50, six months: 20/40, one year: 20/30, two years: 20/25.

There is, of course, a high variability of vision in any series of elderly patients undergoing ocular surgery, especially, DLEK. The interface may clinically appear exceptionally clear, but it likely contributes about one line of visual loss to the macular potential.13,14

The endothelial survival after small incision DLEK surgery is quite remarkable. Even with folding the tissue

and other manipulations described above, the average endothelial cell count after small incision DLEK surgery is comparable to PKP surgery and it is not significantly different from large incision DLEK where the tissue is not folded.14

The postoperative medical therapy after DLEK surgery is identical at this time to what is done with PKP surgery patients. Topical prednisolone acetate 1% is used four times a day for 3 months, then three times a day until 6 months, then twice a day until 9 months, and then once a day until one year postoperatively. The steroids are then tapered down further until discontinued. We have experienced only a 3% rejection rate after DLEK surgery, and so steroid therapy may not be as critical as after PKP, but this remains speculative at this time. Fluoroquinolone antibiotics are used on a four times a day dosage for two weeks and then discontinued.

Outside of a scientific protocol, DLEK patients do not require the same degree of monitoring as standard PKP patients and therefore require less postoperative clinic time. With no corneal sutures or incisions, wound healing or ulcerations are not an issue. Astigmatism management is also not an issue after DLEK surgery. The only critical monitoring that is required is for steroid-induced glaucoma as long as the patient is on topical steroids, and this is done according to the clinician’s standard routine.

The DLEK surgical procedure is a difficult one and requires a commitment to exacting detail and thorough practice prior to incorporation of this procedure into the surgeon’s operative repertoire. However, with its superior topography, rapid wound healing and long term safety, the DLEK procedure is well worth the effort.

References

1. Sugar A, Sugar J. Techniques in penetrating keratoplasty: A quarter century of development. Cornea 2000;19:603-10.

2. Abou-Jaoude ES, Brooks M, Katz DG, Van Meter WS. Spontaneous wound dehiscence after removal of single continuous penetrating keratoplasty suture. Ophthalmology 2002;109: 1291-96.

3. Tseng SH, Lin SC, Chen FK. Traumatic wound dehiscence after penetrating keratoplasty: Clinical features and outcome in 21 cases. Cornea 1999;18:553-8.

4. Stechschulte SU, Azar DT. Complications after penetrating keratoplasty. Int Ophthalmol Clin 2000;40:27-43.

5. Akova YA, Onat M, Koc F, Nurozler A, Duman S. Microbial keratitis following penetrating keratoplasty. Ophthalmic Surg Lasers 1999;449-55.

6. Confino J, Brown SI. Bacterial endophthalmitis associated with exposed monofilament sutures following corneal transplantation. Am J Ophthalmol 1985;99:111-3.

7. Ko WW, Frueh BE, Shields CK, Costello ML, Feldman ST. Experimental posterior lamellar transplantation of the rabbit cornea [ARVO Abstract]. Invest Ophthalmol Vis Sci 1993;34(4): S1102. Abstract nr 1967.

8. Melles GR, Eggink FA, Lander F, Pels E, Rietveld FJ, Beekhuis WH, Binder PS. A surgical technique for posterior lamellar keratoplasty. Cornea 1998;17:618-26.

9. Terry MA, Ousley PJ. Endothelial replacement without surface corneal incisions or sutures: Topography of the deep lamellar endothelial keratoplasty procedure. Cornea 2001;20:14-8.

10. Terry MA, Ousley PJ. Deep lamellar endothelial keratoplasty in the first United States patients: Early clinical results. Cornea 2001;20:239-43.

11.Terry MA, Ousley PJ. Replacing the endothelium without corneal surface incisions or sutures: The first United States clinical series using the deep lamellar endothelial keratoplasty procedure. Ophthalmology 2003;110:755-64.

12.Terry MA, Ousley PJ. In pursuit of emmetropia: Spherical equivalent refraction results with deep lamellar endothelial keratoplasty (DLEK). Cornea 2003;22:619-26.

13.Terry MA, Ousley PJ. Rapid visual rehabilitation after endothelial transplants with deep lamellar endothelial keratoplasty (DLEK). Cornea 2004;23:143-53.

14.Terry MA, Ousley PJ. Small incision deep lamellar endothelial keratoplasty (DLEK): 6-month results in the first prospective clinical study. Cornea 2004 (in press).

15.Terry MA. Endothelial replacement: The limbal pocket approach. Ophthalmol Clin North Am 2003;16:103-12.

16.Terry MA. Deep lamellar endothelial keratoplasty (DLEK): Pursuing the ideal goals of endothelial replacement. Eye 2003;17:982-8.

17.Terry MA. A new approach for endothelial transplantation: Deep lamellar endothelial keratoplasty. Int Ophthalmol Clin 2003;43:183-93.

18.Terry MA, Ousley PJ. Corneal endothelial transplantation: Advances in the surgical management of endothelial dysfunction. Contemporary Ophthalmology 2002;1(26):1-8.

19.Terry MA. Endothelial replacement: New surgical strategies. In: Krachmer J, Mannis M, Holland E (Eds). Cornea. Surgery of the Cornea and Conjunctiva (2nd edn). St. Louis: Mosby-Year Book, Inc. 2004 (in press).

20.Terry MA. The evolution of lamellar grafting techniques over twenty-five years. Cornea 2000;19:611-6.

21.Melles GR, Lander F, Rietveld FJ. Transplantation of Descemet’s membrane carrying viable endothelium through a small scleral incision. Cornea 2002;21:415-8.

22.Duran JA, Malvar A, Diez E. Corneal dioptric power after penetrating keratoplasty. Br J Ophthalmol 1989;73:657-60.

23.Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol 1988;105:637-45.

24.Isager P, Hjortdal JO, Ehlers N. Stability of graft refractive power after penetrating keratoplasty. Acta Ophthalmol Scand 2000;78:623-26.

25.Davis EA, Azar DT, Jakobs FM, Stark WJ. Refractive and keratometric results after the triple procedure: Experience with early and late suture removal. Ophthalmology 1998;105:62430.

26.Dursun D, Forster RK, Feuer WJ. Surgical technique for control of postkeratoplasty myopia, astigmatism, and anisometropia. Am J Ophthalmol 2003;135:807-15.

27.Segev F, Voineskos AN, Hui G, Law MS, Paul R, Chung F, Slomovic AR. Combined topical and intracameral anesthesia in penetrating keratoplasty. Cornea 2004;23:372-6.

28.Armour RL, Wilson DJ, Ousley PJ, Terry MA. Invest Ophthalmol Vis Sci 2004;45:ARVO E-Abstract 2898.

Introduction

Endothelial dysfunction caused by pseudophakic bullous keratopathy (PBK) and Fuchs’ endothelial dystrophy is the leading cause of corneal visual loss in the United States.1,2 Penetrating keratoplasty (PKP) with implantation of an irisfixated or sclera-fixated posterior chamber intraocular lens (PC IOL) is the standard procedure for treating cases of PBK with an anterior chamber intraocular lens (AC IOL).³ Deep lamellar endothelial keratoplasty (DLEK) is a good alternative to PKP for endothelial replacement.4-13 In cases of aphakic or pseudophakic (AC IOL) bullous keratopathy, placement of a scleral-fixated PC IOL or replacement of the AC IOL with a scleral-fixated PC IOL may be performed by using the superior incision of DLEK together with a small superior and inferior scleral flaps.

Surgical Objective and Anesthesia

The surgical objective is to exchange the posterior corneal lamella including the damaged endothelium for a healthy donor corneal disk of the same size combined with an automated anterior vitrectomy and implantation of a scleral-fixated PC IOL in cases of aphakia and in cases in which replacement of the anterior chamber IOL is necessary. It is preferable to place the IOL in the posterior chamber as shown by Holladay.14 The scleral-fixation of the PC IOL in cases with inadequate posterior capsular support has shown encouraging results as an alternative method of lens implantation.15-21 Dissection and excision of the posterior corneal lamellar disk allows a good surgical view of the anterior segment and facilitates performing anterior vitrectomy and scleral-fixated PC IOL even in severe cases of bullous keratopathy. Intraoperative epithelial scraping also can be performed in cases of severe epithelial edema, to improve visualization of the anterior segment.

The use of general anesthesia is preferable. Monitored anesthesia care (MAC) can also be attempted if the patient has a high-risk of potential anesthesia-related complications with general anesthesia.

Surgical Procedure

The basic surgical procedure of DLEK through a 9.0 mm superior limbal incision as described by Terry and Ousley8 is carried out [See also Section 8, Deep Lamellar Endothelial Keratoplasty (DLEK)]. This is combined with an automated anterior vitrectomy and scleral-fixated PC IOL as described by Helal et al.21 The DLEK instruments used for this procedure are shown in Figure 18-1.

Figure 18-1: Instrument tray showing Devers dissectors, scissors, Terry trephine, and artificial chamber.

The surgical steps are as follows:

1.A superior conjunctival periotomy of 11 mm is made with a Castroviejo corneal scissors (Katena, Denville, NJ) and the bleeding vessels are cauterized.

2.A 9.0 mm incision is made at the superior limbus (Figure 18-2) with a disposable super-blade (Alcon Surgical, Fort Worth, TX).

Surgical tip: The incision should be 1 to 2 mm anterior to the original cataract incision so as not to perforate the sclera, if using the same incision, or posterior to it.

Figure 18-2: Limbal incision using a super-blade.

3.Sodium hyaluronate (Healon, Pharmacia, Peapack, NJ) is injected through a paracentesis into the anterior chamber at the 3 o’clock position.

4.A lamellar dissection is carried out (Figure 18-3) from the superior incision starting with a sclerotome blade (Katena). This lamellar dissection is performed about 350 µm from the corneal surface.

dissectors (Bausch & Lomb, St. Louis, MO). The straight Devers dissector (Figure 18-4) is used for the lamellar dissection of the superior half of the cornea until the middle of the cornea (3 to 9 o’clock meridian) is reached and then a curved Devers dissector (Figure 18-5) is used for the lower half of the cornea.

6.A 7.5 mm, low-profile, Terry trephine (Bausch & Lomb) is introduced into the corneal pocket (Figure 18-6) and centered to the patient’s limbus. Trephination of the posterior corneal lamella including the Descemet’s membrane and the endothelium is then carried out after increasing the intraocular pressure by injecting

Healon 5 (Pharmacia) into the anterior chamber. Entry into the anterior chamber is marked by distortion of the pupil and iris entry into the corneal pocket.

7.Following entry into the anterior chamber and removal of the Terry trephine, superior entry into the anterior chamber is carried out using a 15-degree super-blade, if needed, and a right and left corneal micro-scissors (Katena) are used to cut the trephined disk on both sides (Figures 18-7 and 18-8). A highly curved Cindy I scissors (Bausch & Lomb) is used to cut the inferior part of the disk, which is then removed from the corneal pocket (Figure 18-9).

Figure 18-7: Right corneal scissors being used.

Figure 18-8: Left corneal scissors being used.

8.An anterior vitrectomy (Figure 18-10) is then carried out through the same superior incision by using an automated ocutome (Alcon Surgical).

9.An inferior 5.0 mm periotomy is made and the bleeders are cauterized. A 2.5 mm triangular scleral flap is then fashioned inferiorly at the 5:00 or 7:00 o’clock position. A second triangular flap is fashioned at the 11:00 or 1:00 o’clock position.

Surgical tip: Avoiding the 6, 12, 3, and 9 o’clock positions decreases the risk of intraoperative bleeding, because the anterior and long posterior ciliary arteries are at the vertical and horizontal meridia.

Figure 18-9: A completely cut posterior lamellar disk is being removed through the superior limbal wound.

Figure 18-10: Anterior vitrectomy is performed using an automated ocutome unit.

10.A double-armed straight needle (Ethicon, Johnson & Johnson,Brussels,Belgium,W1713,16mmlong,micropoint plus and 150 µm diameter) with 10-0 polypropylene (Prolene) is passed vertically about 0.75 mm from the posterior surgical limbus under the inferior flap (Figure 18-11).

Surgical tip: This is the closest position to the ciliary sulcus as shown in cadaver eyes.22

11.A 27-gauge needle that is bent vertically (Figure 1812) is passed under the superior flap (Figures 18-13 and 18-14).

12.Thestraightneedleisthendirectedtangentiallytobefed into the lumen of the 27-gauge needle(Figure 18-15).