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

Figure 15-21: Cornea on punch block—before punch.

Figure 15-22: Cornea on punch block—after punch.

familiar “crunch” sound that is so common with full thickness PKP donor trephination. Instead the sound is much quieter or not present at all. While it is best to have good centration of the punch, if the stromal dissection of the donor has been carried out all the way to the limbus for 360 degrees, it will be fine. If the dissection has not been carried all the way out to the limbus, and the surgeon has an eccentric punch, then the posterior donor disc may have a 1 mm thick edge and an opposite 100 micron thick edge. This wedge of tissue will not adhere to the recipient bed, and so care in completion of the total donor stromal pocket is advised prior to punching out the tissue.

The donor posterior disc is prepared for insertion into the eye by placing the donor disc on an Ousley insertion spatula (Bausch and Lomb) (Figures 15.23A and B). The Ousley spatula is a round, flat spatula with a diameter of 8.5 mm and a proximal anterior ledge that helps to prevent proximal movement of the donor tissue. The Ousley spatula is coated with a very thin layer of Healon to protect the endothelium, and then the donor disk is gently grasped at the stromal edge with fine forceps, separated from the

A

B

Figures 15-23A and B: Tissue placement onto Ousley spatula.

anterior stromal tissue and then placed endothelial side down onto the Ousley spatula (Figures 15-23A and B) . The donor tissue is then brought over to the operative field for insertion.

Transplantation of the Donor Tissue

With the microscope in place, the temporary scleral sutures of the superior wound are cut. The anterior chamber of the patient is then filled completely with an air bubble (Figure 15-24). The Ousley spatula with the donor tissue is then brought into position by the limbal wound, the anterior lip of the wound is stabilized with a fine-toothed forceps, and then in one deft movement, the Ousley spatula is inserted into the anterior chamber while the anterior lip of the wound is slightly elevated (Figures 15-25 and 15-26). The spatula is inserted parallel to the iris and once in the anterior chamber it is lifted anteriorly until the stromal surface of the donor and recipient are coapted (Figure 15-27). The spatula is then gently removed from the eye (Figure 15-28), sliding on a layer of Healon, leaving the donor tissue behind, supported by a residual air bubble in the anterior chamber (Figure 15-29). A

Figure 15-24: Air bubble in recipient anterior chamber.

Figure 15-25: Insertion of disk—beginning stage.

Figure 15-26: Insertion of disc—middle stage.

Figures 15-27 and 15-28: Insertion of disk—end stage.

Figure 15-29: Air bubble behind donor corneal graft.

single suture of 10-0 nylon is then used to close the central scleral wound to secure the chamber and prevent escape of the donor tissue. An air bubble is then gently injected into the anterior chamber to further support the donor tissue. If the air is injected too rapidly and the superior wound does not have a suture in place, then the donor disk will be rapidly expulsed from the eye.

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. If positioning is necessary, then the superior 9.0 mm wound must be completely closed first with 10-0 nylon suture (interrupted or running) to stabilize the chamber. Once secured, a large air bubble is injected into the anterior chamber to fill the

Figure 15-30: Positioning of graft with a Sinskey hook.

chamber. A reverse Sinskey hook (Bausch and Lomb) is used for endothelial side positioning. The hook is placed through the stab incision, the peripheral endothelium is engaged, and the tissue moved over to whatever position is desired (Figure 15-30). Although this maneuver undoubtedly causes endothelial damage at that point of peripheral contact, we have not found that the central endothelial cell counts 6 months after surgery are any worse than after 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 disc, 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. 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 the 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, even when the donor tissue appears to be already in a 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 late dislocation of the donor disc.

Once satisfied that the donor disk is in final position with good edge position, the surgeon then removes the air in the anterior chamber and replaces it with BSS (Figure 15-31). Care is taken to avoid pupillary block by the air bubble in the anterior chamber, but if it occurs, simple suctioning of the air from the pupillary surface resolves the problem. Occasionally air can get trapped behind the iris, giving the impression of posterior pressure with the iris coming forward to the donor edges. Suctioning the air from the pupillary surface with a cannula will resolve this issue. The BSS placed into the anterior chamber creates a normal IOP and the chamber deepens. A small (3.0 mm wide) air bubble is usually left in place to help further stabilize the donor disc position over the first 24 hours postoperatively. All of the scleral wound sutures are tied slightly tight to induce about 2 diopters of vertical, steep, with-the-rule astigmatism. This is done because the 9.0 mm wound has a tendency to cause 1 or 2 diopters of against-the-rule astigmatism over time if the wound is left topographically neutral at the conclusion of surgery. The suture knots are cut short, and buried on the scleral side. The wound is checked to be watertight. The conjunctival peritomy is closed. We routinely place on the corneal surface a 24-hour collagen shield soaked in antibiotics and steroids at the end of the 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 certainly acceptable.

Figure 15-31: Appearance at end of surgery.

An occlusive patch and shield are routinely placed over the operated eye, 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 this outpatient procedure 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 standard cataract surgery and that they did not require any narcotic medication for relief of pain. Patients usually do not have eye pain after DLEK surgery. 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 disc 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 disc was dislocated on the first postoperative day. All 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 disc repositioned as before. This is usually a 15-minute operation. 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 solid 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 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 as follows: One day, 20/400; one week, 20/100; one month, 20/60; three months, 20/50; six months, 20/40; one year, 20/30; and two years, 20/25. Of course, there is a high variability of vision in any series of elderly patients undergoing ocular surgery, but 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 postoperative medical therapy after DLEK surgery is identical at this time to what is done with PKP surgery patients. Topical prednisolone acetate 1% suspension (Pred Forte 1%, Allergan Inc., Irvine, CA) 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 entirely. 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 as a speculation at this point. Fluoroquinolone antibiotics are used on a four times a day dosage for two weeks only 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 sutures or corneal incisions, wound healing or corneal ulcerations are not an issue. Astigmatism management is also not an issue after DLEK surgery, much to the joy of patient and the surgeon alike! The only critical monitoring 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;109:1291-6.

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 # 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;20:14-18.

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): Six-month results in the first prospective clinical study. Cornea 2005; 24:59-65.

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

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

23.Isager P, Hjortdal JO, Ehlers N. Stability of graft refractive

power after penetrating keratoplasty. Acta Ophthalmol Scand 2000;78:623-6.

24. 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;105:624-30.

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

26.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.

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

Introduction

Penetrating keratoplasty (PKP) has long been the standard treatment for patients with vision loss from advanced corneal edema due to endothelial dysfunction.1 However, the surface sutures and the vertical wounds which are produced by PKP present an inherent liability for long-term graft survival and visual function with most patients suffering some visual degradation from irregular astigmatism and a few suffering total visual loss from suture induced infections or wound induced traumatic globe rupture.2-6 A technique of selective endothelial keratoplasty (EK) which would avoid corneal sutures and vertical stromal wounds would eliminate many of the risks of transplant surgery and speed the visual recovery for the patient.

In 1993 Drs Ko and Feldman from San Diego, California presented an animal study at the annual ARVO meeting which described a new technique for endothelial replacement through a scleral limbal incision7 (See also Chapter 14, History of Lamellar and Penetrating Keratoplasty). Dr Gerrit Melles, a Dutch ophthalmologist working as a fellow with Dr Perry Binder in San Diego developed this technique further in monkeys, utilizing a 9 mm scleral incision size.8 In 1998 he described this technique in the first human patient and called it posterior lamellar keratoplasty (PLK)9 (See also Chapter 14, History of Lamellar and Penetrating Keratoplasty). Terry and Ousley began laboratory work in 1999 on this technique, and after their technical modifications, re-design of instrumentation, and safe introduction of Healon (Pfizer, New York, NY) to the procedure, this surgery was made considerably easier. Terry performed the first United States cases in 2000 and called the surgery Deep Lamellar Endothelial Keratoplasty (DLEK).10-19 All of this work represents a radical departure from the PKP technique in that the DLEK surgery accomplished the goal of endothelial replacement without surgically violating the surface of the recipient cornea. By eliminating surface corneal sutures and incisions, the advantages of normal corneal topography and faster wound healing were obtained, leading to faster visual rehabilitation and a more stable globe for the patient.20,21 In 2002, a small, 5 mm length scleral incision technique of PLK surgery was described in a case report by Melles et al.22 We have investigated this technique in the largest prospective series of small incision DLEK in the world and have found it to be valid for endothelial replacement surgery.15,21

Currently, further modifications have been made in the field of EK. A technique whereby only the posterior Descemet’slayerisstrippedoffwasoriginallydescribedby Melles and termed PLK with Descemetorhexis23 (See also

Chapter 14, History of Lamellar and Penetrating Keratoplasty).

It was later popularized by Frank Price in the US as Descemet’s Stripping Endothelial Keratoplasty (DSEK),24 and most recently has been further popularized by Mark Gorovoy as Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK). Regardless of the name, the Descemet’sstrippingtechniqueofEKhasbeenproventobe a technically easier alternative to DLEK surgery, and it has nowbeenembracedby50%ormoreofthecornealtransplant surgeonsintheUSastheprocedureofchoiceforEKsurgery. OtherdevelopmentsinEKsuchastheuseofthefemtosecond laser for stromal dissections25-27 [See also Chapter 26, Femtosecond Laser (Intralase®)—Descemet’s Stripping Endothelial Keratoplasty (Femto-DSEK)]: Initial Studies of SurgicalTechniqueinHumanEyes),theuseofamicrokeratome for donor preparation28,29 (See also Chapter 12, Artificial Anterior Chambers),andtheuseofdonortissuethathasbeen “pre-cut” by the distributing eye bank (See also Chapter 19, Eye Banking and Donor Corneal Tissue Preparation in DSAEK, andChapter30,UseofEyeBankPre-cutDonorTissueinDSAEK), are also contributing to the mainstream acceptance of EK surgery.

Indications and Rationale for DLEK Surgery

Although DSAEK surgery is currently our procedure of choice for standard endothelial replacement surgery [See also Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)] we have found that DLEK surgery still has a place in selected complex cases which require EK surgery, and DLEK should remain part of the surgical armamentarium of the EK surgeon. Certain cases of endothelial dysfunction would entail too much risk of dislocation or graft failure with the standard DSAEK surgical treatment, and would be better off with a simple DLEK surgery. For example, in cases of pseudophakic bullous keratopathy (PBK) with the presence of an anterior chamber lens, we feel that DLEK is by far a safer procedure than DSAEK if the anterior chamber lens is to be retained postoperatively. This is due to the fact that maintenance of the air bubble placed at the end of DSAEK surgery is critical to the success of this surgery. If the recipient eye has an anterior chamber IOL in place, then an air bubble cannot be maintained in the anterior chamber long enough to support the tissue in DSAEK surgery because it migrates into the posterior chamber as soon as the patient sits up. Loss of the air bubble support in DSAEK with subsequent dislocation of the endothelial donor graft onto the plastic surface of the anterior chamber IOL can result in permanent

endothelial damage and possible graft failure. However, in DLEK surgery, an air bubble is not even necessary postoperatively for the support of a DLEK graft. In over 250 cases of DLEK, we routinely removed the entire air bubble at the conclusion of DLEK surgery without any significant graft dislocation (dislocation rate of 4%), and in all cases of DLEK with an anterior chamber IOL left in place, we have never had a dislocation. Therefore, in any instance in which an air bubble cannot be maintained for an extended period of time postoperatively for graft support due to an open communication between the anterior and posterior chambers (e.g. aphakic bullous keratopathy, PBK with an anterior chamber IOL in place, aniridia, or presence of a larger peripheral iridectomy), then, a small incision DLEK surgery is the procedure of choice.

The purpose of this chapter is to describe the technique and results of standard small incision DLEK surgery in a large prospective series. The data from this DLEK prospective series21 should be used as a benchmark to determine the advantages and disadvantages of further modifications in EK.

The Small Incision DLEK Procedure

We originally utilized a 9 mm length, scleral limbal incision for DLEK surgery [(See also Chapter 15, Deep Lamellar Endothelial Keratoplasty (DLEK): Large Incision Technique)] and this was utilized in our first 36 eyes in our series. It has been well described in our previous reports.10-12 With the advent of the smaller 5 mm incision technique, we then adopted this as our procedure of choice for the remainder of the 62 eyes in this study. The technique described here is the small incision technique of DLEK, with or without concurrent cataract extraction. We have previously described this surgical technique in both print and video,15-21,30 the step by step description given below is for more extensive instruction and explanation (See Figures 16-1A to L).

Anesthesia

DLEK surgery is usually done under retrobulbar block anesthesia especially by the more experienced surgeon, but general anesthesia has also been used. General anesthesia (either endotracheal or laryngeal mask airway technique) is preferred for the novice EK surgeon because it minimizes posterior pressure on the globe and this is important during the recipient resection and donor implantation phases of the surgery. Nonetheless, the surgery is safely accomplished with good retrobulbar anesthesia combined with seventh nerve block (orbicularis block) local anesthesia as

well. It is also quite possible, for the severely medically frail patient, that this surgery could be accomplished with only topical anesthesia, similar to what has been done in PKP surgery under similar circumstances. However, this has not yet been done with DLEK surgery and likely would require a surgeon with the ability to accomplish this surgery in less than an hour.

Preoperative Preparation

Like all intraocular procedures, the patient’s ocular health should be maximized beforehand and any blepharitis, dry eye, or lid abnormality should be treated prior to surgery. Patients with some mild to moderate corneal surface haze or scarring from long-standing bullous keratopathy can still undergo DLEK surgery successfully. The surface scarring is simply scraped off at the time of surgery or weeks later in clinic after the stromal edema has completely resolved. This eliminates the induced irregular astigmatism from the scars and restores the normal topography.

In the usual case of patients with pseudophakia (posterior chamber IOL) the pupil is constricted in order to stabilize the iris-lens diaphragm during the surgery. This is also done if the patient has a clear crystalline lens and concurrent cataract surgery is not planned. Preoperative medications include two sets of pilocarpine 1% drops applied one hour prior to surgery. One set of aproclonidine 0.5% drops is also given just prior to surgery to reduce pressure and minimize conjunctival injection. Preoperative antibiotics are used according to the surgeon’s preference. The eye is prepped in the usual sterile ophthalmic fashion with the use of povodone-iodine solution.

Recipient Surgery: Small Incision

DLEK Portion

The operating microscope is positioned for the surgeon to be seated at the temporal side of the patient. (For small incision DLEK surgery, the scleral access incision is 5 mm, and therefore the incision is usually placed at the temporal limbal region rather than superiorly). The patient’s head should be positioned facing the ceiling, parallel to the floor. In addition, if general anesthesia is employed, the endotracheal tube is also positioned by the anesthesiologist to exit the mouth from the side opposite the surgical field to facilitate the surgeon’s field of movement. A superior and inferior rectus bridal sutures can also be placed if necessary to aid in positioning and stabilizing the globe during DLEK surgery.

A temporal limbal peritomy of the conjunctiva is performed with scissors allowing exposure of about 6 mm