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

Figure 24-14: “Taco-folded” donor corneal disk is positioned nasally.

Figure 24-15: I and A unit is used to unfold the donor corneal disk.

Figure 24-17: Air is injected under the donor corneal disk in the anterior chamber.

Figure 24-18: Drainage of fluid through the stab incisions if any donor-recipient interface fluid.

Figure 24-16: A second corneal suture is applied and the donor corneal disk is centered.

Grave, IL) and intravenous sedation as needed are utilized. The pupil is left neutral, i.e. no miosis or mydriasis.

A lid speculum is placed after the lid margin and lashes are draped with tegaderm (3M, St. Paul, MN). The surgeon is seated temporally, with the operating microscope and the corneal surface is marked with a 9.0 mm trephine marker inked with a sterile marking pen. This allows the surgeon to judge the trephine size for donor tissue trephination. The surgeon almost always uses a 9.0 mm donor corneal disk unless this corneal marking approaches 2.0 mm to the limbus, in which case, a smaller diameter trephine is preferable such as an 8.5 or 8.75 mm trephine. Avoid the donor lenticule from impinging too close to the AC angle. The patient’s eye is left open with the eyelid speculum and attention is then directed to the donor corneal tissue preparation. This air drying allows a swollen cornea to deturgesce to some extent and improve operative visibility.

In the operating room, Betadine 5% ophthalmic solution (Alcon Laboratories, Fort Worth, TX) to the skin and lids is performed with direct instillation onto the ocular surface.

The donor cornea is placed within the ALTK system (Moria, Doyleston, PA) and the donor cornea is cut with a 300 µm microkeratome head (Moria, Doyleston, PA). Air is used to

inflate the donor cap within the Moria ALTK system. A very firm corneal dome is verified with finger palpation. The donor corneal rim must be a consistent 16 mm rim size, without any edge irregularities or defects. The eye bank must be made aware that a large donor scleral rim size is required. The anterior cap is then removed from the keratome head and the remaining posterior lamellar donor tissue is removed from the ALTK system and placed on a cutting block and trephined endothelial side up. When lifting up the outer ring, simultaneous forced air pressure prevents the donor tissue from collapsing on the ALTK central post. Centration of the donor tissue on the cutting block is essential to avoid a decentered cut and a fullthickness donor disk edge. If that occurs, recenter the tissue and recut it to remove the full-thickness section. A perfectly round donor tissue is not required and causes no optical problems. A drop of Optisol GS (Bausch and Lomb Surgical, Irvine, CA) is placed on the donor cornea and attention is directed to the patient’s cornea. Using a 1.0 mm diamond blade vertical limbal paracentesis are made superiorly, inferiorly and nasally. A clear cornea 2.75 mm keratome incision is made temporally. Through the right handed paracentesis, the Gorovoy irrigating Descemet stripper (Harvey Instruments, Rotonda West, FL) is introduced into the AC and Descemet’s membrane is scored along the surface trephination mark for close to 360°. Descemet’s membrane is then stripped for 2-3 mm for several clock hours. The I and A 4.0 mm port handpiece (B&L millennium) is introduced through the keratome incision and the loose Descemet’s membrane edge is aspirated and removed through the wound. This may take several passes with the I and A unit to remove all of the Descemet’s membrane within the scored area. Three full-thickness stabs using the same diamond paracentesis blade are made equal distance in the mid-periphery for future interface fluid drainage as described by Dr. Frances Price. The temporal incision is enlarged to 5.0 mm.

Donor Corneal Disk Insertion

The donor corneal tissue within the cutting block is placed under the microscope and excessive fluid is removed with a Weck-cel™ spear (Medtronic Xomed Inc., Jacksonville, FL). Several drops of Healon (Advanced Medical Optics, Santa Ana, CA) are placed on the donor corneal tissue which is then folded over like a taco in a 60%/40% fold. It is then held with Goosey insertion forceps (Moria, Doyleston, PA) and the donor corneal disk is then inserted into the AC. A single 10-0 nylon suture (Ethicon # 9061) is applied to partially close the incision and sterile balanced

salt solution (BSS) is used to deepen the AC. The donor corneal disk may unfold spontaneously. If it does not unfold, the I and A handpiece is used to deepen the AC and hold the underside of the “taco” and unfold it. A final 10-0 nylon suture is placed on the wound and the donor disk is centered to the limbus. This is accomplished by reforming the AC about 50% depth and applying gentle pressure indentations at the limbus with any device, even your finger. The donor corneal disk will move away from the spot at the limbus where focal pressure is applied. Once the donor corneal disk is well centered, a full air bubble fills the AC outlining the donor disk edge. If the donor disk decenters during this step, the air is removed and the donor corneal disk is re-centered. The corneal stab incisions are then probed with a spatula or cannula and any interface fluid is expressed out. Dilating drops are applied and the patient is left in a supine position for 1 hour in the holding area. After 1 hour, a slit-lamp exam verifies the position of the donor and air is expressed out thru the paracentesis or the main wound site, until the lower air bubble meniscus is above the inferior pupil edge. This prevents potential pupillary block. A shield is applied. Topical antibiotics and corticosteroid eyedrops qid are begun and the patient is examined the next day in the office. Patient leaves the operating room with a patch and a shield taped over the eye.

Postoperative Day 1

Biomicroscopic examination confirms the position of the donor corneal disk. Is the cornea grossly edematous? Has the donor disk slipped inferiorly? If the answer is “yes” to those two questions, then donor dislocation is likely. Careful slit-lamp examination can identify very tiny adhesion gaps, even with 4-plus corneal edema (scale of 1-4). Repeat air injection into the AC is done in the minor operating room using the surgical microscope. Removal of excess air bubble is done as needed in the operating room. I have had to place three bubbles in several patients. There is no harm to the “loose” donor disk in the AC as the aqueous humor provides endothelial nourishment independent of stromal attachment. One patient had a delayed donor disk adhesion at 7 weeks, and has a perfect result with an excellent endothelial cell count. The goal is a donor disk dislocation rate of less that 5%. Postoperative topical medication regimen is 1 week of antibiotic drops, and corticosteroid drops qid for 3 months. After 3 months, the corticosteroid medication is tapered to once a day for six months. Steroid responders with increased IOP may need accelerated tapering and even a switch to loteprednol

etabonate ophthalmic suspension 0.5% (Lotemax, Bausch & Lomb, Rochester, NY) bid plus glaucoma drops. Cyclosporine ophthalmic emulsion 0.05% (Restasis, Allergan Inc., Irvine, CA) are used for dry eye and to decrease local inflammation. BSCVA is obtained at 6 and 12 weeks at which time a new eye glass prescription can be given. Limbal sutures are cut after 6 weeks for astigmatism control.

Discussion

DSAEK has revolutionized the surgical management of corneal endothelial failure. This is a significant paradigm shift in corneal replacement surgery worldwide. It allows the surgeon to explain the improved benefits of this new surgical procedure while minimizing some of the potential complications associated with an open-sky full-thickness procedure like the penetrating keratoplasty. In the absence of concomitant retinal and/or optic nerve disease, one can expect a BSCVA of 20/40 by 6 weeks in over 80% of the patients. This improves to over 90% by 12 weeks. BSCVA of 20/20 is reached in 16% by 6-12 months following surgery. There are no significant refractive surprises. Patients with bilateral disease are requesting second eye surgery by 3 months. However, appropriate patient counseling must never ignore the risks of any corneal transplant surgery; namely, infection, primary graft failure, graft rejection and secondary glaucoma. I no longer recommend DSAEK as an alternative to penetrating keratoplasty. DSAEK has replaced

PKP in my surgical practice and such a paradigm shift is expected to continue globally.

Bibliography

1. Gorovoy MS. Descemet stripping automated endothelial keratoplasty (DSAEK). Cornea 2008;27:632-3.

2. Melles GRJ, Eggink FAGJ, Lander F, et al. A surgical technique for posterior lamellar keratoplasty. Cornea 1998;17:618-26.

3. Melles GRJ, Lander F, Beekhuis WH, et al. Preliminary clinical results of posterior lamellar keratoplasty for a case of pseudophakic bullous keratopathy. Am J Ophthalmology 1999; 127:340-1.

4. Melles GRJ, Lander F, Dooren BTH, et al. Preliminary clinical results of posterior lamellar keratoplasty through a sclerocorneal pocket incision. Ophthalmology 2000;107:1850-7.

5. Melles GRJ, Landerd F, Nieuwendaal C. Sutureless, posterior lamellar keratoplasty. Cornea 2002;21:325-7.

6. Melles GRJ, Wijdh, RHJ, Nieuwendaal CP. A technique to excise the Descemet membrane from a recipient cornea (Descemetorhexis). Cornea 2004;23:286-8.

7. Price F, Price M. Descemet stripping with endothelial keratoplasty in 200 eyes. Cataract and Refractive Surgery 2006;32:411-8.

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

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. Rapid visual rehabilitation after endothelial transplants with deep lamellar endothelial keratoplasty (DLEK). Cornea 2004;23:143-53.

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.

Background

A sutureless small incision surgery is most desirable in the modern era of micro-incisional cataract surgery. There are several advantages of such a technique when considering DSEK. Less pain, less patient anxiety, less induced astigmatism and lower incidence of complications such as iris prolapse or wound leak. However, the concern has been that placing an 8.0 mm or larger donor corneal graft through a small entry-wound can result in crush injury to the donor endothelial cells and endothelial cell loss can occur. Perhaps, the benefits of small incisional DSEK would likely be vanquished in the potential high graft failure rate. As it turns out, the techniques of folding the endothelial graft in half and unfolding it in the limited confines of the anterior chamber under low pressure requires a bit of skill and patience. Often times, the additional manipulations in “unsticking” the two halves, can further damage the endothelial cells or even cause an inversion of the tissue with the donor endothelium facing the patient’s corneal stroma, an undesired incident. Considering that most anterior chamber depths are only a 2.0 to 3.0 mm deep, the iris or lens may obstruct the proper unfolding of an 8.0- 9.0 mm diameter endothelial graft. Conversely, a tri-folding or “burrito” configured endothelial graft, is quite easily unfolded with plenty of space for the edges to unfold. Thus a trifolded donor corneal disc requires less room within the AC to unfold as compared to a bifolded donor corneal disk. The author is of the opinion that tri-folding the endothelial graft is likely to be a distinct advantage for both the patient and the surgeon.

Description of Technique

The donor corneal disk that is “freshly” trephined and a “S” mark is made on the stromal surface of the donor corneal disk using a surgical marking pen (Figure 25-1)

(Editorial Note: Recent study seem to indicate that stromal

Figure 25-2: Healon being placed on the endothelial cells of the donor corneal disk.

markings with a marking pen may be associated with increased endothelial cell loss). It is then placed on a stable surface with the endothelial side up. A small amount of viscoelastic, namely, Healon (American Medical Optics, Inc., Santa Ana, CA) is placed over the endothelial cells (Figure 25-2). Using a toothed forcep, the edge of the anterior lamellar cap is secured, while peeling the edge of the endothelial graft up and across with a pair of folding forceps (Goosey or Phakic IOL insertion Forceps) (Figure 25-3). Once one-third of the tissue is folded over, the stromal side of the donor graft is grasped across the length of the graft, parallel to the initial fold (Figure 25-4). Using the right hand the tissue is then supinated and rolled over so that the tissue now is in a “stroma out/endothelium in” configuration much like a cinnamon roll (Figures 25-5A and B). Prior to insertion, the anterior chamber is filled with air to prevent collapse during insertion. The tissue roll is then inserted through the entry wound, taking care not to allow the loose edge to unfold exposing endothelial cells (Figure 25-6). Once this is

Figure 25-1: Schematic representation of the tri-fold technique.

Figure 25-3: Forceps peeling 1/3rd of the donor graft back as the initial step in the tri-fold technique.

Figure 25-4: Forceps being applied across the stromal side of the donor corneal disk.

Figure 25-5A: Tissue rolled over forceps into a “burrito” fold prior to insertion into patient’s anterior chamber.

Figure 25-6: Insertion of rolled endothelial graft through a 3.0 mm clear corneal wound.

Figure 25-7: Forceps grasping entry wound and graft to prevent tissue from slipping.

Figure 25-5B: Tissue rolled around forceps in a “burrito” fold.

accomplished, the tissue is released within the anterior chamber without irrigation. The edge of the endothelial graft and wound should be grasped as the insertion forceps are retracted out of the eye (Figure 25-7). The endothelial graft typically remains in its tri-folded configuration within the anterior chamber (Figure 25-8). Evacuation of any remaining air, followed by gently deepening the anterior chamber with irrigating balanced salt solution will typically automatically unfold the “wings” of the endothelial graft. Occasionally, a small amount of air is required to be placed in the middle of the endothelial graft which further facilitates the unfolding of the donor corneal disk. No instruments are required in the anterior chamber at this stage of the procedure, and in some cases an externo pressure can be used to complete unfolding of the donor cornea, prior to injection of an air bubble.

Figure 25-8: Endothelial graft in anterior chamber in tri-fold configuration.

Advantages Over the Bi-fold

Method

In most cases, the tri-fold technique allows one-third or two-third of the tissue to be unfolded and in the correct position immediately after the release of the donor disk within the anterior chamber. The portion of the corneal graft that is rolled and not grasped typically unfolds at the 3 o’clock position with the stroma against stroma. The remaining one-third requires very little manipulation. Less tissue manipulation and negligible risk of inversion affords a great benefit to endothelial survival. With a smaller 3 mm incision, the procedure can be performed through a clear corneal incision. Such a sutureless surgical technique results in less corneal astigmatism and possibly less postoperative pain for the patient. Additionally, such a small 3.0 mm incision can also decrease or prevent potential iris prolapsed during DSEK surgery.

Learning Curve and Precautions

The surgeon acquiring endothelial transplant skills must be cautious when manipulating the graft tissue. Specifically, using the tri-fold technique requires that the surgeon take special care not to damage the endothelium when folding or grasping the tissue. The use of Healon probably “cushions” the endothelial cells and provides some additional safety in this procedure. The folding should be gentle and avoid any direct contact with the endothelial cells. Care should be taken when grasping the tissue with the forceps and only apply minimal pressure to hold the tissue. The tissue should not be crushed between the holding forceps. Additionally, one tong of the forceps will touch the endothelial side (Figure 25-1), so downward

pressure should not be used when inserting. Also, a small enlargement to 3.5 mm or 4 mm may be necessary if the wound tunnel is long or the graft is especially large (greater than 8.5 mm) or the donor graft is thick. The tissue should slide easily through the entry wound and not force the tissue which can result in crush injury to the donor endothelial cells.

Combining with Phaco

Using the Tri-fold technique through a small cataract incision is an excellent way to combine phacoemulsification with endothelial cell replacement. After routine clear corneal cataract surgery, and immediately following IOL insertion, the viscoelastic (Healon, AMO) can be retained during Descemet’s stripping. After this, the viscoelastic can be removed with irrigation/aspiration and the corneal graft is prepared in the usual fashion using the tri-fold technique. The pupil should remain dilated and no miotics should be used to prevent the air bubble from getting behind the iris

(Editorial Note: Alternative techniques include removing the patient’s Descemet’s membrane prior to phacoemulsification and IOL insertion, and constricting the pupil and removing the Healon prior to insertion of the donor corneal disk. Also, upsidedown phacoemulsification technique (John technique) may be considered for cataract surgery with DSEK). The tissue is inserted through the same cataract incision into the anterior chamber and then unfolded in the usual fashion described above. Care must be taken so as to not inject the air into the capsular bag but only in the anterior chamber. Only a small amount of additional time is required to perform this triple procedure of combined cataract and corneal surgery. Intraocular lens selection should be targeted towards myopia which will compensate for the typical hyperopic shift seen after DSEK. Using the Tri-fold technique prevents the surgeon from having to enlarge the wound and later suture it.

Future Considerations

The tri-fold technique will likely be precursory to the evolution of an even better technique for small incisional sutureless endothelial transplantation. An insertion tool that would limit any crushing forces and deploy the tissue in the correct orientation would be readily accepted by the corneal surgeons worldwide. Such an instrument would likely bear resemblance to the current IOL injectors (Editorial Note: Currently, various donor corneal insertion cartridges are in various stages of development). The tissue could be rolled or tri-folded for loading and then inserted through a protective sheath.

Introduction

Among the most frequent indications (30-40%) for penetrating keratoplasty in developed countries are pseudophakic or aphakic bullous keratopathy and Fuchs’ corneal dystrophy. For these corneal endothelial diseases, Melles and associates1 in Europe and Terry2 in the United States introduced the technique of posterior lamellar keratoplasty (PLK), namely, deep lamellar endothelial keratoplasty (DLEK), to selectively exchange patient’s corneal endothelium, Descemet’s membrane (DM), and adjacent deep corneal stroma with a similar donor corneal disk with healthy endothelium. A limbus-to-limbus intrastromal lamellar dissection was carried out within the host cornea through a 9.0 mm scleral incision. The posterior lamellar disk, consisting of posterior corneal stroma, DM, and endothelium, was excised by using an intralamellar trephine, and a disk of similar donor posterior lamellar tissue was placed in the recipient opening without suture fixation. Donor disk adhesion was made possible by using an air bubble in the anterior chamber (AC).

Melles has subsequently described two important modifications in this procedure. The first was reducing the size of the scleral incision to 5 mm,3 which mandates removal of the posterior lamella with corneal microscissors. More important, with a 5 mm incision, donor posterior lamellar tissue, which is typically 8.0 to 9.0 mm in diameter, is folded into a “taco” configuration with the endothelium on the inside and coated with viscoelastic material such as Healon (American Medical Optics, Santa Ana, CA). The folded graft is then inserted into the AC and unfolded and positioned against the host corneal stroma. The second modification was to prepare the host cornea by stripping DM and endothelium without removing the posterior corneal stroma,4 a technique known as Descemet stripping with endothelial keratoplasty (DSEK). With preparation of lamellar donor tissue evolving from manual to microkeratome-assisted dissection, the descriptive terminology is Descemet stripping with automated endothelial keratoplasty (DSAEK). This is an important improvement in the surgical preparation of the posterior corneal lamella from the donor cornea. The donor cornea with its scleral rim is mounted on an artificial anterior chamber (AAC), namely, the Moria ALTK system (Moria SA, Antony Cedex, France) and a Moria microkeratome with a 300 μm head is used to excise the anterior corneal lamella. The anterior corneal cap is discarded, and the posterior corneal lamellar tissue is placed in the corneal storage medium. At the beginning of the surgery, the posterior corneal lamellar tissue is punched from the endothelial side using a corneal trephine of chosen

diameter. The donor corneal lenticule is then placed into the recipient AC.

Femtosecond Laser

The femtosecond laser (IntraLase® Corp.) is a solid-state laser used to create flaps in laser in-situ keratomileusis (LASIK) and recently to perform penetrating keratoplasty with different shapes of stromal cuts. The laser uses an infrared wavelength (1053 nm) to deliver closely spaced, 3 μ spots that can be focused to a preset depth to photodisrupt tissue within the corneal stroma.5-10

The laser bursts are short (1 quadrillionth of a second). The resultant plasma produces a cavitation bubble, consisting of water and carbon dioxide primarily. We used the femtosecond laser to create a dissection plane on the donor cornea mounted on an AAC. After laser dissection of the donor cornea, the donor tissue was then transferred to a punching system and cut with an 8.0 mm diameter trephine. Forceps separation of the posterior lamella from the anterior stroma is then carried out before placement into the AC.

To study the feasibility of the femtosecond laser to prepare posterior corneal lamellae, three eye bank corneoscleral buttons, not suitable for corneal transplantation, underwent a femtosecond laser lamellar dissection of 400 μm stromal depth, with subsequent side cuts completed by manual trephine. In all the corneoscleral buttons, the posterior disk was peeled off the cornea easily with forceps after laser treatment, and all posterior lamellae presented with smooth stromal surface and no gaps or breaks occurred during manual separation from the anterior stroma. Good results encouraged us to apply the same technique in 4 patients requiring endothelial replacement due to endothelial failure by pseudophakic bullous keratopathy and Fuchs’ corneal dystrophy.

Surgical Technique

For DSEK, the donor cornea was prepared first in the femtolaser room. This was followed by surgery on the recipient cornea. Time interval between donor corneal preparation and recipient surgery ranged between 1.0 to 26 hours. An AAC seated firmly under the femtolaser and the corneoscleral rim preserved in organ culture storage media was accurately placed within the AAC (Figures 26-1A to D). To reduce the number of air bubbles beneath the cornea, rims were placed on the chamber base after the infusion was released. Once the cornea was stabilized and centered and the absence of air bubbles was confirmed, the infusion was closed, the superior metal support was placed