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

arc length of limbal tissue (about 3 clock hours). Prior to forming the DLEK scleral access incision, two clear corneal limbal stab incisions (about 1 mm diameter) are placed on either side of the peritomy area, to be used as access points to the anterior chamber later in the operation. Through one of the stab incisions, the cohesive viscoelastic Healon (Pfizer, New York, NY) is placed into the anterior chamber to replace the aqueous fully and to maintain normal pressure. We strongly oppose the use of Viscoat (Alcon, Fort Worth, TX) or other dispersive viscoelastic materials during any portion of DLEK surgery as the dispersive materials can cause stromal interface coating with subsequent non-adherence and dislocation of the donor tissue. In cases of corneal endothelial decompensation with cataract, a triple procedure can be performed, namely, DLEK combined with phacoemulsification and PC IOL.31, 32

Prior to creating the deep lamellar pocket of DLEK, a template mark is placed on the corneal epithelial surface. A circular marker with a diameter of 8.0 or 8.5 mm (depending upon recipient corneal diameter and surgeon preference) is used to make a circular impression on the central epithelial surface. If the position and centration of the mark is acceptable to the surgeon, then it is accentuated with ink marks. This circle on the cornea will later be used as a template for resection of the posterior recipient lamellar corneal tissue.

A trifaceted, guarded, diamond knife is then set to a depth of 350 microns and a 5.0 mm length incision is made approximately 1 mm posterior to the corneal limbus and concentric with it. We have found that a deeper initial incision gives less of a beveled wound closure and also a greater chance of early perforation into the anterior chamber during DLEK surgery. In lieu of a diamond knife, a sharp crescent blade or other steel scalpel can be used for the initial incision. A sharp crescent blade is then utilized to create a deep scleral-corneal lamellar pocket down to about 75 to 85% corneal depth along the entire length of the wound. Perfect accuracy of the depth of the corneal stromal pocket does not appear to be critical for a good visual outcome. Pockets should be deeper than 50% in order to avoid interface scarring or haze, and conveniently should not be deeper than 95% depth in order to avoid donorrecipient thickness mismatch. Judgment of the initial depth of the pocket is based upon inspection of the anterior lip thickness and by the clarity of the underlying stromal bed. Experience with the procedure and with lamellar dissections in general aids in the confidence that the desired depth has been achieved.

A specialized semi-sharp stromal dissector is then used to extend the pocket to the mid-pupillary region of the cornea and then a curved stromal dissector (Devers

Dissector, Bausch and Lomb, St. Louis, MO) extends the pocket further. We prefer to have a pocket that extends at least 1 mm peripheral to the diameter of the surface template circular mark (i.e. 10.0 mm pocket diameter for an 8.0 mm mark). This creates a large area, deep lamellar corneal pocket. The Devers Dissectors are designed with a tip that is not as sharp as a crescent blade, but is sharper than a blunt dissector. The width of the dissecting heads are especially good for maintaining the stromal depth consistently throughout the dissection of the edematous deep stroma and the surgeon can actually feel the increased resistance to dissection if he/she deviates too anteriorly. The dissection is accomplished with a slow and methodical sweeping motion of the dissector heads, from central to peripheral tissue, and the surgeon can often see the reflections of Descemet’s membrane wrinkling during the sweeping motion, which is an assurance that the depth of the dissection is adequate. It is important that the pocket stromal dissection be carried out over the entire desired area of the cornea, in order to allow adequate edge space for the donor disk.

The resection of the posterior recipient tissue begins by first entering the anterior chamber through the temporal scleral corneal pocket incision. We utilize a standard cataract surgery diamond blade with a 2.8 mm width, but any blade is acceptable. Entry into the anterior chamber is preferred at the exact corresponding position of the temporal edge of the surface template mark.

It is through this entry point that the recipient posterior resection is started utilizing special scissors designed for posterior lamellar tissue resection (Cindy I and Cindy II Scissors, Bausch and Lomb, St. Louis, MO). The Cindy I scissors are placed with one blade in the anterior chamber and one blade in the stromal pocket. The scissors is used to perform a free-hand cut, following the marks of the circular template on the overlying epithelial surface. The Cindy I scissors have long, highly curved and low profile blades and are ideally suited for this procedure. Once the resection has progressed distally to about the 5 o’clock and 7 o’clock positions, then the Cindy II scissors are utilized for completion of the distal resection. The Cindy II scissors have long, low profile blades that are set at nearly a right angle to easily complete the more difficult distal resection. Once the posterior recipient disk has been cut for the full 360 degrees, then the tissue is removed from the eye and placed on the corneal surface for inspection. It is washed with balanced salt solution (BSS, Alcon, Fort Worth, TX), and dried with a sponge. The stromal surface is inspected for smoothness and the edges for regularity of cut, as well as the thickness of the resected tissue. With removal of the recipient posterior edematous stromal tissue, the view into

the anterior chamber through the central cornea clears dramatically, and often other intraocular surgery such as cataract surgery, vitrectomy, IOL exchange, and iridoplasty can be performed at this stage of the DLEK procedure.

After removal of the recipient posterior corneal tissue, the temporal scleral wound is temporarily closed with 1 interrupted 10-0 nylon suture. An irrigation/aspiration tip is then introduced into the anterior chamber and extensive effort is expended to remove all of the viscoelastic material from the eye. No residual Healon should remain in the anterior chamber prior to insertion of the donor disk or the donor tissue will not “stick” in place. Therefore, care is taken to irrigate and aspirate the anterior chamber, pupillary area, angle, and even the peripheral pocket as necessary. Once the surgeon is confident that all Healon has been removed, then the pressure is left slightly soft and attention is directed to the preparation of the donor corneal disk.

Donor Corneal Preparation

This step of donor corneal preparation can be done just prior to the surgery on the patient’s eye, depending on surgeon preference. “Pre-cut” tissue is also available now through several EBAA certified Eye Banks (See also Chapter 30, Use of Eye Bank Pre-cut Donor Tissue in DSAEK) and its use is described below.

The operating microscope is brought over to the separate donor table for preparation of the donor tissue. Because whole globes are rarely available here in the United States, an artificial anterior chamber is necessary for preparation of the donor posterior disc (See also Chapter 12, Artificial Anterior Chambers). The only automated microkeratome system available for DSAEK surgery is from Moria (Moria, Antony, France). The Optisol-GS preservation fluid (Bausch and Lomb, Rochester, NY) from the donor tissue container is aspirated into a syringe (which has a three way stopcock) and the syringe is then used to fill the I/A port of the artificial anterior chamber. The syringe is also attached to the port to be used to vary the pressure inside the chamber for the duration of the resection. The standard donor corneoscleral cap tissue is first coated with a thin layer of Healon on the endothelium. It is then placed with the endothelial side down onto the post/piston of the artificial anterior chamber (taking care not to include an air bubble in the chamber) and the tissue is oriented with the largest diameter of the cornea in the horizontal meridian. The post/ piston of the unit is then raised until the tissue is firmly locked into place (See also Chapter 12, Artificial Anterior Chambers). The Optisol filled syringe is then used to raise the pressure in the artificial chamber to over 65 mm Hg and

the stopcock is closed to stabilize the high pressure. The epithelial cells are then wiped from the surface of the cornea with a Miracel sponge. The horizontal meridian is marked at the peripheral cornea with a marking pen so that the horizontal meridian of the donor corneal tissue can be identified, and these marks are also used for the proper orientation of the anterior corneal cap following the microkeratome cut.

For anterior automated lamellar keratoplasty, the guide ring for the microkeratome can be adjusted in height to yield the desired diameter for the tissue resection. For EK surgery, the greatest diameter possible of at least 10 mm is required, and therefore the guide ring should be placed at the lowest possible position.

Usually, a 300 µm head is used with the microkeratome, and the diameter of resection is at least 9.5 mm or more. Intraoperative pachymetry is advised to determine if the tissue is thick enough to allow the 300 micron head resection and therefore avoid the occurrence of posterior perforation or “button holes” of the tissue [See also Section 9, Descemet Stripping Automated Endothelial Kerato-plasty (DSAEK)]. The ideal thickness for the posterior tissue to be transplanted is about 150 microns, but significant variance of greater or lesser depth can occur with the 300 micron head microkeratome. With the pressure in the artificial chamber elevated to at least 65 mm Hg and verified with a gravity tonometer or by finger touch, the microkeratome head is mounted on the guide ring, positioned for resection, and then passed over the donor cornea at a rate of about 4 to 5 seconds for the pass.

A free cap of anterior tissue is resected and remains above the blade on the microkeratome head. After drying the residual stromal bed with Miracel sponges, checking the stromal bed for smoothness of cut and diameter of cut, several marks are placed at the peripheral edge of the resected bed to help with the centering of the subsequent trephination of the donor tissue. The anterior cap is placed back in position, using the previously placed peripheral reference surface marks. One additional mark is then placed at the exact central point of the anterior cap of tissue to further facilitate centration of the posterior trephination. A moment is given for the anterior cap to adhere to the bed.

The donor tissue now must be carefully dismounted from the artificial anterior chamber without damaging the endothelial cells from chamber collapse. We have found that the easiest way to avoid chamber collapse is to leave the tissue attached to the post/piston. To achieve this, the stopcock on the syringe is turned to the position to allow Optisol flow from the syringe to the chamber. A tying forceps is then used to sweep along the inside ring of the metal cap which locks the tissue onto the post, pushing

slightly posterior on the scleral rim, and breaking the seal that binds the donor scleral tissue to the metal cap. Very gently the post/piston is lowered, and Optisol is gently infused, as needed, to keep the donor chamber from collapsing. The locking cap is then removed, with the donor tissue left on the post with a formed chamber. The scleral edges of the donor are gently lifted in each quadrant to release the seal of the tissue to the post, and the tissue is removed from the post very slowly, lifting the scleral edge up to allow air to enter the chamber, and as the tissue is further lifted off, the air slowly pushes the Healon along, and the Healon then simply flows off the opposite scleral edge in one cohesive unit from the endothelial layer onto the post. Once again care is taken not to collapse the chamber and damage the endothelium. We believe that minimal irrigation of the endothelium with Optisol during tissue removal from the Moria unit aids in the health of the endothelium and in the subsequent donor adherence to the recipient bed.

Once the donor corneoscleral tissue has been removed from the post, we have been gently irrigating the sclera above and below the endothelial surface of the donor tissue with Optisol solution (taken from the same transport container for the donor tissue) in order to remove excess residual Healon from the donor. We then use a Miracel sponge to dry the excess fluid from the endothelium, placing the sponge tip at the scleral edge, away from the endothelium.

The donor tissue is then placed endothelial side up onto a standard punch trephine block. The previously placed ink mark on the central point of the anterior resected cap is used as a guide to position the tissue for trephination, in order to make sure that the posterior punch trephination is centered on the bed of the previous keratome pass. We utilize a Barron donor punch (Katena, Denville, NJ). The same size diameter punch is used as the diameter of the Descemet’s membrane-stromal disk that was removed from the recipient. The tissue is punched out with the trephine.

Because the 5 mm wound of small incision DLEK surgery is smaller than the 8.0 mm (or larger) diameter of the donor disk, the donor tissue must be folded prior to insertion. To accomplish this, a very thin strip of Healon is placed onto the endothelial surface along the previously identified and marked horizontal meridian of the donor button. Stabilizing the anterior edge of the donor button with a 0.12 mm forceps, the posterior stromal tissue edge is gently grasped with non-toothed delicate forceps such as Utrata forceps. The posterior tissue is then gently folded with the endothelium on the inside protected by the layer of Healon, and it is folded into an asymmetric “taco” shape, in a 60/40% ratio, the most anterior side of the taco being 60% and the posterior

side 40%. We were the first to initiate the idea of an “overfolded, 60/40% ratio” over 6 years ago (in 2001) in order to avoid having the tissue unfold upside-down in the patients anterior chamber. The donor tissue is then brought over to the operative field on the trephine block.

Donor Tissue Preparation Using

Pre-Cut Tissue

When using a donor corneal tissue that was pre-cut by an eye bank using a microkeratome or a femtosecond laser and then shipped to the hospital or a surgery center, the surgeon must fully inspect the tissue prior to transplantation. The surgeon should be very careful to ensure that he knows the exact diameter of the resected bed and that he personally marks the edges of the resected bed of the donor tissue. In this way, the surgeon can avoid an eccentric cut that goes outside of the microkeratome cut bed, with the resultant 1mm thick donor edge.

Using pre-cut tissue is very easy and fast, but to avoid complications, attention to details is paramount. The precut tissue is removed from the Optisol container and simply placed endothelial side down onto the lint-free plastic or metal surface of the donor table. Because the donor scleralcorneal tissue has a 3 mm rim of scleral “skirt” and tends to maintain its convex configuration, this manipulation of the tissue will not collapse the tissue or risk damage to the endothelium. Very gently, the surgeon dries the epithelial surface of the peripheral donor cornea with a Miracel sponge and reveals the edges of the microkeratome cut bed. Although the Eye Bank places marks on the donor corneal tissue prior to shipping, these are often smudged, difficult to see, and may not be accurate to the level of precision to avoid an eccentric cut. After drying, these edges are then measured by the surgeon for diameter and marked with an ink pen so that they are distinctly seen. The central free cap (which was left in place by the Eye Bank prior to shipment) can also be dried and marked centrally. The surgeon then takes the tissue and places it endothelial side up onto the trephine block, using the marks that he personally placed, to determine the best centration on the block, prior to trephination. The trephination and other steps that follow are well described above.

One interesting feature of using pre-cut donor corneal tissue is that when folding the tissue into the 60/40% taco configuration, the adherence between the posterior stroma and the overlying free cap can sometimes seem a lot stronger than tissue that is cut “on site” by the surgeon, and so care should be taken to avoid causing stretching or striae when folding the graft prior to insertion.

Donor Tissue Preparation Without

a Microkeratome

The operating microscope is brought over to the separate donor table for preparation of the donor tissue. Because whole globes are not usually available in the United States, an artificial anterior chamber is necessary for the preparation of the donor corneal disk. We utilized a Bausch and Lomb (St. Louis, MO) artificial anterior chamber that is all stainless steel and has dual irrigation/aspiration ports. The Optisol-GS preservation fluid (Bausch and Lomb, Rochester, NY) from the donor tissue container is aspirated into a syringe and is then used to fill the I/A ports of the artificial anterior chamber. The syringe is also attached to the port to be used to vary the pressure inside the chamber for the duration of the resection. The standard donor corneoscleral cap tissue is first coated with a layer of Healon on the endothelium. It is then placed endothelial side down onto the post of the artificial anterior chamber and oriented with the largest diameter of the cornea in the horizontal meridian. This meridian is marked with a marking pen so that the horizontal meridian of the donor tissue can be identified later in the procedure. The donor tissue is capped into place and the chamber is filled with Optisol-GS and the pressure normalized. There are several ways to create a deep dissection plane in the donor tissue in the absence of a microkeratome. Each method has advantages, and surgeon preference is the over-riding determinant as to which method is utilized. The peripheral incision and central manual trephine approaches are described below.

In the peripheral incision technique, the preparation of the donor cornea is similar to the preparation of the recipient corneal bed at the deep lamellar plane. A diamond knife set to a depth of 350 µm is used to make a 3 or 4 clock hour-length incision in the peripheral donor limbal area, right next to the edge of the metal cap of the artificial anterior chamber. The crescent blade is then used to cut to the deeper stromal tissue and then once the desired plane has been reached, the Devers Dissectors are used to continue the dissection plane all the way to the limbus of the donor tissue for 360 degrees. We have found it helpful to place multiple ink marks onto the surface of the donor tissue. These marks accentuate the visualization of the surface of the donor tissue and therefore allow better depth perception (and estimation of the level of the dissection) when viewing the Devers Dissectors plane compared to the surface plane. It is important to make sure that the dissection plane is carried out all the way to the limbus in every quadrant in order to avoid problems later on that

may result from an eccentric trephination of the donor lenticule.

In the manual trephine approach, an 8.5 mm diameter Barron suction recipient trephine (Katena Products, Denville, NJ) is placed onto the surface of the donor tissue and suction is applied. Trephination is carried out to about 60% depth with the trephine. It is noteworthy that after the blade touches the epithelial surface of the donor, it only takes about 4 or 5 quarter turns of the Barron trephine to reach this depth. This is much sooner than when the same trephine is used on the recipient in standard PKP surgery. The trephine is then removed and the cut inspected for the depth. Ideally, an 80% depth should be attained for the plane of the donor corneal pocket. Any cut deeper than this can result in the donor tissue being very thin and it can spontaneously roll up like a rug, causing confusion as to which side is the endothelial side and undoubtedly causing endothelial damage. If the dissection depth of the donor is less than 60% depth, then the stromal surface may not be as smooth and the tissue may be much thicker than the recipient bed is deep. However, whether disparity between donor and recipient disk thicknesses causes a later visual problem is unknown at this time, but separate reports by Terry and by Price on this issue at the recent ASCRS and ARVO annual meetings suggest that donor thickness is not a factor in final visual results.

Transplantation of the Donor Tissue

With the microscope in place, the temporary scleral suture of the DLEK temporal wound is cut. The anterior chamber of the patient is then filled completely with BSS. The donor tissue is then brought into the field and the Charlie insertion forceps (Bausch and Lomb Surgical, St. Louis, MO) are used to grasp the stromal surface of the donor tissue along the horizontal meridian. The Charlie forceps are non-toothed fine forceps that only coapt at the distal tips and can be used for DLEK or DSEK surgery. The Charlie insertion forceps has a specially designed stop that permits a significant spacing, along the blade length to prevent crushing of the donor tissue. The folded donor tissue is placed into the anterior chamber in one deft 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. The endothelial layer remains protected on the inside by Healon. The tissue can be gently prodded with the forceps along the stromal sides if centration of the tissue within the recipient bed needs to be improved. As the anterior chamber is deepened with injection of BSS through the right paracentesis site, the tissue gently and

spontaneously opens up, 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 sutures of 10-0 nylon is then used to close the scleral wound to secure the donor corneal disk within the anterior chamber. A cannula is then placed through the stab incision and the tip is 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 deepen and fill the chamber. 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 in the correct orientation (i.e. endothelium down), as long as the chamber is deep enough and there is no impediment to unfolding of the donor disk. Once the tissue has unfolded, then an air bubble is gently injected into the anterior chamber to stabilize the tissue. An alternative method of opening the tissue atraumatically involves deepening the chamber with BSS from the right side just enough to have the donor tissue unfold to a nearly perpendicular orientation to the iris surface. Then an air bubble is very slowly and gently injected from the left paracentesis site between the lips of the “taco” to complete the unfolding of the tissue and simultaneously lift it up into position into the recipient bed. (This technique is described in more detail in Chapter 20, Endothelial Keratoplasty: A Step by Step Guide to DSEK and DSAEK Surgery).

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. 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 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 that seen after standard PKP procedure.15,21 Care is taken, however to minimize this maneuver and also to avoid the occurrence of a central posterior striae that 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 proper centration. During both the endothelial

and stromal positioning maneuvers, the anterior chamber is filled with an air bubble of about a 6 or 7 mm diameter.

Oncethetissueisinpropercentration,itiscriticaltomake sure that all of the donor edges are anterior to all of the recipientbededgesfor360degrees.Visualinspectionisnot enough,andmanualverificationismandatory.Ifanyportion 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 (secondaryanteriorchamber).Toaccomplishproperdonor edgeposition,theanteriorchamberisfilledcompletelywith air and the reverse Sinskey hook is placed through a stab incisionintotheanteriorchamber.Thetipofthehookisthen 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 theanteriorchamberimmediatelypushesthedonoredgeup anteriorly,intotherecipientpocket,anduponreleaseofthe 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 in good position. This is done because even small strands of recipient stromal edge tissue can get caught in the edge interfaceandpreventadherenceof thegraft oractas awick foraqueousintotheinterface,causinglaterdiskdislocation. As an alternative to the reverse Sinskey hook, another specialized instrument for recipient edge positioning posterior to the donor tissue is available, and this is called the Nick Pick (Bausch and Lomb Surgical, St. Louis, MO).

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. 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 area and surface of the posterior chamber IOL 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. Again, suctioning with a cannula from the pupillary area 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 to help further stabilize the donor disk position over the first 24 hours postoperatively, but this is not critical.

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. We routinely place on the corneal surface a 24 hours 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.

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 when the patch is removed. Most patients will remark that the eye was no more uncomfortable than after a standard cataract surgery and that they did not require 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 that it is in good position. In our initial, prospective series of 100 cases, there were only 4 cases of donor disk dislocated on the first postoperative day.21 All four cases were easily treated by taking the patient back to surgery, and usually, under topical anesthesia, the disk is repositioned using another air bubble in the anterior chamber. This is usually a 15 minutes procedure. We have been successful with all the four cases of disc re-positioning, and all eyes resulted in a clear graft.

If the graft is in good position on day one, it will heal in good position, and it is extremely rare to see a late disc dislocation. The edges of the graft seal down with solid healing sometime within the first 3 months, permitting any other necessary intraocular surgery (e.g. posterior vitrectomy, retinal detachment surgery, etc.) without the fear of dislocating the graft.33 We have also performed DLEK on eyes without any significant cataract, leaving the crystalline lens in place. However, 50% of these eyes developed cataracts in the first 2 years after DLEK surgery and required subsequent cataract surgery.

The postoperative medical therapy after DLEK surgery is identical to what we do with our 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 entirely. Fluoroquinolone antibiotics are used four times a day for two weeks and then it is discontinued.

Clinical Results Following DLEK

Surgery in a Large Prospective Study

We have previously reported on the results from the largest prospective study in the world of DLEK surgery.21 The data from the study was from 100% follow-up of our initial 100 cases. These prospective results should serve as a benchmark for DLEK surgery.

Visual Results after DLEK

There is, of course, a high variability of vision in any series of elderly patients undergoing ocular surgery, especially DLEK procedure. The interface may clinically appear exceptionally clear, but it likely contributes about one line of visual loss to the macular potential.14,21 The visual results at 6 months after small incision DLEK surgery averaged approximately 20/40, with 55% of the patients seeing 20/ 40 or better and no patients seeing worse than 20/200. In our prospective study, we did not exclude any patient that had known macular disease either before or after surgery. If we exclude those patients that have known macular disease, then approximately 80% will achieve vision of 20/ 40 or better. The vision after DLEK appears to get better from 6 to 12 months, and even from 12 to 24 months, as the stromal interface continues to remodel.14,34 Visual rehabilitation can be very rapid, with some patients seeing as well as 20/25 only one week after surgery (Figure 16-2) but this is highly variable. Visual results are strongly and positively correlated with patient age (younger patients see better than older patients after DLEK) and with preoperative visual acuity (patients that have better vision preoperatively tend to have better vision postoperatively). Finally, in our series we have over 20 patients that have had a prior PKP in one eye and a DLEK in the fellow eye in

Figure 16.2: Five days after DLEK surgery combined with phacoemulsification in a 57-year-old patient with Fuchs’ dystrophy, the vision is 20/25 with a -0.75 + 0.50 x 130° refractive error.

treatment of their Fuchs’ dystrophy. All but one of the patients prefers the vision of the DLEK eye compared to the PKP eye, largely based upon the uncorrected visual acuity attained with each procedure.

Astigmatism after DLEK

The advantage of DLEK surgery is that it usually retains the normal, presurgical corneal topography. While PKP surgery can result in an average of 4 to 6 diopters of astigmatism,35 small incision DLEK surgery has no significant influence on the preoperative astigmatism. In our prospective study,21 we found that the average refractive astigmatism after small incision DLEK at 6 months was only 1.18 ± 0.74 diopters, representing only an insignificant 0.23 diopters of change from the preoperative level. The patients are able to wear spectacles after DLEK surgery, often the same pair of glasses that they wore before the onset of the corneal edema. No patients in this series required a contact lens or refractive surgery (e.g. LASIK, relaxing incisions, etc.) in order to achieve their best vision. Anisometropia was never an issue with DLEK surgery as it often is with PKP surgery.

Donor Endothelial Survival after DLEK

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 at 6 months, from large incision DLEK surgery where the donor tissue is not folded. In our series, we found that the specular microscopy at 6 months after small incision DLEK surgery demonstrated an average central endothelial density of 2121 ± 420 cells/mm2. This represented an average 25% cell loss from preoperative donor eye measurements, and compared well to the 17 to 34% cell loss seen after standard PKP surgery.36,37 In addition, at one year of follow-up, we have not seen a significant decline in the endothelial cell counts from the 6-month measurements, for our large incision DLEK cases.34 It is important to note, however, that our most recent publication on DLEK surgery38 indicates that there is a delayed price to pay for folding the donor tissue in EK surgery. We have found that at the two year postoperative measurements, the large incision DLEK cases (where the tissue is not folded) had only a 27% loss of endothelial cells from the preoperative values, while in the small incision DLEK cases (where the tissue is folded, inserted, and unfolded) there was a 43% loss of endothelial cells compared to the preoperative measurements (p<.001).

Current modifications of EK such as DSAEK [See also Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)] have shown a significantly higher cell loss, with an average of 40% cell loss at just 6 to 12 months after DSAEK surgery. This increase in acute, shortterm donor endothelial cell loss is of concern, and further data is crucial to determine the long-term outcome of eyes undergoing the DSAEK procedure.

Summary

I believe that our prospective work with endothelial keratoplastysurgeryoverthesepast7yearshasestablished EK as a reasonable alternative to PKP for the patient that is suffering from visual loss due to endothelial dysfunction. Visual rehabilitation is faster with EK than with PKP, and the presence and magnitude of irregular astigmatism are largelyeliminated.Theglobeislikelytobesaferfromlongterm dangers of globe rupture secondary to minor trauma, andpatientspreferthequalityofvisionfromEKcompared toPKP. Long-termstudyisnecessaryinordertodetermine iftheendothelialsurvivalrateandthegraftrejectionrateafter EKsurgeryiscomparable(orbetter)thanafterPKPsurgery, and our experience over the past 7 years is encouraging.

On a practical basis, outside of a scientific protocol, EK patients do not require the same degree of monitoring as standardPKPpatientsandthereforetheyrequirelesspostoperative clinic time. With no corneal sutures or incisions wound healing and corneal ulcerations are not an issue. Astigmatism management is also not an issue after EK surgery, much to the joy of patient and surgeon alike. The onlycriticalmonitoringisforsteroid-inducedglaucoma,as long as the patient is on topical steroids, and this is done according to the clinician’s standard routine.

Surgeons learning the DSEK and DSAEK forms of EK surgery [See also Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)] should recognize that DSEK or DSAEK cannot be used safely for every form of endothelial dysfunction. Patients with an open communication between the anterior and posterior chambers (cases such as aphakia, anterior chamber IOL or sector iridectomy) will be unable to maintain an air bubble for support of the EK tissue, creating an extraordinarily highrisk of donor disk dislocation after DSEK/DSAEK surgery. In these specialized cases, DLEK is the EK procedure of choice, due to the adherence of donor tissue without the need of a postoperative air bubble.

The DLEK surgical procedure is a more 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, corneal transplant

surgeons who wish to be able to safely treat all forms of endothelial dysfunction are well equipped when DLEK is included in their surgical armamentarium.

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 Invest Ophthalmol Vis Sci 1993;34(4):1102.

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. Melles GR, Lander F, Beekhuis WH, et al. Posterior lamellar keratoplasty for a case of pseudophakic bullous keratopathy. Am J Ophthalmol 1999;127:340-1.

10.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.

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

12.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.

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

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

15.Terry, MA, Ousley, PJ: Small Incision Deep Lamellar Endothelial Keratoplasty (DLEK): 6 months results in the first prospective clinical study. Cornea 2005;24:59-65.

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

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

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

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

20.Terry MA. Endothelial Replacement. In: Krachmer J, Mannis M, Holland E, eds. Cornea: Surgery of the Cornea and Conjunctiva. St. Louis: Elsevier Mosby; 2005: Chapter 140:1707-18.

21.Terry MA, Ousley PJ: Deep Lamellar Endothelial Keratoplasty (DLEK): Visual acuity, astigmatism, and endothelial survival in a large prospective series. Ophthalmology 2005;112:154149.

22.Melles GR, Lander F, Nieuwendaal C. Sutureless, posterior lamellar keratoplasty: A case report of a modified technique. Cornea 2002 21:325-7.

23.Melles GR, Wijdh RH, Nieuwendaal, CP. A technique to excise the descemets’ membrane from a recipient cornea (descemetorhexis). Cornea 2004;23: 286-88.

24.Price FW, Price MO. Descemet’s stripping with endothelial keratoplasty in 50 eyes: A refractive neutral corneal transplant.

J.of Refractive Surgery 2005; 21:339-45.

25.Terry MA, Ousley PJ, Wills B. A practical femtosecond laser procedure for DLEK endothelial transplantation: Cadaver eye histology and topography. Cornea 2005;24:453-9.

26.Soong HK, Mian S, Abbasi O, et al. Femtosecond laser-assisted posterior lamellar keratoplasty. Ophthalmology 2005;112: 44-49.

27.Sarayba MA, Juhasz T, Chuck RS, et al. Femtosecond laser posterior lamellar keratoplasty: A laboratory model. Cornea 2005;24:328-33.

28.Suwan-apichon O, Rizen M, Reyes JM, Herretes S, Behrens A, Stark WJ, Chuck RS. A new donor cornea harvesting technique for posterior lamellar keratoplasty. British Journal of Ophthalmology 2005; 89:1100-01.

29.Kang PC, McEntire MW, Thompson CJ, Moshirfar M. Preparation of donor tissue for deep lamellar endothelial keratoplasty (DLEK) using a microkeratome and artificial anterior chamber system: Endothelial cell loss and predictability of lamellar thickness. Ophthalmic Surgery, Lasers and Imaging 2005; 36:381-5.

30.Terry MA, Ousley PJ. Deep Lamellar Endothelial Keratoplasty: Small Incision Technique combined with Phacoemulsification and Posterior Chamber Intraocular Lens Implantation. In: John,

T.editor. Surgical Techniques in Anterior and Posterior Lamellar Corneal Surgery. Jaypee Brothers Medical Publishers (P) LTD. 2005;345-64.

31.Terry MA, Ousley PJ. “The New Triple Procedure: First World Wide Patients with DLEK combined with Phaco/IOL surgery”. American Academy of Ophthalmology Video Library, Annual Meeting, “Best of Show”, October 2002.

32.John T. Upside-down Phacoemulsification in Deep Lamellar Endothelial Keratoplasty. In: John T (Eds). Surgical Techniques in Anterior and Posterior Lamellar Corneal Surgery. Jaypee Brothers Medical Publishers (P) LTD. 2005;372-9.

33.Amayem AF, Terry MA, Helal MH, Turki WA, El-Sabagh H, El-Gazayerli E, Ousley PJ. Deep Lamellar Endothelial Keratoplasty (DLEK): Surgery in complex cases with severe preoperative visual loss. Cornea 2005;24:587-92.

34.Ousley PJ, Terry MA. Stability of vision, topography, and endothelial cell density from one year to two years after deep lamellar endothelial keratoplasty (DLEK) surgery. Ophthalmology 2005;112:50-57.

35.Pineros OE, Cohen EJ, Rapuano CJ, et al. Triple vs nonsimultaneous procedures in Fuchs’ dystrophy and cataract. Arch Ophthalmol 1996;114:525-8.

36.Ing JJ, Ing HH, Nelson LR, et al. Ten-year postoperative results of penetrating keratoplasty. Ophthalmology 1998;105:1855-65.

37.Bourne WM. Cellular changes in transplanted human corneas. Cornea 2001;20:560-9.

38.Terry MA, Wall J, Hoar KL, Ousley PJ. Endothelial Keratoplasty:

Aprospective study of endothelial cell loss during the 2 years after deep lamellar endothelial keratoplasty. Ophthalmology

2007 (in press).

38.Gorovoy M. Descemet’s stripping automated endothelial keratoplasty (DSAEK).Cornea 2006;25:886-9.

Introduction

Surgical endothelial replacement for conditions such as Fuchs’ endothelial dystrophy and pseudophakic bullous keratopathy has been successfully accomplished with full thickness penetrating keratoplasty (PKP) for nearly 100 years.1 While the surgical technique of PKP is straightforward and relatively easy, the visual results and stability of the grafted tissue are sometimes poor due to wound healing and suture-related problems.2-6

In 1993 Ko and Feldman presented an animal study at the annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) which described a new technique for endothelial replacement through a scleral limbal incision7 (See also Chapter 14, History of Lamellar and Penetrating Keratoplasty). In 1998, Melles et al described this technique in the first human patients and called it posterior lamellar keratoplasty (PLK)8 (See also Chapter 14, History of Lamellar and Penetrating Keratoplasty). Terry and Ousley began laboratory work in 1999 on this technique and after technical modifications and re-design of instrumentation, performed the first United States cases in 2000 and called the surgery Deep Lamellar Endothelial Keratoplasty (DLEK).9-20 All of this work represents a radical departure from the PKP technique in that the DLEK surgery accomplished the goal of endothelial replacement without altering 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.10-14 Recently, a small incision technique of PLK surgery was described in a case report by Melles et al.21 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.14

While undoubtedly there will be further refinement of the technique and instrumentation in DLEK surgery, it is the purpose of this chapter to describe in detail this small incision method of DLEK, and to describe its combination with other intraocular procedures such as cataract extraction.

Surgical Objective

The purpose of DLEK surgery is to remove the diseased recipient endothelium and replace it with healthy donor endothelium. The advantage of DLEK surgery over PKP surgery is that it accomplishes this primary objective without violating the surface of the cornea with sutures or incisions. We have delineated the five ideal goals for

endothelial replacement in previous papers as being (1) a smooth surface topography without significant change in astigmatism, (2) a highly predictable (and unchanged) corneal curvature, (3) a healthy donor endothelium which resolves all edema, (4) a tectonically stable globe, safe from injury and infection, and (5) an optically “pure” cornea.11,12,15-18 While standard PKP can consistently achieve good results for goals 3 and 5, the other goals have remained elusive.22-26 At the current time, DLEK surgery can accomplish the first 4 goals nearly perfectly, while the fifth goal of an optically “pure” cornea is good, but can still be improved. Instrumentation and technique modification to achieve a more perfect stromal interface between posterior donor tissue and anterior recipient tissue are the current, continued directions of DLEK research.

The small incision technique of DLEK surgery described here reduces the scleral tunnel incision to 5 mm in length and moves it from the superior to the temporal side. It is felt that by making the scleral access incision even shorter than in standard DLEK, there will be less of a tendency for wound-induced corneal flattening over time and also provide more strength to the globe to withstand any future blunt trauma. Moving the position of the incision to the temporal side, allows easier visualization of the anterior segment during the surgery and spares the superior limbus, which may be utilized for cataract or glaucoma surgery at the same time as DLEK or at a later time.

Preferred Anesthesia

DLEK surgery is usually done under general anesthesia, but retrobulbar block anesthesia has also been used. General anesthesia (either endotracheal or laryngeal mask airway technique) is preferred 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 can be 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.27 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