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

Figure 31-3: At the end of DLEK surgery, the air bubble size is decreased without the risk of disk detachment. This is considered to be due to the tissue forces assisting in this attachment process.

may be compared to closing a manhole with a lid (Figure 31-2B). Once the donor corneal disk is placed in position, the AC is filled with an air-bubble (Figure 31-2A) which initially holds the donor corneal disk in place. Next, a reverse Sinskey hook is used to “run-the rim” of the donor corneal disk to ensure proper placement of the donor corneal disk within the surgically created recess within the host cornea. Next, the size of the air-bubble is decreased (Figure 31-3) such that the diameter of this air-bubble is often smaller than the diameter of the donor corneal disk. The donor corneal disk usually stays in place without being detached from the host cornea (Figure 31-3).

Thus, the wound architecture in DLEK is much like a manholethatiscoveredwithalid (Figures 31-1A to 31-2B). Since the donor disk is pushed gently into the host corneal recess, the stroma-to-stroma corneal rim contributes to holdingthedonordiskinplacewithoutbeingdetachedeven when the size of the air-bubble is decreased (Figure 31-3).

In contrast to DLEK, in DSAEK there is no such recess that is created in the host cornea (Figures 31-4A and B). Only the host DM and the attached monolayer of host corneal endothelium is detached and removed as a single

disk (See also Section 9, Descemet’s Stripping Automated Endothelial Keratoplasty). The removal of this circular area of patient’s DM and endothelium, results in the exposure of the host corneal stroma in this central area. Following this, a donor corneal disk comprising of posterior donor corneal stroma, DM, and healthy donor endothelium, of about 150 µm thickness and often about 8.0 or 9.0 mm diameter (occasionally 7.0 mm disk) is created using a Moria mickrokeratome and an artificial anterior chamber (Moria Inc., Antony Cedex, France). This donor corneal disk is usually folded as a taco-fold, introduced into the AC, unfolded within the AC and attached to the patient’s inner corneal surface corresponding to the circular area of exposed host corneal stroma.

An air-bubble is then used within the AC to hold the donor corneal disk in place (Figures 31-4A and B). This is very much like placing a pizza on a ceiling and holding it in place with two hands (Figures 31-4A and B). If one hand is removed, the pizza edge corresponding to the side where the hand is removed will come-off the ceiling (Figures 315A and B and 31-6A and B). If both hands are removed, obviously, the pizza will drop from the ceiling (Figure 31- 7). Similarly, when the air bubble diameter is greater than the diameter of the donor disk, the donor disk will remain attached to the recipient cornea. But, when the air bubble size is decreased, making it smaller than the donor disk diameter, then both sides of the disk will begin to detach from the host cornea (Figures 31-5A and B) in primary position of gaze, and when the eye moves to the left, the air bubble will move to the right and keep the right margin of the disk attached while the left edge of the disk will begin to detach (Figures 31-6A and B), with aqueous humor entering the detached space (Figures 31-6A and B). When the eye moves to the right, a similar sequence of events will result in the detachment of the right side of the donor corneal disk. With aqueous entering the interface from both sides of the disk periphery, it will often result in total disk detachment, with the disk landing in the inferior aspect of

Figures 31-6A and B: (A) When the eye is turned to the left, there is a shift in the air bubble position towards the opposite side and this results in pushing the right edge of the donor disk closer to the recipient cornea and further detachment of the left side of the donor disk with more aqueous humor entering the left side of the donor-recipient interface. (B) Cartoon showing when the pizza is held with one hand on the right edge, there is a left-sided “pizza-drop”.

Figures 31-5A and B: (A) In DSAEK surgery, in primary eye position, if the air bubble is smaller than the donor corneal disk diameter, then the edges of this disk will usually detach and aqueous humor gets into the interface. (B) Cartoon showing, the pizza edge drop from the ceiling when only one hand is used to hold the pizza in the center.

Figures 31-7A and B: (A) When aqueous humor fully enters the donor-recipient interface this results in donor disk detachment in DSAEK surgery.

(B) Cartoon showing a “pizza-drop” when it is not supported onto the ceiling.

the anterior chamber. Thus, in the initial period, immediately after attaching the donor corneal disk to the host cornea, it is only the air-bubble that holds the disk in place. Hence, the diameter of the air-bubble must be greater than the diameter of the donor corneal disk in order for the donor corneal disk to remain attached to the host cornea (Figure 31-4). Unlike DLEK, in DSAEK there is no circumferential tissue “adhesive forces” to hold the donor disk in place.

Thus, the wound architecture is quite different in DSAEK as compared to DLEK (Figures 31-8 to 31-11). Postoperatively, both DLEK and DSAEK look somewhat similar in the frontal view, but differ in the profile view, namely, the

“broad-band-wound” in DLEK (Figure 31-9) and the “narrow-band-wound” in DSAEK (Figure 31-11) are clinically evident under the biomicroscope. These differences in the wound architectures between DLEK and DSAEK are important factors to keep in mind when trying to reduce the donor disk detachment rate following such STCT procedures.

A recent modification is the use of a scraping instrument [Terry Scraper (Bausch & Lomb, Inc., Rochester, NY), John DSAEK Stromal Scrubber (ASICO Inc., Westmont, IL)] to scrape a band of corneal stroma on the inner corneal surface

(Described by Terry, M, personal communication) just within

Figure 31-8: Broad beam slit-lamp photograph of a cornea of a patient, 2 years and 2 months following a deep lamellar endothelial keratoplasty (DLEK) procedure showing a clear and compact cornea, and the wellcentered and fully integrated donor corneal disk to the inner stromal surface of the host cornea.

Figure 31-9: Side profile view of a slit-lamp photograph of a patient’s cornea, 2 years and 2 months after a DLEK procedure (see also Figure 31-8), showing a circumferential broad-band-wound configuration (arrow).

Figure 31-11: Side profile view of a slit-lamp photograph of a patient’s cornea, 9.5 weeks after a DSAEK (see also Figure 31-10), showing a circumferential narrow-band-wound configuration (arrow).

the corneal epithelial circular mark. Such a technique is expected to increase the adhesion of the donor corneal disk to the recipient inner cornea and decrease postoperative disk dislocation rate.

References

1. 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.

2. 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.

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

4. 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.

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

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

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

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

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

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

11.Hyams M, Segev F, Yepes N, Slomovic AR, Rootman DS. Early postoperative complications of deep lamellar endothelial keratoplasty. Cornea 2007;26:650-3.

12.Marcon AS, Terry MA, Kara-José N, Wall J, Ousley PJ, Hoar K. Influence of final corneal thickness in visual acuity after deep lamellar endothelial keratoplasty. Cornea 2007;26:543-5.

13.Yepes N, Segev F, Hyams M, McAllum P, Slomovic AR, Rootman DS. Five-millimeter-incision deep lamellar endothelial keratoplasty: One-year results. Cornea 2007;26:530-3.

14.Price MO, Price FW. Descemet’s stripping endothelial keratoplasty. Curr Opin Ophthalmol 2007;18:290-4.

15.Mearza AA, Quershi MA, Rostron CK. Experience and 12-month results of descemet-stripping endothelial keratoplasty (DSEK) with a small-incision technique. Cornea 2007;26:279-83.

16.Melles GR. Posterior lamellar keratoplasty: DLEK to DSEK to DMEK. Cornea 2006;25:879-81.

17.Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 200 eyes: Early challenges and techniques to enhance donor adherence. J Cataract Refract Surg 2006;32:411- 8.

18.Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 50 eyes: A refractive neutral corneal transplant. J Refract Surg 2005;21:339-45.

19.Price MO, Price FW Jr. Descemet’s stripping with endothelial keratoplasty: Comparative outcomes with microkeratomedissected and manually dissected donor tissue. Ophthalmology 2006;113:1936-42.

20.John T. Descemetorhexis with endokeratoplasty. In: Surgical Techniques in Anterior and Posterior Lamellar Corneal Surgery. John T (Ed) Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, 2006;411-20.

21.John T. Descemetorhexis with endokeratoplasty (DXEK). In: Step by Step Anterior and Posterior Lamellar Keratoplasty. John T (Ed). Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, 2006;177-96.

Introduction

Endothelialtransplant(ET),alsoknownasendothelialkera- toplasty(EK)encompassesvarioussurgicaltechniques,1-17 namely, deep lamellar endothelial keratoplasty (DLEK) (Figures 32-1 and 32-2), Descemet stripping automated endothelial keratoplasty (DSAEK), and Descemet’s membrane endothelial keratoplasty (DMEK). All of these surgicaltechniques,although,varyinthedegreeofsurgical complexity, attains a common end goal of transplanting healthy donor corneal endothelial cells to the inner surface ofadecompensated,recipientcornea,thusbringingcorneal clarity, improved visual acuity without inducing any significant corneal astigmatism following surgery. These newercornealsurgicalproceduresmayreplaceconventional penetratingkeratoplasty(PKP)overtime.

DLEK can be surgically challenging regarding the surgical dissection within the host cornea to create an intracorneal pocket that can temporarily house the Terry trephine for subsequent posterior stromal trephination. It is essential for the intrastromal dissection to be carried out without creating perforations either anteriorly onto the

Figure 32-1: Schematic representation of “no-stitch” corneal transplant (no corneal sutures) in deep lamellar endothelial keratoplasty (DLEK).

corneal surface or posteriorly into the anterior chamber. Further challenges include proper placement of the donor corneal disk within the host cornea, from the anterior chamber, under air. It is also essential that the endothelium on the donor corneal disk is not iatrogenically damaged before placement in the host cornea. The newer surgical technique namely, DSAEK has become easier to perform as compared toDLEK, since thereis nointrastromal dissection in DSAEK, and thus it is continuing to gain rapid popularity among corneal surgeons worldwide. DMEK, however, is in its earlier stages of development and requires further improvement in the surgical techniques before it will become widely accepted. All these surgical techniques do have one common factor, namely, the surgeon looks through a cloudy cornea while doing surgery. This compromised view of the anterior chamber makes it difficult to clearly view the donor corneal disk within the recipient anterior chamber. Staining the donor corneal stromawithdyessuchasindocyaninegreen(ICG)ortrypan blue, enhances the visibility of the donor disk within the recipient anterior chamber.

The author first reported the use of indocyanine green (ICG) within the human cornea, namely, in DLEK.5 This chapter describes the technique of using ICG on the stromal side of the donor corneal disk in DLEK (Figure 32-2) and

the use of trypan blue staining of the donor disk in DSAEK procedures (Figures 32-3 to 32-6). These quick staining methods effectively localizes the donor disk in the host anterior chamber at all times during surgery and increases the accuracy of proper placement of the donor disk on to the inner surface of the recipient cornea.

Surgical Technique of Using

ICG in DLEK

ICG Preparation

ICG (IC-Green, Akorn, Inc., Buffalo Grove, IL) is packaged in a 25-mg vial and a 10-ml ampule of aqueous solvent (Akorn, Inc.). The aqueous solvent (pH 5.5-6.5) is a prepared sterile water for injection used to dissolve the ICG. Aqueous solvent, 0.5 ml, is added to the ICG bottle and 4.5 ml of sterile balanced salt solution (BSS) is added to the bottle containing the ICG. The bottle is shaken until the contents of the bottle are well dissolved.

Two ml of the ICG solution is aspirated into a 5 ml sterile syringe and an additional 2 ml of sterile BSS is aspirated into the same syringe for a total volume of 4 cc (1:1 dilution). A sterile, blunt, 30-gauge cannula is attached to the syringe and the solution is ready for corneal use as described below.

ICG Staining of the Donor Corneal Stroma

The freshly prepared ICG is used to stain the anterior corneal stroma of the donor cornea. Following excision of the anterior lamellar corneal stroma from the donor cornea, the anterior bare stroma is exposed to room air. The freshly prepared ICG from the 5-cc syringe is dropped onto the exposed donor corneal stroma using the 30-gauge cannula to completely cover the donor corneal stroma. The excess ICG is removed using a Meracel sponge (Medtronic, Jacksonville, FL). ICG only stains the bare corneal stroma, and the surrounding full-thickness donor corneal rim with the intact corneal epithelium is not stained.

Completion of Donor Corneal Surgery

Following staining of the anterior corneal stroma of the donor cornea, the donor corneoscleral tissue is removed from the ACC and placed on a Moria Teflon block (Moria

Inc., Doylestown, PA) with the exposed, ICG stained, stromal side down and centered on the Teflon block using the ICG stained area as an indicator of the outer demarcation of the corneal stroma with a total diameter of 9 mm. The outer full-thickness donor cornea with the intact epithelium is devoid of staining. Suction is applied to this donor disk to hold it in place and trephination is carried out using an 8.0 mm diameter Moria (Moria Inc.) trephine in a guillotine fashion (Figure 32-2 upper right). The ICGstained donor disk is seen as a green disk on the white Teflon block following the removal of the remainder of the donor corneoscleral rim. The thickness of the donor disk is not measured directly to avoid distortion to the tissue before transfer into the host corneal opening. The estimated thickness of this disk is between 200 and 300 µm. This deep stromal-endothelial donor disk is carefully transferred onto a Healon-coated, Ousley spatula (Bausch & Lomb) with the endothelial side down.

Donor Disk Transplantation

Additional air is injected into the anterior chamber of the host eye via the side port incision. The scleral sutures were cut and removed. The Ousley spatula with the donor disk is introduced into the pre-dissected corneal pocket wound, dropped into the anterior chamber, and then elevated placing the donor disk into the host bed of the resected central area (Figure 32-2 lower left). The donor corneal stroma is approximated to the host corneal stroma, creating a new corneal interface for the host. The donor corneal disk that is stained green with the ICG dye is well visualized through the host anterior corneal stroma. The donor disk margins are well approximated to the cut edges of the host corneal rim without any overriding of the donor disk edge to the cut edges of the inner host corneal stroma. The Ousley spatula is then gently removed from the eye. The donor corneal disk adheres to the central posterior recipient bed (Figure 32-2 lower right), the interface green dye is visible, and the donor disk is held in place initially by the air bubble in the anterior chamber. Minor adjustments to the

coaptation of the edges of the donor disk and the recipient bed can be made if needed using a Sinskey hook (Stephens Instruments, Lexington, KY). The superior scleral wound is then closed with interrupted 10-0 nylon sutures without adding any additional tension to prevent induced astigmatism. The air bubble is decreased in size and additional BSS is injected into the anterior chamber as needed through the side port incision. A collagen shield soaked in antibiotics and steroid is placed on the ocular surface at the end of the procedure.

Patients are examined the following day in the office.

Trypan Blue Staining of the Donor Corneal Stroma in DSAEK Procedure

The selective staining properties of trypan blue (Vision Blue, Dutch Ophthalmic International, Exeter, NH, USA) were used to visualize and manipulate the donor corneal disk during EK surgery for proper centration and attachment of the donor corneal disk to the recipient cornea

(Figures 32-3 to 32-6).

Surgical Technique

Moria anterior lamellar therapeutic keratoplasty (ALTK) system (Moria Inc., Antony, France) was used as the artificial anterior camber (AAC) and a microkeratome with a 300 µm CB head was utilized for the procedure (Moria Inc., Antony, France). The set-up consisted of a sterile syringe filled with the Optisol-GS solution from the eye bank vial (Illinois Eye Bank, Chicago, IL) containing the donor corneal button. This syringe was attached to one end of a short single-use sterile tubing with a stop-valve, and the other end of the tubing was attached to the ALTK system. Optisol-GS solution was gently injected from the syringe such that the solution filled the well in the central post. The donor corneal button with a large scleral rim was placed with the endothelial side down on the central post of the AAC filled with the Optisol-GS solution. The OptisolGS solution bathed the donor corneal endothelium. The cylindrical fixation ring was then locked in place, encasing the donor corneal button within the AAC.

The corneal epithelium was removed using dry Merocel spear (Medtronic, Jacksonville, FL). A central dot was placed on the dome of the donor cornea with a marking pen and a linear mark was made on the periphery of the cornea. The microkeratome head was moistened with sterile balanced salt solution (BSS) (Meditech Inc, Manassas, VA, USA) and the head was mounted on to the post, and a corneal cap was cut with the CB-microkeratome head in a steady curvilinear fashion. A free-cap was then obtained on the microkeratome head and the donor corneal stroma was exposed in a circular manner in the central opening of the ALTK system.

Stromal Staining

Trypan blue ophthalmic solution (Vision Blue, Dutch Ophthalmic USA, Exeter, NH) was then applied on to the exposed corneal stroma using a sterile syringe with a blunt cannula. The excess trypan blue was dried with Merocel spears (Medtronic, Jacksonville, FL). This step stained the