Title: Hybrid Technique of Posterior Lamellar Keratoplasty

Course IC-37: Hybrid techniques of posterior lamellar keratoplasty (DMEK-S/DMAEK) Studeny P., Sivekova D., Liehneova K., Krabcova I., Price FW Jr, Price MO

1 Department of Ophthalmology, 3rd Medical Faculty, Charles University, Prague, Czech Republic. 2 Ocular Tissue Bank General Teaching Hospital, Prague, Czech Republic 3 Laboratory of Biology and Pathology of the Eye, First Faculty of Medicine Charles University, Prague, Czech Republic

Purpose: To present two hybrid techniques of posterior lamellar keratoplasty (PLK) where Descemet´s membrane (DM) and endothelium supported by peripheral rim of deep stroma is implanted.

Introduction: PLK is becoming a widely used technique in the treatment of corneal endothelial diseases, including endothelial dystrophies, pseudophakic bullous keratopathy and endothelial graft failure. Various grafting approaches to PLK have been introduced in the past several years. There are different types of posterior corneal lamellae (PCL) according to their histological structure. 1. Endothelium–DM–posterior stroma lamellae The first type is composed of the endothelium, DM and part of deep stroma that works as a structural support to allow easier manipulation with the lamella and to prevent massive damage of fragile endothelium. This technique is called Descemet´s stripping endothelial keratoplasty (DSEK) if the lamella is created manually or Descemet´s stripping automated endothelial keratoplasty (DSAEK) if the lamella is made by microkeratome or femtosecond laser. The main advantages of these techniques are: relatively easy manipulation, less stress for the endothelial cells and a good recognition of stromal and endothelial side of the lamella during positioning in the recipient eye. The lamella keeps a convex shape and it is possible to mark the stromal side as well. The main disadvantages are the plus of the stromal tissue and possible inter-lamellar problems that is why the best corrected visual acuity is very often a bit decreased. 2. Endothelium – DM lamellae The second type consists just of DM and endothelim, while the stromal part is completely absent. The donor discs are prepared from the corneoscleral donor button by stripping a circular portion of tissue, and the transplantation technique has been referred to as Descemet’s membrane endothelial keratoplasty (DMEK). The recipient corneal bed preparation is the same as in DSEK lamella. Donor button (9.5mm) is trephined from the endothelial side and consequently stripped from the posterior stroma. In the storage medium, the lamella spontaneously forms a roll with the endothelium outside. The endothelium-DM roll may be evaluated after trypan blue and sucrose treatment. The preparation technique is standardized, and its basic parameters as well as postoperative follow up have been frequently published. This technique seems to be optimal, because the surgeon replaces involved endothelium and DM by the same portion of the tissue. In this approach there are no problems with inter-lamellar opacities, and the vision after surgery is very often excellent, but unfortunately the manipulation with such thin lamella is difficult, especially the unwrapping of the lamellae during the insertion may be quite stressful for the endothelium.

3. Endothelium-DM-stromal support lamellae The third group has a central part that consists of bare DM and endothelium as in DMEK but there is also a peripheral thicker part, similar as lamellae in DSEK or DSAEK. We can call this technique of lamellar preparation a hybrid technique, because it combines the advantages of both previous techniques. The central part without stroma insures the excellent optical results after surgery comparable with successful DMEK patients. The stromal rim fixes the thin, fragile central part and helps to maintain its shape and prevent the scrolling of DM. Moreover the stromal part allows marking of the antero-posterior orientation of the lamella that enables the surgeon to recognize exactly the endothelial side during manipulation with the lamella as well as during positioning in the anterior chamber.

Hybrid technique

Hybrid technique of bare DM-endothelium with a peripheral stromal support we refer as Descemet’s membrane endothelial keratoplasty with a stromal rim (DMEK-S), (Studeny et al., 2009). Next technique for the preparation of lamellae is so called Descemet´s membrane automated endothelial keratoplasty (DMAEK). It is also an endothelial keratoplasty technique where the Descemet membrane is with a peripheral ring of corneal stroma transplanted, but using a graft prepared for Descemet stripping automated endothelial keratoplasty (DSAEK).

The hybrid transplantation techniques combine the superior vision potential of Descemet membrane endothelial keratoplasty with the easier insertion and manipulation of DSEK or DSAEK. The main advantage of DMAEK lamella is a defined thickness of the peripheral part, but the technique is more expensive in comparison with DMEK-S, because of need of cutting equipment and use of pre-cut DSAEK lamella from the eye bank. The preparation of hybrid lamellae

For the separation of the stroma and DM the big bubble technique is used. The air injection into the stromal part with minimal resistance induces bubble formation (between the stroma and DM should be theoretically free space with any connections). This air bubble detaches DM from corneal stroma. The surgeon cuts the stroma over the bubble and afterwards removes it in the central part with scissors or knife. A spatula can be used to protect the DM during cutting the stroma.

In DMAEK technique is first an anterior corneal cap on the donor cornea resected, using a microkeratome. The surgeon creates a big bubble on the pre-cut lamella to detach the central 6.0 to 7.0 mm of Descemet membrane.

The prepared tissue is punched with an 8.5 to 9.0 mm trephine. This leaves a bare central Descemet membrane with an attached peripheral stromal rim. The graft's stromal rim allows it to spontaneously unfold once inside the eye.

The preparation of these types of lamellae was already adopted by the eye banks, where the technique could be standardized and the parameters of corneas intended for manual preparation were established (Krabcova et al., accepted). The main advantage of this procedure is the evaluation of the endothelial cell count density of the lamellae after preparation, the decreasing of the psychical stress for surgeon during surgery and a significant shortening of the surgery duration.

Implantation of the hybrid lamellae / surgical procedure: The manipulation with the lamellae is relatively easy due to presence of peripheral part of lamellae composed of endothelium and DM as well as of stromal tissue. It gives the important mechanical support to the lamellae. This kid of lamellae could be easily implanted in the same way as DSAEK lamellae (forceps, glide, Busin´s insertion instrument). On the other hand it is also possible to implant the lamella in a similar way as DMEK. We present an original technique for the implantation using water flow. An anterior chamber maintainer or an irrigation cannula for keeping the anterior chamber during the implantation can be used. The water pressure must not be too high, to avoid pushing the lamella out of the eye. Peroperative and postoperative complications and their managment The most frequent complication during the surgery is donor lamella malposition (endothelial side up) or decentration. An air bubble disappears sometimes earlier from the anterior chamber and the lamella does not attach properly. This is typical especially in eyes after previous vitreoretinal surgeries, after vitreoretinal complications of cataract surgery, after posterior capsule disruption followed by anterior chamber intraocular lens implantation and in eyes with iris defects or huge basal iridectomies. The most frequent postoperative complication is partial or total detachment of lamellae that can be easily resolved with air bubble reinjection into the anterior chamber. In some cases the donor disc attaches spontaneously. The other postoperative complications could be: intraocular pressure elevation, Urrets-Zavalia syndrome, lamellar decentration etc.

Postoperative care The postoperative care consists of regular follow up schedule where following parameters are analyzed: UDVA, BDVA, intraocular pressure, position of the lamella, endothelial cell density. We can repeat the air bubble instillation into the anterior chamber (re-bubbling) in the case of lamellar detachment. During the first month postoperatively patients use combined antibiotic and steroid eye drops and continue with topical corticosteroid eye drops until one year postoperatively.

Conclusion: Hybrid techniques of PCL in posterior lamellar keratoplasty – transplantation of DM and endothelium with peripheral stromal rim combines the advantages of DMEK and DSEK/DSAEK techniques. Pre-preparation of this kind of lamellae in the eye bank conditions (pre-cut lamellae) can increase the visual outcomes of this surgery and the surgery could be widely adopted by surgeons.