Endoilluminator-Assisted Descemet Membrane Endothelial Keratoplasty and Endoilluminator-Assisted Pre-Descemet Endothelial Keratoplasty

13 Endoilluminator-Assisted Descemet Membrane Endothelial Keratoplasty and Endoilluminator-Assisted Pre-Descemet Endothelial Keratoplasty

Soosan Jacob and Amar Agarwal

Endothelial keratoplasty has evolved from Descemet layer endothelial keratoplasty (DLEK) to Descemet stripping automated endothelial keratoplasty (DSAEK) to Descemet membrane endothelial keratoplasty (DMEK) and Pre-Descemet endothelial keratoplasty (PDEK).1 DSAEK is popular and has become universally accepted and practiced due partly to the ease of the surgery and the short learning curve. However, DMEK/PDEK is practiced in few centers, mainly because of the greater difficulty in performing the surgery. This difficulty is often compounded by the low visibility of the graft through a hazy cornea. Moreover, the graft is transparent, thin, and flimsy. Therefore, it is difficult to visualize the graft clearly in the anterior chamber after insertion. To overcome this, the graft can be stained with trypan blue. Despite this staining, good visualization often remains challenging through an edematous cornea. Also, the dye washes off in time, and, in the case of a longer surgical time, the inserted graft becomes too difficult to visualize. This chapter describes a technique, endoilluminator-assisted DMEK (E-DMEK) and endoilluminator-assisted PDEK (E-PDEK)2,3 that enables easy identification of the orientation and visualization of the graft during all surgical steps. It uses oblique light from a vitreoretinal light pipe or an endoilluminator for better visualization.

13.1 Background

The endoilluminator has been used to provide an oblique source of illumination in anterior segment surgery since 1993. It has been used to visualize the anterior capsular flap during capsulorrhexis in hypermature cataracts, to perform cataract surgery in the presence of corneal opacity, for irrigation and aspiration during combined 23-gauge sutureless vitrectomy and cataract surgery, and as an endoilluminated infusion cannula for bimanual anterior chamber vitrectomy. Chandelier illumination has been used during DSAEK since 2011 via a chandelier illumination fiber inserted through the corneal side port to provide sclerotic scattering-like illumination from the sclerocorneal margin and endoillumination from the anterior chamber, resulting in excellent visibility for Descemet stripping and intraocular manipulation without obstruction from a hazy cornea. However, it has not been reported in patients undergoing DMEK/PDEK. The use of the endoilluminator for DMEK/PDEK is a logical extension of its previous uses. Because DMEK/PDEK is more challenging, the use of an endoilluminator is comparatively more valuable. E-DMEK/E-PDEK makes surgery simpler by allowing good visualization and better surgeon understanding of graft morphology and dynamics.

13.2 Surgical Technique

One of the key steps in DMEK/PDEK is determining the descemetic side of the graft. The descemetic side needs to face the overlying corneal stroma. This will allow the graft to be appropriately apposed to the stroma on injection of an air bubble. The key to being sure about the correct orientation of the graft is to look at the direction toward which the edges of the graft are curling. Because the Descemet membrane is an elastic structure, the graft edges always curl toward the stroma. Therefore, intraoperatively, the graft must be oriented with the curve facing upward. This is often difficult to confirm with the current techniques. Because the graft is transparent, it is difficult to ascertain the direction of the curvature of the edges, even in an eye with good visibility.

In DMEK the graft is prepared as usual with the submerged cornea using backgrounds away (SCUBA) technique described by Gimbel et al.4,5 This allows easy preparation of the graft with less chance of damage and tearing. Another technique is to punch the donor to the desired size, followed by submerging the button in storage medium. The edge of the Descemet membrane is then gently grasped with a fine, nontoothed forceps and stripped from all sides, carefully avoiding any uncontrolled tears ( Fig. 13.1a, b). The graft is sized 0.5 mm smaller than the proposed recipient bed. The recipient bed is prepared by externally marking the surface of the cornea with a blunt trephine. The Descemet membrane is then scored with a reverse Sinskey hook and stripped. Once this is done, the DMEK graft is stained with trypan blue 0.1%. The graft is loaded into an injector using the technique described by Price et al. The spring coil is removed from the Viscoject injector (Medicel), and the silicone tip is replaced ( Fig. 13.1c, d). The graft is then placed into the 1.8 mm Viscoglide cartridge (Medicel) ( Fig. 13.1e, f). The cartridge is loaded onto the injector ( Fig. 13.1g). A microincision keratome is used to create a 2.2 mm temporal clear corneal incision, and a paracentesis is created 90 degrees away temporally. A small inferior peripheral iridectomy is created now (it may also have been created preoperatively using a neodymium:yttrium-aluminum-garnet (Nd: YAG) laser. Using the injector, the surgeon gently injects the graft into the anterior chamber, and the incisions are sutured ( Fig. 13.1h). At this point, the microscope light is turned off, and the endoilluminator or light probe (20, 23, or 25 gauge) is used as an oblique source of illumination to enhance visualization. It is held externally by the surgeon or by an assistant while the surgeon continues surgery bimanually. The tangential light provided by the endoilluminator is used to show details of the graft, folds in the grafts, and the position and orientation of the Descemet membrane in relation to the corneal stroma. The tip of the light probe is moved around the limbus while focusing it tangentially to allow good visualization and three-dimensional perception. The direction of graft edge curvature, and thereby graft orientation, is confirmed by tapping the host cornea gently and appreciating the reflexes created by the light bouncing off the edges of the graft and by seeing the movement induced in the graft ( Fig. 13.2 and Fig. 13.3). Using endoillumination, the graft is oriented the right way up and centered under the stripped recipient site, after which an air bubble is injected under the graft to float it up against the overlying stroma. At any time during the surgery, the surgeon can switch back and forth between the microscope light and the endoilluminator. Intraocular pressure and light perception are checked before closing the eye. The patient is asked to maintain a strict supine position for the first 24 hours.

May 28, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Endoilluminator-Assisted Descemet Membrane Endothelial Keratoplasty and Endoilluminator-Assisted Pre-Descemet Endothelial Keratoplasty

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