22 Complications of Pre-Descemet Endothelial Keratoplasty

The cornea, an exquisite example of physiological engineering, has unique structural characteristics for its very nature. Its normal endothelial cell function is imperative for maintaining transparency. Numerous techniques developed over the last 2 decades have been used to provide vision by endothelial transplantation.1,2,3,4 Though major complications of penetrating keratoplasties, such as suture inflammation, irregular astigmatism, and keratitis, are prevented after endothelial keratoplasty (EK), they are still not free of complications.⁵ Pre-Descemet endothelial keratoplasty (PDEK), a recent modification of EK, involves the transplantation of the pre-Descemet layer (PDL, or Dua layer) along with the Descemet membrane (DM) with endothelium.^6,7 PDEK has many potential advantages over other EKs, such as Descemet membrane endothelial keratoplasty (DMEK) or Descemet stripping endothelial keratoplasty (DSEK); however, learning curve complications are inevitable. These complications are generally manageable, and the risk tends to decline as a surgeon gains experience in the new surgical technique. This chapter discusses the few complications that can arise during the learning curve associated with PDEK and their methods of management.

22.2 Intraoperative Complications

22.2.1 Failure to Form Type 1 Bubble

Type 1 bubble formation is the preliminary step in PDEK surgery for obtaining the donor graft. Failure to form a type 1 bubble can happen intraoperatively, when the correct plane of dissection is not reached. In that case, a small peripheral type 2 bubble or small type 1 bubble is formed (► Fig. 22.1). When the small type 1 bubble is formed, it is enhanced by air or viscoelastic injection in a controlled fashion (► Fig. 22.2). However, when a type 2 bubble is formed, DMEK surgery is performed (► Fig. 22.3). Double bubble formation is also sometimes noted. Very rarely a bubble may not form on repeated attempts with air, in which case a preservation medium—either McCarey–Kaufman (MK) medium (► Fig. 22.4) or Optisol (Chiron Ophthalmics)—can be used for bubble formation. To prevent type 2 bubble formation, one can place multiple peripheral micro-punctures on the Descemet membrane before air injection.

22.2.2 Bubble Burst during Pneumatic Dissection

When the bubble bursts early during pneumatic dissection, the size can be enhanced by slow viscoelastic injection via the ostium. Bubble burst usually happens when the surgeon pushes too much air into a small space and the intrabubble pressure raises exponentially faster (► Fig. 22.5). Once the bubble bursts after reaching its maximum size, Vannas scissors can be used to excise the graft uniformly along its margin. If the bubble bursts in an early stage (i.e., size < 6mm), the results are not predictable in smaller grafts; hence rebubbling in another corneal button is preferred.

22.2.3 Small Graft

Similar to any EK, the graft size is vital in PDEK. A small graft is obtained due to the formation of a small type 1 bubble. Whenever a bubble < 4 mm is seen after pneumatic dissection, viscoelastic can be injected into the bubble to enhance the size. However, too much intrabubble pressure should be avoided, which again can lead to bubble burst. The preferred graft size in PDEK is 7.5 to 8 mm. Grafts smaller than 6.5 mm have the risk of late failure. However, a small graft of 6 mm with good endothelial count and morphology can provide good results (► Fig. 22.6).

Fig. 22.1 Donor graft preparation. (a) Small type 1 bubble formed. (b) Type 1 bubble enhanced with air.

Fig. 22.2 Donor graft preparation. (a) Small type 1 bubble formed. (b) Type 1 big bubble enhanced with viscoelastic substance.

Fig. 22.3 Donor graft preparation. Type 2 bubble formed. (a) During pneumatic dissection. (b) After big bubble formation.

22.2.4 Reverse Graft Unfolding

An endothelial graft always scrolls with the endothelium to the outside. A PDEK graft curling away from the host cornea indicates that the graft is inverted (► Fig. 22.7). This is managed by reinversion by saline in the anterior chamber. Intraoperative optical coherence tomography (OCT) can also guide in visualizing the orientation of the graft (► Fig. 22.8). Care should be taken to prevent too much manipulation on the endothelium while reinverting.

22.2.5 Chamber Collapse

Loss of anterior chamber pressure can result from a wide incision causing excess fluid outflow. A trocar anterior chamber maintainer (► Fig. 22.9) or an air pump-assisted anterior chamber maintainer can help with chamber pressure control. Avoiding too large incisions and proper closure of the main wound immediately after graft injection can prevent intraoperative hypotony.

22.2.6 Poor Graft Visualization

Intraoperative loss of visualization can happen in eyes with chronic corneal decompensation and scarring. Superficial keratectomy or epithelial debridement can be performed in many cases. In eyes with persistent corneal edema visualization can be enhanced by endoilluminator-assisted PDEK (► Fig. 22.10).⁸

Fig. 22.4 Donor graft preparation by McCarey-Kaufman (MK) medium. (a) Small type 1 bubble formed. (b) Enhanced with continuous injection of MK medium.

Fig. 22.5 (a) Small type 1 bubble formed. (b) Bubble bursts when the surgeon pushes too much air into a small space.

Fig. 22.6 Small donor graft about 6.5 mm showed good corneal clearance. (a) Preoperative Fuch’s dystrophy. (b) Postoperative PDEK at 12 months.

Fig. 22.7 An inverted pre-Descemet endothelial keratoplasty graft in optical coherence tomography. Note the graft curling away from the (a) host cornea and (b) reattached graft.

Fig. 22.8 Intraoperative optical coherence tomography-assisted pre-Descemet endothelial keratoplasty. (a) Before air injection. (b) After air injection.

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