17 Pre-Descemet Endothelial Keratoplasty in Failed Grafts

Graft failure in any circumstances can take place due to intrinsic defects in the donor graft or preexisting pathology in the recipient. Inherent graft issues, such as low endothelial count, surgical trauma, and donor endothelial disease, can lead to early graft failure.1,2,3,4 Graft rejection is one of the common etiologies of secondary graft failure, especially in full-thickness or penetrating keratoplasty (PK).^1,2 Lamellar keratoplasties have also shown fewer incidences; but still rejection has been noticed after deep lamellar keratoplasty or endothelial keratoplasty.⁵ Corneal stroma is often the culprit recognized as the cause of rejection because of its antigenic nature. A failed penetrating graft can be replaced by another penetrating full-thickness graft or by an endothelial graft.^{6,7,8,9,10,11} Subsequent PK has a higher failure rate and exposes the patient to an additional period of a prolonged visual recovery, the creation of an unstable wound, and further ocular surface disruption. On the other hand, secondary endothelial keratoplasty (EK) has the advantage of less surgical manipulation, no suture-related inflammation or astigmatism, and early visual recovery.^{12,13,14,15,16} In this section we will be discussing our experience of pre-Descemet endothelial keratoplasty (PDEK) in previous failed grafts.

17.2 Graft Failure

Graft failure can be primary or secondary in origin. Primary graft failure is defined as failure of the graft to clear after surgery due to endothelial dysfunction and presenting with persistent, nonresolving corneal edema.² Primary graft failure presents as a failure to show improvement in visual acuity after the initial surgery. Endothelial trauma, elderly donor, and donor tissue diseases have been hypothesized for the cause of primary failure. Secondary failure refers to failure of graft after an initial period of clearance or normal function. High-risk keratoplasties, repeat PKs, postoperative conditions associated with glaucoma, retinal surgery, suture problems, persistent epithelial defect, infectious keratitis, and graft rejection can be significant causes of failure.^1,2 Persistent ocular surface problem and recurrence of host disease can also cause secondary graft failure in some cases. Even though the incidence of endothelial rejection is lower, graft rejection has been reported with EK. Penetrating keratoplasty is associated with stromal rejection, which demands measures to reduce the incidence be taken in patients post-PK. However, prolonged steroid use places the patient at risk of ocular hypertension and sometimes steroid-induced glaucoma and secondary cataracts, which in turn threaten best corrected vision.

17.3 Resurgery in Graft Failure

In challenging cases the ophthalmologist must decide whether to proceed with another surgery in the event of a failed graft. A failed PK can be corrected by repeat PK or primary endothelial keratoplasty. The advantages of endothelial keratoplasty in the case of a failed PK is the (1) closed-globe procedure, (2) lowered risk of graft rejection, (3) fewer surgical maneuvers, and (4) absence of complications inherent to PK (e.g., suture infection, glaucoma, astigmatism). However, performing endothelial keratoplasty requires suitable training skills, immense ground knowledge, and confidence.

17.4 Pre-Descemet Endothelial Keratoplasty in Failed Graft

17.4.1 Donor Selection

It is always better to use young donor grafts with an endothelial cell count >2800 cells/mm²) and hexagonality >40% in failed graft procedures. Exclude eyes with low cell count, elderly donors, and prolonged storage time.

17.4.2 Donor Graft Preparation

Donor graft preparation is the same as that for any PDEK procedure and has been explained previously.^17,18 A 30-gauge needle attached to a 5 mL syringe is inserted from the limbus into the midperipheral stroma (► Fig. 17.1). Air is slowly injected into the donor stroma until a type 1 big bubble¹ is formed. Viscoelastics can also be used for big bubble formation in eyes with difficulty in pneumatic dissection. The bubble wall is penetrated at the extreme periphery, and trypan blue is injected to stain the graft, which is then cut with a pair of corneoscleral scissors and covered with the tissue culture medium.

17.4.3 Recipient Bed Preparation

Under peribulbar anesthesia, initially a trocar anterior chamber maintainer (TACM) is placed at the limbus. The Descemet membrane (DM) is scored all around, with the diameter being smaller than that of the PK graft (► Fig. 17.2). The graft–host junction should not be disturbed with undue force or manipulation. The DM is then stripped off and gently removed via the main port. The donor PDEK lenticule is inserted into the anterior chamber (AC) with a customized injector. It is attached to the recipient bed by careful unrolling with an air bubble and attached to the overlying recipient stroma. The margins are swept in cases of a tight roll on the endothelial side under air with a reverse Sinskey hook. Intrachamber positive pressure is maintained thereafter for a short time by an air pump connected to the TACM. The main wound is closed with 10–0 monofilament nylon interrupted sutures, and the previous graft–host interface is rechecked for any leaks. The patient is laid supine for 30 minutes in the operating room and then shifted.

Fig. 17.1 (a) A type 1 big bubble formed in donor cornea using viscoelastics. (b) Bubble pierced with knife at the margin. (c) Graft is gently cut with curved Vannas scissors.

Fig. 17.2 (a) Preoperative image of failed penetrating keratoplasty in an eye with coexisting cataract (b) Capsulorhexis and (c) phacoemulsification performed to remove the lens. (d) Air injected to fill the anterior chamber by the end of intraocular lens implantation. (e) Anterior chamber maintainer is inserted and Descemet membrane is scored all around the recipient bed and stripped. (f) Graft loaded in a customized injector is injected into the anterior chamber. (g) Endoilluminator is used to visualize the graft in corneal edema and graft is positioned. (h) Air is injected beneath the lenticule to appose it with the overlying host stroma.

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