Publication Exclusive: Good early results seen with pre-Descemet's endothelial keratoplasty in failed grafts

Graft failure in any situation can happen due to inherent defects in the donor graft or pre-existing pathology in the recipient. Inherent graft issues such as low endothelial cell count, surgical trauma to the graft and endothelial disease in the donor can cause early graft failure. Graft rejection is another main etiology that can happen, especially in full-thickness keratoplasty. Lamellar keratoplasty procedures have been shown to have fewer incidences of rejection, but rejection has been noticed after deep lamellar keratoplasty. The corneal stroma is the culprit often 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. In this article, we will discuss our experience of pre-Descemet’s endothelial keratoplasty in previous failed grafts.

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 presents with persistent, non-resolving corneal edema and failure to show visual acuity improvement after the first surgery. Endothelial trauma, elderly donors and donor tissue diseases have been hypothesized for the causes of primary failure. Secondary failure refers to failure of the graft after an initial period of clearance or normal function. Graft rejection is one of the common causes of secondary graft failure. Graft infections, ocular surface problems and recurrence of host disease are the other causes.

Even though the incidence of endothelial rejection is less with endothelial keratoplasty, it has still been reported. Penetrating keratoplasty is common with stromal rejection, and this demands for measures to be taken to reduce the incidence of rejection. However, prolonged steroids predispose patients to the risk of ocular hypertension and sometimes steroid-induced glaucoma and secondary cataracts, which in turn threaten best corrected visual acuity.

Reoperation in graft failure

Challenging cases often pose a dilemma for the ophthalmologist over whether to proceed with another surgery in patients who have a failed graft. A failed PK can be corrected by repeat PK or primary endothelial keratoplasty. The advantages of endothelial keratoplasty in failed PK cases are the closed globe procedure; less risk of graft rejection; fewer surgical maneuvers; and absence of complications inherent to PK such as suture infection, glaucoma and astigmatism. However, performing endothelial keratoplasty requires suitable training skills, immense ground knowledge and confidence.

PDEK in failed PK graft

In failed graft procedures, it is always better to go for young donor grafts with endothelial cell counts higher than 2,800 cells/mm2 and hexagonality greater than 40%. Eyes with a low cell count, from elderly donors or with prolonged storage time should be excluded. Donor graft preparation is the same as for any PDEK procedure (Figure 1), as we have reported previously. A 30-gauge needle attached to a 5-mL syringe was inserted from the limbus into the mid-peripheral stroma. Air was slowly injected into the donor stroma until a type 1 big bubble was formed. The bubble wall was penetrated at the extreme periphery, and trypan blue was injected to stain the graft, which was then cut with a pair of corneoscleral scissors and covered with the tissue culture medium.

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

Click here to read the full publication exclusive, Complications Consult, published in Ocular Surgery News U.S. Edition, August 10, 2016.