Living-Related Conjunctival–Limbal Allograft (lr-CLAL) Transplantation

Elham Ghahari, Alireza Baradaran-Rafii and Ali R. Djalilian

Indications

In bilateral limbal stem cell deficiency (LSCD), a limbal allograft transplant utilizing donor tissue from a living relative (living-related conjunctival–limbal allograft; lr-CLAL) is an option that may be considered as an alternative or in combination with a keratolimbal allograft (KLAL). The lr-CLAL procedure utilizes normal limbal tissue on a conjunctival carrier that is harvested from one eye of a patient’s living relative and transplanted to the diseased eye of the recipient. This procedure offers two distinct advantages over KLAL. First, in contrast to a KLAL graft which only includes viable limbal tissue, the lr-CLAL graft also includes a significant amount of healthy conjunctiva. The transplanted conjunctiva makes lr-CLAL particularly useful in patients with combined limbal and conjunctival deficiency, such as cicatrizing conjunctival diseases, including mucous membrane pemphigoid (MMP) and Stevens–Johnson syndrome (SJS). In many of the cicatrizing conjunctival cases, it may actually be beneficial to combine the lr-CLAL procedure with KLAL (i.e. the ‘Cincinnati procedure’) in order to provide enough limbal stem cells and the necessary conjunctiva for ocular surface rehabilitation. The other main advantage of lr-CLAL over KLAL is that it provides an opportunity for immunologic matching of the donor and the recipient. Although systemic immunosuppression is still necessary after lr-CLAL, matching the donor and recipient can potentially reduce the risk of immune rejection and the need for continued long-term systemic immunosuppression. The disadvantage of lr-CLAL, compared to KLAL is that the amount of tissue is limited, with fewer limbal stem cells transplanted. In addition there are gap areas between transplanted tissue with the lr-CLAl that can allow invasion of conjunctiva over the cornea in some cases. Lr-CLAL alone may be a particularly attractive option for patients with some residual limbal function, such that 360 degrees of limbal transplantation is not necessary or in cases without severe conjunctival disease.

Surgical Procedure

Donor Eye

A thorough eye examination should be performed in all potential donors. If there is any ocular surface disease, history or suspicion of glaucoma (probability of future trabeculectomy) or history of long-term contact lens use (probability of limbal stem cell compromise), the donor should be excluded. The designated donor is then screened for hepatitis B and C, syphilis, and human immunodeficiency virus. They are also ABO and human leukocyte antigen (HLA I and II) typed and the best-matched consenting relative is selected for donation.

Harvesting the donor tissue is essentially the same as in CLAU. This procedure is typically done under local anesthesia using subconjunctival injection of xylocaine plus epinephrine. In some cases, retrobulbar/peribulbar anesthesia may be necessary. Two 60-degrees arcs of limbal lenticule, each spanning 2–3 clock hours, are harvested from one or both eyes of donor at 12 or 6 o’clock positions. A gentian violet surgical marking pen may be used to mark the conjunctival portions of the grafts (Fig. 41.1). The dissection can be started with lamellar dissection from the corneal side approximately 1 mm anterior and extending 2 mm posterior to the limbus, leaving behind the Tenon’s capsule as much as possible. Alternatively, as the authors prefer, the dissection can be started on the conjunctiva and carried forward towards the limbus about 1–1.5 mm onto the cornea in a superficial manner. Care should be taken to avoid buttonholing of the donor tissue. Dissection onto the peripheral cornea past the palisades of Vogt is critical in order to obtain limbal stem cells. Amputation of the tissue peripheral to this landmark with result in the harvesting of conjunctiva only.

Figure 41.1 Schematic of the lr-CLAL procedure. (A) Marking and harvesting of the conjunctival and limbal grafts of the donor tissue at 12 and 6 o’clock. (B) Preparation of the recipient site with a 360° peritomy and resection of the conjunctiva at 12 and 6’clock for placement of the donor tissue. (C) Superficial keratectomy of the recipient cornea. (D) Placement of the CLAL grafts.

Typically, a 5-mm conjunctival skirt is harvested; however, the amount of the conjunctiva can be increased if the recipient eye also requires symblepharon repair and fornix reconstruction. After excising the donor tissue, the surrounding conjunctiva is undermined and advanced anteriorly and sutured with 10-0 nylon (or dissolvable suture) to close or partially close the conjunctival defect. Although the donor sites heal quickly, closing the defect enhances patient comfort and reduces likelihood of localized pannus formation.¹

The surgical procedure of lr-CLAL is identical to CLAU.¹ Surgery is done under general or retrobulbar/peribulbar anesthesia. After a 360-degree conjunctival peritomy, subconjuntival scar tissues are removed as much as possible, which typically results in the recession of the conjunctival edge to 3–5 mm from the limbus. Hemostasis is achieved with mild wet-field cautery or dilute epinephrine (1 : 10 000). Corneal pannus is removed with special caution not to perforate the cornea. Donor grafts are sutured to the recipient eye at the corresponding anatomic sites by interrupted 10-0 nylon sutures. As an alternative to using sutures, the lr-CLAL grafts can also be directly fibrin glued onto the prepared bed.^2,3 This approach has the potential to decrease operative time, increase ease of technique, and improve patient comfort postoperatively. The surgical site may be covered with an overlain amniotic membrane or a high-DK bandage contact lens. At the end of surgery, upper and lower punctal occlusion and lateral tarsorrhaphy may be performed to protect grafts from the mechanical trauma of blinking, as well as from evaporative moisture loss in the early postoperative period in the more severe cases (Fig. 41.2).