Clara C. Chan and Edward J. Holland

Background

Keratolimbal allograft (KLAL) is a technique in which allogeneic cadaveric limbal stem cells are transplanted to a recipient eye with severe ocular surface disease using peripheral donor cornea as a carrier.¹ A number of techniques for KLAL have been reported, many of which describe strategies to facilitate harvesting the donor limbal grafts and donor tissue dissection. One of the earliest techniques, termed ‘keratoepithelioplasty,’ was to dissect the limbal tissue from a whole globe.² Tsubota and co-workers reported the use of stored corneoscleral rims for limbal stem cell transplantation, which allowed for better coordination of surgery after suitable donor tissue was retrieved.³ Holland and Schwartz further modified the technique to use two stored corneoscleral rims instead of one, in order to fashion a contiguous ring of KLAL lenticules around the recipient limbus, which doubled the quantity of limbal stem cell supply and created a barrier to conjunctivalization.⁴ Djajilian reported a conjunctival-based thin KLAL technique which employed fibrin glue alone to secure the limbal allografts using minimal or no peripheral scleral skirt.⁵

Optical keratoplasty, either deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK), may be required after KLAL, if deeper corneal stromal scarring is present. Sundmacher et al. have described a procedure termed homologous penetrating central limbokeratoplasty, in which a stored corneoscleral rim is intentionally trephined off-center to create a penetrating keratoplasty button.⁶ Using this technique, approximately 30–40% of the graft circumference contains limbal stem cells, and the patient benefits from receiving a clear penetrating graft along with limbal stem cells in a single operation. However, in severe cases of LSCD, it may be more beneficial to have limbal stem cells through 360 degrees. Performing optical keratoplasty as a staged procedure at least 3–6 months after KLAL allows for decreased ocular surface inflammation and stabilization of the corneal epithelium.

Indications

Keratolimbal allograft surgery is performed in patients who have no suitable living-related donor and have either bilateral LSCD or unilateral LSCD and fear damage to the healthy fellow eye (Fig. 42.1). Patients need to be suitable candidates for systemic immunosuppression, which is crucial to the success of KLAL in stabilizing the ocular surface and restoring a normal corneal epithelium phenotype.^7–9

KLAL is ideal for diseases, such as aniridia, contact lens wear-related LSCD, and iatrogenic LSCD that affect mainly the limbus with minimal to no involvement of the conjunctiva.1,7,10 Patients with total LSCD require 360-degree KLAL, while those with sectoral LSCD may require only sectoral KLAL.

In patients with mild chemical injuries, Stevens – Johnson syndrome (SJS) or ocular cicatricial pemphigoid (OCP) and who have LSCD with mild to moderate conjunctival inflammation, it is best if the eye is allowed to quiet for at least a year or more prior to KLAL surgery in order to increase the chances of graft survival. The success rate of KLAL decreases with increasing conjunctival inflammation, such as in severe cases of chemical injuries, SJS, or OCP.¹ In these cases, there is chronic conjunctival inflammation and scarring, decreased mucin and aqueous tear deficiency, and great potential for keratinization of the ocular surface. Since KLAL alone does not provide any healthy conjunctiva, for these severe cases of ocular surface disease, one can use in conjunction with two KLAL segments from one donor corneoscleral rim, living-related conjunctival limbal allograft (lr-CLAL) for bilateral disease and conjunctival limbal autograft (CLAU) for unilateral disease (Fig. 42.2).^11,12

Preoperative Considerations

Prior to any limbal stem cell transplantation procedure, including KLAL, it is crucial that any lid functional abnormalities, exposure, and severe aqueous tear deficiency, be addressed. Eyelid abnormalities, such as lagophthalmos, misdirected lashes, malpositioned or keratinized lid margins, should be operated on prior to KLAL. The prognosis for KLAL is poor in patients with an abnormal or absent blink reflex, as persistent epithelial defects may develop with risk of scarring and infection. Patients with severe aqueous tear deficiency lack essential tear components and may benefit from autologous serum drops used regularly after KLAL.

Patients, such as those after chemical injury, who have glaucoma or uncontrolled intraocular pressure, should undergo glaucoma drainage device implantation prior to KLAL, since multiple glaucoma medications may contribute to additional ocular surface toxicity (Fig. 42.3). Long-term use of topical corticosteroids to prevent graft rejection will also further aggravate any pre-existing glaucoma.