Keratolimbal Allograft

Indications and Contraindications

Keratolimbal allograft (KLAL) surgery involves transplantation of limbal stem cells on a corneal-scleral deceased donor rim and is indicated for eyes with severe bilateral limbal stem cell deficiency (LSCD) or unilateral disease in patients who fear damage to the healthy fellow eye or if there is no available or willing living donor. KLAL is suited for LSCD with no or minimal involvement of the conjunctiva (for example, aniridia, cases of iatrogenic LSCD, and soft contact lens wear–related LSCD. Patients with total LSCD will require a 360-degree KLAL, whereas those with sectoral disease may require only a sectoral graft. KLAL may also benefit patients with LSCD and mild-moderate conjunctival involvement (e.g., chemical injuries). Ideally, the eye is quieted prior to surgery. Patients with mild Stevens-Johnson syndrome (SJS) or ocular cicatricial pemphigoid (OCP), while still high risk, may be treated with KLAL, but the chances of graft survival are higher if inflammation can be controlled beforehand.

KLAL success decreases with increasing conjunctival inflammation. The prognosis is worst for those with active conjunctival inflammation (e.g., severe SJS, OCP, and recent chemical injuries) where conjunctival scarring, decreased mucin and aqueous tear deficiency, and potential for keratinization of the ocular surface are present. KLAL does not provide healthy conjunctiva; thus one might consider the “Cincinnati procedure” where KLAL grafts at 12 and 9 o’clock are combined with LR-conjunctival limbal allografts (LR-CLAL) or conjunctival limbal autografts (CLAU). KLAL surgery would be contraindicated in eyes with frank diffuse keratinization and severe aqueous tear deficiency with decreased reflex tearing.

Systemic immunosuppression is required in patients undergoing KLAL surgery to prevent rejection. Thus the procedure is contraindicated in the following patients: the elderly, those with a history of malignancy, or comorbidities such as obesity, diabetes, and uncontrolled hypertension, cardiac, renal, or liver disease. Also, since KLAL donor tissue is vascularized, donors with a history of metastatic cancer or melanoma should be excluded. ^,

Preoperative Considerations

The lack of a healthy and stable tear film is a poor prognosticator in ocular surface reconstruction. A proper tear film layer must be restored by correcting lid abnormalities, neurotrophic exposure, and severe aqueous tear deficiency. Eyelid abnormalities, such as lagophthalmos, misdirected lashes, and malpositioned or keratinized lid margins, should be reconstructed prior to KLAL. In patients with abnormal or absent blink, persistent epithelial defects may develop. Glaucoma must also be controlled, typically with a tube shunt device. Patients require long-term topical steroids for rejection prophylaxis and control of ocular surface inflammation, which can lead to steroid response glaucoma. Drop toxicity from glaucoma medications is also best avoided.

Uncontrolled severe inflammation is another poor prognosticator for KLAL. Favorable results were observed when amniotic membrane grafting was used in conjunction with KLAL in inflamed eyes. Amnion can suppress inflammation, facilitate epithelialization, and prevent cicatricial complications in acute chemical and thermal burns. Topical and systemic immunosuppression may also be initiated weeks to months prior to KLAL.