Andrea Y. Ang and Edward J. Holland

Introduction

The development of ocular surface stem cell transplantation (OSST) has greatly improved our ability to treat ocular surface disorders arising from limbal stem cell deficiency (LSCD). However, there is still a significant failure rate due to complications, such as stem cell rejection and concurrent disease, such as cicatrizing eyelid pathology and severe tear film abnormalities. This chapter will evaluate the reported success rates of conjunctival limbal autograft (CLAU), keratolimbal allograft (KLAL), living-related conjunctival limbal allograft (lr-CLAL), and ex vivo cultured limbal epithelial transplantation (CLET). We will discuss the complications that may arise and potential strategies to improve outcomes.

Outcomes

When evaluating success rates with different surgical techniques it is important that we compare ‘apples with apples.’ Factors that affect success rates include length of follow-up, preoperative diagnosis and severity of disease, and the immunosuppression (IS) regimen used. Most studies evaluating OSST outcomes are small retrospective case series, and care must be taken in comparing outcomes between studies, due to marked variation in the factors listed above. Most studies use ocular surface stability and improvement in visual acuity as outcome measures.

The length of follow-up should be at least 1 year to ensure that the surface stability is due to repopulation by transplanted stem cells and not from the donor corneal epithelium that can survive up to 13 months postoperatively.¹ Evaluation of shorter-term results may reveal a falsely high success rate initially. For example, an aniridic with conjunctivalization of the cornea and stromal scarring who undergoes a penetrating keratoplasty alone will initially experience dramatic improvement in vision. However, the ocular surface will inevitably fail when the donor epithelium sloughs and is replaced by conjunctivalization.

The preoperative diagnosis and severity of disease will affect outcomes. Schwartz et al.² classified ocular surface disease based on the extent of limbal stem cell loss and the presence or absence of conjunctival inflammation. Patients with partial limbal stem cell deficiency and no conjunctival inflammation (e.g. contact-lens induced keratitis) will be easier to treat and have better outcomes than patients with total limbal stem cell deficiency and active conjunctival inflammation (e.g. Stevens – Johnson syndrome). The preoperative diagnosis will also affect the visual acuity achieved postoperatively. For example, an aniridic with foveal hypoplasia will not have the potential to achieve the same vision postoperatively as a chemical injured eye with a normal retina. Thus improvement in visual acuity is important, but cannot be the sole factor used to compare outcomes between studies.

Studies utilize varying definitions of ocular surface stability. Most describe “failure” as the presence of a combination of the following signs of abnormal corneal epithelium: late fluorescein staining, persistent epithelial defects, neovascularization, conjunctivalization, and inflammation. Most describe “success” as the absence of the above signs and the presence of healthy transparent corneal epithelium. Between stability and failure is another category of ‘improved’ surface, defined as partial failure with areas of healthy corneal epithelium and areas of abnormal conjunctival epithelium on the cornea either in a mosaic or sectoral pattern. Figure 47.1 demonstrates partial limbal stem cell failure in a mosaic pattern.