Abstract:
The human cornea requires a smooth, transparent, robust and renewable surface to maintain its key optical and protective functions. The corneal epithelium is maintained by a local population of “stem cells”, which although not truly pluripotent, are capable of self-regeneration by asymmetric division. These cells are located at the limbus - the region where the conjunctiva-covered sclera meets the cornea. The widely accepted “XYZ” hypothesis of corneal epithelial maintenance postulates that limbal stem cells give rise to transient amplifying cells, which migrate and mature in both a centripetal and anterograde fashion towards the corneal surface. Many diseases and injuries to the limbus can cause the loss of this vital reservoir of cells and, due to subsequent surface irregularity and loss of corneal transparency, result in severe visual impairment, including blindness. Indeed, in some regions of the developing world corneal blindness may be more prevalent than cataract blindness. Such corneal blindness was previously irreversible, but over the past 30 years it has been possible to improve or restore vision using limbal “stem cell” transplants. Pioneering techniques required large tissue grafts that could compromise the donor eye, but recent developments allow the harvesting, ex-vivo expansion and transplantation of limbal stem cells from relatively small biopsies. In this review we outline limbal stem cell physiology in health and disease, describe our surgical approach to limbal stem cell deficiency, illustrate results of this intervention in our practice, and consider current and future advances in this arena.
