Stem cells versus keratoprostheses

Abstract

AbstractRoutine penetrating keratoplasty will not survive well in some circumstances, including harsh ocular surface environment, stem cell deficiency and chronic ocular inflammation. Fortunately, there have been advances to restore vision in these conditions in two directions: artificial keratoplasty and limbal stem cell transplantation. The recipient eye should have an intact lid mechanism and good tear film for stem cell transplantations. There may also be a need for future lamellar or penetrating keratoplasty with a chance for graft rejection. Treatment of unilateral limbal stem cell deficiency is relatively simple with three surgical options: Conjunctival Limbal Autograft (CLAU), Cultivated Limbal Epithelial Transplantation (CLET) and Simple Limbal Epithelial Transplantation (SLET). However, most patients have bilateral diseases like Stevens‐Johnson syndrome (SJS), aniridia and mucous membrane pemphigoid (MMP). In this scenario, an allogenic source for limbal stem cells is needed.Moreover, systemic immunosuppressive will be required to decrease the chance of rejection. Another option is Cultured Oral Mucosal Epithelial Transplantation (COMET) which usually provides less optimal visual acuity. The last option is keratoprosthesis (KPro). Many KPro devices have come and gone through, and two clear winners have emerged: Boston Keratoprosthesis KPro type I Osteo‐odonto‐keratoprosthesis, also known as the ‘OOKP’ OOKP is suitable for patients with severe dry eye and permanent lid damage. These patients should be excluded from any type of stem cell transplantation due to the inevitable chance of failure. However, Boston KPro type I may be considered as an alternative option for stem cell transplantation. Recent meta‐analysis for comparison of Keratolimbal Allograft (KLAL) and Boston KPro I in eyes affected by chemical burn has shown quite similar outcomes. Though, it should be mentioned that there are many limitations in included studies that make it difficult to reach an accurate conclusion. KPro has the advantages of shorter rehabilitation time and no need for systemic immunosuppression.Nevertheless, there is more chance of complications or loss of visual potential with KPro. Corneal surgeons should, in fact, be familiar with both options of KPro and stem cell transplantation to guide their patients towards the correct choice of treatment. The learning curve of such surgical techniques is steep. An extended follow‐up time is necessary to evaluate the safety of any method.