Boston-keratoprosthesis for Idiopathic Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD), a condition caused by the damage to limbal epithelial stem cells or disruption of limbal stem cell niches, causes opacification and vascularization of the cornea, giving rise to diminished vision, pain and photophobia. LSCD can be congenital but is usually acquired following chemical or thermal burns or can be secondary to inflammatory eye diseases. The Boston Type I keratoprosthesis (Boston Kpro) has been used to treat severe corneal vascularization following known causes of LSCD. Here we report our experience of Boston Kpro implantation as a staged primary procedure in treating a case of idiopathic total LSCD. A 50-year-old woman was referred to our tertiary eye care center, with a diagnosis of bilateral LSCD (Nov. 2010), complaining of blurred vision, photophobia, redness, and eye watering for 2 years (more symptomatic in the left eye). There was no history of atopy or vernal keratoconjunctivitis and no history of recurrent episodes of redness in the past. The clinical history was not suggestive of any particular etiology of LSCD. The patient was diagnosed with systemic hypertension 10 years previously and was on medical management. On examination, the best-corrected visual acuity (BCVA) in the right eye (OD) was 20/ 25 and was 20/100 in the left eye (OS). Right conjunctiva had pterygium on both the nasal and the temporal sides. Slit-lamp examination of the right cornea showed conjunctivalization and superficial vascularization in the periphery, the central cornea being clear (Figure 1A). Complete scarring and vascularization were observed in the left cornea, with only a small island of clear cornea inferiorly (Figure 1B). Limbal thickening was also seen in both sides (OS>OD). The examination of posterior segment revealed no abnormality. An OS ultrasound B-scan also showed no obvious abnormality of the posterior segment. Based on the clinical history and ocular features, a diagnosis of bilateral idiopathic LSCD (OD – partial LSCD with double pterygium and OS – total LSCD) was made. LSCD can be primary due to congenital causes, such as aniridia, sclerocornea, ectodermal dysplasia, multiple endocrine neoplasia, etc. or else it can be secondary due to direct stem cell loss, post-chemical injury, post-autoimmune conditions, such as ocular cicatricial pemphigoid, non-autoimmune disorders such as vernal keratoconjunctivitis, atopy, post-herpetic keratoconjunctivitis, iatrogenic such as post-surgery for pterygium or ocular surface squamous neoplasia, etc. However, our patient had no such history except for persistent redness in left eye, for which we kept a differential diagnosis of herpetic keratitis. The pattern of the conjunctivalization affecting both eyes could be that of an aniridic keratopathy with subtle changes in fovea and iris and absence of nystagmus. The patient was prescribed topical lubricants and advised to undergo a trial of prosthetic replacement of the ocular surface ecosystem (PROSE) in OS. After a 1.5-h challenge, the patient felt slightly better with PROSE and was advised for a 4-h challenge during her next visit. This patient could be considered for pterygium excision in OD. However, on presentation, pterygium was not affecting her vision. The patient also had improvement with PROSE lens in OS and hence any limbal graft procedure was not planned initially. The patient visited the PROSE clinic 5 months later (March 2011). During this visit, the patient felt no change with PROSE after an hour of challenge. Three months later (July 2011), a conjunctival nevus (1.5 × 1.7 mm) was noticed in the nasal aspect of OD. There was no evidence of ocular surface squamous neoplasia. At 14 months later (August 2012), OS BCVA worsened to light perception due to the progression of