Limbal Epithelial Stem Cell Deficiency

• Limbus contains small numbers of stem cells in the basal layer of the limbal epithelium

• These generate a continuous supply of daughter cells which differentiate to replenish the ocular surface

• Migrate in a centripetal fashion corresponding to the palisades of Vogt

• At least 25-33% of limbal stem cells must be functional to maintain a normal ocular surface

• Deficiency leads to:

  • Poor epithelization
  • Inflammation
  • Vascularisation
  • Scarring

Causes of deficiency

• Primary causes

  • Aniridia
  • Ectodermal dysplasia
  • Sclerocornea
  • Congenital erythrokeratodermia

• Secondary causes

  • Chemical injury
  • Thermal injury
  • Radiation
  • Contact lens wear
  • Preservative toxicity
  • Malignancy of the ocular surface
  • Neurotrophic cornea
  • PUK
  • Inflammation: MMP, atopic keratoconjunctivits, SJS, OCP, TEN

Clinical features

• Conjunctivalization of the cornea
• Persistent epithelial defects
• Vascularisation and calcification (peripheral pannus)
• Secondary infection
• Loss of palisades of Vogt
• Late staining (‘wave-like’)

Tests

• Diagnosis can be made on immunohistochemistry: mucin containing goblet cells in the corneal epithelium and absence of the normal differentiation markers

Management

• Depends on extent of deficiency and affect on visual axis

• Partial

  • Sectoral conjunctival epitheliectomy
  • Amniotic membrane grafts

• Total

  • Conjunctival limbal allograft from contralateral eye
  • Cultivated limbal corneal epithelial cells from contralateral eye
  • Amniotic membrane graft
  • Living related keratolimbal allograft
  • Cadaveric keratolimbal allograft

• Donors are screened for viruses, syphilis, human T-cell lymphoma and recipients will require immunosuppression