Corneal Epithelium

 Layers of the cornea:



  • Epithelium (Stratified squamous non-keratinized epithelium) 
  • Bowman's membrane - Acellular; does not regenerate
  • Stroma (Thickest layer) - The stroma can scar, but cannot regenerate
  • Dua's layer (Newly discovered, toughest layer)
  • Descemet's membrane- Ends peripherally as Schwalbe's ring; has regenerative potential
  • Endothelium (Most metabolically active layer)- does not regenerate 
The hydration level and transparency of the cornea is maintained mainly by the endothelial cells of the cornea. If the cornea becomes overhydrated, it begins to scatter light and gradually begins to lose its transparency Endothelium possesses Na+/K+ ATPase, which keeps the corneal stroma in a relatively dehydrated state. This helps in maintaining the transparency of the cornea.
Endothelial cells decrease in number with age.

Other factors contributing to the transparency of the cornea are as follows: 

  • Regular arrangement of corneal lamellae (Maurice theory)
  • Peculiar refractive index of corneal lamellae (Goldmann theory)
  • Avascularity of the cornea
  • A balance between the intraocular pressure (IOP) and swelling pressure

Note: Limbal stem cells are located at the corneoscleral limbus, in the palisades of Vogt. Deficiency may result in chronic epithelial defects and "conjunctivalization" of the cornea

Organisms that can penetrate the intact epithelium of the cornea can be remembered with the mnemonic-CHaNNeLS

  • Corynebacterium diphtheria
  • Haemophilus influenza;Haemophilus aegypticus 
  • Neisseria gonorrhea; Neisseria meningitidis
  • Listeria 
  • Shigella

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