, CORNEA
5 layers: -
1. Epithelium
2. Bowman's Membrane
3. Stroma (thickest)
4. Descemet's Membrane
5. Endothelium
Note: New layer discovered between stroma and descemet's membrane. It is called Pre-descemet's Layer (PDL)
or Dua's layer. It is the 6th layer
· Injury to Bowman's membrane is irreversible & heals with a corneal scar.
· Damage to endothelium is also irreversible & causes corneal edema.
· Descemet's Membrane → Strongest layer
- only 1 organism that can penetrate intact membrane – Fungi
® Most important layer – Endothelium
o Maintains corneal transparency
o Pumps aqueous out of cornea
o No. of pumps depends on no. of cells in endothelium
o Each cell has 1.5 X 106 pumps.
o Normally endothelial cell count is 3000/mm2
o Each year no. of cells keep on decreasing
o Critical density – min no. of cells reqd. to keep cornea clear is 500 cells/mm2
If no. of cells ↓ than this –corneal edema
o For corneal donation min cells reqd – 2000 cells/ mm2
5 layers: -
1. Epithelium
2. Bowman's Membrane
3. Stroma (thickest)
4. Descemet's Membrane
5. Endothelium
Note: New layer discovered between stroma and descemet's membrane. It is called Pre-descemet's Layer (PDL)
or Dua's layer. It is the 6th layer
· Injury to Bowman's membrane is irreversible & heals with a corneal scar.
· Damage to endothelium is also irreversible & causes corneal edema.
· Descemet's Membrane → Strongest layer
- only 1 organism that can penetrate intact membrane – Fungi
® Most important layer – Endothelium
o Maintains corneal transparency
o Pumps aqueous out of cornea
o No. of pumps depends on no. of cells in endothelium
o Each cell has 1.5 X 106 pumps.
o Normally endothelial cell count is 3000/mm2
o Each year no. of cells keep on decreasing
o Critical density – min no. of cells reqd. to keep cornea clear is 500 cells/mm2
If no. of cells ↓ than this –corneal edema
o For corneal donation min cells reqd – 2000 cells/ mm2
