L9 - Corneal defects

Question 1

What is the function of the cornea?

Answer 1

1. Aid sight - transparency and refractive power

2. Eye protection

Question 2

How is the cornea structured?

Answer 2

Epithelium
Stroma
Endothelium

Question 3

What is the epithelium?

Answer 3

Outermost layer, highly innervated. Acts to prevent fluid loss, create a barrier and rapidly respond to wounds. 3 layers of cells:
- Superficial (outermost), wing and basal (innermost)

Question 4

What is the stroma?

Answer 4

90% of thickness, mainly acellular, collagens, proteoglycans and glycoproteins.
Functions - strength and transparency.
Cells - keratinocytes

Question 5

What is the endothelium?

Answer 5

Single cell layer, metabolically active, maintains stromal hydration.
Allows solutes and nutrients from aqueous humour into the cornea
Active pump to draw water from the stroma

Question 6

Is the cornea innervated/vascularised?

Answer 6

Most densely innervated structure in the body but is completely avascular

Question 7

Current regenerative therapies

Answer 7

Corneal transplantation

Keratoprosthesis - for repeated failed grafts. Need lifelong antibodies

Question 8

Approaches for corneal epithelium

Answer 8

LIMBAL EPITHELIAL SC
- Between sclera and cornea
- Asymmetric division
- Cultured for transplant
Cells from mucosa can also be used is both eyes are damaged ( there is increased risk of vascularisation)

Question 9

Holoclar

Answer 9

Cultured autologous limbal SC for TP

74/105 patients: stable corneal surface, little/no ingrown BV, decreased pain and inflammation and better vision

Question 10

Approaches for stromal injury

Answer 10

Biomaterial approach
- Acellular implant - promote repop by host cells
Cell-based approach
- Limbal stromal SC

Question 11

Challenge for TE in cornea

Answer 11

Epithelium - continuous replacement, maintain integrity as barrier, transparency
Stroma - high tensile strength, transparency

Question 12

Endothelial regeneration

Answer 12

DOESN’T NORMALLY REGENERATE
Limited prolif ability in culture
Can be immortalised but this has implications
RECENT - can be derived from PSCs