Wound healing

Question 1

Name the 5 stages of corneal wound healing and time they occur

Answer 1

1. Immediate phase
2. Leukocytic phase - at 30mins
3. Epithelial phase - At 1 hour
4. Fibroblastic phase
5. Endothelial phase - 24hrs

Question 2

Describe the Immediate phase of corneal wound healing.

Answer 2

• Retraction of DM and stromal collagen
• Anterior and posterior wound gaping of the wound
• Fibrin plug formation from aqueous fibrinogen
• Stromal oedema

Question 3

Describe the leukocytic phase of corneal wound healing

Answer 3

At around 30mins

PMN leukocytes from conjuctival blood vessels and aqueous invade the wound

Limbal wounds have an invasion of mononuclear cells from the limbal vessels - these can transform into fibroblasts at 12-24hrs

Question 4

Describe the Epithelial phase of corneal wound healing

Answer 4

Regenerates at the limbus and spreads across the cornea

Full thickness ingrowth is prevented by healthy endothelium

Question 5

Describe the Fibroblastic phase of corneal wound healing

Answer 5

Central corneal wound fibroblasts are derived from keratocytes

They produce collagen and mucopolysacharides to form an avascular matrix

Question 6

Describe the Endothelial phase of corneal wound healing

Answer 6

At 24hrs endothelial sliding allows for coverage of the posterior wound

Question 7

Describe the epidermal skin response to healing

Answer 7

1. Cell migration
2. Proliferation
3. Differentiation

Question 8

Describe the dermal skin response to healing

Answer 8

• Invasion of fibrin clot by buds of endothelial cells from intact vessels
• Form blood vessels within 1 week
• Macrophages and fibroblasts invade the wound
• Macrophages clear clots
• Fibroblasts produce collagen and glycosaminoglycans
• Myofibroblasts allow wound contraction by 1 week

Question 9

Describe the Conjunctiva response to healing

Answer 9

Can form granulation tissue

Epithelium heals by sliding, similar to cornea or skin

Question 10

Describe the Corneal epithelium response to healing

Answer 10

Regenerates at the limbus and spreads rapidly across the cornea

Question 11

Describe the Corneal Bowman’s layer response to healing

Answer 11

DOES NOT REGENERATE - heals by scarring

Question 12

Describe the Corneal Stroma response to healing

Answer 12

Keratocytes form fibroblasts to heal stromal wounds

Question 13

Describe the Corneal DM response to healing

Answer 13

Can regenerate if damaged - is elastic and recoil at the edge of a defecit

Question 14

Describe the Corneal endothelium response to healing

Answer 14

Fills in defects by sliding - therefore deposits secondary layers in DM

Question 15

Describe the Iris response to healing

Answer 15

• Fibrinolysis in the aqueous Inhibits fibrin clot formation –> hence the patency of iris defects if the wounds edges appose
• Reactive proliferation of the iris pigment epithelium can occur

Question 16

Describe the Lens response to healing

Answer 16

Epithelium responds to trauma by fibrous metaplasia

Question 17

Describe the Retina response to healing

Answer 17

• Glial cells replace damaged nerve cells
• These are derived from perivascular astrocyes and muller cells
• RPA can become metaplastic and proliferate to form fibrous tissue e.g. preretinal membranes

Question 18

Describe the Choroid and ciliary body response to healing

Answer 18

• Melanocytes do NOT proliferate after damage
• Granulation followed by scar tissue from fibroblasts

Question 19

Describe the Sclera’s response to healing

Answer 19

• Scars
• From episcleral and uveal fibroblasts

Question 20

Describe the ON response to healing

Answer 20

• Axonal loss and demyelination
• With reactive proliferation of glial cells and connective tissue cells