9- Corneal Repair

Question 1

What 3 molecules direct corneal wound healing?

Answer 1

Integrins
Cytokines
Growth factors

Question 2

What is the role of corneal integrins

Answer 2

Facilitate interactions between cells

Matrix assembly

Cell adhesion

Sense change in extracellular environment and communicate to the cell

Question 3

What is the role of cytokines?

Answer 3

Signaling

Communication between cells

Control growth of corneal cells

Question 4

What is the role of growth factors

Answer 4

Promote proliferation

Induce migration

Maintain transparency

Question 5

How many layers thick is the epithelium

Answer 5

5-7

Question 6

What is the process of epithelial replacement

Answer 6

1. Stem cells divide
2. Become basal cells
3. Become wing cells
4. Become surface cells
5. Shed into tear film

Question 7

What is the turnover time for epithelium

Answer 7

7 days

Question 8

What process stops when there is corneal injury

Answer 8

Mitosis

Question 9

What is the process of epithelium wound healing

Answer 9

1. Mitosis stops
2. Cytokines and growth factors released from damaged cells
3. Hemidesmosomes dissemble
4. Cytoskeleton changes and the shape of the cell changes. Cells at the edge develop extensions and migrate to cover the wound.
5. Adhesion molecules pull cells as a sheet
6. Junctions formed between cells
7. Mitosis resumes. Proliferation and apoptosis
8. Hemidesmosomes come back

Question 10

How long does it take a small lesion of the epithelium to heal?

Answer 10

24-48 hours

Question 11

What long does it take for basement membrane damage to heal

Answer 11

Several months

Question 12

What is recurrent corneal erosion

Answer 12

When the corneal epithelium sloughs off due

Question 13

What are the 2 causes of corneal erosion

Answer 13

1. Poor adhesion between epith and BM

2. Poor adhesion between BM and underlying tissue

Question 14

When does corneal erosin occur

Answer 14

After I complete healing of an abrasion OR a dystrophy

Question 15

What is the treatment for corneal erosion

Answer 15

Artificial tears
Oph. Ab
Bandage CL
Ant. Stromatolites micropuncture
Superficial keratectomy 
PTK

Question 16

What is bowmans layer

Answer 16

Acellular layer
Made of collagen
Resistant to penetration and damage

Question 17

T/F Does Bowmans Layer regenerate?

Answer 17

No

Question 18

What heals Bowmans Layer

Answer 18

It replaced by stomach scar tissue or by epithelium

Question 19

What is the stroma

Answer 19

90% of corneal thickness

Composed of collagen fibrils, keratocytes, and ground substance

Question 20

What is the healing process of the stroma

Answer 20

1. Keratocytes increase in number
2. Some become myofibroblasts
3. Wound bed contracts
4. Wound covered by epithelium

Question 21

What are changes that occur in repaired stroma

Answer 21

The collagen is larger and alignment is not as precise

Increased probability of scarring

Question 22

What happens after the stroma is healed

Answer 22

Myofibroblasts undergo apoptosis or revert back to keratocytes

Question 23

How long does it take for the stroma to repair

Answer 23

Months

Question 24

What is Descemets Membrane

Answer 24

Basement membrane of endothelium

Made of collagen fibrils

Thickens throughout life

Question 25

How is Descemets Membrane repaired

Answer 25

Regenerated by stromal keratocytes and endothelium

Question 26

What is the endothelium

Answer 26

Single layer
Flat cells
80% hexagonal
20% heptagonal 
Little mitosis occurs

Question 27

What is the healing process of endothelium

Answer 27

1. Neighboring cells enlarge and flatten to cover area of loss (decreasing cell density)
2. Cells removal into polyhedral shape
3. Ppm and barrier fxns re-established