Fundamental of Cornea

Question 1

List a function of Cornea ?

Answer 1

1.Transparent.
2.Refeact light.
3.Contain IOP.
4.Provide a protective.
5.Reparative.

Question 2

Properties of cornea : Refeactive index ?

Answer 2

1.376

Question 3

Cornea Biology

Spehric
Curvature
Refractive power
Nutrients

Answer 3

Aspheric
- Curve
7.8 mm anterior
6.5 mm posterior

• Refract 43.25 ( 74% )
  Air - Tear 43.6
  Tear Cornea 5.3
  Cornea Aqueous -5.8
• Nutrients
  Glucose from Aqueous Humor
  Oxygen from tear film and peripheral from limbal

Question 4

Corneal thickness ?

Answer 4

520 - 540 mm
peripheral 670 mm

Question 5

Surface area of cornea ?
and size

Answer 5

1.3 cm2

vertical = 10-11
Horizontal = 11-12

Question 6

Descripe Optical Zone?

Answer 6

Central 1/3 is Optical zone
approx 5.4 mm
in lasik 6.5 mm

Question 7

Explain Zone of Cornea ?

Answer 7

Apical zone
- Central + Paracentral

Transitional zone
- Peripheral zone
- Greates flattening and asphericity

Optical zone
- 5.4 mm and for Lasik 6.5 mm

Question 8

Component of Cornea ?

Answer 8

• Water
• Collagen
• Protein
• Keratan
• Chondroitin / dermatan sulphate
• HA
• Salts

Question 9

Which component is abundant in cornea ?

Answer 9

Water : 78 %

Question 10

Describe collagen in cornea ?

Answer 10

Type 1 : 50-55 %
Type 3 : 1 %
Type 4 : 8-10 %
Type VI - 25-30 %

Question 11

Describe Corneal sensation ?

Answer 11

• High density nerve ending
• > 100 times at conjunctival
  Nerve - Posterior long ciliary nerve
• Stromal Plexus
• Subepithelial plexus
• Intra epithelial plexus

Question 12

Corneal Blood supply ?

Answer 12

Corneal is avascular tissue .

at peripheral 1 mm
- anterior ciliary vessels
so vascular is not in cornea but subconjunctiva surround cornea.

Question 13

describe Corneal Embryology

Answer 13

Wks 4 - Neuroectoderm - Optic Vesicle
Wks 5 - Surface ectoderm > Lens Placode
> Cornea and conjunctiva epithelium
Wks 6 : 1st wave > Corneal endothelium
Wks 7 : Corneal stroma and sclera

Month 2 : Eyelid fuse develop conjunctiva .
Month 3 : All corneal component present except bowmans layer.

Month 6 : Eyelid Open

At birth : Infant globe is 80 % of adult size .

Question 14

Embryonic origin of cornea ?

Answer 14

Corneal epithelium : Surface ectoderm
Bowman Layer : Mesenchyme
Stroma : Mesenchyme and neural crest
Descemet : Synthezide by Endothelium
Endothelium : Neural crest

Question 15

Fx of corneal epithelium

Answer 15

Barrier

Question 16

Fx of corneal stroma

Answer 16

Transparency

Question 17

fx of corneal endothelium

Answer 17

Barrier and metabolic pump