The Cornea

Question 1

Function of the cornea

Answer 1

To refract light entering the eye

Question 2

Width

Answer 2

11.6mm

Question 3

Height

Answer 3

10.6mm

Question 4

Centre thickness

Answer 4

0.5mm

Question 5

Edge thickness

Answer 5

0.7mm

Question 6

Anterior Radius

Answer 6

7.8mm

Question 7

Posterior Radius

Answer 7

6.7mm

Question 8

Dioptric power

Answer 8

+42.00D

Question 9

Refractive Index

Answer 9

1.376

Question 10

Thickness: Epithelium

Answer 10

50um

Question 11

Thickness: Bowman’s Layer

Answer 11

10um

Question 12

Thickness: Stroma

Answer 12

450um

Question 13

Thickness: Dua’s Layer

Answer 13

6um

Question 14

Thickness: Decement’s membrane

Answer 14

4-10um

Question 15

Thickness: Endothelium

Answer 15

5um

Question 16

3 cells located in the epithelium

Answer 16

Squamous
Wing
Columnar

Question 17

What makes up the bulk of the Stroma

Answer 17

Fibroblast (stellate cells)

Collagen fibrils

Question 18

What nerve supplies innervation

Answer 18

Trigeminal Nerve – CN 5

Question 19

What is the most sensitive part of the cornea

Answer 19

The centre - decreases with age

Question 20

Day time source of nutrients

Answer 20

Tear film
Aqueous
Limbal blood vessels

Question 21

Night time source of nutrients

Answer 21

Aqueous
Limbal blood vessels
Palpebral conjunctiva

Question 22

Layer 1 of the Cornea (top to bottom)

Answer 22

The Epithelium

Question 23

Layer 2 of the Cornea (top to bottom)

Answer 23

Bowman’s Layer

Question 24

Layer 3 of the Cornea (top to bottom)

Answer 24

Stroma

Question 25

Layer 4 of the Cornea (top to bottom)

Answer 25

Dua’s Layer

Question 26

Layer 5 of the Cornea (top to bottom)

Answer 26

Decement’s Membrane

Question 27

Layer 6 of the Cornea (top to bottom)

Answer 27

The Endothelium

Question 28

Another name for Bowman’s Layer

Answer 28

Anterior Limiting Lamina

Question 29

Another name for Decement’s Membrane

Answer 29

Posterior Limiting Lamina

Question 30

Function: The Epithelium

Answer 30

Provides protection due to thickness and sensitivity – causes reflex lid closure and lacrimation.

Provides route for metabolic exchange and a smooth surface for refraction

Question 31

Function: The Stroma

Answer 31

Provides strength stability and protection for internal structures.

Question 32

Function: The Endothelium

Answer 32

Regulates corneal hydration and transports metabolites from aqueous to stroma.

Question 33

Cornea vascular or avascular?

Answer 33

Avascular - meaning no blood vessels

Question 34

What makes the cornea transparent? (5 facts)

Answer 34

Avascular

Equal spacing of collagen fibrils (stromal lamellae) creates diffraction grating

Spacing between fibrils less than a wavelength apart

No Schwann cells in superficial layers

Cornea hydration is strictly regulated

Question 35

Location (what is the cornea in contact with): Anteriorly

Answer 35

Tear film
Atmosphere
Conjunction of eyelid

Question 36

Location (what is the cornea in contact with): Periphery

Answer 36

The limbus – where it connects to the conjunctiva, sclera, ciliary body, iris and fascia of the globe.

Question 37

Location (what is the cornea in contact with): Posteriorly

Answer 37

Aqueous Humour

Question 38

Pathologies of the cornea (name 4)

Answer 38

Keratoconus

Arcus Senilus

Keratitis - Viral/Bacterial

Acanthameoba