9- Corneal Function Flashcards Preview

Ocular Physiology > 9- Corneal Function > Flashcards

Flashcards in 9- Corneal Function Deck (42):
1

What is the primary function of the cornea

To refract light

2

What are some factors that affect refraction

-Curvature of anterior surface
-change in refractive index from air to cornea
-corneal thickness
-curvature of the posterior surface
-change in refractive index from cornea to aqueous

3

What is the approximate power of the eye

60 D

4

What is the power of the cornea

40-48 D

5

What is the 2nd primary function of the eye

To transmit light

6

How do you want the eye to transmit light

Minimal scattering
Minimal distortion
Maximum transmission

7

What are some factors that help to maximize the light transmission

-Smooth optical surface
-Regularly of surface epithelial cells
-Absence of blood vessels
-Arrangements of correct partial arrangement of collagen fibrils in stroma
-Less than 1% light scatter

8

How does the cornea act to protect your long term vision

Minimize risk of infection
Prevent damage to retina
Avoid penetration injury
Swift healing

9

T/F the cornea is densely innervated

True

10

What is the cornea cornea sensitive to

Touch, temperature (especially cold), and chemicals

11

When you touch the cornea what happens

Involuntary lid closure

(Corneal blink reflex (In on 5 out on 7))

12

What is the normal CV of the corneal endothelium

0.25

13

Stroma makes up what percent of the cornea

90%

14

When is corneal transparency optimal

When the stroma is 75-80% water

15

Lack of these structures helps maintain the transparency of the cornea

Blood vessels
Lymph vessels
Myelin sheaths

16

What is Bowman's Layer composed of?

Collagen and laminin

17

PRK surgery destroys what layer of the cornea

Bowman's layer

18

Bowman's layer is resistant to this (3)

Deformation
Trauma
Foreign bodies

19

What is Dua's layer?

The 6th layer of the cornea

20

T/F Dua's layer is able to withstand high pressures

True

21

What cellular linkages held the epithelium together

Epithelium

22

What cellular linkage holds the stroma together

An ionic proteoglycans that pull water in

23

This layer of the cornea slowly leaks fluids into the cornea and stroma

Endothelium

24

What is corneal hydration dependent on?

1. Barrier function of epithelium and endothelium
2. Anionic characteristics of molecules in stroma
3. Water and ion transport in epithelial and endothelial cells

25

What is the movement of water out of the cornea mediated by?

Ion flow and osmotic gradients

26

What molecules are the major driving force for water transport across the epithelium and endothelium

Cl and Na

27

What is Phthisis bulbs

A shrunken eye

28

What are aquaporins

Small integral membrane proteins that reside in the plasma membrane

29

If IOP is very high in the eye the cornea will take on what look

Cloudy

30

What is a corneal abrasion

A minor abrasion of the epithelium that causes a loss of the zonular occludens

31

Most of the oxygen fro the cornea comes from this

Air

32

What does healing of the cornea rely on?

Peptide growth factors

33

T/F the cornea is the fastest healing tissue in the body

True

34

How long does it take for the cornea to heal?

24-48 hours

35

How long does it take to replace the corneal epithelium

2 weeks

36

What consumes the most oxygen: endothelium, epithelium, or stroma?

Endothelium and epithelium

37

T/F the epithelium can store glycogen

True

38

What is a corneal ulcer

Inflammation of infection that compromises the integrity of the epithelium

39

Are the epi/endothelium hydrophobic or hydrophillic?

Hydrophobic

40

What layer of the cornea has a high water content

Stroma

41

What layer is impermeable to ions

Epithelium

42

What are some conditions that cause loss of stability and structure in the cornea

Keratoconus
Ectasia
High/low pressure