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Ocular Physiology > 9- Corneal Function > Flashcards

9- Corneal Function Flashcards

1
Q

What is the primary function of the cornea

A

To refract light

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2
Q

What are some factors that affect refraction

A
  • 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
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3
Q

What is the approximate power of the eye

A

60 D

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4
Q

What is the power of the cornea

A

40-48 D

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5
Q

What is the 2nd primary function of the eye

A

To transmit light

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6
Q

How do you want the eye to transmit light

A

Minimal scattering
Minimal distortion
Maximum transmission

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7
Q

What are some factors that help to maximize the light transmission

A
  • 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
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8
Q

How does the cornea act to protect your long term vision

A

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

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9
Q

T/F the cornea is densely innervated

A

True

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10
Q

What is the cornea cornea sensitive to

A

Touch, temperature (especially cold), and chemicals

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11
Q

When you touch the cornea what happens

A

Involuntary lid closure

Corneal blink reflex (In on 5 out on 7)

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12
Q

What is the normal CV of the corneal endothelium

A

0.25

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13
Q

Stroma makes up what percent of the cornea

A

90%

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14
Q

When is corneal transparency optimal

A

When the stroma is 75-80% water

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15
Q

Lack of these structures helps maintain the transparency of the cornea

A

Blood vessels
Lymph vessels
Myelin sheaths

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16
Q

What is Bowman’s Layer composed of?

A

Collagen and laminin

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17
Q

PRK surgery destroys what layer of the cornea

A

Bowman’s layer

18
Q

Bowman’s layer is resistant to this (3)

A

Deformation
Trauma
Foreign bodies

19
Q

What is Dua’s layer?

A

The 6th layer of the cornea

20
Q

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

A

True

21
Q

What cellular linkages held the epithelium together

A

Epithelium

22
Q

What cellular linkage holds the stroma together

A

An ionic proteoglycans that pull water in

23
Q

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

A

Endothelium

24
Q

What is corneal hydration dependent on?

A
  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
Q

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

A

Ion flow and osmotic gradients

26
Q

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

A

Cl and Na

27
Q

What is Phthisis bulbs

A

A shrunken eye

28
Q

What are aquaporins

A

Small integral membrane proteins that reside in the plasma membrane

29
Q

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

A

Cloudy

30
Q

What is a corneal abrasion

A

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

31
Q

Most of the oxygen fro the cornea comes from this

A

Air

32
Q

What does healing of the cornea rely on?

A

Peptide growth factors

33
Q

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

A

True

34
Q

How long does it take for the cornea to heal?

A

24-48 hours

35
Q

How long does it take to replace the corneal epithelium

A

2 weeks

36
Q

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

A

Endothelium and epithelium

37
Q

T/F the epithelium can store glycogen

A

True

38
Q

What is a corneal ulcer

A

Inflammation of infection that compromises the integrity of the epithelium

39
Q

Are the epi/endothelium hydrophobic or hydrophillic?

A

Hydrophobic

40
Q

What layer of the cornea has a high water content

A

Stroma

41
Q

What layer is impermeable to ions

A

Epithelium

42
Q

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

A

Keratoconus
Ectasia
High/low pressure

Ocular Physiology (8 decks)

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