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Ocular Physiology > 9- Corneal Function > Flashcards

9- Corneal Function Flashcards

(42 cards)

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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

Study These Flashcards
A

Bowman’s layer

18
Q

Bowman’s layer is resistant to this (3)

Study These Flashcards
A

Deformation
Trauma
Foreign bodies

19
Q

What is Dua’s layer?

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A

The 6th layer of the cornea

20
Q

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

21
Q

What cellular linkages held the epithelium together

22
Q

What cellular linkage holds the stroma together

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A

An ionic proteoglycans that pull water in

23
Q

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

24
Q

What is corneal hydration dependent on?

Study These Flashcards
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
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

Ocular Physiology (8 decks)

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