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Ocular Phys > Corneal Function > Flashcards

Corneal Function Flashcards

1
Q

What are the primary functions of the cornea?

A
  • refract light
  • transmit light
  • protects the internal parts of the eye
  • –fast healing
  • –minimize infection
  • –avoid injury/damage
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2
Q

What are the factors that affect refraction?

A
  • curvature of the anterior surface
  • curvature of the posterior surface
  • corneal thickness
  • change in refractive index from air to cornea
  • change in refractive index from cornea to aqueous
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3
Q

What is the total power of the eye?

A

~60D

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4
Q

What is the power of the cornea?

A

~40-48D

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5
Q

The cornea is __ the power of the eye

A

2/3 to 3/4

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6
Q

We want ___scattering, _____ distortion, and ___ transmission

A
  • decreased scattering
  • minimal distortion
  • maximal transmission
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7
Q

What are the 5 keys to maximize light transmission?

A
  • smooth optical surface
  • regular surface of epithelial cells
  • absence of blood vessels
  • correct spatial arrangement of collagen fibrils in the stroma
  • less than 1% light scatter
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8
Q

T/F: the cornea is one of the most sensitive tissues in the body

A

True

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9
Q

Where is the cornea most densely innervated?

A

The center

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10
Q

What nerve supplies the cornea?

A

Ophthalmic division of the trigeminal nerve

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11
Q

What is the normal CV of endothelium?

A

0.25

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12
Q

What shape of endothelial cells?

A

Hexagonal

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13
Q

T/F: endothelial cells grow back

A

False. Once they are gone, they are gone

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14
Q

The stroma makes up ___%of the cornea

A

90%

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15
Q

What is the regular size of collagen fibrils and the spacing?

And why is this important

A

Size: 300A
Spacing: 550A

Important for corneal transparency

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16
Q

The corneal transparency is optimal when the stroma is ____ water

A

75%-80%

17
Q

Tough layer of collagen and laminin that protects the underlying layers

A

Bowmans layer

18
Q

In PRK what layer do you destroy?

A

Bowmans layer

19
Q

What type of junctions does corneal epithelium have?

A

Tight junctions

20
Q

This layer has anionic proteoglycans that pull water in

A

Stroma

21
Q

This layer of the cornea slowly leaks fluid into the cornea

A

Endothelium

22
Q

Corneal hydration is dependent on?

A
  • barrier function of epithelium and endothelium
  • anionic characteristics
  • water and ion transport
23
Q

What are the major driving forces or water transport across epithelium and endothelium?

A

Cl- extrusion and Na absorption

24
Q

Small integral membrane proteins residing in the plasma membrane

A

Aquaporins

25
Q

What are some roles of aquaporins?

A
  • channels
  • cellular processes
  • cel migration
26
Q

What does high IOP do to water?

A

It can move excessive water into the stroma from the anterior chamber and overwhelm the endothelial transport system

27
Q

A minor abrasion of the epithelium causes the loss of?

A

Zonular occludens

28
Q

What are 2 results of a corneal abrasion?

A
  • edema

- haziness

29
Q

What does an epithelial edema do to VA?

A

Decreases VA

30
Q

When do corneal abrasion often heal?

A

24-48 hours

31
Q

When can epithelium be replaced?

A

In 2 weeks

32
Q

What are the 3 required nutrients of the cornea?

A
  • oxygen
  • glucose
  • glycogen
33
Q

The endothelium and endothelial consumes most of what nutrient?

A

Oxygen

34
Q

Inflammatory or infective condition that compromises the integrity of the epithelium.

A

Corneal ulcer

35
Q

Are the epithelium and endothelium hydrophobic or philic?

A

Hydrophobic

36
Q

T/F: epithelium is impermeable to ions

A

True

37
Q

T/F: lipid soluble materials can generally penetrate the cornea more easily

A

True

38
Q

Are the nerves in the cornea Myleinated or non?

A

Non myelinated

39
Q

As we get older how will this affect our CV?

A

The CV will increase because of the differences between the cells that die off

Ocular Phys (6 decks)

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