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Ocular Block 8 > Optic Nerve > Flashcards

Optic Nerve Flashcards

1
Q

Where do the ganglion cell bodies reside

A

Retinal ganglion cell layer

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2
Q

Where do the dendrites of the ganglion cells reside

A

IPL

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3
Q

Where do the axons of the ganglion cells reside

A

RNFL

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4
Q

How many retinal ganglion cells are there

A

1.2 to 22 mill

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5
Q

These are the output cells of the retina that convey all of the processed visual information to the brain

A

Retinal ganglion cells

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6
Q

How is the RNFL formed

A

By the axons of the retinal ganglion cells.

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7
Q

What is the average diameter of optic nerve fibers

A

1 micron

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8
Q

Where is the deep plexus from CRA

A

INL

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9
Q

Where is the superficial plexus of CRA

A

RNFL

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10
Q

A nerve fiber tract of the central nervous system

A

Optic nerve

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11
Q

Why is the optic nerve prone to many of the same neurological diseases as the brain

A

It is a nerve fiber tract of the CNS

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12
Q

What kind of neurological diseases can affect the optic nerve

A

All of them really, but especially demyelinating diseases such as MS

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13
Q

What are the different parts of the optic nerve

A
  1. Intraocular
  2. Infraorbital
  3. Intracanalicular
  4. Intracranial
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14
Q

What is the approxiamte length of the optic nerve

A

4-5cm

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15
Q

What part of the optic nerve do you see on a fundus exam

A

Intraocular

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16
Q

What part of the optic nerve is the longest

A

Infraorbital

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17
Q

What part of the optic nerve is when it passes through the optic canal and before it meets at the chiasm?

A

Intracanalicular

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18
Q

What part of the optic nerve is where it joins at the optic chiasm

A

Intracranial

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19
Q

What is the smallest part of the optic nerve

A

Intraocular part of the optic nerve

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20
Q

What are some things you look at when looking at the ONH

A 
Size 
Shape
Color
Vessels
Border, contour
Lamina cribrosa
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21
Q

Shape of the optic disc

A

Oval shape and is longer in the vertical dimension vs horizontal

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22
Q

What is the diamter of the ONH in the vertical direction

A

1.9mm

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23
Q

What is the diamter of the ONH in the horizontal direction

A

1.5mm

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24
Q

How is the optic cup displaced compared to the disk

A

Temporally

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25
Q

Optic cup and nerve fibers

A

The optic cup is devoid of nerve fibers

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26
Q

Where can you sometimes see the lamina cribrosa

A

Optic cup

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27
Q

Contains the nerve fibers and it located between the margin of the optic disk and cup

A

Neuroretinal rim

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28
Q

How does the thickness of the neuroretinal rim go

A

Follows the ISNT rule

  • inferior should be thickest
  • temporal should be thinnest
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29
Q

Compares the diamter of the cup with the overall diameter of the optic disc and is used to assess changes in neuroretinal rim thickness over time

A

Cup to disc ratio

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30
Q

What side of the cup do the CRA/CRV emerge

A

Nasal side

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31
Q

Is the CRA or the CRV usually more nasal

A

Artery

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32
Q

What are the two different portions of the intraocular portion of the opticnerve

A

Prelaminar

Laminar/scleral

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33
Q

What is considered the prelaminar part of the intraocular portion of the optic nerve

A

Retinal layer

Choroidal layer

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34
Q

What is considered laminar/scleral portion of the intraocular portion of the optic nerve

A

Scleral ayer (lamina cribrosa)

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35
Q

What does glaucoma do to lamina cribrosa

A

Causes the lamina to pinch the nerves that are going through it and kills them

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36
Q

PR and the optic nerve

A

There are no PR in the ONH so this is a blind spot

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37
Q

Retinal layer of the pre-laminar part of the intraocular portion of the optic nerve

A

The optic disc is located in the retinal layer because it is the axonal fibers of the retina ganglion cells that converge to form it

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38
Q

The choroidal layer of the pre laminar layer of the intraocular portion of the optic nerve

A

At the level of the choroidal tunic. The lamina cribrosa begins in the outermost portion of the choroidal layer of the optic nerve and continues into the scleral layer of the optic nerve

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39
Q

What are the glial borders around hte optic nerve

A
  • meniscus of Kuhnt
  • ILM of Elschnig
  • border tissue of Elschnig
  • border tissue of jacoby
  • intermediate tissue of Kuhnt
  • ILM of retina
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40
Q

What are the glia cells involved in the glial border around the optic nerve

A

Astrocytes. There are no muller cells here because there is no retina here

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41
Q

What are the glial borders around the optic nerve that are considered to be retinal layer

A
  • meniscus of Kuhnt
  • ILM of Elschnig
  • ILM of retina
  • intermediary tissue of kuhnt
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42
Q

Glial plaque (astrocytes) that lines the optic cup

A

Meniscus of Kuhnt

43
Q

Peripheral continuation of meniscus of Kuhnt that lines surface of neuroretinal rim

A

ILM of Elschnig

44
Q

Formed by the footplates of muller cells, continuous with ILM of Elschnig

A

ILM or retina

45
Q

Glial tissue that separates outer retina from bundles of optic nerve fibers

A

Intermediary tissue of Kuhnt

46
Q

What are the glial borders of the choroidal layer of the intraocular portion of the optic nerve

A

Border tissue of Elschnig

Border tissue of jacoby

47
Q

Collagen separating choroid from bundles of optic nerve fibers

A

Border tissue of Elschnig

48
Q

Glial tissue situated between border tissue of Elschnig and bundles of optic nerve fibers. It merges with intermediary tissue of Kuhnt

A

Border tissue of jacoby

49
Q

Remnant of meniscus of Kuhnt tissue surrounding the hyaloid vasculature during development

A

Bermeisters papilla

50
Q

Optic cup size at birth

A

Is related to disc size and resorption of glial tissue surrounding hylaoid vasculature

51
Q

What is to be said about the cups of large discs

A

Large discs have large cups. Don’t always assume a large cup is glaucomatous, always make sure its not just a large cup

52
Q

Scleral layer of the laminar portion of hte optic nerve

A

The scleral layer is continuous with the scleral tunic of the eyeball and is the layer in which the lamina cribrosa resides

53
Q

What layer does the lamina cribrosa reside

A

Scleral layer of the laminar portion of the optic nerve

54
Q

Myelination of optic nerve

A

There is only myelin post-laminar, oligodendrocytes lay down myelin here but none in the eye

55
Q

Myelin in the eye

A

Not normally any myelin in the eye, but some people are born with a little bit in there and you can see it on a fundoscopic exam. Won’t affect vision too much, just document and move on

56
Q

Why does the diameter of the retrobulbar optic nerve increase

A

Myelin

57
Q

Astrocytes in retrobulbar optic nerve

A

Form thick columns that keep the axonal fibers organized into bundles in the optic nerve. Can be IDed on histology because their nuclei form long columns between the axonal bundles

58
Q

How long is the infraorbital portion of the optic nerve

A

25mm

59
Q

Where is the intraorbital portion of the optic nerve

A

From the sclera to the apex of the orbit

60
Q

What is responsible for the increase in size of the optic nerve from 1.5mm to 3-4mm in diameter in the intraorbital portion of the optic nerve

A

Myelin

61
Q

Where does the optic nerve pass through at the apex of the orbit

A

Passes through the optic canal in the lesser wing of the sphenoid

62
Q

Where is the optic nerve sheath?

A

Parts of the optic nerve that reside outside of the eye

63
Q

What is the optic sheath comprised of

A

Dura mater, arachnoid mater, and pia mater

All three of these layers fuse with the retina
CSF is contained within the subarachnoid mater

64
Q

Bilateral swelling of the optic disc caused by elevated ICP within the subarachnoid space

A

Papilledema

65
Q

How does papilledema present

A

Indistinct margins of the disc, engorged venous blood vessels, small peripalliary hemorrhages, and loss of spontaneous venous pulsation

66
Q

Why is it that the veins are the vessels to get engorged in papilledema

A

More likely to become damaged because they are thinner than arteries. They cant get the blood back out of the retina so it is stuck in there

67
Q

What causes venous pulsation

A

Pressure differential between IOP and ICP

68
Q

When is venous pulsation important

A

When you have documented that someone has SVP, but at some point do not have it. Indicative of increased ICP

69
Q

What is the difference between papilledema and pseudopapilledema

A

Papilledema is cause by high ICP

Pseudopapilledema does not have increased ICP, but it is more ONH drusen that makes the ONH appear odd

70
Q

Cause of pseudopapilledema

A

Buried disc drusen. These small tumors develop within the substance of the nerve tissue and can lead to an elevated disc, they also may lead to a loss of VF or central acuity

71
Q

What is the difference in appearance of papilledema and pseudopapilledema

A

Pseudopapilledema has defined borders and papilledema does not. Also pseudo has no venous engorgement

72
Q

How long is the intrcanalicular portion of the optic nerve

A

5mm

73
Q

How does the intrcanalicular portion of the optic nerve pass

A

Through the lesser wing of the sphenoid bone via the optic canal and is accompanied by the ophthalmic artery

74
Q

How does the ophthalmic artery sit relative to the optic nerve

A

Inferolateral

75
Q

What is the subarachnoid space of the optic nerve continuous with

A

The subarachnoid space of the brain

76
Q

Where does the central retinal artery pierce the optic nerve

A

12-15mm from the sclera

77
Q

How does the ciliary ganglion sit relative to the optic nerve

A

Just lateral to it

78
Q

Where does the optic nerve reside within in the apex of the orbit

A

Common annular tendon of Zinn

79
Q

What are the nerves outside of the annular tendon of zinn

A

Lacrimal nerve
Frontal nerve
Trochlear nerve

80
Q

What nerves are within the annular tendon of Zinn

A

Superior oculomotor nerve
Nasociliary nerve
Inferior oculomotor nerve
Abducens nerve

Optic nerve

81
Q

How long is the intracranial portion of the optic nerve

A

10mm

82
Q

What does the optic nerve do once it leaves the optic canal

A

Passes within the subarachnoid space of the brain where it will merge with nerve fibers from the contralateral optic nerve at the optic chiasm

83
Q

Where is the optic chiasm located

A

Floor of the 3rd ventricle

84
Q

What is the branch of the ICA that supples the optic nerve

A

Ophthalmic artery

85
Q

How does the central retinal artery run

A

Along the optic nerve, then at about 1.25cm behind the eyeball through lamina cribrosa

86
Q

What does the pia do for the optic nerve

A

Supports it

87
Q

What is the retinal layer of the optic disc supplied by

A

Retinal capillaries (non fenestrated)

88
Q

What does the choroidal layer of the optic nerve get its blood supply from

A

Only the peripheral portion of the lamina choroidalis receives some nutrition via diffusion from the surrounding choroidal vasculature

89
Q

What are the lamina cribrosa and adjacent pial plexus supplied by

A

The arterial circle of Zinn-Haller, which is supplied by the short posterior ciliary arteries

90
Q

What is the connection between the retinal and posterior ciliary arterial systems

A

None

91
Q

Venous drainage of the optic nerve

A

Central retinal vein

92
Q

Where does the central retinal artery enter the eye

A

Through an aperture in the lamina cribrosa of the optic disc

93
Q

How is the CRA positioned

A

Slightly nasal in the nerve and nasal to the central retinal vein

94
Q

Why is it important to notice that the vessels emerge nasally in the optic disc

A

Some disorders can nasalize the vessels, meaning they will be pushed much more nasally than normal

95
Q

Weiss’ ring

A

Vitreous has pulled away from the optic nerve

96
Q

ISNT rule

A

Inferior neuroretinal rim is thickest and the temporal neuroretinal rim is the thinnest

97
Q

Tilted disc

A

Some people have an obliquely placed optic nerve, which means that certain parts of the disc are actually much flatter than others

98
Q

Scleral crescent

A

Choroid and RPE don’t reach all the way to ONH margin, sclera showing through, whitish

99
Q

Peripapillary crescent

A

RPE stops before the choroid does, appears darker

100
Q

What happens if there is a disc with no cup

A

Nothing, can be completely normal. Just document

101
Q

When is it OK to have a large cup

A

When you have a large disc. As long as it follows the ISNT rule, its fine

102
Q

How can you tell if someone is glaucomatous or if they have large cups

A

Large cups will follow the ISNT rule

-glaucomatous will not follow the ISNT rule and you can see the lamina cribrosa through it

103
Q

What is one of the earliest signs of glaucoma

A

Inferior notch

104
Q

What would cause pallor in one eye but not the other

A

Ischemic optic neuropathy in that one eye or some sort of compression on the optic nerve of that eye

Ocular Block 8 (6 decks)

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