Optic neuropathies

Question 1

how long is the intraocular portion of the optic nerve?

2. The intraorbital
3. Intracannalicular
4. Intracranial

Answer 1

1. 1mm in length
2. 25 mm
3. 9mm
4. 16mm

Question 2

what are the 3 clinical pearls about the optic nerve?

Answer 2

1. Longer than orbital length (stretch)
2. Attached to dura in optic canal (site of injury)
3. 2 nerves form the chiasm - pathology there is chiasmopathy, optic neuropathy or both

Question 3

What is a disorder that preferentially affects ganglion cells?

Answer 3

Glaucoma - will respect horizontal midline

Question 4

What is the cup of the optic nerve composed of?

Answer 4

Dead tissue

Question 5

What part of the eye is mostly responsible for central visual acuity?

Answer 5

The maccula/fovea

Question 6

If you have a lesion of the right optic tract what defects do you expect?

Answer 6

1. RAPD in the left eye

2. Heminiopia

Question 7

Vast majority of optic neuropathies are…

Answer 7

Asymmetric

Question 8

What is the function of the RAPD?

Answer 8

Compares the amount of light perceived by each optic nerve

Question 9

What disease is RAPD present in?

Answer 9

1. Most optic neuropathies
   ALWAYS IN OPTIC NEURITIS
2. Diseases producing diffuse retinal dysfunction

Question 10

A lesion in the optic tract is enough to produce a RAPD why?

Answer 10

There is a 6% difference in the proportion of fibers that cross behind the chiasm

Question 11

Will patient with cataracts have a RAPD?

Answer 11

Never!

Question 12

How do you evaluate an optic nerve clinically?

Answer 12

Borders (are they sharp)
color (pink is normal, pallor is pathologic)
cup (yellow hole in the middle)
are there hemorrhages?

Question 13

What are Drusen

Answer 13

Small calcium deposits in the nerve

Question 14

What is Pepilledema?

Answer 14

Swelling of the optic nerve due to increased ICP, and swelling is BILATERAL

Question 15

What is the general flow chart from increased ICP to optic nerve swelling?

Answer 15

–> narrower spaces for CSF circulation, CSF excess around the optic nerve

Question 16

Papilledema is swelling of which portion of the optic nerve?

Answer 16

VISIBLE portion - secondary to increased ICP

Question 17

In papilledema is swelling often uni or bilateral?

Answer 17

bilateral

Question 18

When might papilledema appear unilateral?

Answer 18

If one of the nerves is atrophic

Question 19

What is the mechanism for papilledema?

Answer 19

Axoplasmic stasis - slowing axoplasmic flow at lamina cribrosa - transmitted along meningeal sheaths IN SUBARACHNOID SPACE

Question 20

What is the difference between papilledema and other optic neuropathies?

Answer 20

Central vision is NORMAL

Question 21

When does central vision fail?

Answer 21

when nerve swells and fluid accummulates around the nerve seeps into the maccula

Question 22

If disc swelling is chronic how will the disc appear?

Answer 22

Axons die, whitish color, cup disappears

Question 23

What is the first step in diagnosing papilledema?

Answer 23

MRI

Question 24

If MRI for suspected papilledema is normal what do you do?

Answer 24

Do a lumbar puncture and assess opening pressure and measure CSF composition -

Question 25

what is the most common inflammatory - infectious cause of optic neuropathy?

Answer 25

Syphillis, TB, viruses, fungi

Question 26

what is the most common inflammatory - non- infectious cause of optic neuropathy?

Answer 26

Demyelinating optic neuritis, sarcoid,

Question 27

Most common causes of optic neuropathies for patients under 50

Answer 27

Demyelinating neuropathies - usually UNIlateral visual loss, RAPD and pain on eye movement

Question 28

Most common causes of optic neuropathies for patients OVER 50

Answer 28

Ischemic - non arteritic (more common) and arteritic (rarer can lead to bilateral blindness)

Question 29

In patients under 50 with demyelinating neuropathies what proportion have optic nerve head swelling?

Answer 29

1/3 with variable swelling, | 2/3 with normal appearing nerve

Question 30

describe the visual loss in non-arteritic ischemic optic neuropathies

Answer 30

Altitudinal - respects horizontal midline due to hypo-perfusion of the optic nerve head

Question 31

What age group does giant cell arteritis affect?

Answer 31

Older patients over 70

Question 32

What are common systemic symptoms of giant cell arteritis ?

Answer 32

1. Jaw claudications 2. Headache 3. scalp tenderness 4. wt loss 5. shoulder pain and fatigue

Question 33

Which two inflammatory markers are high in giant cell arteritis?

Answer 33

ESR and CRP