10 - non-arteritic anterior ischemic optic neuropathy (NAAION)

What causes posterior ischemic optic neuropathy?

1. after severe blood loss

2. post surgery

3. anemia

4. radiation to ON

What does posterior ischemic optic neuropathy look like?

no apparent disc swelling → eventual pale nerves

can be uni or bilateral

what imaging is done in patients with PION?

consider carotid Doppler to rule out internal carotid artery stenosis → prevent future stroke

What is the pathogenesis of NAAION?

insufficiency in one or more short posterior ciliary arteries and subsequent infarction of ganglion cell axons

what does axonal edema in a structurally crowded optic disc cause?

apoptically induced retinal ganglion cell death

Who gets NAAION?

age 40-80

any gender

Caucasians

What is the most common cause of sudden vision loss due to optic nerve disease in patients over 40?

NAAION

What are risk factors for NAAION?

1. systemic vascular disease → chronic HTN, diabetes, atherosclerotic disease

2. small crowded disc

3. nocturnal hypotension

4. smoking

5. sleep apnea

6. ED drugs

What are the visual signs of NAAION?

1. VAs → majority 20/40 or better or 20/200 or worse

2. decrease CV/red desaturation

3. RAPD

4. NF bundle defects → esp inferior altitudinal

What is the fundus appearance of NAAION?

1. pale or hyperemic swollen ONH → often sectoral swelling, sup > inf

2. may have peripapillary hemes

3. constricted retinal arterioles

What tests can you order to diagnosis NAAION?

ESR/CRP to rule out AAION

what diagnostic imaging can be used for NAAION?

FANG → may show delayed filling of ON

OCT → may show swelling of RNFL in acute stages, reductions in RNFL after resolution

What is the time course of vision loss + recovery in NAAION?

vision loss progresses over 48 hours → then is stable and irreversible (42% have improvements in vision)

What is the time course of fundus appearance in NAAION (what resolves and what remains)?

disc edema and hemes resolve in 2-8 weeks

atrophy and NFL loss remain

What is the recurrence rate of NAAION?

5%

What is the chance of having a NAAION attack in the other eye?

25% in 3 years

25-50% in 5 years

>50% in 10 years

What are the differentials for NAAION or AAION?

1. atypical optic neuritis due to infection or sarcoid

2. infiltrative optic neuropathy

3. diabetic papillitis

What are the rules for a safe NAAION diagnosis (what characteristics must be met to diagnose NAAION)?

ALL MUST BE TRUE:

1. >40 years old

2. vascular risk factor + no history of cancer

3. unilateral + sudden vision loss that has not worsened after a week

4. (+) RAPD and ONH swelling

5. any VF loss in affected eye

6. no eye pain or other neuro symptoms, no hard exudates/inflammation, normal exam in other eye

What is the management for NAAION?

1. rule out GCA/AAION

2. refer to PCP for blood tests for vascular disease

3. follow up in 2-4 weeks

What should be true at the follow up for NAAION? What do you do after?

vision loss should not have progressed

if stable, see again in 3 months

What is the treatment for NAAION?

no proven treatment → but steroids and Brimonidine (until disc swelling is resolved) are often used

What lifestyle changes should be made for someone with NAAION?

1. stop smoking

2. manage cardiovascular disease, sleep apnea

Why did we try optic nerve sheath fenestration for NAAION?

relieve pressure at the nerve head to increase blood flow to optic nerve

Why don't we do optic nerve sheath fenestration for NAAION?

not effective and is even harmful (results in worse acuity)