AAION AND NAION

Question 1

What are the symptoms of AAION?

Answer 1

• Rapid onset and profound unilateral visual loss
• Periocular pain (common)
• Headache (most common), localised to frontal, occipital, or temporal areas, or can be generalised
• Scalp tenderness, first noticed when combing hair
• Jaw claudication (cramp-like pain on chewing) – virtually pathognomonic –> Caused by ischaemia of the masseter muscles
• Non-specific: fever, LOW, LOA, night sweats, malaise, joint and muscle pain

Question 2

What are the signs of AAION?

Answer 2

• Decreased visual acuity, typically severe: < 20/200 in over 60% of patients, commonly to light perception (LP) or worse
• RAPD
• Chalky-white pallor of optic disc with oedema (which may be severe) – hallmark of AAION
• Also may not uncommonly present with hyperaemic swelling, which is indistinguishable ophthalmoscopically from NAION

Question 3

What are the investigations of AAION?

Answer 3

• ESR: often very high; > 60 mm/hr
• CRP: invariably raised
• FBC: reactive thrombocytosis (elevated PLT), anaemia of chronic inflammation (normocytic normochromic anaemia)
• Temporal artery biopsy (TAB) – diagnostic: transmural granulomatous inflammation, disruption of the internal elastic lamina, proliferation of the intima, and gross narrowing of the lumen, chronic inflammatory infiltrates with giant cells

Question 4

What is the management of AAION?

Answer 4

Treatment of AAION is aimed at preventing blindness of the fellow eye, as visual loss in the index eye is unlikely to improve even with immediate treatment; the second eye may still become involved in 25% despite early steroid administration.

• (Basically, early high dose corticosteroids, then oralise and taper)
• teroid treatment should be accompanied by bone and gastrointestinal protection, e.g. a weekly bisphosphonate, calcium/vitamin D supplementation and a proton pump inhibitor (PPI).

Immunosuppressive agents such as methotrexate (MTX), cyclosporine may be used as adjuncts in steroid-resistant cases or as steroid-sparing agents when extended treatment is required, though with caution as their benefit is considerably less proven than that of steroids.

Question 5

What are the risk factors for NAION?

Answer 5

• Structural crowding of the optic nerve head so that the physiological cup is either very small or absent
• CVRF: HTN (very common), DM, HLD
• Collagen vascular disease, antiphospholipid antibody syndrome, hyperhomocysteinaemia, sudden hypotensive events, cataract surgery, sleep apnoea syndrome, erectile dysfunction

Question 6

What are the symptoms of NAION?

Answer 6

Sudden painless monocular visual loss (vs painful in AAION), frequently discovered on awakening, suggesting a causative role for nocturnal hypotension

Question 7

what are the signs of NAION?

Answer 7

Reduction in VA. VA is normal or only slightly reduced in about 30%.
- Visual field defects are typically inferior altitudinal, but central, paracentral, quadrantic and arcuate defects may also be seen.
- Dyschromatopsia is usually proportional to the level of visual impairment, in contrast to optic neuritis in which colour vision may be severely impaired when VA is reasonably good.
- RAPD
- Diffuse or sectoral hyperaemic disc swelling, often associated with a few peripapillary splinter haemorrhages (as compared to chalky white disc of AAION)
Disc swelling gradually resolves and pallor ensues 3–6 weeks after onset.
Asymptomatic eye: small, crowded disc (disc at risk, C/D ratio < 0.3)