Introduction
Occurs in discs at risk, especially in Px over age 50, who have vascular risk factors or sleep apnoea
Pathophysiology:
- Obstruction of the short posterior ciliary artery causes ischaemia and external oedema
- A small crowded optic disc is the biggest risk
- If even a small embolus occurs in a small crowded disc that blocks the short posterior arteries, or an extending capillary, mass swelling occurs
- This is exacerbated by the minimal space. More crowding means compressed capillaries, more ischaemia and more swelling
- The self-propagation is known as compartment syndrome
Dead Giveaways
A major differential from AAION lies in the fundus image, disc image and associated signs
Associated Signs:
Unlike AAION, typically associated with systemic disease, NAAION typically is not accompanied by symptoms from elsewhere in the body, presenting with none to mild (<10%) pain
Whilst the mean age of onset for AAION is 72 years, NAAION is 52 years
No gender bias
Vision is generally not bad (6/9 - 6/12)
1/7 chance of fellow eye involvement after 5 years
Fundus Image:
Considerably normal. No CWS, and usually retinal signs are uncommon
Disc Image:
Disc is not pallor, but hyperaemic and swells. Cup is very small, or absent. After resolution, may be pallor Following oedema, cup returns to normal, and does not have cupping unlike AAION
diagnostic features
Signs and Symptoms:
Sudden painless vision loss occurs
RAPD is still present
73% with VA > 6/18
Like AAION:
Disc pallor can occur after resolution, as well as RNFL thinning
RNFL still thick during oedema, but thins afterwards due to death VF defects still respect the horizontal midline
RE superior hemianopia But, there is no cupping seen