Having overheard a discussion between an enraged Neurologist and an Ophthalmologist about the necessity of carotid Doppler for NAION, we aim to discuss this important differential of acute unilateral vision loss – here is one by location
- Anterior chamber
- Retinal: detachment, bleeding, infection
- CRAO/BRAO (an atherosclerotic, stroke-like problem) <-> AION (an inflammatory or hemodynamic problem) <-> papillitis
- Retrobulbar: PION, optic neuritis
- Optic tract problems
You cannot stress enough that acute vision loss is an interdisciplinary problem that requires a properly performed ophthalmologic examination, possibly fluorescence angiography and neurologic assessment.
Once you arrive at the AION, you ask about signs and symptoms of giant cell arteritis, do an ESR and perhaps a duplex, thus deciding whether the AION is arteritic or not.
Finally, the non-arteritic form (NAION): it is usually not a neurologic problem, practically never embolic in nature and only very rarely a hemodynamic consequence of carotid stenosis. If it were, it should be a common carotid artery disease rather than one of the ICA, b/c o/w the ECA should take over. The precise pathology behind NAION is still elusive, but a lot points toward the combination of an hemodynamic compromise and a secondary compartment syndrome in the papilla due to the inflammatory reaction to that. The latter requires an habitually small cup which you tend to also find on the other side. Thus the other eye (the ophthalmologists call it fellow eye) is just important as the symptomatic one, since it is the one to suffer from a relapse. The symptomatic papilla atrophies, so it cannot develop another episode of NAION, regardless of any recurring cause.
With respect to treatment, it makes sense to me to use steroids, despite the fact that it is not evidence-based. The intention is the same as in Bell’s palsy – reduce the swelling and thus any secondary injury. Curiously, this leads to similar acute treatment in NAION as in GCA-AION: high dose steroids.