Diagnosis: Non-arteritic ischemic optic neuropathy (NAION)
NAION is the most common cause of optic edema cause in patients over 50 years old. In terms of pathogenesis, it is hypothesized that decreased blood supply to the optic head is the likely mechanism. Decreased blood supply leads to ischemia and swelling of the part of the optic nerve that goes through the scleral canal, causing compartment syndrome. Apoptosis, and compartment syndrome lead to vision loss experienced by patients. Most patients maintain the vision experienced at the onset of the event. 30% of patients gain 3 or more lines of vision after edema clears within 2 years. 20% lose 3 or more lines of vision even at 2 years. Risk factors include atherosclerotic plaques of the ophthalmic artery and intimal thickening. This can be caused by metabolic syndrome and its risk factors including hyperlipidemia, smoking, DM2, and hypercholesterolemia. Sleep apnea is also been a risk factor. Small optic nerve heads with a cup-to-disc ratio of 0.2 or less is also considered a risk factor and such nerves are often described as a, “disc at risk.”
The differential diagnosis for optic nerve head edema is extensive and includes the following:
- Anomalous optic discs: buried drusen, tilted disc, hypoplastic discs
- Diabetic papillopathy
- Hypertensive papillopathy
- Intraocular or peri-ocular inflammation: posterior scleritis, perineuritis, uveitis with associated optic disc edema ( e.g. sarcoidosis, toxoplasmosis, and VKH), neuro-retinitis
- compressive optic neuropathy (ie optic nerve sheath meningioma, thyroid ophthalmopathy)
- Optic neuritis
- Central Retinal Vein Occlusion
- Non-arteritic ischemic optic neuropathy
- Infiltrative optic neuropathy and tumors (lymphoma, leukemia)
Work up should include neuroimaging to rule out any compressive etiologies, along with visual field testing and OCT of the RNFL. CBC, ESR/CRP should be checked to rule out Giant Cell Arteritis and risk of evolution to the fellow eye. Additionally, Hgb A1c should be assessed. If symptoms are suggestive of carotid occlusive disease or sleep apnea, carotid dopplers and sleep study respectively, may be indicated.
Treatments are limited for this condition and there are no proven beneficial cures. The majority of patients keep vision they had at the onset of the event. The optic disc edema will resolve over time and the optic nerve will later demonstrate pallor in the affected areas.
The Ischemic Optic Neuropathy Decompression Trial (IONDT) evaluated treatment with optic nerve decompression surgery vs. observation and found no benefit from ONDS in terms of visual improvement.
References and Additional Resources:
1. Kelman SE. “The Ischemic Optic Neuropathy Decompression Trial.” Arch Ophthalmol. 1993;111(12):1616-8.
2. Gabrielle Weiner. Case Studies of Optic Disc Edema. American Academy of Ophthalmology: EyeNet Magazine. October 2015. Available from https://www.aao.org/eyenet/article/case-studies-of-optic-disc-edema.
3. Edmon J. Fitzgibbon, MD. Papilledema. American Academy of Ophthalmology. Danah Albreiki, Eds. April 23, 2021. Available from https://eyewiki.aao.org/Papilledema.
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