A review of ischemic optic neuropathies--arteritic and nonarteritic.
Biousse V, Newman NJ. Review Article: Ischemic Optic Neuropathies. N Engl J Med. June 18, 2015; 372:2428-2436. DOI: 10.1056/NEJMra1413352
Carla Rothaus. Ischemic Optic Neuropathies. Now@NEJM. June 19th, 2015.
Ischemic optic neuropathy (ION) is the most feared complication of giant cell arteritis (GCA).
This review is divided into nonarteritic and arteritic ION, and into anterior (90% of cases) and posterior ION. In posterior ION, there is no visible disc edema.
Nonarteritic anterior ION is not associated with GCA. While the cause is unknown, it involves small vessel disease leading to hypoperfusion and ischemia of the anterior optic nerve, with edema of the optic disc. It is diagnosed by a cup-to-disc ratio of 0.15, which is most easily seen in the unaffected eye. There is no established treatment. Typically, the edema resolves itself, but leaves permanent visual impairment. The authors recommend a strategy of “first, do no harm.” Oral glucocorticoids have a small benefit, which only outweighs the risks in severe cases.
Nonarteritic posterior ION is exceedingly rare. It typically presents as a sudden loss of vision, and is a difficult diagnosis of exclusion. GCA must be excluded.
Arteritic ION. About 20% of GCA patients experience visual loss. Systemic symptoms of GCA may precede visual loss by months, although 25% of GCA patients present with isolated ION. Transient visual loss often precedes permanent visual loss by days to weeks.
Arteritic anterior ION is more severe than nonarteritic anterior ION, and the unaffected eye usually has a normal optic disc. Associated retinal or choroidal ischema is highly suggestive of GCA.
Untreated arteritic ION becomes bilateral in days to weeks in at least 50% of cases.
Most neuropthalmologists prescribe high-dose intravenous methylprednisolone for acute visual loss. Glucocorticoids prevent visual loss in the unaffected, eye, but often do not reverse existing visual loss.