A 65-year-old woman with hypertension and diabetes presents with new awareness of blurred vision OD for two days. The visual acuity was 20/40 OD and 20/20 OS. No visual field is performed. The pupil examination showed a relative afferent pupillary defect (RAPD) OD. Ophthalmoscopy showed a normal optic nerve OD. The remainder of the eye exam was normal OS. A diagnosis of “posterior ischemic optic neuropathy” (PION) is made and the patient is instructed to return for a “next available” visual field test. The patient returns two months later and reports that “his vision is worse”. The vision is now 20/400 OD and 20/25 OS. There is a right RAPD. The Goldmann visual field showed a bitemporal hemianopic visual field loss with a superimposed central loss OD. There is now optic atrophy OD. A cranial MRI showed a pituitary adenoma compressing the optic nerve OD. A new eye doctor sees the patient and tells her that “If only you'd come to me sooner you would not be blind.”\nThe diagnosis of posterior ischemic optic neuropathy (PION) is one of exclusion. PION does occur and can be classified as arteritic (i.e., related to giant cell arteritis) or non-arteritic. The non-arteritic form is generally seen in the setting of perioperative or post-operative ischemic optic neuropathy after spine or cardiovascular surgery. Post-operative PION however has been seen after multiple surgical procedures.\nSadda et al. reported a retrospective chart review of 72 patients (98 eyes) with a clinical diagnosis of PION: perioperative (28 patients), arteritic (6 patients), and nonarteritic systemic vascular disease (38 patients). Among eyes with nonarteritic PION, 34% experienced improvement in vision, 28% remained stable, and 38% worsened.\nIt is my opinion that before the diagnosis of PION can be made two conditions must be excluded. First giant cell arteritis and second a compressive lesion producing a retrobulbar optic neuropathy. The key feature differentiating AION from PION is the presence of optic disc edema in the acute setting. Retrobulbar optic neuritis is typically a disorder of young patients and most commonly associated with multiple sclerosis. Retrobulbar optic neuritis however is rare in the elderly and the diagnosis should not be made without an imaging study. Compressive lesions can mimic an acute onset as seen in ischemic disease. In addition, corticosteroids a common treatment of retrobulbar optic neuritis can be disastrous in a patient harboring a fungal orbital apex lesion producing the retrobulbar optic neuropathy. Thus the diagnosis of retrobulbar “optic neuritis” should be made with extreme caution in the elderly. I generally recommend that a fluorescein angiogram be considered in elderly patients with suspected PION. The finding of choroidal perfusion deficit in the setting of PION is strongly suggestive of giant cell arteritis. Corticosteroids might be useful empirically for both arteritic and nonarteritic PION but an imaging study as mentioned above might be advisable prior to starting treatment.\nI would accept the diagnosis of PION of the clinical findings are consistent with an optic neuropathy (i.e., visual loss, RAPD, optic neuropathy related visual field), there is a clear etiology (i.e., post-surgical PION or giant cell arteritis), and optic atrophy develops over time. If there is no clear etiology for the PION, then a neuroimaging study is recommended (preferably cranial MRI with contrast and orbital fat suppressed views).
A 25-year-old woman presents with chronic and unresolved loss of vision OD that occurred acutely two months prior to presentation. There is a right RAPD, a central scotoma OD on visual field testing, and a normal optic disc. Computed tomography (CT) scan of the head in the emergency room was normal. A diagnosis of chronic optic neuritis” is made.\nChronic “optic neuritis” is a real diagnosis but the clinician should be careful to insure that the patient has a confirmed diagnosis of multiple sclerosis and no alternative etiology for the optic neuropathy. Typical optic neuritis resolves (20/40 or better vision) in over 90% of cases and lack of improvement should be a big “red flag” that the diagnosis is incorrect. In my experience patients with chronic”“optic neuritis” due to demyelinating disease often have a systemic MS course that mirrors the course of their optic neuropathy (i.e., primary or secondary progressive rather than relapsing-remitting course). One should also be cautious of using the term “optic neuritis” when one truly means optic neuropathy. Misusing or mixing terms (e.g., papilledema) or creating neologisms (e.g., “ischemic optic neuritis”) also is potentially misleading to your colleagues. The bottom line is that typical optic neuritis usually gets better over time and patients with an atypical course (e.g., “chronic optic neuritis”) should have evaluation for alternative etiologies for their optic neuropathy including neuroimaging. There are potentially dangerous conditions that could mimic the presentation of acute painful optic neuropathy and suggest a diagnosis of demyelinating optic neuritis (e.g., pituitary apoplexy or ophthalmic artery aneurysm). In addition there are subsets of variants of demyelinating optic neuropathy that may not have as favorable a rate of recovery and therefore might suggest alternative diagnoses (e.g., neuromyelitis optica). Finally, some patients with the mitochondrial disorder, Leber hereditary optic neuropathy (bilateral acute visual loss with cecocentral scotomas in a young male) can be associated with MS like illness. Although rare, I would accept the diagnosis of “chronic optic neuritis” as a diagnosis of exclusion if a high quality MR scan of the head and orbit with gadolinium has excluded a compressive lesion, the patient has clear diagnosis of prior multiple sclerosis, and alternative MS mimics have been considered and adequately excluded. I typically will inform the treating neurologist of the findings and my concerns and if there is any history of transverse myelitis or if the optic neuropathy is bilateral then I would consider evaluation for neuromyelitis optica (NMO) including NMO antibody testing. I would also consider ordering the mitochondrial genetic testing for Leber hereditary optic neuropathy if the patient has bilateral central or cecocentral scotomas especially in a young man.