Generality/Definition
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Anterior ischemic optic neuropathy (AION) is the most common cause of acute optic neuropathy in older age groups. It can be nonarteritic (nonarteritic anterior ischemic optic neuropathy [NAION]) or arteritic, the latter being associated with giant cell arteritis. It is characterized by visual loss associated with optic disc swelling of a pallid nature, sometimes with flame hemorrhages on the swollen disc or nearby neuroretinal layer, and sometimes with nearby cotton-wool exudates. Visual loss usually is sudden, or over a few days at most, and it usually is permanent, with some recovery possibly occurring within the first weeks or months. Optic atrophy of varying degrees ensues within the next few weeks, and it usually is generalized but may be sectorial (NAION).
Source: Optic Neuropathy, Anterior Ischemic (emedicine.com)
Epidemiology
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In the US: Patients with both arteritic and nonarteritic forms of AION are usually older than 50 years, with females predominating in the arteritic group. The incidence of the nonarteritic type is 2.3-10.3 per 100,000 in the US, and for the arteritic type 0.36 per 100,000. In the arteritic group, incidence, like that of giant cell arteritis, increases almost exponentially with advanced age. The literature seems to support the notion that whites are affected more commonly than blacks in the nonarteritic group, and people of Scandinavian or European ancestry are the most commonly affected ethnic group in the arteritic type.
Internationally: In the nonarteritic group, incidence is higher in Caucasians and uncommon in other races. The countries with the highest incidence of arteritic AION are the Scandinavian countries (ie, Norway, Denmark, Sweden), followed by Germany. The arteritic form is not as well recognized in non-Caucasians. Recent genetic evidence may help to explain this incidence.
Source: Optic Neuropathy, Anterior Ischemic (emedicine.com)
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Prevention
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Causes: AION is an ischemic disease, but the cause is yet to be found definitively. In the nonarteritic form, atherosclerosis is assumed to be the basis, with its effect on the circulation of the optic nerve head. The posterior ciliary arteries feed the optic nerve head, and, despite variable results in animal primate models with ligation of the posterior ciliary arteries, their susceptibility to atherosclerosis and arteriosclerosis in a widespread manner seems to be the underlying cause. In the arteritic form, the basis for the ischemia is identical in pattern, with a giant cell arteritis involving most of the orbital vessels, including the central retinal artery, and the posterior ciliary arteries. Involvement of the branch retinal arterioles is rare presumably because of the lack of internal elastic lamina.
Source: Optic Neuropathy, Anterior Ischemic (emedicine.com)
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Symptoms
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Arteritic Ischemic Optic Neuropathy:
This condition usually presents with sudden and severe vision loss in one eye, pain in the jaw with chewing, tenderness in the temple area, loss of appetite, and a generalized feeling of fatigue or illness.
Source: Ischemic Optic Neuropathy (eyemdlink.com)
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They often have one or more symptoms from two complexes:
1) polymyalgia rheumatica: malaise, limb girdle aches, and poor appetite;
2) external carotid hypoperfusion: headache, scalp tenderness, and pain on chewing.
Source: Ischemic optic neuropathy (kellogg.umich.edu)
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Diagnosis
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Non-arteritic Ischemic Optic Neuropathy:
If the condition is evaluated in the acute stage, the ophthalmologist usually finds an abnormal pupil, a swollen optic nerve (disc edema), and peripheral or central vision loss (or both).
Arteritic Ischemic Optic Neuropathy:
When the ophthalmologist suspects that ischemic optic neuropathy is due to temporal arteritis, or is unable to "rule it out" as a cause, a blood test, indicative of generalized inflammation, known as a "sed rate," is ordered. If the sed rate is significantly elevated, arteritic ischemic optic neuropathy secondary to temporal arteritis may be present, and the patient is started on steroids. Once steroids are started, the patient is usually scheduled for a temporal artery biopsy in attempt to confirm the diagnosis.
Source: Ischemic Optic Neuropathy (eyemdlink.com)
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The diagnosis is urgent, because if the patient is not treated, there is a good chance that the other optic nerve will become infarcted within days. Diagnosis is based on finding inflammation on biopsy of the temporal artery. It shows fragmentation of the internal elastic lamina and sometimes Langerhans giant cells.
Source: Ischemic optic neuropathy (kellogg.umich.edu)
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Treatment
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Treatment consists of oral prednisone 1.5 mg/kg/day or intravenous methylprednisolone 1-2 gm/day. Temporal artery biopsy is performed within 1 week of starting treatment. Treatment often prevents infarction of the second eye, but does not reverse damage due to a pre-existing infarction.
Source: Ischemic optic neuropathy (kellogg.umich.edu)
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Medical Care: Comanagement with an internist, especially a rheumatologist, is helpful in patients with giant cell arteritis. Control of blood pressure and diabetes, often comorbid conditions, is helpful in the general sense, but it is of little use in the recovery of visual loss.
- In giant cell arteritis, the steroid regimen is as follows: The initial dose is 40-60 mg/d of prednisone, depending on the size of the patient and the severity of the disease. If starting at 40 mg/d hold for 2-4 weeks; then, reduce as below. If starting at 60 mg/d, reduce by 10 mg every 2 weeks to 40 mg, then 5 mg reductions every 1-2 weeks to 20 mg/d, then 2.5 mg every 1-2 weeks. Below 10 mg/d, reduce 1 mg per month. The reduction schedule depends of the course on the patient.
- Obtain ESR and/or CRP at monthly intervals to monitor the course of the patient. Brief interviews at monthly intervals are helpful. If recurrences develop, the reduction schedule needs to be delayed, and, sometimes, small increments need to be given again for flare-ups. Avoid large increments for flare-ups if possible.
- Some authors have advocated larger doses, even intravenous doses of a gram daily for several days, followed by the standard treatment as above. Support for this is currently lacking, but, in an ongoing study at the Mayo Clinic, a double-masked study is underway to determine if intravenous doses accelerate the recovery and shorten the need for months of long-term steroids.
- At a later stage in the steroid management, it is sometimes useful to add antimetabolites, such as methotrexate or cyclosporin, to reduce the dosage of steroids, particularly if adverse effects are becoming a problem. Careful monitoring of liver function and blood counts is essential and is best left to the rheumatologist.
- Steroid treatment for the nonarteritic type of AION has its advocates, but data do not support its use. In those cases where the diagnosis is in question, a short-term trial is warranted. Once temporal arteritis has been ruled out, there is little point in continuing, as the long-term complications of steroids are considerable.
Surgical Care: Optic nerve fenestration was advocated for AION until the completion of the Ischemic Optic Neuropathy Decompression Trial (IONDT). This study conclusively showed no effect of the surgery. Advocates for decompression in the patient with progressive AION still exist, but, to date, no evidence is available to establish the effectiveness of this treatment.
Source: Optic Neuropathy, Anterior Ischemic (emedicine.com)
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Arteritic Ischemic Optic Neuropathy:
Patients with temporal arteritis will be followed clinically and with laboratory evaluations of the sed rate to determine the response to treatment. Unfortunately, treatment with steroids is not associated with any visual recovery in the involved eye, but prevents ischemic optic neuropathy in the opposite eye.
Source: Ischemic Optic Neuropathy (eyemdlink.com)
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Illustrations
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Source: Ischemic optic neuropathy (kellogg.umich.edu)
Swollen optic disc. The margins of the optic disc are fuzzy, and there are cotton wool spots on the superior border. These signs tell you that axoplasm is not flowing normally through the optic nerve.
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