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AION: a quick and accurate diagnosis is critical
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While little is known about anterior ischemic optic neuropathy (AION), we do know that patients presenting with the arteritic form of AION must be treated quickly and aggressively.
There are two types of AION, nonarteritic (NAAION) or arteriosclerotic, and arteritic, also known as giant cell arteritis or temporal arteritis. “It is important to distinguish between the two, because the arteritic variety is inflammatory and needs to be diagnosed and treated aggressively,” said Leonid Skorin Jr., OD, DO, FAAO, FAOCO. “The potential is there for a person to have bilateral blindness in a very short time if it’s not diagnosed and treated appropriately.”
Although AION is not exclusive to older patients, those 50 years or older are at high risk. The arteritic AION patient is an average of 10 years older than the nonarteritic AION patient. The older the patient, the greater the risk for AION.
There is little treatment available for the nonarteritic form. In 1995, the Ischemic Optic Neuropathy Decompression Trial showed that optic nerve sheath decompression, a surgery that is supposed to relieve pressure around the optic nerve, not only did not significantly improve the outcome for patients who underwent surgery, but actually increased the instances of complications. This surgery is no longer recommended, said Dr. Skorin.
A recent study led by Lenworth N. Johnson, MD, of the University of Missouri — Columbia, Mason Institute, showed that levodopa may improve some ischemic optic neuropathies. The study is preliminary and the Food and Drug Administration has not approved this agent for treating AION.
Symptoms of AION
Typical presentation of AION is sudden, painless loss of vision and usually an afferent pupillary defect. It sometimes appears congested and hyperemic in the acute phase and then becomes swollen and pale later. These symptoms will be present in both types of AION. “Although one of the symptoms listed in most articles on arteritic AION is painless loss of vision, patients are not free from pain,” said Andrew Gurwood, OD. “Their jaw can hurt when moving it, they may have referred pain to the teeth and it may hurt to comb their hair.”
Arteritic AION is caused by inflammation that clogs blood vessels at the optic nerve head. This must be distinguished quickly to prevent vision loss. NAAION does not usually cause vision loss as severe as temporal arteritis.
“The patient will complain of headaches, vision loss, jaw claudication, tongue claudication, sores in the mouth, polymyalgia rheumatica, feeling tired and, in some cases, diplopia,” said Dr. Skorin. “Other than vision loss, these symptoms are usually not present in the nonarteritic patient, but they’re very common in the arteritic patient,” he added.
Causes of NAAION
NAAION indicates systemic disease — usually of a vascular nature — such as diabetes, hypertension, hypercholesterolemia, hyperlipidemia and other vessel diseases.
“These individuals may be on medication, and so the theory is that there’s a problem in the normal blood flow to the optic nerve head through the posterior ciliary artery blood vessels,” said Dr. Skorin. “Essentially, these patients have what amounts to a stroke in the eye. If they have a problem, usually it will occur in the early morning hours, when the blood flow is at its lowest.”
The most common cause of NAAION is nonperfusion or hypofusion to the optic nerve head. “In general, the optic nerve becomes cut off at its blood supply. Other causes include microvascular disease and emboli,” said Dr. Gurwood.
Diagnosing and treating AION
| Characteristics of Arteric Anterior Ischemic Optic Neuropathy |
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Tests to distinguish between arteritic and NAAION include a Westergren sedimentation (sed) rate, C-reactive protein and a complete blood cell count (CBC), said Dr. Skorin. “The CBC is to look for anemia, because any significant anemia will affect the results of the sed rate. So you need all three in tandem to get a proper diagnosis,” he added.
“Usually, if the sed rate and C-reactive protein come back positive, there’s a very good chance that it’s giant-cell arteritis. An ESR [erythrocyte sedimentation rate] greater than 50 and a C-reactive protein higher than 2.45 to 2.50 are 98% specific positive for giant-cell arteritis,” according to Dr. Gurwood.
The definitive diagnosis for temporal arteritis is done with a temporal artery biopsy, according to Dr. Skorin. “All of these patients need a temporal artery biopsy, even if the blood tests come back positive, because these patients are going to be treated with steroids for long-term therapy. So you want to make sure you have the correct diagnosis, because the steroids can cause problems such as osteoporosis, diabetes, atherosclerosis and psychoses,” said Dr. Skorin.
When to refer
“Once test results are in, I immediately send the patient to a neuro-ophthalmologist,” said Dr. Gurwood. “The neuro-ophthalmologist will do one of two things: admit the patient, pulse him or her on IV methylprednisone and get a temporal artery biopsy or start the patient on high doses of oral steroids.”
Dr. Skorin recommends sending nonarteritic patients to an internist or general practitioner. “First of all, I would take their blood pressure in-office, then refer them to an internist or general practitioner for a work-up for their general condition,” he said. “They need to have their blood sugar taken and their cholesterol and other lipid levels measured,” he said.
“It’s important to get test results back for the sed rate, CBC and C-reactive protein immediately,” according to Dr. Skorin. “You need to get same-day results because of the rapid onset of blindness associated with the temporal arteritis variety of AION.”
According to Dr. Gurwood, “giant-cell arteritis can be among the great masqueraders. It can look like a toothache, earache or herpes zoster. The clinician has to be sharp at looking for it. Vision loss associated with this disease is devastating and permanent.”
For Your Information:
- Andrew Gurwood, OD, can be reached at the Pennsylvania College of Optometry, 1200 West Godfrey Ave., Philadelphia, PA 19141; (215) 276-6134; fax: (215) 276-1329; e-mail: Agurwood@pco.edu.
- Leonid Skorin Jr., OD, DO, FAAO, FAOCO, practices in a multispecialty group in Dixon, Ill. He may be reached at the Medical Arts Center, 1620 Sauk Rd., Dixon, IL 61021; (815) 288-7711, ext. 2830; fax: (815) 288-5077.