DEFICIENT BLOOD SUPPLY TO THE OPTIC NERVE
Ischemia means a lack of blood supply.
Non-arteritic means that the arteries are not inflamed.
Arteritic means the blood vessel is inflamed, that a biopsy of the blood vessel might be beneficial, and that steroids might help.
Anterior refers to the front (visible) portion of the optic nerve.
Optic neuropathy means optic nerve disease.
NON-ARTERITIC ANTERIOR ISCHEMIC OPTIC NEUROPATHY (NAION)
NAION is the second most common “aging problem” of the optic nerve problem after glaucoma. NAION is a usually painless optic neuropathy that occurs in patients who are usually older than 50 years of age (6% – 23% of patients may be < 50 years old). Patients with diabetes, hypertension, elevated cholesterol, and obstructive sleep apnea may be at higher risk for NAION. Low blood pressure at night may account for why some patients with NAION wake up noticing vision loss. It is possible but not definitely proven that the use of phosphodiesterase-5 inhibitors (viagara, cialis) increases the risk for NAION.
Just as patients can be tall, short, fat or thin, optic nerves can be big or small. Small optic nerves have small cups (see Optic Nerve 1). Patients with NAION tend to have small cups and small optic nerves (disc at risk).
As we age, we get little strokes and may not even realize it. In very simplistic terms, sometimes littles strokes of the optic nerve occur. The stroke causes the optic nerve to swell. If the optic nerve has no room to accommodate the post-stroke swelling, even more optic nerve damage may occur. This “ischemic spiral” in patients with small optic nerves is thought to be the mechanism of NAION. Since the optic nerves of patients tends to be symmetric, there is about a 15% risk of NAION occuring in the other eye. The risk of contralateral involvement may be higher in patients younger than 50 years old.
There is NO rigorously proven treatment for NAION yet. Most patients only have a modest recovery of vision (42.7% of patients may notice visual acuity improvement of >=3 lines of vision) , if at all. Aspirin may decrease the short term risk of NAION in the other eye, but as of yet we do not have any neuro-protective agents. Most people do not think the anti-Parkinsonian medication has any beneficial effect on the disease process. Some clinicians will consider steroid injection or steroid pills for NAION, but this remains controversial. Avastin injections into the eye have not helped NAION. Intravitreal erythropoietin and siRNA antiapototic agents (QPI-1007) are being studied.
ARTERITIC ISCHEMIC OPTIC NEUROPATHY (Giant Cell Arteritis / Temporal Arteritis)
Arteritic ischemic optic neuropathy is a disease of the elderly, and most patients are 65 years of age or older and complain of discomfort.
Arteritic ischemic optic neuropathy is thought to be an autoimmune diseease. As patients age, the immune system may go awry and start attacking the patient’s own body. If the immune system attacks the blood vessels, arteries may become inflamed causing an ARTERITIS (NOT to be confused with arthritis). Since the optic nerve and eye are supplied by very tiny blood vessels, when the blood vessels are inflamed and become clogged up, blindness may result in one or both eyes.. With arteritic ischemic optic neuropathy, the optic nerve is usually pale and swollen. If there is inadequate blood supply to the extraocular muscles that move the eye, double vision may result. Because other blood vessels throughout the body may also be inflamed, patients may have headache, scalp tenderness, and pain in the jaw muscles with prolonged chewing, skin ulcers and mouth ulcers.. Patients may also have a rheumatologic condition of sore shoulders and sore hips (polymyalgia rheumatica). Giant cell arteritis patients may have weight loss, chills/fever, and a general feeling of malaise.
There is usually no cure for the vision loss with giant cell arteritis. However once arteritis is suspected, high dose steroids should be started quickly in hopes of preserving what vision remains. The initial 1-3 day dose of steroids may be as high as 500-1000 mg intravenous methylprednisolone, which is the equivalent of 625-1250 mg oral prednisone.
BLOOD TESTS such as the “ESR” and “CRP” are non-specific but somewhat helpful indicators of inflammation. In most arteritis patients these blood tests are quite elevated until steroids are initiated.
The role of ocular pulse amplitude (blood flow) is being studied at Toronto East General (Michael Garron) Hospital.
TEMPORAL ARTERY BIOPSY: A biopsy of one of the scalp arteries in the temple (which should not affect the vision or brain circulation) may help confirm the diagnosis. Sometimes biopsy of the scalp vessels on both sides of the head is required.
If the patient is felt to have giant cell arteritis, STEROIDS (glucocorticoids) for a year or more are required. Steroids have many, many potential side effects, and patients must be followed in conjunction with the family doctor or internist. Potential SIDE EFFECTS OF STEROIDS include: diabetes mellitus, hypertension, osteoporosis, hip/bone softening/avascular necrosis, stomach ulcer, increased infection rate, bleeding and bruising, mood changes and psychosis, fat face, rounded shoulders, unwanted hair growth, cataracts, glaucoma and drug interactions. Most arteritis patients will continue steroid treatment faithfully because they realize the alternative is potential blindness. Always know the dose of steroids that you are taking, or bring the pill bottle to your doctor(s). Tocilizumab may have a future role in giant cell arteritis.
