| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (HHC) Class of 2020, Baylor College of Medicine, Houston, Texas |
| Transcript |
We're going to talk about nonarteritic anterior ischemic optic neuropathy - abbreviated NAION. The N is for neuropathy, which means you have a disease in the nerve. The nerve that's involved is the optic nerve: Optic Neuropathy. The cause is presumed to be ischemia: Ischemic Optic Neuropathy. Because we can see the swelling that's anterior, anterior to the lamina cribrosa: Anterior Ischemic Optic Neuropathy. There are two flavors: nonarteritic, N-A-I-O-N and the arteritic A-A-I-O-N. The arteritis that we are worried about is giant cell arteritis, and you should be considering the arteritic form of AION in every patient who has AION, but NAION, the nonarteritic form is way more common. So when we're dealing with the nonarteritic form we want to make sure it's not a giant cell by talking to the patient making sure there are no symptoms of giant cell arteritis: headache, scalp tenderness, jaw claudication, polymyalgia rheumatica. We also want to make sure there are no premonitory symptoms of ischemic symptoms, the TIA symptoms of transient diplopia or transient loss of vision - amaurosis fugax - which do not occur in the nonarteritic form of AION. And the laboratory tests: sedimentation rate, C-reactive protein and platelet count. Of course, if you think they have GCA and AAION, you should give steroids and do a temporal artery biopsy. If the tests are negative, the patient doesn't have any symptoms and you don't think it's arteritis, then it's nonarteritic ischemic optic neuropathy. We're going to be looking for and treating the vasculopathic risk factors: hypertension, hyperlipidemia, diabetes, smoking any of the other risk factors that could lead to ischemic events: hypoxia like sleep apnea and we need the internist to treat and work up all the risk factors. There is no effective treatment for NAION; normally we give them an aspirin a day if there's no contraindication. It's not an embolic disease, so we don't do carotid dopplers, echocardiograms, or MRI of the brain for NAION. If it is NAION for fellow eye for structural disc at risk, which is the small cup-to-disc ratio it is the small crowded optic nerve that is the risk factor for nonarteritic form of anterior ischemic optic neuropathy. And so if we look in the fellow eye and we have an increased cup-to-disc ratio, that is NOT the structural disc at risk, you should be thinking about AAION arteritis or you should be thinking about other causes of optic neuropathy other than ischemia. If you were to do an MRI scan, there should be no enhancement although there are some papers reporting this. In general, if it's enhancing you should be thinking about infectious, inflammatory and infiltrative optic neuropathy and not nonarteritic. Although steroids have been used in the past in NAION, there's never been a randomized controlled clinical trial to show benefit. In the small control trials that have been done, no benefit was seen with steroids even though those trials were quite small. Steroids definitely reduce the duration of the disc edema, and so some people, we still offer it to-especially the incipient form. The incipient form has not lost the vision yet so they're there for some other reason and we see the disc edema by accident you might treat that patient with steroid still, even though that is a could do, not a should do, not a must do, and certainly not a standard of care recommendation. So aside from treating the vasculopathic risk factors and an aspirin a day, really there's still no effective treatment event of NAION. It is a clinical diagnosis, and your main job is to make sure it's not arteritic AION before you you make the diagnosis of the nonarteritic formed NAION. |
