| Transcript |
I want to tell you a little bit about a common disorder called non-arteritic anterior ischemic optic neuropathy. And NAION has its own video you can watch that if you want, but really what I want to cover is: "when is it not non-(AION)?" Which is a double negative. When is it not non-(AION), and the reason is there is no diagnostic test for NAION. It is completely a clinical diagnosis. So, what does this sound like (NAION)? So, you need to know what a duck quacks like, flies like, and looks like; because if it quacks like a duck, looks like a duck, flies like a duck it's probably a duck. So, this is what NAION quacks like: acute unilateral decreased visual acuity and/or visual field in the nerve fiber layer defect, in an older patient with vasculopathic risk factors like hypertension, diabetes, hyperlipidemia, etc. They are going to have a relative afferent pupillary defect in the involved eye, and they have to have this "a". That "a" is anterior, and that anterior is super important because it's anterior to the laminar cribrosa which means we have to see the disc edema. And in the fellow eye, the cup-to-disc ratio is the structural disc at risk. A small, crowded optic nerve is the risk factor mechanically, and structurally for NAION. So, the closer it looks to this duck: older patient, acute, unilateral, loss of vision, RAPD, swollen disc, small cup-to-disc in the fellow eye; that's a duck called NAION. When is it not non-arteritic anterior ischemic optic neuropathy? And that is the "Goldilocks principle". So, as you're familiar, the little girl with the golden locks, "Goldilocks": she visits the home of the three bears. She sits in one chair, it's too big. She sits in the other chair, it's too small. And then she finds one that's just right. And she eats the porridge: one's too hot, one's too cold, one's just right. And then she sleeps in the bed: one's too big, one's too small, one's just right. And the bears catch her. So, you need to know the Goldilocks principle as it applies to non-arteritic anterior ischemic optic neuropathy. So, I already told you what this duck looks like. So, what if we changed the age of the patient from 65 years old with acute vision loss, to 35 years old: well, that's too young. So, in the "Goldilocks principle": too young. What if we change it to chronic, from acute: too long. What if we change it to no vasculopathic risk factors: that's too little of a vasculopathic risk factor to drive this stroke event in the "I" (ischemia), which is a microvascular, small vessel ischemia. What if there is no RAPD: that's too little. What if the cup-to-disc ratio is too big-it's 0.5 in the fellow eye, or they have glaucoma in the fellow eye, or they get cupping after the ischemic optic neuropathic event: that's too much. What if there's no disc edema: that's too little, too little. And it's supposed to be unilateral, that's too much if it's bilateral. So, you should be thinking about not "non-(AION)", the double negative, if they're too young, too chronic, too much, or too little of the risk factors. And the things we're going to be looking for ophthalmoscopically for too much are if the disc edema is too much. So, normally the Frisén scale is used for grading papilledema. If you have too much disc edema, like Frisén grade four or five type of disc edema where you have obscuration of the nerve fiber layer centrally, or you have too much cotton wool patch, or too much hemorrhage, or too much exudate, or too much subretinal fluid-the Goldilocks principle says that that is not non-(AION). That that is too much of what you're expecting. So, in summary, you should know non-arteritic anterior ischemic optic neuropathy is the most common acute optic neuropathy in older patients. It flies like this, this duck: 65-year-old white male, with acute unilateral loss of vision and visual field, older patient with vasculopathic risk factors, an RAPD, a swollen nerve, the "a" in AION (anterior), disc edema during the acute phase followed by sector atrophy, and a small cup-to-disc ratio in the fellow eye. You should apply the Goldilocks principle to NAION to determine whether this is not non-(AION), a double negative. It's not non-arteritic anterior ischemic optic neuropathy if it's too young, too chronic, too little risk factor, too little RAPD, too little swelling or no swelling, or too much swelling, Frisén grade 4 or 5, or too much cotton wool patch, exudate, subretinal fluid, or if you have to big a cup in the fellow eye: you should be thinking not non-(AION). |
