||Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX, Professor of Ophthalmology, Weill Cornell Medicine; Akash Gupta, Baylor College of Medicine, Class of 2022
||Summary: CRAO/NAION: 1. Risk factors for both 2. Presentation a. Patient has vasculopathic factors i. Hypertension ii. Diabetes iii. Hyperlipidemia iv. Smoker b. Acute unilateral vision loss c. Ipsilateral RAPD (relative afferent papillary defect) d. This presentation could result from CRAO or NAION i. To differentiate, look at the fundus 3. Central Retinal Artery Occlusion (CRAO) a. Central retinal artery supplies the retina with blood b. Central retinal artery is occluded by an embolus leaving the retina opaque since it is not being perfused with blood c. Underlying choroid still visible and intact at the fovea leaving a "cherry red spot" in the center d. Intravascular problem and patient should be admitted to the hospital for embolic stroke workup 4. Non-arteritic Anterior Ischemic Optic Neuropathy (NAION) a.Optic nerve supplied with blood by many small posterior ciliary arteries b.In NAION, there is hypoperfusion through these posterior ciliary vessels causing the nerve to swell c.Anterior to lamina cribrosa and visible as disc edema d. Non-embolic cause, so the patient does not need to be admitted to the hospital [Transcript of video] "So, I was asked to talk to you today about Central Retinal Artery Occlusion (CRAO) vs. (NAION) Non-arteritic Anterior Ischemic Optic Neuropathy. It's super important to differentiate a Central Retinal Artery Occlusion (CRAO) from Non-arteritic Anterior Ischemic Optic Neuropathy (NAION) because they have totally different pathogenesis and workup; however, they usually present in the same kind of person in the same way. So it's usually an older patient who has vasculopathic risk factors like hypertension, diabetes, hyperlipidemia, smoker, and the patient presents with acute unilateral loss of vision and so when we have that presentation of an acute unilateral loss of visual acuity or visual field it could be a stroke in your retina (central artery occlusion) or it can be a stroke in your optic nerve (non-arteritic anterior ischemic optic neuropathy). In both they're going to have a RAPD (relative afferent papillary defect) on the same side (an ipsilateral RAPD) and the key differentiating feature is going to be what does the fundus look like because the presentation and the symptoms are exactly the same. So in a central retinal artery occlusion as you know the retinal artery is an end artery and so when we look in the eye, here's the optic nerve, if the central retinal artery is occluded by an embolus then the retina that receives the blood will not be perfused. That means the whole retina perfused by the arterial segments occluded will be opaque. But at the fovea (it's the thinnest at the fovea), and so we'll be able to see the opaque retinas pushed to the side and what you'll be able to see is the underlying choroid and if we can see the underlying choroid surrounded by the opaque retina, that we call a cherry red spot - so a spot that is red, a cherry red spot, in the dead center in the fovea where the photoreceptor elements are pushed away and we can see the underlying choroid is intact. And actually, the only part that's normal in a cherry red spot is the actual cherry red spot. Everything else is abnormal because the opacified retina that is ischemic is no longer transparent. So someone who has a CRAO - they have a cherry red spot, and that person should be admitted to the hospital to have an embolic workup because the most common causes of a retinal artery occlusion are an intravascular problem and that could be a cardiogenic emboli or Hollenhorst plaque or a piece of thrombus from the carotid. And so that person is basically a stroke in the eye that needs a stroke workup, and if it's in the acute setting we want to admit them to the hospital. In contrast, NAION is not embolic, so the blood supply to the optic nerve, the central retinal artery goes to the retina, but the optic nerve is supplied by the smaller vessels which are the posterior ciliary arteries and there are many posterior ciliary arteries so it's hard to make it an embolic disease. So as opposed to CRAO, NAION is not characterized by a cherry red spot. It's characterized by a swollen optic nerve - either a sector or diffuse swollen optic nerve. So, the key differentiating feature for NAION is anterior, which is going to be visible as disc edema, it's anterior to lamina cribrosa so we will see a swollen optic nerve, either sector or diffuse. And because it's posterior ciliary artery, hypoperfusion, and not an embolus, we don't have to admit NAION to the hospital, we don't have to do an echocardiogram, an EKG, or a carotid Doppler - all the stuff that we would do on CRAO. So big difference, stroke in the retina or stroke in the nerve. Huge difference - stroke in the retina should be treated like a stroke in the brain. Stroke in the optic nerve is usually NAION, hypoperfusion, and does not need to be admitted to the stroke workup."