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I'd like to talk a little bit about the eyeball

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including the globe and the retina.

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Obviously, there's a couple of eyeballs right here.

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Here they are.

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And they're secured in part by some extraocular muscles.

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We're more interested in the optic nerve and the

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nerves that sit within the orbital cavity.

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Now, most of these are clustered around the fovea,

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so there's a higher concentration right around the optic nerve

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than there is off to the side.

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So, I'd like to make three points on this vignette.

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I want to talk about the layers of the globe,

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the field orientation of the retina and the retinal projections,

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and the appearance of retinal and choroidal detachment.

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So let's start out with the layers.

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If you look sagittally, you can see a somewhat pigmented,

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hyper intense appearance to the back

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of the optic nerve right here.

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And this consists of pigmented structures that

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include rods and cones, especially the cones.

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And then you've got a few layers including

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this darker scleroid layer in the back.

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Then it's very hard at this resolution to separate out the

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other layers which include a choroidal and a retinal layer.

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Now, the reason that that's important is that

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in detachments on MRI, the pattern is usually indicative

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of the type of detachment you have.

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So if you have a detachment that looks kind of like this

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that comes to a V in the back where the effusions and the

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hemorrhage is margined by what we call the ora serata and

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it makes this coalescent V then it's a retinal detachment.

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On the other hand,

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if it goes the other way if it's convex inward and then sort

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of makes almost like a column like this but doesn't converge

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that's going to be more consistent

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with a choroidal detachment.

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Just a little pearl for your perusal and interest.

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The third point I'd like to make is regarding

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the fields in the orbit.

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Now, most people know this from medical school training

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but let's make some fields here.

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We've got a field on the left and a field on the right.

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Now, I use something like red to show you the temporal field.

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There's the temporal field on the patient's left side and

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here's the temporal field on the patient's right side.

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The temporal field, in other words,

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what you see on the outside is going

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to project here and here.

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So the outer field contend this is the outer field here is

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going to project to the medial portion of the globe which

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is a little bit confusing.

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Let's pick another color.

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Let's go with something like light green.

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On the other hand, the medial field, which would be here.

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In other words, the outside world, medially.

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Is going to project on the lateral aspect

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of the globe and the retina.

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So that's a little bit confusing.

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So now that it projects on the lateral side,

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where is it going to come back?

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It's going to come back to

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it's going to come along the optic nerve laterally.

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And when it gets to the optic chiasm,

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it's going to stay laterally in the optic chiasm,

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whereas the medial component, which we'll see in red,

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is going to stay medially within the optic nerve and

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it is going to decussate to the contralateral side.

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Where it'll go to?

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It'll have that little temporal knee or temporal

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occipital knee is the optic radiations.

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Where it'll go to the calcarine cortex.

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Same thing on this side.

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This one's going to decussate over to the opposite side and

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supply the innervation right around the calcarine sulcus

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right there. So that, again, is a little bit confusing.

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So you've got lateral field going to medial retina going to

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medial nerve decussating over to the contralateral optic

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chiasm going to the contralateral peri calcarine area

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in the cortex of the occipital lobe or Cuneus.

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Let's move on, shall we?

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Pomeranz out.