0:00

On this axial CT scan,

0:02

we can review some of the anatomy.

0:04

The most superficial thing that we

0:06

are seeing is the skin surface of the eyelids.

0:15

The next thing that is outlined is the cornea.

0:20

And as you can see,

0:21

this is continuous with the sclera.

0:27

We do not resolve the retina choroid and

0:29

sclera on CT scanning or MRI scanning.

0:33

They are called the ocular membranes.

0:35

You notice that this patient has had a lens implant

0:39

as this little waferlike structure here,

0:42

replacing the normal lens.

0:44

But it does allow us to see the anterior

0:46

chamber of the globe very well.

0:50

You recall that we are not able

0:52

to see the posterior chamber,

0:54

but that area behind the lens in

0:58

the globe is the vitreous

1:00

or the posterior segment.

1:04

When we shift from ocular anatomy

1:06

to the orbital anatomy,

1:10

one can see the fat of the intraconal space.

1:15

As one scrolls,

1:17

you can see the extraocular muscles, as well as the

1:24

optic nerve inserting into the back of the globe.

1:27

Within the muscles, one finds the dark density fat

1:34

and we also see outside the muscle

1:36

we have dark density fat.

1:38

So this is the difference between the intraconal fat

1:41

versus the extraconal fat of the extraconal space.

1:46

Here we are seeing a portion of the superior oblique

1:49

muscles attachment to the globe,

1:51

but we also see the medial rectus and lateral rectus

1:54

muscle, as well as more inferiorly, the inferior

1:57

rectus muscle as it inserts on the globe.

2:01

In the coronal plane,

2:02

one can see this anatomy quite nicely.

2:05

One has the superior rectus muscle,

2:07

medial rectus muscle,

2:09

inferior rectus muscle and lateral rectus muscles.

2:13

In this particular patient,

2:14

they are enlarged because of thyroid

2:18

eye disease or thyroid orbitopathy.

2:22

Within that space, within the cone,

2:25

or the intraconal space, one has intraconal fat.

2:28

But you also see that there is fat outside

2:31

the muscles in the extraconal space.

2:34

You also note the close proximity of the ethmoid

2:39

sinus to the medial aspect of the orbit,

2:43

which is why one can have sinus inflammatory

2:46

complications that affect the orbit.

2:49

Here is the superior oblique muscle,

2:52

again, innervated by the trochlear nerve,

2:55

cranial nerve four.

2:56

And again, the lateral rectus muscle innervated

2:59

by cranial nerve six, the abducens nerve.

3:06

As you can see, below the orbit,

3:08

one has the maxillary sinus, and above the orbit,

3:12

the brain.

3:14

This small area here,

3:16

which can be seen bilaterally in the floor of the

3:19

orbit is the opening for the infraorbital nerve.

3:23

This is a nerve that is a branch of the second

3:27

division of the fifth cranial nerve,

3:28

the trigeminal nerve of the maxillary nerve.