L50 Choroid

Question 1

What happens at the Ora Serrata?

Answer 1

The pars plana merges with the choroid

Question 2

What is the anterior limit of the choroid?

Answer 2

The Ora Serrata

Question 3

How thick is the choroid at the Ora Serrata?

Answer 3

About 60 microns thick roughly

Question 4

How thick is the choroid at the macular behind the retina?

Answer 4

Could be 160 microns (its thickest)

Question 5

When the eye is unnaturally stretched like it is in myopia would the choroid be thicker or thinner?

Answer 5

Thinner

Question 6

What are the layers of the Choroid?

Answer 6

Supra Choroid Stroma - which can be split into Haller’s layer & Sattler’s layer Choriocapillaris Bruch’s membrane (diagram shows these - remember sclera surface even covers the back of the eye)

Question 7

What does the suprachoroid act as?

Answer 7

A border between the sclera and vascular choroid and serves as a pathway for nerves. (This is how long and short ciliary nerves get from the back of the eye to the front).

Question 8

What is Haller’s layer known for containing?

Answer 8

Large blood vessels ,

(To remember think H for huge)

Question 9

What is Sattler’s layer known for containing?

Answer 9

Small blood vessels

Question 10

What is the choriocapillaris known for containing?

Answer 10

Capillaries

Question 11

If blood vessels naturally go from larger to smaller why are their distinct layers for size of vessels in the choroid?

Answer 11

Vessel branching occurs close together which produces a layered appearance.

Question 12

What does Bruch’s membrane separate?

Answer 12

The retina from the choroid

Question 13

How thick is Bruch’s membrane?

Answer 13

When you are born its about 2 microns. As you get older it goes up to 6 microns thick.

Question 14

How many layers does Bruch’s membrane contain and what are they?

Answer 14

5 Layers

Basal Lamina - which is the basement membrane layer

Collagen layer

Elastin layer

Collagen Layer

Basal Lamina- the other basement membrane layer

(RPE stands for retinal pigment epithelium).

Question 15

What does Bruch’s membrane do?

Answer 15

It controls the movement of fluids from the choriocapillaris into the retina.

Question 16

What happens when Bruch’s membrane breaks down?

Answer 16

Because of its function to control movement of fluids from choriocapillaris into the retina when it breaks down you get oedema.

Question 17

Why can Bruch’s membrane have local thickenings?

Answer 17

Because of drusen- drusen are sites of accumulated debris

Question 18

Why are drusen potentially troublesome?

Answer 18

Because they push the retinal pigment epithelium away from the choriocapillaris and therefore sufficent exchnage of nutrients with the retina does not occur. Therefore photorceptors become starved of essentials.

Question 19

What are drusen?

Answer 19

Accumulations of debris in Bruch’s membrane

Question 20

What is the function of the choroid?

Answer 20

To provide nutrients to the outer 5 layers of the retina

Question 21

What’s interesting about blood flow in the choriocapillaris and why does this happen?

Answer 21

It flows 20x faster than it actually needs to. The idea is that this is to cool down the retina. (Because don’t forget you have a lot of light focussed on a very small point in the retina).

Question 22

What does the melanin/melanocytes of the choroid do?

Answer 22

The melanin of the choroid, along with that of the ciliary body, iris, and retina, contributes to the eye’s black box effect, serving to absorb stray light.

Question 23

Where does the eye’s main blood supply come from?

Answer 23

The eye’s blood supply comes from the ophthalmic artery which is a branch of the internal carotid artery which is a branch off the aorta.

Question 24

The short posterior ciliary arteries and the long posterior ciliary arteries are branches off what artery?

Answer 24

The ophthalmic artery

Question 25

What is the globe supplied by?

Answer 25

Anterior and posterior ciliary arteries

Question 26

Where do anterior ciliary arteries pierce the globe?

Answer 26

Anteriorly near the limbus.

Question 27

What arteries supply the choroid?

Answer 27

Short posterior ciliary arteries supply the choroid

Question 28

Fill in the gaps:

Posterior ciliary arteries pierce the …….. near the …….

Answer 28

Posterior ciliary arteries pierce the sclera near the optic nerve head

Question 29

What does the long posterior ciliary artery supply?

Answer 29

Long posterior ciliary arteries (lpca) pass forward to mainly supply the iris.

Question 30

Why are short posterior ciliary arteries called short posterior ciliary arteries (spca) ?

Answer 30

Short because they don’t go very far.

Posterior because they go in the back of the eye.

(Found in Haller’s layer, Satler’s Layer and ultimately choriocapillaris)

Question 31

Where do the long posterior ciliary arteries go up to?

Answer 31

All the way up to the front of the eye to the major iridic circle (from the back of the eye).

Question 32

Where do anterior ciliary arteries go towards?

Answer 32

The major iridic circle

Question 33

What does it mean for a vessel to be recurrent?

Answer 33

(of a nerve or blood vessel) turning back so as to reverse direction.

Question 34

FILL IN THE GAPS

……. run anteriorally and join anterior ciliary arteries to supply blood to the iris and ……….

Answer 34

Long posterior ciliary arteries (lpca) run anteriorly and join anterior ciliary arteries to supply blood to the iris and ciliary body

Question 35

Some recurrent branches of the long posterior ciliary arteries (lpca) and anterior aciliary arteries (aca) supply what?

Answer 35

The anterior choroid