Choroid

Question 1

What does the choroid supply?

Answer 1

nourishment to the outer retina

Question 2

is the choroid vascular or avascular?

Answer 2

vascular

Question 3

the choroid is separated from the RPE by what?

Answer 3

bruchs membrane

Question 4

What kind of tissue makes up the choroid?

Answer 4

connective tissue (vascular)

Question 5

Can the choroid absorb light?

Answer 5

YES due to high pigmentation.

Question 6

How thick is the choroid posteriorly? anteriorly?

Answer 6

post. 200um
ant. 100um
(overall thin tissue)

Question 7

What are the six layers of the choroid?

Answer 7

bruchs membrane (considered part of inner layers of choroid)
Choriocapillaris
Sattlers (medium sized BV)
Hallers (big BV)
Suprachoroid
Lamina Fusca (most outer)

Question 8

How big is the suprachoroid layer (including lamina fusca)? What types of cells are located here? is the suprachoroidal space vascular or avascular?

Answer 8

30um
melanocytes, fibroblasts and connective tissue fibres.
avascular!

Question 9

Stroma of the choroid is made up of which layers? vacular or avascular? What cells are located here? How does this layer differ in darker people compared to lighter skinned people?

Answer 9

sattlers and hallers
vascular
collagen one, fibroblasts, collagen fibres and melanocytes also has mast cells, macrophages and lymphocytes.
it will be darker pigmented in darker people.

Question 10

The vascular layers of the choroid are supplied from? how do they drain?

Answer 10

short posterior ciliary arteries (supply posterior choroid)
vortex veins (4-6, each vein drains one section of choroid) which further drain into sup/inf opthalamic veins after piercing sclera.

Question 11

what do the long posterior ciliary arteries supply? central retinal artery?

Answer 11

anterior part of choroid.

supplies the major circle of iris.

Question 12

where is the density of choriocapillaris layer greatest? it extends to what structure? how are the capillaries fed?

Answer 12

at the fovea.
ora serratta.
from feeder arterioles in sattlers layer (one feeder supplies one hexagonal patch of capillaries).

Question 13

venules all come together to form what?

Answer 13

larger veins (vortex veins)

Question 14

What are some main functions of the choroid besides blood supply to outer retina?

Answer 14

thermoregulation by blood flow
blood flow regulation can affect IOP
possible role in eye growth regulation?
possible role of another means of accommodation? (i.e. large changes in thickness in response to defocus in animals, changes are smaller in humans but still present).

Question 15

In chickens it has been found that the choroid does what in response to myopic defocus? hyperopic lens? difference between chickens and humans?

Answer 15

thicken (therefore if positive lens held to eye, choroid will thicken)
thin (if a negative lens held to eye, choroid will thin)
in chickens this happens within seconds, for humans it can take hrs.

Question 16

The choroid is highly pigmented due to what? high pigmentation is characteristic of what type of animals?

Answer 16

melanin/melanocytes

primates

Question 17

microvilli at the RPE intercalate with?

Answer 17

photoreceptors

Question 18

O2/nutrients pass through what to get to the RPE?

Answer 18

fenestrated capillaries->bruchs->RPE

Question 19

What type of cells are present in lamina fusca?

Answer 19

melanocytes therefore pigmented.

Question 20

photoreceptors are part of inner or outer retina?

Answer 20

outer

Question 21

How many SPCA? How many LPCA?

Answer 21

10-20 (they pierce sclera in a ring around optic nerve)

2 of these, pierce sclera further anteriorly.

Question 22

How many anterior ciliary arteries? what do they travel along? to form what?

Answer 22

seven of these they go with EOMs and form major circle of iris.

Question 23

Since the choroid sits in front of the sclera, what can it do?

Answer 23

protect the sclera from increases in IOP.

Question 24

Intrinsic neurons are scattered throughout the choroid, what is their function?

Answer 24

UNKNOWN.