Choroid/Retina

Question 1

What is the mean arterial pressure of the arteries entering the eye?

Answer 1

65 mmHg

Question 2

What is the pressure in the episcleral veins leaving the eye?

Answer 2

15 mmHg

Question 3

What is perfusion pressure in the eye?

Answer 3

Approximately 50 mmHg

Question 4

How is ocular perfusion pressure (OPP) calculated?

Answer 4

OPP = diastolic blood pressure - IOP

Question 5

What effect does a decrease in diastolic BP have on OPP?

Answer 5

OPP decreases

Question 6

What is autoregulation in the context of blood vessels?

Answer 6

The process by which blood vessels alter their diameter to increase or decrease resistance to blood flow

Question 7

Which cells are most likely responsible for autoregulation within the blood supply of the retina and optic nerve?

Answer 7

Pericytes

Question 8

Fill in the blank: A smaller blood vessel diameter offers more _______ resulting in a decrease in blood flow.

Answer 8

resistance

Question 9

Which arteries offer more resistance: retinal arteries or choroidal arteries?

Answer 9

Retinal arteries

Question 10

What does transmural pressure describe?

Answer 10

The pressure across the blood vessel wall

Question 11

How is transmural pressure calculated?

Answer 11

Pressure inside the vessel - Pressure outside the vessel

Question 12

What is critical closing pressure?

Answer 12

The pressure at which the blood vessel collapses and blood flow stops

Question 13

What effect does elevated IOP in acute glaucoma have on blood flow through the central retinal artery?

Answer 13

Reduces blood flow

Question 14

What happens to the perfusion pressure of retinal tissue when blood flow is reduced due to elevated IOP?

Answer 14

Decreases

Question 15

How do retinal vessels respond to changes in transmural pressure during elevated IOP?

Answer 15

Increase their vessel diameter through autoregulation

Question 16

What can happen if IOP remains acutely elevated for too long?

Answer 16

Central retinal artery reaches its critical closing pressure, resulting in CRAO

Question 17

What is the immediate threat to vision in acute glaucoma?

Answer 17

CRAO

Question 18

Automatic Nervous System Control

Question 19

Sympathetic Innervation

Question 20

Sympathetic fibers are prevalent throughout the uveal tract but they DO NOT

Question 21

innervate the central retinal artery past the lamina cribrosa and therefore do

Question 22

not influence retinal blood flow (18).

Question 23

Sympathetic innervation causes vasoconstriction of uveal blood vessels.

Question 24

It is important in maintaining adequate blood flow through the uvea during

Question 25

sudden increases in blood pressure.

Question 26

A sudden spike in blood pressure increases the force of blood floW

Question 27

through the small vessels of the uvea. The sympathetic system

Question 28

responds by causing constriction of the blood vessels

Answer 28

resulting in a

Question 29

compensatory reduction in blood flow.

Question 30

Parasympathetic lnnervation

Question 31

Parasympathetic fibers from the oculomotor and facial nerves are also

Question 32

prevalent throughout the uveal tract. Parasympathetic innervation is most

Question 33

prominent in the anterior uvea and has a minimal influence on choroidal and

Question 34

retinal blood flow.

Question 35

Parasympathetic innervation causes vasodilation of the uveal blood vessels

Question 36

in response to sudden decreases in blood pressure.

Question 37

Unlike the choroid

Answer 37

retinal vasculature is NOT under autonomic control.

Question 38

Unique Environment in the Eye

Question 39

The following unique characteristics of the eye allow for appropriate structure and

Question 40

function:

Question 41

IOP must be greater than the episcleral venous pressure so aqueous humor

Question 42

can drain from the anterior chamber

Answer 42

through the corneoscleral meshwork

Question 43

and into the venous system.

Question 44

IOP must be greater than the intracranial pressure in order to maintain an

Question 45

axoplasmic (i.e.

Answer 45

pressure) gradient that flows from the optic nerve towards

Question 46

the brain.

Question 47

Papilledema results from a reversal in the axoplasmic gradient between

Question 48

the eye and the brain due to an increase in intracranial pressure. This

Question 49

reversal causes cerebrospinal fluid to spill from the subarachnoid space

Question 50

onto the optic disc margins and the surrounding RNFL.

Question 51

• IOP must be lower than the pressure in the retinal and uveal arteries

Answer 51

allow-

Question 52

ing nutrients to be delivered from the choriocapillaris to the RPE cells.

Question 53

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Answer 53

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