Aqueous Humor

Question 1

What are the primary purposes of aqueous humor?

Answer 1

1) Maintain globe shape
2) Nourishment & waste removal for the avascular cornea & lens.
3) Source of antioxidants for corneal epithelium & lens
4) Shock Absorber

Question 2

Refractive index of aqueous humor is…?

Answer 2

1.333

Question 3

Aqueous humor is secreted by which part of the eye?

Answer 3

ciliary epithelium of ciliary process

Question 4

Name the 3 vascular circles in the ciliary body.

Answer 4

Episcleral circle
intramuscular circle
major arterial circle (near iris root)

Question 5

Ciliary process is supplied by which 2 branches of the Major Arteriole Circle?

Answer 5

Anterior ciliary process arteriole

Posterior ciliary process arteriole

Question 6

Aqueous humor formation follows a _____ rhythm.

It is greatest in which part of the day?

Answer 6

circadian.

8am-noon, then afternoon, then least after midnight.

Question 7

Which two enzymes are involved in aqueous humor formation?

Answer 7

Na+ K+ ATPase

Carbonic Anhydrase

Question 8

What does carbonic anhydrase do?

What do inhibitors of carbonic anhydrase do?

Answer 8

Turns carbonic acid into CO2 & H2O.

Inhibitors can decrease aqueous humor production.

Question 9

Where is Na K ATPase found?

Answer 9

Bound to plasma membrane of non-pigmented epithelium of ciliary process.

Question 10

What are the primary and secondary pathways for aqueous humor outflow?

Answer 10

Primary: Trabecular meshwork route
Secondary: Uveoscleral/posterior route

Question 11

The Retinal Pigmented Epithelium and the Non-PIgmented Epithelium are joined by _____ which created a ______ between the blood vessels and aqueous humor.

Answer 11

tight junctions

blood aqueous barrier

Question 12

Which of these have fenestrated capillaries?
Which have nonfenestrasted?
ciliary process
iris
choroid
retina

Answer 12

Fenestrated:
ciliary process
choroid

Nonfenestrated:
iris
retina

Question 13

Inflow rate + outflow rate of aqueous humor = ?

Answer 13

Intraocular Pressure (IOP)

Question 14

A breakdown in the blood aqueous barrier increases _____.

Answer 14

IOP

Question 15

How does increased plasma components in anterior chamber and increased net inflow of fluid from blood to aqueous humor affect IOP?

Answer 15

Increases IOP

Question 16

When aqueous humor inflow by ultrafiltration is suppressed it is called _____?
Does this increase or decrease IOP?
This inflammatory process also reduces or increases secretion of aqueous humor?

Answer 16

Pseudofacility.
Decrease IOP.
Reduces secretion.

Question 17

Mean IOP magic # is _____?

Answer 17

21

Question 18

Which factors increase IOP?
Which factors decrease IOP?
Increased age
Women over 40
Winter
Supine Posture
Exercise
Blinking hard
Alcohol, marijuana, heroin
Caffeine, Tobacco

Answer 18

Increase:
Increased age
Women over 40
Winter
Supine Posture
Blinking hard

Decrease:
Exercise
Alcohol, marijuana, heroin

Question 19

The test performed to measure IOP is called ____?

Answer 19

tonometry

Question 20

What is this equation called?
W + S = P x A + B
What is it used for?

Answer 20

Modified Imbert-Fick Law.
Used to ascertain IOP.

W (external force)
A (area)
P (pressure inside sphere)
S (surface tension)
B (force req'd to bend cornea)

Question 21

What factors affect IOP measurements?

Answer 21

central corneal thickness
corneal curvature
age-related corneal changes
biomechanics (rigidity, hydration, elasticity)

Question 22

The cornea’s physical properties can be described as _____?

Answer 22

visco-elastic

Question 23

The Pulsatile Ocular Blood Flow is a calculated value that represents ______ circulation?

Answer 23

Choroidal

Question 24

What are some reasons 24-hour IOP measurement would be helpful?

Answer 24

evaluate efficacy of drug testing,
check for Normal Tension Glaucoma progression,
identify IOP spikes over short & long term

Question 25

What are some methods of noninvasive and temporary 24-hour IOP measurement?

Answer 25

contact lenses | continuous applanation or indentation devices

Question 26

What are some methods of invasive and permanent 24-hour IOP measurement?

Answer 26

``` subconjunctival ante chamber implants in AC as IOL hap tics scleral buckle scleral fixated sensor post chamber implants - choroidal ```

Question 27

80-90% of aqueous humor formation is done by which process? | Which two processes form the rest of aqueous humor?

Answer 27

Secretion. Diffusion & Ultrafiltration.

Question 28

What are the 4 layers of the ciliary process?

Answer 28

Capillaries Strome Pigmented Epithelia Nonpigmented Epithelia

Question 29

What kind of outflow represents 70-95% of aqueous humor outflow?

Answer 29

Trabecular meshwork

Question 30

What kind of outflow represents 5-30% of aqueous humor outflow?

Answer 30

Uveoscleral

Question 31

What does Na K ATPase do in aqueous humor formation? | What does this cause water to do?

Answer 31

Pushes Na+ ions into posterior chamber from ciliary process. | Water follows it from the ciliary process cells, contributing to aqueous humor.

Question 32

Aqueous humor formation works against or with the concentration gradient?

Answer 32

Against.

Question 33

What are the 3 muscles in the ciliary body?

Answer 33

longitudinal circular radial

Question 34

The Major Arterial Circle is made of paralimbal branches of which arteries?

Answer 34

Long Posterior Ciliary Arteries

Question 35

The longitudinal fibers attach the ciliary body to the _____?

Answer 35

limbus

Question 36

The circular muscles are found in which portions of the ciliary body?

Answer 36

anterior and inner portions

Question 37

The radial muscles connect which two other muscles in the ciliary body?

Answer 37

longitudinal and radial muscles

Question 38

Which time of the day is aqueous humor produced at about 2.97 µl/min.?

Answer 38

8am - noon

Question 39

Which time of the day is aqueous humor produced at about 1.28 µl/min.?

Answer 39

midnight - 6am

Question 40

Which time of the day is aqueous humor produced at about 2.68 µl/min.?

Answer 40

afternoon

Question 41

What is a pneumotonometer?

Answer 41

An instrument that blows a puff of air at the cornea to cause flattening and hence measure intraocular pressure. It is commonly used in tests for glaucoma.

Question 42

What is a Perkins tonometer?

Answer 42

A type of portable applanation tonometer

Question 43

What is applanation tonometry?

Answer 43

A method which measure IOP based on the force required to flatten (applanate) a constant area of the cornea.