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OCULAR PHYSIOLOGY > Aqueous Humor > Flashcards

Aqueous Humor Flashcards

2
Q

What are the primary purposes of aqueous humor?

A

1) Maintain globe shape2) Nourishment & waste removal for the avascular cornea & lens.3) Source of antioxidants for corneal epithelium & lens4) Shock Absorber

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3
Q

Refractive index of aqueous humor is…?

A

1.333

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4
Q

Name the 3 vascular circles in the ciliary body.

A

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

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5
Q

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

A

Anterior ciliary process arteriole

Posterior ciliary process arteriole

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6
Q

Aqueous humor is secreted by which part of the eye?

A

ciliary epithelium of ciliary process

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7
Q

Which two enzymes are involved in aqueous humor formation?

A

Na+ K+ ATPase

Carbonic Anhydrase

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8
Q

Aqueous humor formation follows a _____ rhythm.It is greatest in which part of the day?

A

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

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9
Q

What does carbonic anhydrase do?What do inhibitors of carbonic anhydrase do?

A

Turns carbonic acid into CO2 & H2O.Inhibitors can decrease aqueous humor production.

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10
Q

Where is Na K ATPase found?

A

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

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11
Q

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

A

tight junctions

blood aqueous barrier

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12
Q 
Which of these have fenestrated capillaries?
Which have nonfenestrasted?
ciliary process
iris
choroid
retina
A 
Fenestrated:
ciliary process
choroid
Nonfenestrated:
iris
retina
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13
Q

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

A

Primary: Trabecular meshwork routeSecondary: Uveoscleral/posterior route

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14
Q

Inflow rate + outflow rate of aqueous humor = ?

A

Intraocular Pressure (IOP)

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15
Q

A breakdown in the blood aqueous barrier increases _____.

A

IOP

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16
Q

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?

A

Pseudofacility.
Decrease IOP.
Reduces secretion.

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17
Q

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

A

Increases IOP

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18
Q

Which factors increase IOP?Which factors decrease IOP?Increased ageWomen over 40WinterSupine PostureExerciseBlinking hardAlcohol, marijuana, heroinCaffeine, Tobacco

A 
Increase:Increased
 age
Women over 40
Winter
Supine 
Posture
Blinking hard
Decrease:Exercise
Alcohol, marijuana, heroin
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19
Q

Mean IOP magic # is _____?

A

21

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20
Q

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

A 
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)
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21
Q

What factors affect IOP measurements?

A

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

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22
Q

The test performed to measure IOP is called ____?

A

tonometry

23
Q

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

A

visco-elastic

24
Q

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

A

Choroidal

25
Q

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

A

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

26
Q

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

A

contact lensescontinuous applanation or indentation devices

27
Q

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

A

subconjunctivalante chamber implants in AC as IOL hap tics scleral buckle scleral fixated sensorpost chamber implants - choroidal

28
Q

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

A

Secretion.Diffusion & Ultrafiltration.

29
Q

What are the 4 layers of the ciliary process?

A

CapillariesStromePigmented EpitheliaNonpigmented Epithelia

30
Q

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

A

Trabecular meshwork

31
Q

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

A

Uveoscleral

32
Q

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

A

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

33
Q

Aqueous humor formation works against or with the concentration gradient?

A

Against.

34
Q

What are the 3 muscles in the ciliary body?

A

longitudinalcircularradial

35
Q

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

A

Long Posterior Ciliary Arteries

36
Q

The longitudinal fibers attach the ciliary body to the _____?

A

limbus

37
Q

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

A

longitudinal and circular muscles

38
Q

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

A

anterior and inner portions

39
Q

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

A

8am - noon

40
Q

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

A

midnight - 6am

41
Q

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

A

afternoon

42
Q

What is a pneumotonometer?

A

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.

43
Q

What is a Perkins tonometer?

A

A type of portable applanation tonometer

44
Q

What is applanation tonometry?

A

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

45
Q

What are the conditions to Imbert-Fick law?

A

Must be perfect sphere, dry, infinitely thin

W= P1 x A

46
Q

Aqueous humor secreted by ciliary epithelium of ciliary process enters posterior chamber by what three ways? and describe them

A

Diffusion- lipid soluble substances

Ultrafiltration- water and water soluble substances

secretion - larger size substances of greater charge

47
Q

What is hypotony?

A

low intraocular pressure oftern related to chronic intracolular inflammation (uveitis) , wound leaks after eye surgery or retinal detachment

48
Q

pneumotonometer also gives____ amplitude and calculates _____ volume

A

pulse, pulse

49
Q

pneumotonometer measures ___ pulses and selects ___ best to calculate IOP and POBF

A

7 , 5

50
Q

T/F the IOP measurement you take inside , could be different then the one you take outside

A

T

51
Q

T/F the pneumotonometer has a large range of normality and the values are derived making numerous assumptions which makes accurate

A

F. it makes it INACCURATE

OCULAR PHYSIOLOGY (13 decks)

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