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theory and methods fall 2015 > Theory Exam 2 > Flashcards

Theory Exam 2 Flashcards

1
Q

Thick cornea ____estimates IOP

A

Thick overestimates IOP

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2
Q

Which tonometer can cause apprehension?

A

NCT

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3
Q

What is the area of the Goldmann probe?

A

3.06mm^2

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4
Q

Which pressure range can Perkin’s measure?

A

0-80 mmHg (similar to Goldmann)

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5
Q

What are corneal pulsations?

A

The IOP fluctuates because of the cardiac cycle

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6
Q

Overnight Goldmann sanitation is done with…

A

Hydrogen Peroxide

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7
Q

Which tonometer is dynamic contour tonometry?

A

Pascal

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8
Q

What can cause IOP lower than 7?

A

Retinal detachment, uveitis, wound leak, corneal penetration

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9
Q

How does environment change IOP?

A

IOP decreases with cold air

IOP increases with sudden gravity reduction

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10
Q

Which tonometers are good for supine patients?

A

Tonopen, Perkins, Transpalpebral tonometry requires supine.

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11
Q

Which tonometer uses disposable tip and measures impedance?

A

Icare

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12
Q

5-80 mm Hg is the pressure range for which tonometer?

A

Tonopen

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13
Q

What is pressure range for Icare?

A

7-50 mmHG

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14
Q

What fixation angle is required for transpalpebral tonometry?

A

45 degrees downward. You put the device on the upper eye through the eyelid.

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15
Q

What drops are used in Goldmann?

A

Sodium fluorescein and benoxinate combo

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16
Q

Which accuracy method is for tonopen? Tonopen avia?

A

Tonopen uses statistical coefficient (5% is good)

Tonopen avia uses confidence percepts? (95% is great)

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17
Q

Which tonometer has the highest pressure range?

A

Pascal with 1 to 200 mm Hg

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18
Q

How does Anterior Uveitis influence IOP?

A

It decreases IOP because of prostaglandins from inflammation , but then inflammation causes increased IOP (clogging TM)

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19
Q

What is the measurement range of the tonopen? The tonopen avia?

A

5 - 80 mmHg. Avia is 5-55 mmHg

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20
Q

How does a retinal detachment influence IOP?

A

It decreases IOP because RPE drains aqueous fluid

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21
Q

What are the 3 parts of the Goldmann tonometer?

A

Applanting probe, probe arm, measuring drum

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22
Q

What are the Goldmann assumptions?

A

Sphere should be dry, thin, perfectly elastic and flexible.
Displaced volume during process of applanation from within the sphere should be small in relation to total volume of sphere

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23
Q

Which tonometer takes 8-12 seconds for a measurement?

A

Pascal

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24
Q

How does systemic conditions affect IOP?

A

IOP increases
-As systolic level increases in hypertensive patients
-With systemic hyperthermia
-Obesity
-Increased pulse rate, and hemoglobin concentration
In response to hormones and steroids such as ACTH,
glucocorticoids and growth hormones

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25
Q

What is the pressure range for NCT?

A

0-60 mmHg

26
Q

Goldmann ton is based on ____ principle

A

Imbert Fick

27
Q

Which technique appears to measure IOP independent of Central Corneal Thickness?

A

Pascal

28
Q

Which tonometer has auto-mode?

A

NCT

29
Q

What kind of damage can happen from Goldmann reading?

A

Probe toe mark, lasts for only a couple of hours

30
Q

Thick mires ___estimates IOP

A

Overestimates, subtract 1 or 2 from your reading

31
Q

Thin mires ___estimates IOP

A

Underestimates, add 1 or 2 from your reading

32
Q

What is Pressure Phosphene Tonometry?

A

You need patient input to report the phosphene. Good for glaucoma patients that don’t make sense. It has a limited scale. It touches the eyelid.

33
Q

How does applanation tonometry differ from indentation tonometry?

A

Indentation records the force needed to indent the cornea (includes Air puff and obsolete Schiotz)
Applanation measures force to flatten cornea (coldmann, Perkins, Tonopen)

34
Q

How does Pascal measure quality of pressure reading?

A

Q of 1-4

35
Q

How can IOP change with eye movement?

A

IOP increases with blinking, lid squeezing, holding your eyes open, gazing upward

36
Q

Functions of the aqueous:

A

Transport nutrients
Provide internal pressure
Refractive media

37
Q

Which tonometer doesn’t need anesthetic?

A

Icare, NCT

38
Q

Name tonometry method: components:
Micro strain gauge
Uses a 1.5mm transducer tip and microprocessor to calculate IOP
Self contained battery powered device

A

Tonopen

39
Q 
Name tonometry method: Advantages
 Very light, small, & portable
 Patient positioning
 Less apprehension
 Less affected by corneal thickness
 Can be used on peripheral corneas
A

Tonopen

40
Q

Corneas thinner than ___um increase/decrease Goldmann reading?

A

Thinner than 540 decreases Goldmann reading.

41
Q 
Name tonometer: Diasadvantages
 Less stable
 Fixed magnification
 Cannot examine cornea before and after
 Easier to be off axis
 More difficult to get accurate readings
 Uses anesthetic
A

Perkins Tonometer

42
Q

What is normal IOP? Normal difference between eyes

A

7-21. 4 between

43
Q

How does Genetics, age, gender, refractive error, and race affect IOP?

A

Enlarged C/D and familial OAG. As age increases iop increases, women over 40 might have higher iop, myopes -10 or worse have higher IOPs (with axial length), and AA, asian, and latinos tend to have higher IOP.

44
Q

At what age is corneal at adult thickness?

A

5-9 years

45
Q

IOP influence: alcohol

A

Decreases

46
Q

Which tonometer is second best gold standard?

A

Perkins tonometer

47
Q

IOP influence: Marijuana

A

Decreases

48
Q

IOP influence: LSD

A

Increases

49
Q

What is serial tonometry?

A

Multiple measurement over the same day

50
Q

IOP influence: tobacco

A

Increases

51
Q

IOP influence: heroin

A

Decreases

52
Q

Which part of the eye has the most resistance to aqueous outflow?

A

Juxtacanalicular portion of the trabecular meshwork. The aqueous ultimately goes to the episcleral venous area.

53
Q

When is the tonopen ready to measure?

A

When it says ===

54
Q

IOP influence: caffeine

A

Increases

55
Q

What can cause IOP higher than 21?

A

Ocular HTN, Glaucoma

56
Q

When is IOP the highest during the day? What short term IOP changes can happen?

A

It’s the highest at 3 am!
IOP increases in the supine position
IOP decreases with prolonged and brief exercise
IOP increases with physical straining (Valsalva’s maneuver)

57
Q

IOP influence: Corticosteroids

A

Increases

58
Q

IOP influence: fat free diet

A

Decreases

59
Q

What is the mean IOP?

A

16 mm Hg

60
Q

Which tonometer tends to overestimate IOP?

A

iCare, pascal, NCT in high range

61
Q

Which tonometer will struggle with flat corneas?

A

Pascal

62
Q 
Name tonometry method: Disadvantages.
 Needs corneal anesthetic
 Expensive latex covers (and allergy potential)
 Require calibration (not a big deal)
 Less accurate at higher IOPs
A

Tonopen

theory and methods fall 2015 (4 decks)

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