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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
What is the pressure range for NCT?
0-60 mmHg
26
Goldmann ton is based on ____ principle
Imbert Fick
27
Which technique appears to measure IOP independent of Central Corneal Thickness?
Pascal
28
Which tonometer has auto-mode?
NCT
29
What kind of damage can happen from Goldmann reading?
Probe toe mark, lasts for only a couple of hours
30
Thick mires ___estimates IOP
Overestimates, subtract 1 or 2 from your reading
31
Thin mires ___estimates IOP
Underestimates, add 1 or 2 from your reading
32
What is Pressure Phosphene Tonometry?
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
How does applanation tonometry differ from indentation tonometry?
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
How does Pascal measure quality of pressure reading?
Q of 1-4
35
How can IOP change with eye movement?
IOP increases with blinking, lid squeezing, holding your eyes open, gazing upward
36
Functions of the aqueous:
Transport nutrients Provide internal pressure Refractive media
37
Which tonometer doesn't need anesthetic?
Icare, NCT
38
Name tonometry method: components: Micro strain gauge Uses a 1.5mm transducer tip and microprocessor to calculate IOP Self contained battery powered device
Tonopen
39
``` Name tonometry method: Advantages Very light, small, & portable Patient positioning Less apprehension Less affected by corneal thickness Can be used on peripheral corneas ```
Tonopen
40
Corneas thinner than ___um increase/decrease Goldmann reading?
Thinner than 540 decreases Goldmann reading.
41
``` 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 ```
Perkins Tonometer
42
What is normal IOP? Normal difference between eyes
7-21. 4 between
43
How does Genetics, age, gender, refractive error, and race affect IOP?
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
At what age is corneal at adult thickness?
5-9 years
45
IOP influence: alcohol
Decreases
46
Which tonometer is second best gold standard?
Perkins tonometer
47
IOP influence: Marijuana
Decreases
48
IOP influence: LSD
Increases
49
What is serial tonometry?
Multiple measurement over the same day
50
IOP influence: tobacco
Increases
51
IOP influence: heroin
Decreases
52
Which part of the eye has the most resistance to aqueous outflow?
Juxtacanalicular portion of the trabecular meshwork. The aqueous ultimately goes to the episcleral venous area.
53
When is the tonopen ready to measure?
When it says ===
54
IOP influence: caffeine
Increases
55
What can cause IOP higher than 21?
Ocular HTN, Glaucoma
56
When is IOP the highest during the day? What short term IOP changes can happen?
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
IOP influence: Corticosteroids
Increases
58
IOP influence: fat free diet
Decreases
59
What is the mean IOP?
16 mm Hg
60
Which tonometer tends to overestimate IOP?
iCare, pascal, NCT in high range
61
Which tonometer will struggle with flat corneas?
Pascal
62
``` Name tonometry method: Disadvantages. Needs corneal anesthetic Expensive latex covers (and allergy potential) Require calibration (not a big deal) Less accurate at higher IOPs ```
Tonopen

Theory and Methods Fall 2015 (4 decks)

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