Measurements of IOP

Question 1

Describe Palpation (tactile) measurement of IOP

Strong correlation to Goldmann?, When is it used? Can it detect pressure differential?, How do you document tactile?

Answer 1

• Poor correlation to Goldmann
• Useful when other methods are unavailable
• Can detect pressure differential
• Soft, equal by tactile

Question 2

Describe manometry

Invasive?, How does it measure IOP, is it accurate?

Answer 2

• Highly invasive
• Measurement of fluid column in needle reflects IOP
• Very precise measurement inside eye

Question 3

Name two fixed forced tonometers

Answer 3

• Maklakoff

- Posner

Question 4

Name five fixed area tonometeres

Answer 4

• Goldmann
• Perkins
• Non Contact
• Ocular Response Analyzer
• Dynamic Observation Tonometer

Question 5

Describe Maklakoff tonometer

How it works, does it require anesthetics? two disadvantages

Answer 5

• Weighted instrument
• requires local anthestics
• Disadvantage:
• eye movement smears area, resulting in an inaccurate reading
• Heavy weighted instrument could increase IOP in resting state

Question 6

Describe Posner tonometer

Disposable? What material is it made out of?

Answer 6

• Disposable plastic tonometer

Question 7

Describe advantages and disadvantages of Goldmann

Answer 7

• Advantage: Quick, moderate cost

- Disadvantage: Error control, not portable, need to have infection control, corneal abrasions

Question 8

Describe Perkins tonometer

Based on Goldmann principle?, advantages

Answer 8

• Based on Goldmann Principle
• Portable
• Useful for children, elderly, obese
• Still requires infection control

Question 9

Describe Non-contact tonometer

Based on Goldmann principle? How does it calculate IOP

Answer 9

• Based on Goldmann Principle
• Air puff
• Corneal flattening measured by optical sensor and calculated IOP

Question 10

What are the advantages and disadvantages of Non Contact Tonometer?

Answer 10

Advantages: No anesthesia, minimum infection control, can be done by technician.

Disadvantage: Not portable, expensive, need to be calibrated, patients do not like.

Question 11

Non Contact Tonometer and Goldmann have a very good correlation? TRUE/FALSE

Answer 11

• TRUE

Question 12

Describe Ocular response analyzer

How does it calculate IOP?
Note: Can factor in corneal elasticity and viscosity

Answer 12

• takes the average of two pressure readings (inward and outward applanation)

Question 13

Describe Dynamic Observing Tonometer

Why is it dynamic, why is it no longer used

Answer 13

• measure IOP over time

- difficult to learn

Question 14

Is Schiotz tonometer simple, reliable and accurate to use? YES/NO

Answer 14

• YES

Question 15

What are the advantages of the tonopen?

(Handheld device, Is it accurate? Can it be used on scarred, irregular corneas? What happen for low IOP’s and high IOP’s?)

Answer 15

• portable device
• good correlation between 10-20 mmHg
• Can be used on scarred, irregular, transplanted corneas
• low IOP’s are overestimated, high IOP’s are underestimated

Question 16

Describe the advantages/disadvantages of a combination-applanation (Pneumatic)
tonometer

(Single/continuous reading? Underestimate/Overestimates IOP?)

Answer 16

• allows continuous IOP readings

- Disadvantage: tends to overestimate IOP readings 2-4 mmHg compared to Goldmann

Question 17

What are the advantages of dynamic contour tonometers?

Hint: Goldmann reading depends on cornea characteristics

Answer 17

• non-invasive direct IOP measurement

- continuously and accurately measures IOP irrespective of corneal characteristics

Question 18

Describe the I-Care (Rebound tonometry)

How does it measure IOP, does it require anesthetic? how do results compare to Goldmann?

Answer 18

• handheld device
• measure deceleration of probe
• no anesthetic required
• may overestimate compared to Goldman