Tono 3 Flashcards
Applanation instruments
Goldmann
Perkins
Tonopen (microstrain gauge)
Dynamic contour instrument
Pascal
Rebound instrument
iCare
Indentation instrument
Non contact (puff) , Contact (Shiotz)
Pressure phosphene instrument
Proview
Transpalpebral instrument
Diaton
Tono methods (6)
Applanation (includes microstrain gauge) Dynamic Contour Rebound Indentation Pressure phosphene Transpalpebral
Indentation method
- Measures what?
- Two types
- Measures amount of force required to indent entire cornea
- Non contact (air puff) or contact (shiotz)
Applanation technique
- Measures what?
- Examples
Measures amount of force required to flatten the corneal surface only.
Goldmann, Perkins, tono
Tonopen
- method
- useful when
- Measurement affected by what?
- Tends to measure low or high?
- Statistical coefficients
- Measurement range
- Applanation technique with microstrain gauge
- Useful in children, supine patients, gross corneal path
- Affected by central corneal thickness
- Tends to measure high
- 5% is the best, 10%, 20%
- range is 5-80 mmHg (less accurate at higher IOPs)
Can use on peripheral cornea
Consider latex allergies
Main differences between ton open and ton open avia
Avia is smaller and averages 10 readings instead of only 3-4.
Larger LCD display
Measurement range is lower: 5-55 mmHg. Pen is 5-80 mmHg.
Perkins applanation tono
- Advantages
- Disadvantages
- Pressure range
Advantage: Portable, good for supine patients
Disadvantage: Fixed mag, cannot examine cornea before and after, use anesthetic.
Range: 0-80
Dynamic contour tono (pascal)
Slit lamp mounted instrument
Very expensive
Independent of central corneal thickness !!!!!
Measures cardiac cycle
Average reading given with a Q value for quality
Requires several seconds of steady fixation
Range 5-80
calculated and displayed on screen
i care rebound tono range and pros/cons
range is 7-50
pros: no anesthesia required
Cons: Can be influenced by CCT, over estimate IOP by 0.6-1.8
- can get i cares at home to measure by self.
NCT range
Pros and cons
Range is 0-60
Pros: easy to use, no anesthetic
cons: Less reliable than goldmann. Overestimates. Can be affected by apprehension, keratometry and cardiac cycles.
Pressure phosphene tono (PPT)
How do you admin test
Pressure is applied to the patients globe on eyelid by pressing the plunger. Have patient look down and out. Once the pressure in the globe equals the pressure applied by probe, the patient will see a phosphene- circular or arc shaped light.
pressure phosphene tono (PPT)
pros/cons
range
pros: good for anyone who can report seeing the phosphene
Cons: Not relibable, must have compliant patient, limited scale
8-40
Transpalpebral tono how to admin
Set patient fixation at a 45 degree angle
Position rod on lid and perform 5-6 x then average.
It calculates the eyeballs resistance at cornea and converts to IOP.
Ranges 5-60
Corneal hysteresis
What is it and what are the ranges
How well the cornea can absorb energy and dissipate it. Also depends on IOP.
Less than 8mmHg= Risk for glaucoma. K can’t take impact well and ON will likely have same properties.
Medium is 8-12 mmHg
High is 12+ mmHg = good. Less glaucoma risk.
