GLAUCOMA 3- Automated Perimetry 1 and 2 Flashcards
What is the difference between kinetic and static?
Kinetic = the stimulus moves around (Goldmann)
Static = stimulus stays in same place (Humphrey/Henson)
What is threshold perimetry?
This gives us a depth of a VF. The depth of the scotoma
what spot sizes do we use?
Goldmann spot size 3
(research point = using larger spot sizes)
What is the DB scale?
0DB is the brightest DB
- Normal value is normally 33db.
This is a weird scale.
What is the Humphrey field analyser (HFA)?
- Full threshold and it is the gold standard
- Found in HES but also some optom clinics
Octopus
What are some advantages to the Humphrey field analyser 2?
- Compact size
- User friendly
- Gaze trackers
- “smart” data acquisition
What two programs can run on the Humphrey 2 analyser?
Central 30-2 :
- 30 degrees
- 76 test points
Central 24-2:
- 24 degrees
- 54 test points
Which one of the two is the gold standard and why?
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24-2 becasue of the speed time
What can be the down side to the 24-2?
It will neglect 80% of the feild
WHat can 24-2 be used to see?
Early Glaucoma
Why is one good thing about manual perimetry ?
You can go above 30 degrees of feild
when do we test binocular visual feild?
120 degrees, for DVLA
what are the seed/primary points?
4 points are assessed : representing the 4 quadrants. This will be used as a starting point for the rest of the feild
How do we reach the threshold?
and what is this technique called?
- The first point it is brighter then the px should see. (calculated on age)
- The machine then will go 4db higher to make it dimmer
- It will keep going 4db until they cannot see it : FIRST REVERSAL
- It will then go brighter by 2db.
- If the px cannot see this it make it brighter by 2 db until seen : SECOND REVERSAL.
STAIRCASE PROCEDURE!
what is the measured threshold?
the difference between the last unseen point and the second reversal.
What if the brightest stimulus was not seen?
This is the first reversal! The stimulus will then get bigger
What are the advanatges to automated perimetry?
- stimulus parameters standardised
- Exam stratategy is known and reproducible
- No observer bias
- computer records
- Non opthalmic qualified person can handle this
what is the bearing of the blind spot?
This blind spot can get bigger due to scotoma.
glaucomatous defect
What defect is more likely to occour first?
Superior
Which half of the field is more important on day to day?
Inferior, as we use this to walk about ect
What is a big issue with VF?
Measurement variablity.
Why might a VF have variability?
- artefacts
- pupil size
- media opacities (cat)
- poor fiaxtion
What can cause issues?
- Lens rim
- Refraction
- Pupil size
- Lid/brow
- Blinking (make sure they do blink)
What is the learning effect?
People get better at feilds the more they do the test this a pyschological thing that happens. We should consider the first two field sessions as training visits