Assessment of VF reliability

Question 1

What % of fixation losses means that the test is unreliable?

Answer 1

> 20%

Question 2

What % of false positives means that the test is unreliable?

Answer 2

> 15%

Question 3

What % of false negatives means that the test is unreliable?

Answer 3

> 20%

Question 4

What happens when a fixation loss occurs?

Answer 4

The px has seen a stimulus which should be in their blind spot, so they are looking around
OR
blind spot was not properly located at the start of the test

Question 5

What happens when a false positive occurs?

Answer 5

Px is clicking too much or responding to a fake stimulus (e.g. auditory but no light)
Px responds before 180ms min response time
Px responds after response window

Question 6

What happens when a false negative occurs?

Answer 6

Machine shows a stimulus at 9dB brighter than threshold, and px doesn’t respond

Question 7

How do HFAs track fixation losses?

Answer 7

Infrared tracking of corneal reflexes relative to pupil centre - the distance between the two is measured. If px looks away, the distance changes (pupil centre moves but corneal reflex doesn’t)

Question 8

What is the listening time?

Answer 8

Time from the start of the auditory cue to 180ms after stimulus presentation

Question 9

What is the response window?

Answer 9

Starts 180ms after stimulus presentation, ends at mean of px’s response times

Question 10

What causes variability within and between tests?

Answer 10

Increased defect depth
Increased eccentricity
Increased severity of loss