Visual Field Analysis ?

Question 1

what personal details should you?

Answer 1

..Is it the correct patient
..Record ID number 
..name 
..DOB (Age) 
..Refractive Error

Is the data correct
..Date of test
..correct eye

Question 2

How is the reliability criteria classified?

Answer 2

False positive
False negatives
Fixation losses

Question 3

When is the data unreliable?

Answer 3

False positive >33%
False Negative >33%
Fixation losses >20%

Question 4

What does False positive mean?

Answer 4

Patient says they can see a light when no light is shown or responds faster than usual humanly possible

Question 5

What does False negative mean?

Answer 5

Patient says they cant see a light when they are shown a brighter light in a location where they said they could see it before

Question 6

What does fixation loss mean?

Answer 6

Patient responds to a light which is shown in their blind spot

Question 7

What does data representation have?

Answer 7

Numeric printout 
Greyscale
Global visual field indices
Total and pattern deviation maps
Probability analysis
Glaucoma analysis

Question 8

What does the numeric printout show?

Answer 8

Numeric representation of the threshold sensitivity. Higher the number the higher the threshold sensitivity

Question 9

what does 0dB mean?

Answer 9

Just able to see the perimeters brightest max light

Question 10

What does <0dB mean ?

Answer 10

Not able to see detect the perimeters brightest light cannot see anything then

Question 11

what do the brackets mean in numeric printout?

Answer 11

Threshold measured twice

Question 12

What does the grey scale show?

Answer 12

the grey scale is a graphical representation of the numeric printout ?

Question 13

what does threshold sensitivity change with?

Answer 13

age

Question 14

what happens as we get older?

Answer 14

decline in sensitivity?

Question 15

how much sensitivity changes with age?

Answer 15

0.7 dB per decade

Question 16

What is relative visual field sensitivity?

Answer 16

The difference between the measured visual field sensitivity and the age-corrected normal visual field sensitivity. This is also called the Total Deviation Decibel map

Question 17

What does the Total deviation decibel map mean?

Answer 17

Total deviation decibel map= patients measured threshold sensitivity - the normal threshold sensitivity for their age at each test location

Question 18

what does the negative numbers mean?

Answer 18

the number of dB less than they should have seen for their age

Question 19

what are confidence intervals?

Answer 19

If the measured sensitivity is outside the confidence interval it is registered as abnormal and a probability level is assigned.

Question 20

what does grey probability symbols mean?

Answer 20

the darker the more genuine pathology there is

Question 21

what does localised visual field loss do?

Answer 21

Age matched normal field

measured field

Question 22

what does cataract show?

Answer 22

a cataract of 20dB will register with the darkest probability symbol and mask any localised loss.

Question 23

what does the diffuse lost do?

Answer 23

diffuse loss hides the localised lost and hides the pathology

Question 24

what does the pattern deviation probability map show in cataract?

Answer 24

Pattern deviation plots exposes localised loss by adjusting the general height of the hill

Question 25

What does the global visual field indices do?

Answer 25

Global visual field indices summarises the information about one aspect of the entire test.

Question 26

what type of three global indices are there?

Answer 26

Diffuse loss Focal loss variability

Question 27

What is Mean Deviation (MD)?

Answer 27

average of the total deviation values?

Question 28

When is MD abnormal?

Answer 28

if the mean deviation is greater than -2.00dB

Question 29

when do you increase MD?

Answer 29

in the presence of cataract and or large areas of focal loss

Question 30

What is pattern standard deviation PSD?

Answer 30

the standard deviation around the mean of the total deviation

Question 31

What are PSD sensitive to?

Answer 31

non uniformity in the visual field

Question 32

when is PSD abnormal ?

Answer 32

abnormal when value greater than +2.00dB

Question 33

what is advantage of global indices?

Answer 33

Give a single measure about the state of the visual field | can be used to monitor visual field change over time(Progression)

Question 34

What is the disadvantage of global indices?

Answer 34

There is loss in spatial information

Question 35

What is glaucoma hemifield test?

Answer 35

visual field sectors corresponding to the retinal nerve fibre arrangement in the upper hemifield are comp[ared for asymmetry with their mirror image sectors in lower hemifield

Question 36

how does glaucoma hemifield classify pathology?

Answer 36

``` within normal limits outside normal limits borderline general reduction in sensitivity abnormally high sensitivity ```

Question 37

what might artificially affect visual field plot?

Answer 37

mistakes are often made on the first examination repeat fields at a later date repeat at least once before considering referral repeating on the same day would be affected by fatigue

Question 38

what is the affect of fatique on VF ?

Answer 38

Clover leaf pattern on grey scale resulting from fatigue fixation losses increase in false negative

Question 39

what might happen in fatigue effect?

Answer 39

increase in false +ve and false -ve responses - fixation losses - contraction opf the visual field due to droopy eyelids

Question 40

How can you reduce the fatigue affect?

Answer 40

talk to the patient encourage the patient

Question 41

what happens to fatigue effect in pathology?

Answer 41

effects maybe exaggerated in patients with pathology

Question 42

what other contraction due to external factors are there?

Answer 42

- droopy eyelids-maybe fatigue related - heavy facial features - spectacle rim - lens holder - hair - poor positioning occluder

Question 43

what happens in functional or hysterical field loss?

Answer 43

Failure of the patient to respond to visible stimuli typically produces variable responses Kinetic perimetry- peripheral isopter tends to decrease in size throughout testing -spiral or star shaped isopter

Question 44

Give examples of functional loss?

Answer 44

>Produce falsely low sensitive values at various location >>high false negative rate >>High spatial frequency value >>High no at the primary seed points give distinct clover shaped pattern >>long test duration particularly with SITA

Question 45

What is true pathology of cataract?

Answer 45

General reduction in sensitivity >HIGH mean deviation >LOW pattern standard deviation/CPSD >large no of significant pionts on Total deviation map

Question 46

What is true pathology of early Glaucoma?

Answer 46

> nasal step is an early vf defect in glaucoma > note that MD and PSD are low > significant total and pattern deviation maps

Question 47

what is true pathology of cataract and glaucoma ?

Answer 47

> cataract and glaucoma often co- exist > note general reduction in sensitivity on the total deviation map >the pattern deviation reveals the focal loss