1. An Introduction to Visual Fields
Professor David Henson
University of Manchester

2. What are they used for? Diagnosis / Management Glaucoma
Space-occupying lesions of visual pathway
other optic nerve disorders
Functional Assessment of Vision
Occupational (e.g. Driving, Flying, Police)
Blindness / Low Vision registers
Litigation

3. Extent of Visual Field
100 60
Line of sight
Line of sight 60 75
Definition: All the space that any one eye can see at any given instant.

4. Visual field chart
Limit of the
visual field

5. Extent of binocular field90 60
Binocular Field
Monocular temporal
crescent

6. Island of Vision
Isopters, lines joining points of equal sensitivity

7. Sensitivity Differential threshold +
Stimulus intensity
(I+ΔI)
Intensity
Background
Intensity (I)
Differential threshold
How much brighter than the background does the stimulus need to be to be seen +

8. Measuring the visual field
Stimulus
Angle
subtended
Fixation
point
Patient
Cupular

9. Current test strategies
Conventional
Examination Strategies
Unconventional
Examination Strategies
Kinetic
Static
Ring perimetry,
Frequency doubling,
Displacement perimetry,
Noise perimetry,
Resolution,
Blue on yellow
Threshold
SITA
ZATA
Full Threshold
Suprathreshold
Single
Multiple

10. Examination Strategies
Kinetic perimetry
Conventional
Examination Strategies
Kinetic
Stimulus size and
intensity kept constant
for each isopter

11. Kinetic perimetry
3 different stimuli to plot 3 isopters

12. Advantages of kinetic perimetry
Perimetrist has more control
area examined
direction and speed
re-instruct patient
repeat measures
Severe field loss
Children
Elderly

13. Disadvantages of kinetic perimetry
Time consuming
Less sensitive
not fail safe
Too much flexibility
operator dependent
You can also do static testing on a Goldmann perimeter although this is rarely done

14. Decibel scales Widely used in perimetry
High values mean dimmer test intensity
High values mean the patient is more sensitive
Decibel number can be thought of as the density of a filter placed in front of a fixed intensity lamp

15. Decibel Scales Not a measure of intensity but attenuation
3 dB down is half as bright
10 dB down 1/10 as bright
Log scale
Each instrument has a specified 0dB test intensity
dB scales refer to this
It is often difficult to transfer the findings from one instrument to another

16. Static perimetry Static Threshold Suprathreshold Monitoring Detection/
screening

17. Suprathreshold strategy
Stimuli presented at intensity calculated to be above threshold
If seen no other testing of that location
It is very fast
Developed for screening/driving test

18. Suprathreshold strategy
Missed stimuli are normally retested and only recorded as a miss if missed on both occasions
Missed stimuli may be tested at a series of higher intensities or thresholded
Some suprathreshold test present more than one stimulus at a time and the patient verbally reports the number they see

19. How does the patient respond?
Verbally
Kinetic perimetry
Multiple stimulus suprathreshold perimetry
faster (screening)
helps maintain vigilance
Button press
single stimulus (threshold and suprathreshold)

20. Suprathreshold perimetry
Advantages
Disadvantages
Faster per test location
Less than 5 mins for both eyes
Ideal for detecting defects
Ideal for screening
Can miss shallow defects
Does not give precise measure of defect depth (unless test establishes the thresholds of missed locations)

21. Threshold perimetry Used to monitor defects
Routine strategy in eye departments
Much more time consuming
You can also undertake kinetic testing on some static perimeters

22. Threshold perimetry
Measures threshold at series of predetermined locations
Uses repetitive bracketing
On average ~4 presentations per test location

23. Print out Thresholds Grey scale Defects Probability values
age corrected
height corrected
Probability values

24. Visual field advantages
Direct measure of visual function
What you are trying to preserve
Non invasive
Relatively cheap, high cost of service due to time commitment
High sensitivity and specificity

25. The End
Ref:
D B Henson. Visual Fields 2nd Edition, Butterworth Heinmann