hvf

1. AUTOMATED PERIMETRY
SIVATEJA CHALLA

2. INTRODUCTION
• Automated way of mapping the visual field
• Important diagnostic test in glaucoma
• Diagnosing and monitoring progression of other disease

3. TRAQUIARS HILL OF VISION

4. NORMAL VISUAL FIELD

5. BASICS
• Current standard unit of luminous intensity is candela/m²
(cd/m²)
• Apostilbs [asb units] – HVF
• asb to cd/m², multiply by 1/pi (0.31831)
• 1 asb is the least intense stimulus that can be seen foveally.
LIGHT INTENSITY

6. • describes retinal
sensitivity
• Lower intensity (asb)
required at particular
point, higher is the
sensitivity (db value) at
that point.
DECIBELS

7. • HIGH db VALUE------- low asb intensity of light
stimulus ------ HIGH RETINAL SENSITIVITY
• LOW db VALUE------ high asb intensity of light
stimulus ------ LOW RETINAL SENSITIVITY
• Background illumination in HFA is 31.6 asb

8. STIMULUS SIZE

9. THRESHOLD
• The intensity of stimulus which is appreciated 50% times and
missed 50% times is called threshold intensity
starting with a stimulus which the patient is very likely to observe
reducing it by 2-4 dB to non seeing intensity
again increasing the intensity to cross the threshold

10. TYPES
• KINETIC
Eg. Goldmans projection perimeter
• STATIC and KINETIC
Eg. Humphreys visual analyser, octopus

11. STATIC KINETIC
Computerised Manual
Stimulus size constant Stimulus is moved from a non seeing area
to a seeing area along a set meridian
contrast sensitivity is tested thru out speed,size,colour and brightness of target
are the different variables
ADVANTAGES
quantifiable,reproducable
statistical manipulation easy
inexpensive and durable machines
Statistical manipulation difficult
Threshold detection is more sensitive Patients are comfortable
reduces the need for highly trained
technicians
can define scotomas rapidly
DISADVANTAGES
Large amounts of unfamiliar data
interpretation difficult
skill,training important
tedious and time consuming and
expensive
early or subtle changes can be
overlooked

12. ANATOMICAL BASIS OF FIELD OF VISION
FORMATION OF OPTIC NERVE

13. STAGES OF ARCUATE FIELD DEFECTS

14. OTHER FIELD DEFECTS
• Centro caecal defect (optic nerve disease)
• Altitudinal defects (advanced glaucoma/AION)
• central scotoma (optic neuruitis or mac disease)
• Hemianopic defects
Heteronymous defects
Homonymous defects

15. INTERPRETATION OF
FIELDS

16. APPROACH
1 Check patient and
test data
Obtain general
impression
2
Observe defects
and defect curve
3
Review statistics4
PATIENT DATA
CORRECTED COMPARISONS
PDNP
COMPARISONS
TDNP
PROBABILITY
TDPP
CORRECTEDD PROBABILITY
PDPP
GLOBAL INDICES
GREY SCALE
VALUES
RAW DATA
BABIE’S CURVE
TEST DATA

17. WANDER
• What was done?
• Accuracy (Reliability)
• Normal or abnormal
• Defect pattern
• Evaluate compatible disease
• Review

19. ZONE 1
Patient data and test parameters

20. PATIENT DATA
• Name
• Age/sex
• Eye
• Pupil size
• V/A with refractive status
EXAMINATION DATA
• Programme
• Strategy
• Stage/ Phase
• Test target/ duration
( Goldmann size III )
• Background illumination
( 31.5 apostilb )

21. ZONE 2
reliability indices

22. RELIABILITY
• Fixation loss >20% is unreliable
• False positive >33% is unreliable
• False negative >33% is unreliable

24. ZONE 3
Grey scale

25. GRAY SCALE
• Most Colourful- Least reliable

26. ZONE 4
total deviation

27. NORMAL RETINAL
SENSITIVITY
PATIENT’S RETINAL
SENSITIVITY
DIFFERENCE
HUMPHREY
TOTAL DEVIATION NUMERICAL PLOT

28. - media opacities.
- cataracts .
- corneal opacities.
- refractive errors.
- rarely miosis.

29. Normal ‘Hill’ Of Vision

30. Generalised Depression of Hill

31. ZONE 5
pattern deviation

32. Total
deviation
Generalized
depression in
field
Pattern
deviation

35. • Probability values (P) :Indicates the significance of the
defects .
• Shown as P< 5%, P< 2% , P<1% and P< 0.5%.
• The lower the P value, the greater is its clinical
significance
clinical significance : if there are abnormal points in
total deviation plot that persist in the pattern deviation
plot, we are looking at scotomas .

36. ZONE 6
global indices

38. GLOBAL INDICES - MD
A
B

39. <-6dB MILD GENERALISED DEPRESSION
-6 TO -12dB MODERATE GENERALISED
DEPRESSION
->-12dB SEVERE GENERALISED DEPRESSION
GLOBAL INDICES - MD

40. MEAN
DEVIATION
NO OF
POINTS
<5%
NO OF
POINTS
<1%
CENTRAL FIELD
EARLY <6DB <18 <10 O POINTS <15 DB
MODERATE 6-12 DB 18-37 11-20 No points ‘0’ db and
1point <15 db in one
hemifield
SEVERE >12 DB >37 >20 No points ‘0’ db and
1point <15 db in both
hemifields

41. GLOBAL INDICES – PSD OR LV
150
160
150
150
150
140
170 110
MEAN STANDARD
DEVIATION
0
10
40

42. GLOBAL INDICES
MD: NORMAL
PSD: NORMAL
MD:ABNORMAL
PSD: NORMAL
MD: ABNORMAL
PSD:ABNORMAL
MD: ABNORMAL
PSD: ABNORMAL
SHAPE
(PATTERN STD DEVIATION)
HEIGHT
(MEAN DEVIATION)

43. Short term fluctuation ( STF)

44. Corrected pattern standard deviation
(CPSD):
• Measure of variability within the field after correcting for
short term fluctuation ( intra-test variability )
• Newer programs like SITA do not determine CPSD and
STF.
PSD STF CPSD

45. Interpretation of the field defect using the
MD and CPSD :

47. ZONE 7
Glaucoma hemifield test

49. ZONE 8
Numerical display

50. • Gives the threshold for all points checked
• Value in () indicates that the point has been tested twice

51. IS THE DEFECT DUE TO
GLAUCOMA??

52. CPSD 4 dB P <5%
GHT – outside normal limits
ANDERSON’S CRITERIA
1
2
3
CPSD 4 dB p< 5%

53. Step wise interpretation
Basic data
Reliability
Total & Pattern deviation
Statistical indices
Glaucoma hemi field test
Actual threshold values/fovea
Is it abnormal –Anderson’s criteria
Is it glaucoma –correlate clinically
Establish a baseline

54. TEST 30-2 24-2 10-2 MAC
PROGRAMME
TEST POINTS 76 54 68 16
DENSITY
(DEGREES)
6 6 2 2
BARE AREA
AROUND
FIXATION PT
3 DEGREES 3 1 1

55. PIT FALLS

58. ARTEFACTS
• OBSTRUCTION
RIM ARTEFACTS
PTOSIS
MEDIA OPACITIES
ANGIOSCOTOMA
• MIOSIS
• REFRACTION ARTEFACTS
• HIGH POWER PLUS AND MINUS LENSES

59. PRACTICAL PEARLS
(DURING RECORDING)
• pause the test in between if he/she is tired
• >50% stimulus will not be seen so that he is reassured
and does not press the trigger due to impatience
• Should have taken enough rest,may be given coffee,
ensure he is attentive
• Give practice sessions esp to glaucoma patients
• Close other eye well
• If test is abnormal repeat
• Always record same program which was done earlier