Automated perimetry

1. Automated Perimetry
Dr.Vikram.S.Nakhate
Dr.Vijay.Shetty

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

3.  Traquair described it as a field of vision in a sea of
darkness
 It has a shape of a hill
 Peak representing fovea
 2 slopes representing nasal and temporal field of
vision

6. Kinetic perimetry
 Stimuli is moved from a non seeeing area to a seeing
area along a set meridian
 Aim is to find points in the visual field of equal retinal
sensitivity
 Lister perimetry
 Campimetry
 Goldman perimetry

7. Static perimetry
 Intensity of the stimuli at the same pre determined
spot is varied
 Find out threshold at those locations
 More accurate than kinetic perimetry
 Gives a 3D picture of the hill of vision
 Picks up field defects more accurately

8.  Apostlib is an absolute measure of luminance and is
equal to 0.3183 candela m2 or 0.1 mililambert
 Decibel is a measure of sensitivity of retina
 Inversely proportional
 It is a relative measure varies from machine to
machine

9. Testing strategy
 Full threshold
 Threshold
 Suprathreshold

10. Full threshold strategy
 Staircase method (4-2 bracketing strategy)
 Used to detect threshold

11. 4-2 bracketing
 Intensity of stimulus is decreased in 4-db step till
stimulus is no longer seen
 Increasing the stimulus in 2-db step till stimulus is
seen again

12. Threshold perimetry
 Threshold found at predetermined points
 Time consuming process

13. Suprathreshold perimetry
 Intensity of stimulus shown at a spot much higher
than threshold at that spot
 Mainly for screening
 Picks up gross visual defects

14. Newer threshold strategy
 Fastpac:
 Decreases the test time by 40%
 3-db increment instead of 4-db
 Threshold crossed only once

15.  Sita standard:
 Takes half time than full threshold method
 Sita fast:
 Takes half time than fast pac threshold method

16. 30-2
 Number of test points:76
 Density :6 degree
 Only 3 degree bare area is left surrounding the
fixation spot

17. 24-2
 Number of test points:54
 Density: 6 degree
 Only 3 degree bare area is left surrounding the
fixation spot

18. 10-2 central threshold test
 Number of test points: 68
 Density: 2 degree
 Only 1 degree bare area is left surrounding the fixation
spot

19. Macular programme
 Number of test points: 16
 Density: 2 degree
 Only 1 degree bare area is left surrounding the fixation
spot

20. Reliabilty indices
 Fixation losses:
 Indicates steadiness of gaze
 Presenting stimuli at blind spot
 loss.>20% is unreliable

21.  False positives
 Trigger happy patients
 Responds to an audible stimuli when no target is
presented
 >33% is unrelible

23.  False negative:
 Fails to respond to a suprathreshold stimuli
 Indicates fatigue,inattentiveness
 >33% is unreliable

26. Zone 1
 Colour of the stimulus
 Background illumination: 31.5 asb
 Stimulus size: III
 Testing strategy

28. Zone 3

29. Zone 4 total deviation
 Depicts difference between patients threshold fom
that of age matched normals
 Reveals generalised depression
 Cannot confirm scotoma

30. Zone 5 pattern deviation
 Reveals focal defects after adjusting for overall
depression
 Confirms scotoma

37. Global indices
 Mean deviation:
 Indicates overall deviation of the visual field from
normal
 Positive number indicates an elevated field
 Negative number indicates a depressed field
 Cannot confirm scotoma

38. Psd
 Derived from total deviation
 Indicates the degree to which the numbers differ from
each other
 Highlights pot-holes in hill of vision
 Calls attention for scotoma

39. Short term fluctuation
 Measure of intra-test variability
 Threshold at 10 pre selected points is tested
 Difference between 1 & 2 measurement noted

40.  Cpsd is psd corrected for sf
 If sf is due to unreliability
 Then cpsd is better
 If sf is due to pathology
 Then psd is better

42. GHT
 5 set of points above horizontal meridian
 Compared to mirror image below horizontal meridian

44. Zone 8
 Numerical display:
 Gives the threshold for all points checked
 Value in () indicates that the point has been tested
twice

45.  Never rely on first report
 Always correlate clinically
 Correct any significant refractive error before
proceeding

46. Sources of error
 Miosis:
decreases the threshold sensitivity in peripheral field
Increases the variability in central field
 Uncorrected refractive errors:
Threshold sensitivity appears less
 Hyperopic patient with contact lens:
Defect gets magnified & vice versa

47.  Spectacles can cause rim scotomas
 Ptosis :
Suppression of superior visual field

48. Principle
 Is there a field defect ?
 Is it due to glaucoma ?
 Is the defect progressing ?
 Compare to selected baseline
 Discard learning fields from baseline
 Recognise false progression

49. False progression
 Learning curve
 Long term fluctuation
 Pupil size

50.  Pupil: 1 mm

51.  Pupil: 2.5 mm

52. Andersons criteria
 1. pattern deviation plot:
 3 non-edge points with p<5%
 One point with p<1%
 Cluster in arcuate area
 2.cpsd
 Abnormal with p<5% on 2 consecutive occasion
 3.abnormal GHT

53. CATARACT

54. GLAUCOMA

55. CATARACT & GLAUCOMA

56. Detecting progression
 Overview printout
 Glaucoma change probability analysis

57. Overview print out
 Sequential series of field of same patient over a period
of time
 Displays gray scales,total &pattern deviation
 Statistical analysis is however not provided

58.  This patient developed cataract,which was extracted
later
 Pattern deviation plot remained clear

60. Glaucoma progression

61. Glaucoma change probability
analysis
 Compares rate of change in patients visual field,with
that of stable glaucoma patient
 Clear triangle represents improvements
 Solid ones shows points of deterioration
 Progression represented by a cluster of black triangles
in same area increasing in size with time

64.  2 or more points deteriorate on 2 consecutive test

65.  3 or more points deteriorate on 3 consecutive test

66. Advanced field defects
 Why pattern deviation plot not showing defect

67.  Not enough points with sensitivity to produce pattern
deviation plot

68. Follow up with 10-2
 Enough sensitive points to produce pattern deviation

69.  Advanced defect f/u with a size V target(64mm2)

70.  Macular programme in advanced defects

71. Size V target:macular split
 Macular split (0 db) next to fovea may indicate wipe
out

72.  Thank you