Perimetry is a test that measures the visual field and is important for diagnosing and managing glaucoma. There are two main types of perimetry - kinetic and static. The Humphrey visual field test is a type of static, automated perimetry that uses thresholds to test the central and peripheral visual field. It provides reliable indices and plots like total deviation and pattern deviation to analyze visual field defects and monitor for progression of glaucoma. Common visual field defects seen in glaucoma include localized defects, arcuate scotomas, nasal steps, and advanced defects like tunnel vision.

1. PERIMETRY
&
HUMPHREY VISUAL FIELD ASSAY
Lt Col A.K.M. Rashed-Ul-Hasan
Long Term Fellow Trainee(Glaucoma)
CMH Dhaka

2. VISUAL FIELD
Visual field is an island hill of vision surrounded by a sea of blindness – Traquair
Visual field is all the space that one eye can see at any given instant ---Tate & Lynn

3. 60
50 50
90 90
70 70
Fixation
X X
= Physiological Blind spot
X
NORMAL VISUAL FIELD LIMITS

4. Visual Field Testing Methods
Central Field
Amslar Grid- 20°
Tangent (Bjerrum) Screen- 30°
Goldmann
Automated (Octopus/Humphrey)- 30°
Peripheral Field
Confrontation
Goldmann
Automated 90° programm

5. Location of Visual Field Defects
Peripheral
> 30º
 Central
5º or less from the point of fixation
Paracentral
>5º – 30º
Ceacal
Paraceacal
Periceacal
Centroceacal

6. Perimetry is defined simply as the study of the visual field .
PERIMETRY & PERIMETER
Perimeter is an instrument designed for perimetry.

7.  Kinetic
Stimulus moves
 Confrontation
 Lister
 Tangent screen
 Goldman
Type of Perimetry
 Static
Stimulus does not moves
 HVFA
 OCTOPUS

8. Static Kinetic
 VFD detect earlier with 20% defect
 Area fixed but stimulus varies in intensity
 3D
 Computarized
 Threshold type
 Less error
 Both glaucoma and neurological
 VFD detect earlier with 40% defect
 Intensity fixed but stimulus moves from non-seeing to
seeing area
 2D
 Not Computarized
 Non Threshold type
 More error
 Good for neurological, periphery of field & adv glaucoma

9. Role of Perimetry
1.To diagnose clinical conditions.
A) Ocular- Glaucoma, Optic nerve disorders.
B) CNS conditions- Optic nerve pathway disorders.
CNS Tumors.
Occipital lobe disorders.
2. To manage glaucoma.
To set target IOP
Follow up.

10. Different types of Automated Perimetry

11. THRESHOLD
If a particular intensity of light is shown 100 times and if it is
appreciated 50 times then that particular intensity of light is
termed as threshold.

12. Determination of threshold

13. APOSTILB (Asb)
 Absolute units of light intensity / brightness
 Humphrey : 1 - 10,000 asb
 Goldman & Octopus : 1 - 1000 asb

14. DECIBEL (dB)
 Tenth of logarithm unit ( 1 dB = 0.1 log unit )
 Relative units of light intensity
Higher the dB lower intensity of light stimulus high retinal sensitivity.

15. 0 dB = 10,000 asb
10 dB = 1,000 asb
20 dB = 100 asb
30 dB = 10 asb
40 dB = 1 asb
0 dB = Brightest light = low retinal sensitivity.
40 dB = Dimmest light = high retinal sensitivity.

16. Humphrey visual field test
Threshold test
Central Test
a. Central 30-2 ( 76 )
b. Central 24-2 (54)
c. Central 10-2 (68)
d. Macular progm (16)
Peripheral Test
a. Peripheral 60-4
b. Nasal Step
c. Temporal crescent
Speciality test
a. Neurological 20
b. Neurological 30
Strategy
Standerd threshold
strategy
a. Full Threshold Strategy
b. Fast Pac
Newer threshold strategy
a, SITA Standerd
b. SITA fast
Screening or
suprathreshold test
NB: Central 30º : 66% of ganglion cell & 83% visual cortex

17. Interpretation

18. Zone 1 Patient data & test data
Zone 2 Foveal Threshold & Reliable
indices
Zone 3 Gray Scale
Zone 4 Total Deviation
Zone 5 Pattern Deviation
Zone 6 Global Indices
Zone 7 Glaucoma Hemi-field Test
Zone 8 Raw Data

20. 0.2 second duration
The effect of size of pupil:
 Pupil should be 3-4 mm
 Constricted pupil
 Diffuse visual field depression
 Edge scotoma
 Very important in follow up test

21. RELIABILITY INDICES

23.  Central :
Yellow light at centre of bowl.
 Small diamond :
Below the central target
Macular degeneration
 Large diamond :
When central fixation lost
Central scotoma
 Bottom LED:
Superior field test
Fixation of target

24. Fixation loss
 Indicates steadiness of gaze during the
test
 >20% is unreliable
 5% Stimulus is presented over blind spot

25. False positive
>15% is unreliable (SITA Standard)
>33% is unreliable (Full threshold)
 Trigger Happy
Abnormally pale

26. False Negative
>15% is unreliable (SITA Standard)
>33% is unreliable (Full threshold)
 Fatigue, inattention, malingering
Clover leaf patern

27. Gaze Tracker
Upward spikes: indicating eye movements
Downward spikes: indicating blinking during stimulus presentation.

28. Total Deviation plots
1. Numeric value in upper plot
Diff. in dB between the patients test results and the age corrected normal values a
each tested point in the visual Field.
Value is abnormal : if >5 dB less than normal .
2. Gray scale symbols in lower plot
translates values of upper plot, Darker the symbols, more the depth of defect
3. Generalized depression:
A. Media opacities
B. Refractive error
C. Miosis

29. Pattern Deviation
 It is derived from total deviation values and
adjusted to demonstrates the localized defect.

30. P Value

31. Global Indices
It’s the summary values that represent distilled statistical information.
Used to monitor progression of glaucomatous damage
Consist :
1. VFI: Patient’s overall VF function.
2. MD: Overall sensitivity of the field.
3. PSD: Focal loss within the field.

32. Glaucoma Hemifield Test
Compare 5 zone of upper field with mirror image of lower field to see asymmetric field
loss in glaucoma.
5 comments
1. Outside normal limit
2. Borderline
3. General reduction of sensitivity
4. Abnormal high sensitivity
5. With in normal limit

33. Localized Field defect
 The TDPP and PDPP looks similar.
 Causes-
Early glaucomatous ON damage
AION
ON pathway defect
Occipital lobe infarcts

34. Generalized field defect in TDPP.
Localized defect in PDPP.
Found in advance stage of glaucoma.
Cataract associated with glaucoma
Irregular Generalized Field defect

35. Generalized defect in TDPP.
Normal PDPP.
Cause
Media opacities.
Advanced and end stage glaucoma.
Optic neuritis.
Uniform Generalized Field defect

36. PRACTICE

37. Nasal Step Pattern

38. Arcuate pattern

39. Advanced case of
glaucoma

40. Enlargement of blind
spot

41. Left Sided Homonymous Haemianopia

42. Bi-nasal hemianopia

43. Bi-temporal hemianopia

44. AION

45. Upper Haemiretinal Vein Occlusion

46. Tubular field
defect due to RP

47. Toxoplasma
choroidoretinitis

48. Glaucomatous Field Defect

49. Progression of field defects in POAG
 Initially observed in Bjerrum’s area ( 10 ˚ -25 ˚ from fixation)
Generalised contraction of field
Baring of blind spot : exclusion of the blind spot from the central
field due to inward curve of the outer boundary of 30° central field
(Fig A)
Small wing-shaped paracentral scotoma (Fig B)
Seidel’s scotoma : paracental scotoma joins the blind spot (Fig C)
Arcuate or Bjerrum’s scotoma: by the extension of Seidel’s
scotoma in an area either above or below the fixation point to
reach the horizontal line (Fig D)
Ring or double arcuate scotoma & Roenne's central nasal
step : when the two arcuate scotomas join (Fig E)
Advanced glaucomatous field defects : Tubulur vision