4. 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
5. 60
50 50
90 90
70 70
Fixation
X X
= Physiological Blind spot
X
NORMAL VISUAL FIELD
LIMITS
6. Visual Field Testing Methods
Central Field
Amslar Grid- 20°
Tangent (Bjerrum) Screen- 30°
Goldmann
Automated (Octopus/Humphrey)- 30°
Peripheral Field
Confrontation
Goldmann
Automated 90° program
7. Location of Visual Field Defects
Peripheral
> 30º
Central
5º or less from the point of fixation
Paracentral
>5º – 30º
Ceacal
Paraceacal
Periceacal
Centroceacal
8. Perimetry is defined simply as the study of the
visual field .
PERIMETRY & PERIMETER
Perimeter is an instrument designed for
perimetry.
10. 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
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
11. 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.
13. 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.
16. 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.
17. 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.
18. 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 represent : 66% of ganglion cell & 83% visual cortex
20. 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
21.
22. 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
25. 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
26. Fixation loss
Indicates steadiness of gaze during the
test
>20% is unreliable
5% Stimulus is presented over blind spot
27. False positive
>15% is unreliable (SITA Standard)
>33% is unreliable (Full threshold)
Trigger Happy
Abnormally
pale
28. False Negative
>15% is unreliable (SITA Standard)
>33% is unreliable (Full threshold)
Fatigue, inattention, malingering
Clover leaf pattern
30. Total Deviation plots
1. Numeric value in upper plot
Diff. in dB between the patients test results and
the age corrected normal values at each tested point
in the visual Field.
Value is abnormal : if >5 dB less than normal .
1. Gray scale symbols in lower plot
Translates values of upper plot,
Darker the symbols, more the depth of defect
1. Generalized depression:
A. Media opacities
B. Refractive error
C. Miosis
31. Pattern Deviation
It is derived from total
deviation values and
adjusted to demonstrates
the localized defect.
33. Global Indices
It’s the summary values that represent distilled statistical
information.
Used to monitor progression of glaucomatous damage
Consists :
1. VFI: Patient’s overall VF function.
2. MD: Overall sensitivity of the field.
3. PSD: Focal loss within the field.
34. Glaucoma Hemifield Test
Compare 5 zone of upper field with mirror image of lower
field to see asymmetric field loss in glaucoma.
1. Outside normal limit
2. Borderline
3. General reduction of sensitivity
4. Abnormal high sensitivity
5. With in normal limit
35. Localized Field defect
The TDPP and PDPP looks
similar.
Causes-
Early glaucomatous ON
damage
AION
ON pathway defect
Occipital lobe infarcts
36. Generalized field defect in
TDPP.
Localized defect in PDPP.
Found in advance stage of
glaucoma.
Cataract associated with glaucoma
Irregular Generalized Field
defect
37. Generalized defect in TDPP.
Normal PDPP.
Causes
Media opacities.
Advanced and end stage glaucoma.
Optic neuritis.
Uniform Generalized Field
defect
51. 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
Editor's Notes
A typical automated strategy present a (4-2 dB) stimulus higher than expected intensity is shown; if seen the intensity is decreased in 4 dB steps until no longer seen then it is increased again by 2 dB step until seen once more
Central 30 : 66% of ganglion cell & 83% visual cortex
