2. VISUAL FIELDS
• The visual field is defined as that part of the
environment that is visible to the steadily
fixing eye. The extension of visual field is
as follows.
3. • Traquair defined visual field as
“ islandor hill of vision
surroundedby the sea of
darkness”.
• It has a shape of a hill which
correlates to density of
photoreceptors and their
receptive field sizes.
• Peak representing fovea
• 2 slopes representing nasal and
temporal field of vision
4. PERIMETRY
• Perimetry is the systematic measurement of
visual field function.
• It is the measurement of Hill of Vision in
terms of establishing the patient’s
differential light sensitivity across the
visual field.
5. HISTORY
• 1970 - The original octopus perimeter was first
introduced. Because of its room size and high
expensive nature it became unpopular
• 1982 - Humphrey field analyzer was first displayed at
American Academy of Ophthalmology.
• 1983- Michael Patella showed its first clinical trail
• 1984 –started production and became very popular
because of its small size and affordable price.
6. INDICATIONS OF
PERIMETRY
• Detection of glaucoma, progression
• Chorioretinal lesions
• Optic disc and optic nerve lesions
• Neuro-ophthalmological diseases
8. KINETIC PERIMETRY
o Manual
o AIM: To find points in the visual field of equal retinal
sensitivity
o METHOD: Stimulus is moved from a non seeing area
to a seeing area of visual field.
o Procedure is repeated with the use of same stimulus
along a set of meridians , usually spaced every 150
o The speed ,size , color and brightness of target are the
different variables
9. When the island hill-of-vision is kinetically
explored along the X-Y axes i.e. a planeparallel to
the surface of the sea, the locations of points with
the same threshold are identified; these are
isopters
10. ADVANTAGES
• Moving targets can define isopter contours and
scotomasrapidly
• Mapping the extent of scotoma is more precise with
kinetic
• Relatively inexpensive and durable
• Patients are comfortablewith humancontact of
examination
14. GOLDMANN’
s
PERIMETER
• Bowl type
• Standardization
• Peripheral as well as central
• Background intensity of 31.5
apostilbs (asb)
• The size and intensity of
targets may be varied to plot
different isopters kinetically
and determine local static
thresholds .
15. • The stimuli used to plot
an isopter are identified
by a roman numeral, a
number, and a letter.
• The roman numeral
represents the size of the
object.
16. • The number and letter
represent the intensity
of the stimulus.
• A change of one
number represents a 5-
dB (0.5 log unit) change
in intensity, and each
letter represents a 1-dB
(0.1 log unit) change in
intensity
17. STATIC PERIMETRY
• Computerized
• Aim: To find out the threshold of retina at various
fixed points.
• METHOD: Patient looks into a white hemispherical
bowl at a small fixation point at the center.
• Visual field stimuli are briefly presented at fixed
stationary locations
• Duration of presentation is about 200 milliseconds
• Patient presses a response button when the stimulus
is detected.
18. • Stimulus sizeandlocation is maintained constant
• Brightness varied at various predetermined
constant locations in order to find out the
thresholdat these locations
• In other words contrast sensitivity istested thru
out the extent of area perceived
• This type is concerned with altitude or verticalZ
axisof island of vision
19. When island hill of vision is explored along Z
axis: plane perpendicular to the surface of sea,
varying points of sensitivity is identified.
These are thresholdsdisplayed as meridional cuts
20. ADVANTAGES
• The data are quantifiable, reproducable, amenable
to statisticalmanipulation
• Thresholddetection is more sensitive
• The standardized technology reducesthe need for
highly trainedtechnicians
• Depth of scotoma is more accurate with static
perimetry
21. DISADVANTAGES
• Large amounts of unfamiliar dataare
generatedmaking interpretation difficult
• Tediousand time consuming
• The equipment is expensive.
22. HUMPHREY FIELD ANALYSER
THE MACHINE HAS 2
PARTS-
-perimetric unit- bowl type
screen
- control unit- computer
• Use static stimuli
• Viewing distance of 33cms.
• Background luminance- 31.5asb
• Stimulus size-( Goldmann
stimulus size 1-V )
23. Stimulus Size and Intensity
• Most commonly GoldmannsizeIIIis used
• The stimulus intensity can be made upto 10,000 asbin
humphrey
• As intensity increases stimulus size decreases.
28. THRESHOLD
• If a particular intensity of light is shown 100
times and if it is appreciated 50times and that
particular intensity of light is termed as
THRESHOLD .
• If the stimulus intensity is seen 90% of times it is
termed as SUPRATHRESHOLD.
• If it is seen 15%of times, it is termed as
INFRATHRESHOLD
33. THRESHOLD TEST POINT
PATTERN
• The point pattern where the threshold has to be
determined is usually designed according to the
disease pattern.
• Points to be noted:
1.Extension of visual field testing.
2.Number of test points.
3.Point density (the distance between two points in
degrees).
4.The degree of bare area around the fixation spot.
5.The relation of the points to the horizontal and vertical
34. 30-2
• Number of test
points:76
• Density :6 degree
• Bare area : 3degree
• Area of testing from
the fixation point is 30°
• Indication: suspicious
casesof glaucoma
35. 24-2
• Number of test
points:54
• Density: 6 degree
• Bare area : 3degree
• Area of testing from the
fixation point is 24°
• Indication : established
caseof glaucoma
36. 10-2
• Number of test points:
68
• Density: 2 degree
• Bare area : 1degree
• Area of testing from
the fixation point is
10°
• Indication : advanced
casesof glaucoma
37. MACULAR PROGRAMME
• Number of test points: 16
• Density: 2 degree
• Bare area : 1degree
• Area of testing from the
fixation point is 5°
• Indication : advanced
casesof glaucoma
38. NASAL STEPTHRESHOLD
PATTERN
• It is the peripheral test
pattern
• it explores from 30°to 50°.
• Number of points :14
• The nasal step test points
provide 2 points above and
below the horizontal axes at
30°, 40°, 50°as well as 2
accentric central points
39. SELECTION OF THE POINT PATTERNS IN
PATIENTS OF GLAUCOMA ACCORDING TO
THE STAGE OF GLAUCOMA
43. FASTPAC
• Less time consuming
• It changes the stimulus intensity in 3 db steps
either increasing it or decreasing it depending
on patients initial response
• High intratest variability i.e., Short-term
fluctuation
44. SITA ( SwedishInteractive Threshold
Algorithm)
• More efficient estimation of threshold
• 2 strategies- SITA standard
Sita fast
• Short test time without compromising on the
sensitivity
• It creates prior probability models for normal and
glaucomatous populations
• The pace of the test is dependent on patient’s
response
45. SELECTIONOF TESTING
STRATEGY
• Does not depend on the cup/disc ratio of
glaucomatous optic atrophy
• Usually SITA Standard or Full Threshold testing
strategy will be selected
• If the patient is old and not able to concentrate for
a longer time SITA Fast or FAST PAC can be
selected.
49. ZONE 1
PATIENTS DATA
• Name of the patient :
• Date of birth and age :
• Pupil diameter :
• Visual acuity :
• Refractive error correction
for N.V.
THE TEST DATA
• Fixation monitor - blind
spot
• Colour of the stimulus -
white
• Back ground illumination -
31.5asb
• Fixation target - central
• Stimulus size - goldmann
size III
• Threshold test pattern
• Testing strategy
50. • AGE OF THE PATIENT : Since the interpretation of
raw data by STATPAC is agedependent, it it is the very
important to enter the age of patient accurately.
• SIZE OF THE PUPIL : Normally the size of the pupil
should be between 3-4 mm.
Constricted pupil give rise to diffuse visual field
depression or edge scotomas.
• REFRACTIVE ERROR: The patient’s near vision
refractive error must be properly corrected. Otherwise
the visual field will show generalized depression
51. FIXATION TARGET
• Central—Yellow light in the
center of the bowl
• Smalldiamond —It is located
below the central target .
Used in macular
degeneration
• Large diamond— used for
patient with central scotoma
• BottomLED—tests that
require a lower fixation light
52. STIMULUS SIZE
• The standard size of the stimulus is sizeIIIfor all
routine tests.
• But in situations like advanced glaucoma, the test
will be conducted with size V to know the status of
macular split.
53. ZONE 2
• Reliability Indices
1. Fixation loss >20% is unreliable
2. False positive >33%is unreliable
3. False negative >33%is unreliable
4. Short- term fluctuations.
54. ZONE 3–RAW DATA
• Retinal sensitivity in
db units of the
selected points
calculated by field
analyzer
• ‘0’indicates absolute
scotoma
• 40 indicates response
to 1asb unit, highest
retinal sensitivity
55. ZONE 4 GREY SCALE
• Shows thresholds for each spot
tested in db
• Areas of high sensitivity are
denoted by lighter shades and areas
of low sensitivity are denoted by
darker shades.
• Quickly identifies overall
depressions
• Not used for diagnosis
• Good for patient education
• No comparison for age related
normals
58. • Words 0 indicates retinal
sensitivity is equal to mean normal
values of the sameage group.
• Value without sign(positive)
indicates the measured retinal
sensitivity is better than mean
normal values of the same age
group.
• The numerical value with negative
sign indicates the measured retinal
sensitivity is worse than the mean
normal values of the same age
group.
59. • The TDNP becomes the platform for the
calculations of global indices
• TDNP values in the range of 0 to -2db – no field
loss
60. ZONE 6 - TOTAL DEVIATION
PROBABILITY PLOT
Aim of the field chart is to show the field loss in scotomatous
form.
61. P VALUE
• Probability values (P) :Indicates the
significance of the defects .
• The lower the P value, the greater is its
clinical significance
clinicalsignificance:: if there are abnormal
points in total deviation plot that
persist in the pattern deviation plot,
we are looking at scotomas .
63. • 7th best retinal sensitivity of TDNP is
converted to zero.
• Addition of the threshold value that
converts the 7th best retinal sensitivity of
TDNP to 0 to all points in TDNP
• The pattern deviation numerical plot is also
the basis for glaucoma hemi field test
analysis.
64. ZONE 8 - PATTERNDEVIATION
PROBABILITY PLOT
• It is the symbolic representation of Pvalue of each
numerical threshold deviation values of pattern
deviation numerical plot .
65. • It bring out deep scotomas in a generalized
depression.
• It differentiates uniform generalized depression
from the irregular generalized depression.
• It is almost normal in uniform generalized
depression and in irregular generalized depression
the pattern deviation probability plot shows
localized field defects
66. ZONE 9 –GLOBAL
INDICES
1. Mean deviations (MD)
2. Short term fluctuation (SF)
3. Pattern standard deviation (PSD)
4.Corrected pattern standard deviation
(CPSD)
67. Hill of vision
The hill of vision has two
components:
1) Height of hill of vision
(represented by mean
deviation index),
2) 2) The contour of hill of
vision (represented by PSD
value).
68. Mean deviation
• Signifies average overall severity of
field loss.
• It is the average of all the numbers
shown in the total deviation plot
except the two points nearer to the
blind spot.
• Expressed in db units with p value.
• The positive value indicates that
the patient’s overall sensitivity is
better than normal observer
• Negative value indicates that the
patient’s overall sensitivity is
worse than the average normal
69. SIGNIFICANCE
• In glaucoma suspect on the basis of assymmetry
of intra ocular pressure or of disc cupping, the
difference of mean deviation index between
both the eyes of 2db should be taken as a clue in
conforming the diagnosis of glaucoma.
• Inthe follow-up tests : normally mean deviation
index will be changed by 0.08 db to 0.1 db
• Printed along with a solid triangle to indicate
degradation or an open triangle to indicate
improvement.
70. DEVIATION
• Index of irregular loss of retinal
sensitivity.
• It is the standared deviation
around the mean that
constitutes the MD index
• The contour of hill of vision will
be represented by PSD value.
• PSD zero indicates no departure
from the average
• Positive number indicates
depature from the normal slope
of hill of vision.
71. SHORT TERM
• Index of in
F
tr
L
a t
U
est
CTUATION
variation
• Indicator of reliability
• It measures the variation
at each point on
repeated thresholding in
the same test.
• Value is almost always
less than 3dB
• used to correct PSD to
produce CPSD.
73. ZONE 10- GLAUCOMA HEMIFIELDTEST
Compares mirror imagelocations of
superior and inferior retina and gives five
comments
1. GHT—OUTSIDE NORMAL LIMIT ,if
difference found in 1%population
2. GHT—BORDERLINE , if difference
found in up to 3%population
3. GHT—ABNORMALLY LOW
SENSITIVE, best sensitive part is seen
in less than 5%of the population
4. GHT—ABNORMALLY HIGH
SENSITIVE, best sensitive part seen is
more than that found in 99.5%
population
74. GAZE MONITORING
• Heijl-Krakau method of fixation monitoring- It
provides index of quality of patient fixation during
examination by periodically exposing stimuli in
blind spot
• Eye Monitoring by perimetrist
• Infra red Gaze Monitors
75. ❖ Upward spike indicate that patient has lost fixation
❖ Spike reaching the top horizontal means 10degree off fixation
❖ Spike reaching half way to top line indicate 5degree off
fixation
❖ Downward spike indicate
❖ Short spike indicates that gaze at the time cannot be
determined by software
❖ Long spike indicate patient blinked at the time of fixation
check
76. SCREENING TEST
PATTERN
Glaucoma test point
pattern
Central test point
pattern
Full field test point
pattern
Peripheral field test
point pattern
STRATEGY
Two-zone
strategy(threshold-
related strategy)
Three-zone strategy
Quantify defects
screening strategy
Single intensity strategy
82. CUSTOMTEST
• Feature of automated static field analyzers
• It focuses an area where the first test indicated
defects.
• We can design a custom point pattern where we want
to concentrate more
• We can create points separated by 1°in an area where
we are expecting the progress of the disease
• Used for the follow-up tests
• No progrssion in disease is concluded only after it is
85. OCTOPUS PERIMETRY
• Projection system
perimeters which can
perform full threshold
programme
• Stimulus is Goldmann
target size III
• Stimulus intensity can
reach upto 1000 asb
• Background luminance is 4
asb
86. ZONES IN OCTOPUS
VISUAL FIELDANANLYSIS
• Reproducibility (Zone-1)
• Reliability factors (Zone-2)
• Gray scale (Zone-3)
• Comparison (Zone-4)
• Corrected comparison (Zone-5)
• Numeric data/raw data(Zone-6)
• Visual field indices (Zone-7)
• Bebie.’s curve (Zone-8)
88. SWAP
Short Wave Automated Perimetry
• Helps to diagnose damage due to glaucoma at an early
stage
• Yellow background is used to highlight isolated blue cone
response
• PRINCIPLE:Green and red cone pigments are bleached by
the intense yellow background where as the blue cones are
much less affected.
• INDICATION: Significant signs and risk factors of
glaucomabut normal fields on white on white perimetry
• Goldmann target V stimulus is used to enhance spatial
89. DISADVANTAGE OF
SWAP
• It is influenced by nuclear sclerosis as lens acts a
blue filter
• Time consuming
• The mean normal SWAP threshold values are
lower than for white stimuli and the SWAP gray
scale is darker in its appearance and maymislead
clinicians accustomed to the gray scale for white on
white perimetry.
92. RETINAL GANGLION
CELLS
PARVOCELLULA
R
•P Cells
•Small axon diameter
•Slow conduction velocity
•High spatial frequency(
fine details)
•Low temporal frequency
( constant stimuli)
MAGNOCELLUL
AR
•M Cells
•Large axon diameter
•Fast conduction velocity
•Low spatial frequency (
broad pattern)
•High temporal
frequency( flickering
stimuli)
93. • FDP is based on detecting
damage to M ‘y’cells
which are a subset of
Magnocellular cells
• Test stimulus- series of
white and black bands
flickering at 25Hz
• Uses target of 10deg
square
• The non linear response
to stimuli produces
frequency doubling
appearance.
94. • It is cheap, desk mounted and sensitive
• Not reliable for progression analysis.
95. FLICKER PERIMETRY
• It detects light and dark stimulus alternations
(flicker) at various locations in the field
• It targets magnocellular pathway (responsible for
flicker perception)
• Not influenced by media opacities and refractive
error
Two types-
1)Critical Fusion Frequency
2) Temporal Modulation Perimetry
96. HPRP [High PassResolution
Perimetry]
• Ring perimetry
• It tests the parvocellular system
selectively
• Based on resolution method rather than
differential light sensitivity
• Series of ring of different sizes and
having a light centre and dark annular
surround are presented
• These targets are spatially high pass
filtered vanishingtargets for
determination of resolution of central 30
98. FIELD DEFECT
PATHOLOGY
Nerve fibre bundle damage at
the disc
Area of loss of visual
sensitivity supplied by the
bundle
Scotoma or localised
depression
99. CHARACTERISTICS OF
GLAUCOMATOUS
VISUAL FIELD DEFECTS
• Almost always localized
• Respect horizontal meridian
• Begin nasal to the blind spot
• Upper pole affected more than lower pole
• Almost always detectable within the central
30°
100. STAGES OF
GLAUCOMATOUS DAMAGE
Based on
• Number of axons damaged indicated by MD
• location of the defect
1. EARLY DEFECT
2. MODERATE DEFECT
3. SEVERE DEFECT
101. ANDERSON CRITERIA
• SIGNIFICANCE: To detect early
glaucoma.
CRITERIAS
• Abnormal glaucoma hemifield test.
• Pattern standard deviation abnormal at P
< 5%level
• Three non-edge adjacent points in total or
pattern deviation probability plot. The
points must be in a cluster in an expected
locations.
• Two points P< 5%
• One point P< 1%
115. REFERENCES
• A visual field evaluation with automated
devices by GR Reddy
• Diagnosis and therapy of glaucoma by
Becker and Shaffers
• Ophthalmology –Yanoff and Duker
• Visual fields examination and
interpretation- Thomas J. Walsh
• Automated Perimetry - Anderson DR,
Vincent Michael Patella.
