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Visual field testing and interpretation
1. Visual Field
Testing and Interpretation
Raman P Shah
Optometrist
B. P. Koirala Lions Center for Ophthalmic Studies
2. References and recommended readings
• Walsh TJ. Visual fields Examination and
Interpretation, Ophthalmology monographs, AAO
• J Boyd Eskridge. Clinical procedures in Optometry.
Mosby
• Automated Perimetry; Visual Field Digest: 5th
edition
• David O. Harrington, Michael V. Drake. The visual
fields .7th
edition
3. Presentation layout
• Introduction on Visual field
• Normal limits of Visual field
• Short overview on history of VF
• Terminologies related to VF
• Visual field testing methods
– Kinetic, static
• Interpretation of VF reports
9. Short History of Visual Field
• In B.C 150, Ptolemy: used some form of
perimetric device to measure extend of VF
• First clinical investigation of VF defect –
Hippocrates in 5th
century, hemianopic field
defect
• Finally in 1604 Kepler explained the principle of
sight in term of an inverted retinal image –
– an stage for modern investigation of VF
10. History….
• In 1666, Mariotte discovered
physiological blind spot
• In 1801, Young stated the normal
extend of VF of an eye
• Von Graefe mapped out blind spot,
central scotomas, construction of
isopter.
– Introduced VF in clinical medicine
for the first time
• Until 1869, Foerester invented arc
perimeter, till then VF plotted on
flat surface
Thomas
Young
Von
Graefe
11. History……
• In 1880, Bjerrum
developed Tangent screen
• In 1940, Marc Amsler
introduced Amsler grid
• In 1939 Sloan described
static perimetry
• In 1945 Goldman
Perimeter
• In 1960 Tubinger- manual
testing of both static and JannikPetersonBjerrum
HenningRønne
Dr.HansGoldman
12. Few Terminologies
• Threshold: The weakest test stimulus that is just
visible in a particular location under the specific
testing condition.
– Varies across the visual field.
• Sensitivity: most subtle characteristics of a
stimulus that is visible at a specific point in space.
• Fixation: that part of visual field corresponding
to fovea centralis.
13. Terminologies…
• Isopter:
– Line connecting all points in the visual field with the same
threshold ( for a given test spot)
– Boundary between area of visibility to the area of non-
visibility for a particular stimulus
14. Terminologies…
• Scotoma: Localized defectsdepressions surrounded by
normal visual field.
– Absolute: defect that persists when the maximum stimulus is
used e. g blind spot.
– Relative : defect that is present to weaker stimulus but
disappears with brighter stimulus.
15. Location of Visual field defects
• Central
– 5 degrees or less from the point of fixation
• Paracentral
– >5 degress – 30 degrees
– Ceacal, paraceacal, periceacal
– Centrocecal
• Peripheral
– >30 degrees
16.
17. Descriptive components of VF
defects
• Monocular descriptions
– Density
• Absolute (no visual sensation) or relative (depressed visual sensation)
– Area
• General or local
– Shape
• Sectorial (hemianopic) or non-sectorial (regular or
irregular)
– Extent
• Total or Partial
– Position
• Rt. Or Lt. . Temporal, nasal, superior, inferior
18. Descriptive components of VF
defects
•Binocular description
• Laterality
•Unilateral or bilateral (homonymous/heteronymous)
•Equalness
•Congruous or incongruous
•Additional description
•Awareness
•Positive (defect perceived) or negative (defect not perceived)
19.
20. Significance of Visual field testing
• Find out the extent of VF
• To diagnose and detect diseases as well as
extent of damage caused in VF by the disease
• To locate possible lesion in neurological
disorder
• To find out the progression of diseases
22. Perimetry
• Systematic measurement of VF by the use of a
perimeter
• Modern Perimeter
– Consist of a bowl positioned at a fixed distance
from the eye,
• enable the controlled presentation of stimuli with in the
bowl
• Enables assessment of the visual function through out
the visual field
• Detection & quantification of damage to the visual
field
• Monitoring the change over a time
23. Perimetry types
Kinetic Static
• measures extent of visual field
by plotting isopters ( locus of
retinal points having same
sensitivity)
•Stimulus moves from non-
seeing to seeing area.
•Result depends upon the
experience of the operator.
• e.g, Goldman perimetry,
confrontation, Tangent screen,
Arc perimetry
• measures the sensitivity of
each retinal points.
•The stimulus is stationary but
increases in luminance.
• Mostly automatic, very little
role of the operator.
•e. g, Automated perimetry,
Goldman perimetry
24. Goldman Perimetry
• The most widely used instrument for manual
perimetry.
• Has a calibrated bowl projection instrument
– with a background intensity of 31.5 apostilbs (asb),
• Test Targets: dots
– Varying size and illumination
26. Goldmann Targets
• The stimuli (Dot) used to plot an isopter
denoted by
– Roman numeral, a number, and a letter.
• Roman Numerals = 0 to V (Size)
• Number = 1 to 5 (Luminance) use of Filter
• Alphabet = a to e ( ‘’) use of filter
V4e , I4e, IV3e
27. Goldmann Perimetry: Roman numeral
• Sizes of Stimuli [0...V scale]
• Each size increment equals
• a twofold increase in diameter and a fourfold
increase in area.
Diameter (mm) Area (mm2
)
0 0.28 1/16
I 0.56 ¼
II 1.13 1
III 2.26 4
IV 4.51 16
V 9.03 64
28. Target illumination
• Luminance settings
• Expressed in units called Apostilbs
(candela/m2
)
• 2 sets of filters – 5 each
– 10 steps
• Standard Vs Fine settings
• (1...5 and a...e scales)
• 1, 2, 3, 4 settings represent 0.5 log
unit changes = 5 db
• a, b, c, d and e settings represent 0.1
log unit changes = 1db
29. Target Range in Goldmann
• More than 100 combinations of size and intensity
of test targets are Possible
– but only a few isopter are needed to define the visual
field.
• Size “0” generally is omitted
– because results of the plots are inconsistent.
• The fine-intensity filter is usually set to the letter “e”
– which eliminates the small-increment light filters.
– Test target : Denoted by – Size + (Std. + fine)
Luminance
• Eg: V4e, I4e, II3e
30. Some interesting facts
• A change of one number of intensity
– is roughly equivalent to a change of one Roman
numeral of size i.e. III4e = IV3e
• Isopter plotted with Targets of equal Sum of
– Roman Numerals (size) & Number (Intensity)
• are considered equivalent.
– For example,
• the I4e isopter is roughly equivalent to the II3e isopter.
• I + 4 = 5, II + 3 = 5
35. Guideline to Plot
• First demonstrate the procedure
to patient
– by statically presenting large test
General rules for plotting
“Isopters”
– An isopter is mapped for the
particular stimulus size and
intensity
• move from NON-SEEING TO
SEEING while presenting stimulus
• move at a rate of 5 degrees per second
inside
• present kinetically every 15 degrees
interval
36. Guidelines for plotting
• Begin in the far periphery and kinetic plot isopter in
all meridians
–Use a V4e, I-3e , I-2e or target (depending
upon age
–Plot the Blindspot
• only 4 meridians are required( more if irregular or
Large)
– Use the I-4e for the blind spot
• within isopter of I-2e or I-3e
37. Guidelines
• Central static test with I-2e
– Explore for any scotomas
• Kinetic plot with I-3e stimulus only in suspected defect
area
• Static test between I-3e and I-2e isopters with the
I-3e stimulus (scotoma search)
38. Guidelines
• Special case plots
– Glaucoma suspects
– Plot more points along the nasal edge of the isopter
– Plot approximately
• every 3-5 degrees,
• 15 degrees above and below the horizontal raphe
Repeat for central, intermediate and peripheral plots
• Suspected neurological lesions
– Plot more points on either side of the vertical meridian
– Repeat for central, intermediate and peripheral plots
39. Recording
• All recording should be done on
the Goldmann recording paper
– Patient name,
– Date,
– Rx used,
– Pupil size,
– Eye tested and
– Patient cooperation / Fixation
– Indicate the target sizes used in
the bottom right hand block (color
marker)
40. Color coding of Isopters
• I-2e Blue
• I-3e Orange
• I-4e Red
• II-4e Green
• III-4e Purple
• IV-4e Brown
• V-4e Black
41. Expected findings for normal Isopters
• Patients under 50 years of age
i. Peripheral I-4e (size=same, brighter luminance)
ii. Intermediate I-3e
iii. Central I-2e (size=same, dimmer luminance)
42. Expected findings for normal
Isopters
• Patients 50 years or older
i. Peripheral II-4e (size=larger, brighter luminance)
ii. Intermediate I-4e
iii. Central I-2e or I-3e (size=smaller, dimmer luminance)
43. Interpretation
• The visual field is considered abnormal if:
– the threshold values are significantly brighter
(0.5 log units or more) than the expected values
AND / OR
– Scotomas or depressions are present
47. Automated Perimetry ( Static)
• Machine constructed along the basic lines of
a Goldman perimeter + sophisticated software
programs.
• Key reason for increased interest in automated
perimetry has been due to the standardization
automated perimetry allows.
48. Automated Perimetry
• Visual threshold is measured at a series of
fixed points in the visual field.
• The brightness of the test spot is varied, but
not its location.
• Threshold is usually plotted relative to normal
fields, to reveal defects
53. Threshold determination
• Age matched normal data are used to compare
patient’s data
• Normal range determined by
– Sensitivity of each retinal points 10,000
individuals
– Upper 95% as normal
– Lower 5% as abnormal
54. Testing strategies
• Octopus
– Normal
– Dynamic
– TOP ( Tendency oriented perimetry)
• Humphrey
– SITA (Swedish Interactive threshold algorithm)
– SITA fast
– Full threshold
56. Factors affecting Automated
Perimetry
• Background luminance
• Stimulus size
• Fixation control
• Refractive errors
• Cataracts and other media opacities
• Miosis
• Facial structure
• Fatigue
• Experience of a perimeter
57. Validity of the test
• False positive response
– > 20% unreliable
• False negative
– >20% unreliable
• Short term fluctuation
– 1-3 dB normal fluctuation
• Fixation loss
– >33% unreliable
58. Choosing an appropriate program
Examination procedure
Test program(G1, G2, 32, M2)
+
Test strategy (Normal, dynamic, top)
+
Perimetry method( W/W, flicker, B/Y, kinetic)
59. Programs
G1/G2
• Central 30 degree
• Glaucoma screening
• 59 points
• Locations more closely with topography of
retina (in areas of concern of glaucoma)
• 2.8 deg spacing
60. Programs
32 ( general examination)= 30-2 in Humphrey
• introduced with early automated perimetry
• 76 test locations
• Wide spacing (6 degrees) ( not appropriate for
glaucoma)
61. Programs
Macula program(M2)
• Central and paracentral visual defects in
neurological and macular problems
• Central 10 deg
• 56 test locations
• spacing 2 degrees
• 0.7deg spacing in the macula
62. Programs
LVC (central low vision)
• To test how much sensitivity is remained in
the central foveal area.
• 77 locations
• 30 degrees
• End stage glaucoma
63. Strategies
• Normal strategy
– Standard
– 4-2-1 bracketing procedure
– 10-15 min
– Early and shallow defects
– Younger patients ( good condition in answering
the question till the end of a long program)
64. Strategies
• Dynamic strategy
– One threshold crossing
– Small steps in regions with Normal sensitivity and
large towards depressed field
– Test duration reduced by two
– Especially when focal defects are expected
65. Strategies
• TOP ( tendency oriented perimetry)
– Light sensitivity of the retinal is interrelated rather
than having an individual value
– 2 minutes
– For patients with depressed fields, for children,
elderly ones who are not capable of finishing a
longer examination
76. Glaucoma Hemifield test
• 5 sectors in the upper field are compared to
five mirror images in the lower
• If value in two sectors differ to an extent that
found in
– <0.5% of the normal population ( highly sensitive)
– <1% of normal population (outside normal limit)
– <3% of the normal population (Boderline)
– <5% of the normal population ( can be a normal
plot)
77.
78. Global indices
Octopus
• Mean sensitivity (MS)
• Mean deviation (MD) (–
2dB to +2dB)
• Loss variance (LV) (0-
6dB)
• CLV(0-4dB)
• SF (1.5dB- 2.5dB)
• RF < 15%
Humphrey
• GHT
• Mean deviation
• PSD
• CPSD
• SF
82. Recent advances in automated
perimetry
• Goldman kinetic module
• High-pass resolution perimetry - Uses thin rings instead of
spots
• Short wavelength sensitive perimetry - Blue on Yellow for S
cones
• Flicker Perimetry - Flickering targets instead of static flashes
• Aulhorn's Snow field campimetry - Uses TV “snow” and
pointing
• Motion perimetry - Detect moving targets instead of flashed
ones
• Rarebit perimetry- uses very small, bright spots
• Pupil Perimetry - measures pupil responses instead of subject
reports
• Multifocal VEP - measures cortical evoked potentials instead of
subject reports
83. Summary
• Principle of kinetic and automated perimetry
• Appropriate selection of visual field testing for
a particular patient
• Accurate interpretation of VF reports