CHAPTER 8 CLINICAL INTERPRETATION OF A …...128 Chapter 8 | Clinical interpretation of a visual...
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127 CHAPTER 8 CLINICAL INTERPRETATION OF A VISUAL FIELD INTRODUCTION ϐ - ȋǤǤǡ - ȌǤ ϐ ǡ ǦǤ - ǡ ϐǤ ϐ ϐ Ǥ - ǡ ϐ ȋFIG 8-1ȌǤ ϐǡ ϐ ǡ ǡ ǡ ϐ Ǥ - Ǥ - Ǥ ǡ - ǦǦ ϐǤ ǡ ϐǡ - Ǥ Ǥ
Transcript of CHAPTER 8 CLINICAL INTERPRETATION OF A …...128 Chapter 8 | Clinical interpretation of a visual...
127
CHAPTER 8CLINICAL INTERPRETATIONOF A VISUAL FIELD
INTRODUCTION
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FIG 8-1
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128 Chapter 8 | Clinical interpretation of a visual field
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NORMAL
1 Correct patient & examination parameters?
2 Reliable, free of artifacts and trustworthy?
3 Diffuse loss?
Defe
ct (
dB
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Rank Rank Rank
4 Significant local loss?
BORDERLINE EARLY TO MODERATE
Diffuse defect
DE
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EP
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D P
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1.3 dB
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0.1 dB 6.2 dB
0.2 dB 0.6 dB
EXAMPLES OF SIX TYPICAL VISUAL FIELDS
FIGURE 8-1 A systematic approach to visual field interpretation is recommended and this workflow can be used as a guide
(this figure is also included as a poster in the back cover of this book).
129Introduction
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1Correct patient & examination parameters?
2Reliable, free of artifacts and trustworthy?
Rank RankRank
3Diffuse loss?
4Significant local loss?
Local defect
DE
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CU
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EP
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BA
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EARLY TO MODERATE ADVANCED
1.3 dB 5.9 dB 19.3 dB
7.0 dB 6.1 dB 4.7 dB
130 Chapter 8 | Clinical interpretation of a visual field
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NORMAL
5 Assess shape & depth of defect.
BORDERLINE EARLY TO MODERATE
Diffuse defect
GR
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(C
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PA
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S)
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ON
SC
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RE
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D G
RA
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CA
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(C
O)
EXAMPLES OF SIX TYPICAL VISUAL FIELDS (CONTINUED)
131Introduction
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5Assess shape & depth of defect.
Local defect
GR
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Local & diffuse defect
EARLY TO MODERATE ADVANCED
132 Chapter 8 | Clinical interpretation of a visual field
102030[dB]
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IN T
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CLU
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MD
sLV
NORMAL BORDERLINE EARLY TO MODERATE
Diffuse defect
CO
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D C
LU
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SIS
7 For glaucoma: Where to look for structural defects.
8 Severity?
PO
LA
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NA
LY
SIS
1.5 dB 1.9 dB 2.5 dB
-0.2 dB 1.0 dB 6.3 dB
EXAMPLES OF SIX TYPICAL VISUAL FIELDS (CONTINUED)
133Introduction
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Local defect
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8Severity?
PO
LA
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SIS
Local & diffuse defect
EARLY TO MODERATE ADVANCED
8.3 dB 7.2 dB 5.6 dB
6.5 dB 10.1 dB 21.7 dB
FIGURE 8-2 A systematic approach to visual field interpretation is recommended and this workflow can be used as a guide.
134 Chapter 8 | Clinical interpretation of a visual field
Patient name & age
Refraction
Pattern/strategy
False positives
False negatives
Repetitions
Duration
Defect Curve
DD, LD
Probabilities
Corrected Probabilities
Grayscale (Comparisons)
Corrected Grayscale (Comparisons)
Comparisons
Corrected Comparisons
Cluster Analysis
Corrected Cluster Analysis
Polar Analysis
MD, sLV
Correct patient & examination parameters?
Yes
Yes
Yes No
Yes
Yes Yes
Yes
Yes
No
No
No
No
No
No
Diffuse loss? Caused bypathology?
Reliable, free ofartifacts & trustworthy?
Retest if clinicallyrelevant
Potentially unreliable,retest if clinically relevant
Normal visual field OR
Diffuse defect only
Consider non-glaucomatous field defects
Consider non-glaucomatous field defects
Consider non-glaucomatous field defects
Consider glaucoma
Yes Consider glaucoma
Consider pathologyleading to diffuse defect
Borderline or significant local loss?
Assess shape & depth of defect.Typical for glaucoma?
Glaucoma only: Significant cluster defects?
Glaucoma only:Where to look for structural defects.
Is there a relationship?
Severity?
1
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4
5
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7
8
VISUAL FIELD INTERPRETATION WORKFLOW
STEP-BY-STEP INTERPRETATIONOF A VISUAL FIELD
OVERVIEW OF STEP-BY-STEP WORKFLOW
135Step-by-step interpretation of a visual field
Correct patient & examination parameters?1
FIG 8-4
in FIG 8-2
STEP 1 – CONFIRM PATIENT AND EXAMINATION PARAMETERS
STEP 1 – CONFIRM PATIENT AND EXAMINATION PARAMETERS
IMPORTANCE OF CONFIRMING PATIENT AND EXAMINATION PARAMETERS
FIGURE 8-3 Before interpreting visual field results, it is important to confirm that the correct patient data has been entered
and that the correct examination parameters have been used during the test.
STEP 2 – DETERMINE WHETHER THE VISUAL FIELD CAN BE TRUSTED
IMPORTANCE OF ASSESSING WHETHER THE VISUAL FIELD CAN BE TRUSTED
136
Defe
ct
(dB
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Rank
EyeSuite™ Static perimetry, V3.5.0OCTOPUS 101
Demo, John, 1/5/1942 (63yrs)
Left eye (OS) / 01/24/2005 / 16:25:23Seven-in-One
Comment:
NV: T21 V2.1
Good fixation
Pupil [mm]: 5.6 IOP [mmHg]:Refraction S/C/A: VA [m]:Catch trials: 1/18 (6%) +, 1/18 (6%) -
-3.5 / 1.25 / 35RF: 5.5
Parameters: 4 / 1000 asb III 100 ms Duration: 15:32Programs: G Standard White/White / Normal Questions / repetitions: 356 / 23 MS [dB]: 19.7
MD [< 2.0 dB]: 9.9sLV [< 2.5 dB]: 8.1
30°
[%]
Grayscale (CO) Values [dB]
24
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Comparison [dB]
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Defect curve
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Diffuse defect [dB]: 5.4
Probabilities Corrected probabilities
[%]
P > 5P < 5P < 2P < 1P < 0,5
OCTOPUS®
MD [dB]17.612.2
6.1 3.9
0..1011..2223..3435..4647..5859..7071..8283..9495..100
Comment:
NV: T21 V2.1
Good fixation
Pupil [mm]: 5.6 IOP [mmHg]:Refraction S/C/A: VA [m]:Catch trials: 1/18 (6%) +, 1/18 (6%) -
-3.5 / 1.25 / 35RF: 5.5
Parameters: 4 / 1000 asb III 100 ms Duration: 15:32Programs: G Standard White/White / Normal Questions / repetitions: 356 / 23
Demo, John, 1/5/1942 (63yrs)
Left eye (OS) / 01/24/2005 / 16:25:23
Reliable, free of artifacts & trustworthy?2
Chapter 8 | Clinical interpretation of a visual field
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OVERVIEW OF PATIENT AND EXAMINATION PARAMETERS
STEP 2 – ASSESS WHETHER THE VISUAL FIELD CAN BE TRUSTED
FIGURE 8-5 Before interpreting visual field results, it is important to confirm that the visual field can be trusted. Visual fields
that are not reliable, contain artifacts or cannot be trusted for other reasons should be retested if this is clinically relevant.
FIGURE 8-4 All patient and examination parameters are displayed for every perimetric result.
137
Reliable normal
Less reliable normal
Normal who experiences difficulties with perimetry
Normal with learning effects (tests 1 to 3)
Normal with artifactual defects (here: lens rim artifact on 1st, 2nd and 4th test)
1st test 2nd test 3rd test 4th test 5th test
Step-by-step interpretation of a visual field
UNTRUSTWORTHY VISUAL FIELD TESTS CAN SHOW SIGNIFICANT DEFECTS
FIGURE 8-6 The examples above show several visual field series from different individuals with clinically confirmed normal
visual fields and no pathology. Note that while some individuals perform perimetric testing consistently, some show improve-
ment over time due to learning effects, and some perform variably from one examination to the next. This results in untrust-
worthy visual field results, which may be misinterpreted.
FIGURE 8-7 The example above shows the impact of a high rate of false positive answers on the visual field. The field on the
left is unreliable because the patient responded in the absence of a stimulus. As a result, the visual field appears better than
the true visual field of the patient, which is shown on the right.
138
1st test 2nd test
HIGH FALSE POSITIVESReal defect is missed
NO FALSE POSITIVESReal defect is visible
Chapter 8 | Clinical interpretation of a visual field
-
FIGURE 8-6
-
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IMPACT OF FALSE POSITIVE ANSWERS ON VISUAL FIELD RESULT
FALSE POSITIVE AND FALSE NEGATIVE ANSWERS
TABLE 7-2
FIG
7-22 FIG 7-23
FIG 8-7
the re-
-
-
139
1st test 2nd test
HIGH FALSE NEGATIVESDefect is deeper
NO FALSE NEGATIVESReal defect shape & depth
Step-by-step interpretation of a visual field
FIG 8-8
-
-
-8
-
FIGURE 8-8 The example above shows the impact of a high rate of false negative answers on the visual field. The field on the
left is unreliable because the patient did not respond to stimuli that should have been seen. As a result, the visual field appears
worse than the true status of the patient’s visual field, which is shown on the right.
IMPACT OF FALSE NEGATIVE ANSWERS ON VISUAL FIELD RESULT
CONSISTENCY OF RESULTS WITH FURTHER DIAGNOSTIC TESTS
-
FIGURE
8-6
9
-
140
Diffuse loss?3
Chapter 8 | Clinical interpretation of a visual field
OTHER INDICATORS TO DETERMINE WHETHER VISUAL FIELD TESTS CAN BE TRUSTED
-
FIG 8-10
TABLE 7-2
STEP 3 – IDENTIFY DIFFUSE VISUAL FIELD DEFECTS
NEED FOR THE DETECTION OF DIFFUSE DEFECTS
TABLE 8-1
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STEP 3 – IDENTIFY DIFFUSE VISUAL FIELD LOSS
FIGURE 8-9 Diffuse visual field loss should ideally be identified early on, as it can be a sign of both a pathology leading to
diffuse defects or an untrustworthy visual field.
141Step-by-step interpretation of a visual field
DEFECT CURVE
- -FIG 8-10
BOX 7A
DIFFUSE
(WIDESPREAD)
DEFECT
LOCAL DEFECT
EXAMPLES OF PATHOLOGIES
•
• Hemianopia
• Vitreous opacity
EXAMPLES OF UNTRUSTWORTHY
RESULTS
THE ETIOLOGY OF DIFFUSE AND LOCAL VISUAL FIELD DEFECTS TABLE 8-1
142
DIFFUSE DEFECT
Parallel downward shift of
Defect Curve
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LOCAL DEFECT
Drop of Defect Curve
on the right
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LOCAL & DIFFUSE DEFECT
Parallel downward shift on
the left and drop on the right
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NORMAL
Defect Curve within normal
band
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BORDERLINE
Limited diagnostic value
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ADVANCED
Limited diagnostic value
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TRIGGER-HAPPY
Steep rise of Defect Curve
on the left
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HEMISPHERE DEFECTS
Vertical drop of Defect
Curve in the center
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QUADRANT DEFECTS
Vertical drop of Defect
Curve towards the right
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Defe
ct
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efe
ct
(dB
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efe
ct
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Rank RankRank
Rank RankRank
Rank RankRank
Chapter 8 | Clinical interpretation of a visual field
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DEFECT CURVE – INTERPRETATION AID
FIGURE 8-10 The Defect Curve alerts the clinician to the presence of diffuse defects and allows a rapid distinction to be
made between local and diffuse defects in early to moderate disease. It furthermore allows the identification of trigger-happy
patients and has a characteristic shape for localized hemisphere and quadrant defects. Note that it is of limited diagnostic
value in borderline (i.e., suspect) situations or in advanced pathology.
143
DIFFUSE DEFECTS OF VARIOUS MAGNITUDE
LOCAL DEFECT
Gra
yscale
(C
om
pariso
ns)
Defe
ct
Cu
rve
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1st test
Defe
ct
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Rank Rank Rank RankRank
2nd test 3rd test 4th test 5th test
Step-by-step interpretation of a visual field
CORRECTING FOR DIFFUSE DEFECTS
-
--
-
in FIG 7-16
FIG 8-12
EXAMPLE OF THE CLINICAL USEFULNESS OF THE DEFECT CURVE
FIGURE 8-11 This example shows a series of five visual field tests of a patient with glaucoma with a local superior nasal
defect that deepens from the 1st to the 5th test. In addition, visual fields 2 to 5 show diffuse defects of various magnitudes. The
diffuse defect is most pronounced on the 3rd test, as can be seen from the large parallel downward shift of the Defect Curve.
An inspection of the Defect Curve thus immediately alerts the clinician to the presence of the fluctuating diffuse defect. In
this example, the near-absence of diffuse defect on the 4th and 5th test indicates that the diffuse loss observed on the 3rd test
was due to fluctuation and not pathology.
-FIG 8-11
144
DIFFUSE DEFECTS OF VARIOUS MAGNITUDE
LOCAL DEFECT
Gra
yscale
(C
om
pariso
ns)
Pro
bab
ilitie
sC
orr
ecte
d P
robab
ilitie
s
1st test 2nd test 3rd test 4th test 5th test
Chapter 8 | Clinical interpretation of a visual field
-
-ples in FIG 8-1
FIG 8-1
-
FIG 8-1
EXAMPLE OF THE CLINICAL USEFULNESS OF THE CORRECTED REPRESENTATIONS
FIGURE 8-12 Example of the glaucoma patient with a local superior nasal defect presented in Figure 8-11. Due to the presence
of fluctuating diffuse defects of various magnitudes, the extent of the local defect is difficult to judge. This is the purpose of
the Corrected Probabilities representation, which eliminates the influence of diffuse defect and allows the identification of
local defects.
145
Borderline or significant local loss?4
Step-by-step interpretation of a visual field
PROBABILITIES AND CORRECTED PROBABILITIES
-
-
FIG 2-11, -
-FIG 8-14
FIG 7-9, 7-10 7-19
-
STEP 4 – DISTINGUISH BETWEEN NORMAL AND ABNORMAL VISUAL FIELDS
NEED TO DISTINGUISH BETWEEN NORMAL AND ABNORMAL VISUAL FIELDS
STEP 4 – DISTINGUISH BETWEEN NORMAL AND ABNORMAL VISUAL FIELDS
FIGURE 8-13 Before analyzing a visual field in detail, statistical analysis is used to assess whether a visual field is within nor-
mal limits, or is abnormal. The Probabilities and Corrected Probabilities are used to achieve this essential step, which results
from the normal fluctuation present in perimetry.
146
Probability that a person with a normal visual fieldshows this result
Correctedfor diffuse
defect
Likely normal location
Potentially abnormal location
Highly likely abnormal location
p > 5%
p < 5%
p < 2%
p < 1%
p < 0.5%
PROBABILITIES CORRECTED PROBABILITIES DEFINITION INTERPRETATION
Chapter 8 | Clinical interpretation of a visual field
The clinical interpretation of the Probabilities repre-
FIG 7-9 7-10
To
typically require the presence of one or more clusters of
FIG 8-15
to clinically interpret the Probabilities plots of several
-
PROBABILITIES AND CORRECTED PROBABILITIES – INTERPRETATION AID
FIGURE 8-14 The various symbols on the Probabilities representations show the likelihood that a person with a normal
visual field would show a given sensitivity loss. For example, the black square (p < 0.5%) indicates that while it is possible
that a person with an average normal visual field could obtain that defect value, the probability of this occurring is very small.
Note that the Corrected Probabilities representation shows the same information, but is adjusted to remove diffuse visual field
defects and is based on the Corrected Comparisons representation.
147
Number of locations atp < 5% 2p < 2% 2p < 1% 1
Random distribution of likely abnormal locations
Likely normal
Number of locations atp < 5% 2
Two adjacent likely abnormal test locations, no cluster
Likely normal
Number of locations atp < 5% 2p < 2% 1p < 1% 1p < 0.5% 2
Five likely abnormal locationsclustered in an inferior partial arcuate defect pattern
One likely abnormal locationat random position
Likely abnormalInvestigate further
Number of locations atp < 5% 7p < 2% 3p < 0.5% 1
Six likely abnormal locationsclustered in a superior partialarcuate defect pattern
Three likely abnormal locationsclustered in an inferior,paracentral defect pattern
Likely abnormalInvestigate further
GRAYSCALE (Comparisons) PROBABILITIES DESCRIPTION INTERPRETATION
Step-by-step interpretation of a visual field
CLINICAL INTERPRETATION OF PROBABILITIES IN BORDERLINE SITUATIONS
FIGURE 8-15 The visual field results obtained from four potential early glaucoma cases are presented. They are challenging
to interpret by simply looking at the relative sensitivity loss, which is marked with yellow in the Grayscale of Comparisons rep-
resentation. In the two examples at the top, the few randomly distributed test locations with a probability smaller than 5% also
occur frequently in normal visual fields. The absence of clusters of likely abnormal visual field locations suggests that these
two examples can be interpreted as likely normal. In the two examples at the bottom, the few test locations with a probability
smaller than 5% are organized in clusters and may be interpreted as likely abnormal.
148
PROGRESSIVE ADVANCED GLAUCOMA
Gra
yscale
(C
om
pariso
ns)
Pro
bab
ilitie
s
1st test 2nd test 3rd test 4th test 5th test
Chapter 8 | Clinical interpretation of a visual field
FIG 8-15
FIG 8-1
-FIG 8-12
-
FIG 8-16
LIMITATIONS OF THE PROBABILITIES REPRESENTATION IN ADVANCED DISEASE
FIGURE 8-16 Example of a series of visual fields from a patient with progressing advanced glaucoma. Even though the
visual field is worsening over time, the change is not apparent in the Probabilities representation because most visual field
locations already show a probability of p < 0.5% in the 1st of the 5 tests.
149
Assess shape & depth of defect.Typical for glaucoma?
5
Step-by-step interpretation of a visual field
-
- FIG 5-1, 5-7 5-9
STEP 5 – ASSESS SHAPE AND DEPTH OF DEFECT
NEED FOR ASSESSING SHAPE AND DEPTH OF DEFECT
FIG 7-5
-
-
FIG 8-18 FIG 7-6,
7-7, 7-17 7-18
GRAYSCALE OF (CORRECTED) COMPARISONS AND (CORRECTED) COMPARISONS
STEP 5 – ASSESS SHAPE AND DEPTH OF DEFECT
FIGURE 8-17 The shape and depth of a defect provide valuable clues to identify and characterize pathology. They can be
analyzed from a graphical (Grayscale of Comparisons and Grayscale of Corrected Comparisons) or numerical (Comparisons
and Corrected Comparisons) map.
150
Sensitivity loss [% of normal]
Normal
Visual field loss(the darker the worse)
Correctedfor diffuse
defect
Normal
Visual field loss(the larger the worse)
Maximum visual field loss
Sensitivity loss < 5 dB
Sensitivity loss [dB]22
Absolute defect(i.e., Sensitivity threshold 0 dB)
+
0..10
11..2223..3435..4647..5859..7071..8283..9495..100
7
+ +5
+
++
5
10
10
22
1221
10
5 17++
15 13
67
30
+
+
6 6
8
10
57 31+8
+ 5
58
13 22
+8
2216
+5
11 +
++
25
7
9 8
+8
+
+ ++
+
++
+
5
+
16
715
5
+ 12++
10 8
++
24
+
+
+ +
+
5
++ 26++
+ +
++
8 17
++
1610
++
6 +
++
20
+
+ +
++
CORRECTED GRAYSCALE (CO) DEFINITION INTERPRETATION
COMPARISONS CORRECTED COMPARISONS DEFINITION INTERPRETATION
GRAYSCALE (Comparisons)
Chapter 8 | Clinical interpretation of a visual field
-FIG 2-9
in FIG 7-7 7-8
-
FIG 7-16 FIG 7-18
-
BOX 8A
GRAYSCALE OF COMPARISONS, COMPARISONS AND CORRECTED COMPARISONS – INTERPRETATION AID
FIGURE 8-18 The Grayscale of Comparisons and the Grayscale of Corrected Comparisons are color maps that are especially
useful to determine the shape of the sensitivity loss, whereas the Comparisons and Corrected Comparisons representations
are numerical maps showing sensitivity loss in dB. The Grayscale of Corrected Comparisons and the Corrected Comparisons
representations show localized loss only. All representations are key to identifying possible causes of disease.
151
Sensitivity loss [% of normal]0..1011..2223..3435..4647..5859..7071..8283..9495..100
OCTOPUS GRAPHIC
Gaps between test points
are interpolated
REALISTIC GRAPHIC
Poor spatial resolution
in most perimetric tests
Step-by-step interpretation of a visual field
-
small sensitivity loss can be seen in these representa-
--
FIG 7-16 7-17
FIGURE 8-1
GRAYSCALE REPRESENTATIONS ARE INTERPOLATED COLOR MAPS
It is essential to be aware that the Grayscale representations are interpolated visual field maps,
where gaps between visual field points are filled by interpolation (left). Their true spatial resolution
is much poorer, as illustrated in the panel on the right.
BOUNDARIES OF GRAYSCALE OF COMPARISONS CAN BE MISLEADING
FIG 4-4
BOX 8A
152
Glaucoma only: Significant cluster defects?
6
Chapter 8 | Clinical interpretation of a visual field
--
FIG 5-1
-
-
-
-
FIG 8-20
FIG 7-12, 7-13 7-20 BOX 7B
STEP 6 - ASSESS CLUSTER DEFECTS IN GLAUCOMA
NEED TO ASSESS CLUSTER DEFECTS IN GLAUCOMA
CLUSTER ANALYSIS AND CORRECTED CLUSTER ANALYSIS
STEP 6 – ASSESS CLUSTER DEFECTS IN GLAUCOMA
FIGURE 8-19 Assessment of visual field defects in clusters is helpful for the detection of subtle glaucomatous changes. This
is the purpose of the Cluster and Corrected Cluster Analysis.
153
Probability that a person with a normal visual fieldshows this result
Correctedfor diffuse
defect
Likely normal cluster
Potentially abnormal cluster
Highly likely abnormal cluster
p > 5%
p < 5%
p < 1%
2.7
8.3
+9.1
11.315.8
24.99.74.4
2.7
3.55.8
8.3
3.7
5.910.4
19.54.3
+
2.9+
+
+
Cluster
MD [dB]
CLUSTER ANALYSIS CORRECTED CLUSTER ANALYSIS DEFINITION INTERPRETATION
Step-by-step interpretation of a visual field
-
This is BOX 8B
CLUSTER ANALYSIS AND CORRECTED CLUSTER ANALYSIS – INTERPRETATION AID
FIGURE 8-20 The Cluster Analysis representations group defects into ten clusters according to the paths followed by the
nerve fiber bundles in the retina. Highly likely normal clusters (p > 5%) are marked with a “+” symbol, and likely abnormal
Cluster Mean defects are displayed in normal font (p < 5%) or bold font (p < 1%). The Corrected Cluster Analysis representa-
tion is similar, but eliminates diffuse visual field loss and solely considers local loss.
CLUSTER ANALYSIS IS HIGHLY SENSITIVE TO DETECT GLAUCOMA
than --
-
FIG 8-15
H -
BOX 7B
BOX 8B
154
+
+2.3
+++
+
+
+
+
GRAYSCALE (Comparisons) PROBABILITIESTwo superior paracentral locations at p < 5%
CLUSTER ANALYSISSupero-nasal cluster at p < 1%
3.2
++
+
+
+
+
+
+
+
2 1
211
1
3
3
1
30
2
0
1
1
3
3 101
2 3
00
1
1
0
1
1
1
3
0
20 204
4 3
23
2 0
02
2 2
21
6 2
12
5
0
3 1
42
SENSITIVITY LOSS(Adapted Comparisons representation)
PROBABILITIES CLUSTER ANALYSIS
Chapter 8 | Clinical interpretation of a visual field
-
FIG 8-21
-
ILLUSTRATION OF THE HIGH SENSITIVITY OF CLUSTER ANALYSIS TO DETECT GLAUCOMA
FIGURE 8-21 Example of a borderline visual field. By just looking at the Grayscale of Comparisons (left) and Probabilities
(middle) representations, one may interpret this visual field as likely to be normal, as there is no pattern of contiguous ab-
normal locations. However, examination of the Cluster Analysis (right) shows a small, but significant superior arcuate defect
pattern, which calls for further investigation.
ILLUSTRATION OF THE CLINICAL USEFULNESS OF CLUSTER ANALYSIS
This example highlights the high sensitivity of Cluster Analysis for the detection of subtle glau-
comatous visual field defects. When looking at the sensitivity loss of the individual test locations
(left) in the superior arcuate cluster (red shading), only one location is marked as abnormal in
the Probabilities representation (center). However, most locations are slightly, but not significantly
elevated, which results in a significantly abnormal (p < 1 %) Cluster MD in the Cluster Analysis.
155
Glaucoma only:Where to look for structural defects.
Is there a relationship?
7
Step-by-step interpretation of a visual field
--
-
-
-
BOX 8C for
STEP 7– WHERE TO LOOK FOR STRUCTURAL DEFECTS
NEED TO IDENTIFY RELATIONSHIP BETWEEN FUNCTIONAL AND STRUCTURAL DAMAGE IN GLAUCOMA
STEP 7 – WHERE TO LOOK FOR STRUCTURAL DEFECTS
FIGURE 8-22 Knowing where to look for structural defects to identify a spatial relationship between structural and functional
results is helpful for the detection of subtle glaucomatous changes. This is the purpose of the Polar Analysis.
156
S
I
13dB
TN
S
I
NT
S
II
13d13dBBB1111311333113313ddd313d3d33d3d3 BB3ddBBBdd3dBBdBddBBBB
TTNN
VISUAL FIELD ORIENTATION STRUCTURAL ORIENTATION
7
+ +5
+
++
5
10
10
22
1221
10
5 17++
15 13
67
30
+
+
6 6
8
10
57 31
+8
+ 5
58
13 22
+8
22 16
+5
11 +
++
25
7
9 8
+8
COMPARISONS RETINA WITH OPTIC DISC
270
90
0 180
Chapter 8 | Clinical interpretation of a visual field
SPATIAL RELATIONSHIP BETWEEN VISUAL FIELDS AND STRUCTURAL RESULTS
Structural damage and visual field results are flipped across the horizontal midline (i.e., a superior
visual fi eld defect corresponds to an inferior structural defect at the corresponding location at
the optic disc). Note that even though structural and functional results are also flipped across
the vertical midline, the defects are displayed on the same side because of the different viewing
directions of the patient (visual field) and the observing clinician (structure).
ANATOMICAL RELATIONSHIP BETWEEN STRUCTURAL AND FUNCTIONAL RESULTS
-
F -
-
BOX 8C
157
Location of potential structural damage on optic disc
Short bar
Long bar
Normal location
Abnormal location
Defect [dB]
Normal range
SINT
Superior
Inferior
Nasal
Temporal
• Length of bar indicates defect size [dB]
• Position along the optic disc represents the entry
angle of RNFL fibers associated to each test location
(Within gray normal range)
102030[dB]
S
IN T
POLAR ANALYSIS DEFINITION INTERPRETATION
Step-by-step interpretation of a visual field
--
-
FIG 8-23 -FIG 7-14
FIG 8-24 -
POLAR ANALYSIS
POLAR ANALYSIS - INTERPRETATION AID
FIGURE 8-23 The Polar Analysis maps functional results onto the optic disc, to appear like a structural result. This assists in
assessing the spatial relationship between visual field defects and possibly associated structural defects.
158
S
INT
+
+2.3
+++
+
+
+
+
102030[dB]
GRAYSCALE (Comparisons) PROBABILITIESTwo superior paracentral locations at p < 5%
CLUSTER ANALYSISSupero-nasal cluster at p < 1%
POLAR ANALYSISSubtle visual field loss
at 7 o’clock position
FUNDUS IMAGESplinter hemorrhage and subtle RNFL loss
at 7 o’clock position
OCT MACULA MAPRetinal ganglion cell loss
at 7 o’clock position
STRUCTURAL ORIENTATION
Chapter 8 | Clinical interpretation of a visual field
ILLUSTRATION OF THE CLINICAL USEFULNESS OF THE POLAR ANALYSIS
FIGURE 8-24 Patient with suspected very early glaucoma. While the Probabilities representation is not sensitive enough to
show significant visual field loss, the Cluster Analysis shows that the supero-nasal cluster is likely abnormal at p < 1%. The
Polar Analysis shows a potential defect at the 7 o’clock position of the optic disc, where a very subtle disc hemorrhage is also
found in the fundus photo (darker area within the blue circle). The Macula map picks up the loss of retinal ganglion cells at a
comparable location. Due to the spatial relationship between the subtle defect in the visual field (Polar Analysis) and structur-
al measurements (Fundus Image and Macula Map), glaucoma is confirmed.
159
Severity?8
Step-by-step interpretation of a visual field
-
-
-
-
TABLE 7-1
TABLE 7-1
FIG 8-26
-
-
STEP 8 – ASSESS SEVERITY
NEED TO ASSESS SEVERITY OF VISUAL FIELD LOSS
MEAN DEFECT (MD)
STEP 8 – ASSESS VISUAL FIELD SEVERITY
FIGURE 8-25 Global indices provide useful information to quickly characterize a visual field and to assess disease severity.
160
-0.2 dB 1 dB 6.3 dB 6.5 dB 10.1 dB 21.7 dBMD
NORMAL SUSPECT
Diffuse defect Local defect Local & diffuse defect
EARLY TO MODERATE ADVANCED
Chapter 8 | Clinical interpretation of a visual field
ILLUSTRATION OF THE USEFULNESS OF MD
FIGURE 8-26 The Mean Defect (MD) summarizes the severity of visual field loss in one number, for comparison with other
patients and to quickly communicate the severity of visual field loss. The examples above show different visual fields with
increasingly severe visual field loss.
TABLE 8-1
-
FIG 8-27
in TABLE 7-1
-
-
SQUARE ROOT OF LOSS VARIANCE (sLV)
161
6 6
59
+
6
7 766
11 10
68
+
8
5 5
57
5 7
66
+
5
+
5
11 +
515
9 9
55
8 10
610
7
67
8 5
58
+ +
59
5 +79
7 7
+7
2326
+ +
22
+
13155 6
66
+ +
+
+
+8
+ +
1821
+ +
+
+
19
+
1013
+ +
+8
+ +
1017
+ +
22
+12
85
+ +
+15
+ +
1721+ +
1921
+ +
MD6.5 dB
MD6.3 dB
sLV8.5 dB
sLV2.5 dB
78
10
15
11 11
10 10
9 9 9 9 98 8 8 8
7 77776
5 5 5 5 5 5 5 5 5 5 5 5 566 6 66 66 66 6
7 7 7 7 8 8 86
+ ++
++
++ ++++
++++
++++ ++++ +++ +
+++++ +
+
6 655
10 1011
12 1315 15
17 17
19 1918
2121 212222
2623
DIFFUSE DEFECT LOCAL DEFECT
COMPARISONS COMPARISONS
MD 6.3 dB
sLV 2.5 dB
MD 6.5 dB
sLV 8.5 dB
Step-by-step interpretation of a visual field
ILLUSTRATION OF THE USEFULNESS OF sLV
FIGURE 8-27 Visual fields with either diffuse defects (left) or local defects (right) appear fundamentally different, but can
have similar MD values, as this example illustrates. The square root of Loss Variance (sLV) is then useful to distinguish
between the two situations, as sLV is smaller in the case of homogeneous or diffuse visual field defects and larger in the case
of heterogeneous or local visual field defects. In short, sLV is a measure of how much the defects at different test locations
differ from the mean defect, as illustrated in the graphic at the bottom.
162 Chapter 8 | Clinical interpretation of a visual field
163References
REFERENCES
Am J Ophthalmol
Ophthalmology
Ophthalmology
Invest Ophthalmol Vis Sci
Ophthalmology
Invest Ophthalmol Vis Sci
Ophthalmology
reliability? Invest Ophthalmol Vis Sci
Graefe's Arch Clin Exp Ophthalmol
Open Ophthalmol JJ Glaucoma
Invest Ophthalmol Vis Sci
Br J OphthalmolAm J Ophthalmol
Eur J Ophthalmol
Graefe's Arch Clin Exp Ophthalmol
Eur J Ophthalmol
Ophthalmologica
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