Download principles of visual field testing and perimetry

PRINCIPLES OF VISUAL FIELD TESTING AND PERIMETRY
Chris A. Johnson, Ph.D, D.Sc, FAAO, FARVO
Department of Ophthalmology and Visual Sciences
University of Iowa Hospitals and Clinics
200 Hawkins Drive
Iowa City, IA 52240
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I.
Why are visual fields done ?
A.
It is the only clinical test of peripheral vision
B.
Many ocular and neurologic diseases affect peripheral vision before
central vision
C.
Visual fields can assist in the detection of ocular and neurologic diseases
D.
Visual fields have differential diagnostic value and help to localize where
the problem is occurring
E.
Reduced visual acuity is rather non-specific (cannot localize the source of
the problem), but the pattern and location of visual field loss can localize where
the deficit is occurring.
F.
Many people are unaware of peripheral vision loss (particularly if it is
only in one eye) even though it affects their activities of daily living and quality
of life.
II.
A “cookbook” for visual field interpretation
A.
Place the left eye visual field on the left and the right eye visual field on
the right
B.
For each eye, is the visual field normal or abnormal ? (If normal in both
eyes, you’re done)
C.
If abnormal, is it one eye or both eyes ? If on only one eye, it’s ocular
media, retina or optic nerve. If its both eyes, then its chiasm, post-chiasm or
bilateral disease in both eyes.
D.
Where is the defect in general terms ? (superior, inferior, nasal, or
temporal) If it’s extensive, where is the majority of the defect ? (Nasal or
binasal is glaucoma, optic nerve or retina, bitemporal is chiasm, nasal in one
eye and temporal in the other (homonymous, or same side of vision), it is postchiasmal
E.
What is the shape of the defect (respect the horizontal, respect the
vertical, point to the blind sopt, point to fixation, fan shaped, candleflame
shaped (centrocecal), central quadrant, hemifield, etc)
F.
How do the two eyes compare (homonymous, congruent ?)
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G.
Where is the most likely location of the defect ?
H.
Key features to remember
1.
Respect the nasal horizxontal meridian – glaucoma, optic nerve or
retinal casculature
2.
Respect the vertical – chiasm or post-chiasm
3.
Point to the blind spot – optic nerve, glaucoma
4.
Point to fixation – chiasm, post-chiasm
5.
Bitemporal – chiasm
6.
Binasal – glaucoma optic nerve, retina
7.
Ring – retina
8.
Scalloped edges of deficit – retina
9.
Homonymous – post-chiasm
10.
Congruous – Occipital lobe
11.
Moderately incongruous – Parietal lobe
12.
Highly incongruous – Temporal lobe
13.
Pie in the sky (like a piece of pie cut out of the visual field superiorly temporal lobe
14.
Pie on the floor – Parietal lobe
15.
Total homonymous hemianopsia – post-chiasmal
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III.
Kinetic Perimetry
A.
Target is moved from the periphery towards fixation to map out areas of
equal sensitivity (isopters). Multiple isopters are created by doing this for
different sizes and luminances of targets. Areas of non-seeing (scotomas) are
also mapped out. This is a highly acquired skill and requires much interaction
between the examiner and the patient. Few instruments have automated this
procedure.
IV.
Static Perimetry
A.
Target is stationary and luminance is adjusted to find the threshold for
detection (minimum amount of light needed for detection). This has been
automated and has a strong normative database and sophisticated analysis
packages, and is standardized.
V.
Suprathreshold Static Perimetry
A.
Is a rapid screening procedure that is able to determine normal and
abnormal sensitivity locations in the visual field and in some instances the
extent of the abnormality.
VI.
Reliability
A.
Eye Movements (fixation losses – blind spot technique, and gaze
tracking)
B.
False positive responses
C.
False negative responses
VII. Visual Field Indices
A.
Mean Deviation (MD)
B.
Pattern Standard Deviation (PSD)
C.
Glaucoma Hemifield Test (GHt)
VIII. Probability Plots
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IX.
X.
XI.
A.
Total Deviation
B.
Pattern Deviation
Type of test
A.
30,2, 24-2, 10-2, macula
B.
screening tests (full field, 1 level, 3 level, quantify defects)
Test strategy
A.
Full Threshold
B.
Swedish Interactive Threshold Algorithm (SITA)
Target Size
A.
Goldmann sizes I through V
XII. Diffuse Loss and Localized loss
A.
Use of the Total and Pattern Deviation plots to distinguish them
XIII. Artifactual Visual Field Results
A.
Small pupil size
B.
Refractive error
C.
Droopy Eyelid (ptosis)
D.
Lens rim artifact
E.
1.
Total lens rim artifact
2.
Partial lens rim artifact
Fatigue or limited attention span
XIV. Localization of visual field loss
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A.
Cornea, lens and media opacities
1.
B.
C.
D.
E.
Usually produce diffuse or widespread visual sensitivity loss
Retinal problems
1.
Deficits do not generally correspond to anatomical visual pathway
organization.
2.
Retinitis pigmentosa and related diseases produce a ring or partial ring
scotoma
3.
Branch artery occlusions have an arcuate shape extending from the
optic nerve (blind spot) and usually “respect” the nasal horizontal
meridian
4.
Macular defects produce central scotomas
Glaucoma
1.
Produces deficits that correspond to the nerve fiber bundle
arrangement
2.
Deficits “respect” the nasal horizontal meridian
3.
Defects are arcuate, point to the blind spot and fan out towards the
nasal visual field.
4.
Superior and inferior arcuate nerve fiber defects are the most common,
along with nasal steps. Temporal wedge defects are less common.
5.
Other optic neuropathies produce central scotomas, glaucoma-like
defects, centrocecal scotomas, and visual field constriction.
Chiasmal defects
1.
Bitemporal visual field defects (especially superior bitemporal defects)
are most commonly seen with chiasmal lesions. The defects “respect”
the vertical meridian and “point” to fixation.
2.
Junction scotomas (dense central visual field loss in one etye
accompanied by a temporal defect respective the vertical meridian in
the other eye) can occur of the deficit is at the anterior portion of the
chiasm where the optic nerve enters.
Lateral geniculate defects (very, very uncommon)
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1.
F.
Post chiasmal and lateral geniculate defects
1.
Respect the vertical meridian and point to fixation. Also they are
homonymous (on the same side of vision) for both eyes.
2.
In general the greater the congruity (the more similar the visual field of
both eyes appears) the lesion is farther back in the optic radiations.
3.
Temporal lobe lesions have the most incongruous visual field (visual
field loss is greater in one eye than in the other), while parietal lobe
lesions have greater congruity, and occipital lobe lesions are highly
congruous (cookie cutter punched out lesions). Temporal lobe lesions
often produce a “pie in the sky” appearance like a pience of pie has bee
cut out of the visual field superiorly. Parietal lobe lesions often produce
“pie on the floor” visual field appearance.
a
4.
G.
Because of the distribution of nerve fibers, the defects tend to resemble
a “tongue” extending from the blind spot horizontally through to the
nasal visual field. Conversely, the remainder of the visual field can
be affected and this region can be the only remaining visual field.
Things to remember – a total homonymous hemianopsia (half of the
visual field missing for both eyes) means that all of the fibers have been
damaged, so the only localizing ability is to assess that it is postchiasmal; some cookie cutter defects may link up with the blind spot for
one eye, and this should be considered; because the temporal visual
field extends farther than the nasal visual field, so there may be a rim of
visual field for one eye (the temporal crescent) that does not appear for
the nasal visual field of the other eye.
Use the “cookbook” to perform visual field evaluations for a single test
and it will get you through most of the diagnostic dilemmas, but be sure
to perform these steps in the proper order (don’t change the order or
skip steps).
XV. Analysis of progression
A.
There are four methods of evaluating progression: clinical judgment,
classification or staging of disease, event analysis (change from baseline)
and trend analysis (linear or nonlinear regression). All of these
procedures have been used in multicenter glaucoma clinical trials.
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B.
1.
Clinical judgment: advantages – easy to perform, can be conducted in a
busy clinic. disadvantages – is not quantitative, varies greatly from one
practitioner to another, is not evidence-based, users tend to “overcall”
progression or change.
2.
Staging or classification systems – advantages – is simple to use, has a
minimal number of rules. disadvantages - is an ordinal scale (level of
severity is ordered) but intervals are not necessarily equal, the criteria
for a meaningful change for clinical management is not well
determined, all staging systems are different
3.
Event analysis – advantages – establishes a baseline result that is
quantitative and standardized, procedures are available on many
automated devices. Disadvantages – only compares the current visual
field to the baseline results and all intermediate findings are not
considered, because of variability and response errors (false positives
and negatives) single test results can sometimes be questionable.
4.
Trend analysis performs a regression of results from all test procedures,
either using a linear or a nonlinear model. advantages – utilizes all of
the data and can minimize the influence of “outliers”; disadvantages –
requires at least 6 or 7 visual fields over a reasonable time period of 3
years or more to achieve good clinical performance; is limited by the
assumptions associated with a linear or nonlinear model.
Event and trend analysis are the procedures that have been most
commonly used for clinical trials and for assessment of individual patient
status.
XVI. One factor that is a problem for all of these approaches is within
and between test variability. Unlike detection of visual field loss,
there has been no consensus as to the most appropriate method to
determine visual field progression (all of the various methods of
assessing visual field progression only agree with each other about 5060% of the time)
A.
What can be done:
1.
Do not rely completely on the visual field for a determination
2.
When in doubt, repeat the test to confirm a suspected change (In the
Ocular Hypertension Treatment Study, more than 87% of initial visual
field losses were not confirmed on the next test)
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3.
Use all the information available in conjunction with the visual field
(optic disc appearance, retinal nerve fiber bundle, other relevant clinical
information)
4.
Use as many different forms of evaluating progression as possible and
look for concordance
5.
Get opinions from your colleagues.
XVII. Structure-function relationships
A.
For the past 150 years or more, structure-function relationships (visual
field and noninvasive assessment of the retina, optic nerve fibers, and
brain locations involved with vision) show good agreement if large,
general criteria are used, but the agreement becomes smaller as the
questions become more specific
B.
In spite of tremendous technological advances, there has not been much
change in the general issue of structure-function relationships. Why ?
1.
Each procedure has its own variability
2.
Visual field typically examine only a portion of the entire visual field,
while structural assessments are usually associated with all of the
neural fibers associated with vision
3.
The method of assessing these topics is not completely definitive and
different answers can occur with various approaches.
4.
Use the methods that you are most familiar with and don’t change
them unless there is a significant, meaningful reason to do so.
XVIII. New test procedures in perimetry
A.
SWAP (Short Wavelength Automated Perimetry)
B.
HEP (Heidelberg Edge Perimetry) and Flicker perimetry
C.
Motion perimetry
D.
Frequency Doubling Perimetry (Matrix perimetry)
E.
Pulsar Perimetry
F.
Microperimetry
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G.
High Pass Resolution Perimetry
H.
Rarebit perimetry
XIX. Questions ?
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