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Can Swedish Interactive Thresholding Algorithm Fast Perimetry Be Used as an Alternative to Goldmann Perimetry in Neuro-ophthalmic Practice?
Gabriella Szatmáry, MD;
Valérie Biousse, MD;
Nancy J. Newman, MD
Arch Ophthalmol. 2002;120:1162-1173.
ABSTRACT
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Objective To assess the potential role of Swedish Interactive Thresholding Algorithm
(SITA) Fast computerized static perimetry, compared with that of Goldmann
manual kinetic perimetry (GVF), for reliably detecting visual field defects
in neuro-ophthalmic practice.
Background Automated visual field testing is challenging in patients with poor
visual acuity or severe neurological disease. In these patients, GVF is often
the preferred visual field technique, but performance of this test requires
a skilled technician, and this option may not be readily available. The recent
development of the SITA family of perimetry has allowed for shorter automated
perimetry testing time in normal subjects and in glaucoma patients. However,
its usefulness for detecting visual field defects in patients with poor vision
or neurological disease has not been evaluated.
Design and Methods We prospectively studied 64 consecutive, neuro-ophthalmologically impaired
patients with neurologic disability of 3 or more on the Modified Rankin Scale,
or with visual acuity of 20/200 or worse in at least one eye. Goldmann manual
kinetic perimetry and SITA Fast results were compared for each eye, with special
attention to reliability, test duration, and detection and quantification
of neuro-ophthalmic visual field defects. We categorized the results into
1 of 9 groups based on similarities and reliabilities. Patient test preference
was also assessed.
Results Patients were separated into 2 groups, those with severe neurologic
deficits (n = 50 eyes) and those with severe vision loss but mild neurologic
dysfunction or none at all (n = 50 eyes). Overall, GVF and SITA Fast were
equally reliable in 77% of eyes. Goldmann manual kinetic perimetry and SITA
Fast showed similar visual field results in 75% of all eyes (70% of eyes of
patients with severe neurologic deficits and 80% of eyes with poor vision).
The mean ± SD duration per eye was 7.97 ± 3.2 minutes for GVF
and 5.43 ± 1.41 minutes for SITA Fast (P<.001).
Ninety-one percent of patients preferred GVF to SITA Fast.
Conclusions We found the SITA Fast strategy of automated perimetry to be useful
in the detection, and accurate in the quantification of central visual field
defects associated with neuro-ophthalmic disorders. Our results suggest that
for the general ophthalmologist or neurologist, visual field testing with
SITA Fast perimetry might even be preferable to GVF, especially if performed
by a marginally trained technician, even in patients with severely decreased
vision or who are neurologically disabled.
INTRODUCTION
FORMAL VISUAL field testing is commonly ordered in patients with neuro-ophthalmic
disorders such as optic neuropathies or intracranial lesions involving the
visual pathways. However, performing visual field tests may be a challenge
in patients confined to a wheelchair, those who are unable to communicate,
those with cognitive disorders, or patients with severely decreased vision.
Manual Goldmann kinetic perimetry (GVF) is classically considered to be the
standard perimetry technique for patients with neurological disorders. The
technique is easy for the patient, fixation is continuously monitored by a
technician, the test can be shortened depending on the patient's alertness,
and the technician is able to stimulate a sleepy or poorly cooperative patient
as needed. However, not all centers have trained personnel capable of performing
reliable GVF testing.1-2
During the past 2 decades, many different automated perimetry programs
have been developed with the goal of providing a standardized, accurate assessment
of the visual field, with less technical expertise required of the operator.1, 3 Most automated perimetry is superior
to GVF in terms of sensitivity and quantification of the visual field defects.1, 3-7
Automated perimetry has become the standard for visual field testing in glaucoma
patients, and it is now widely available.1, 3
However, few studies have evaluated automated perimetry in patients with neuro-ophthalmic
diseases, and fewer still have compared GVF with automated perimetry in this
group of patients.1, 4-11
Most recent studies used the full-threshold Humphrey field analyzer, which
is now the most common automated perimeter in the United States, and documented
its usefulness in the quantification of neuro-ophthalmic visual field defects.9, 11 They also confirmed, however, that
most automated perimetric testing (especially that which uses the full-threshold
Humphrey field analyzer) requires a higher level of understanding and greater
concentration by the patient, often limiting its use in neurologically impaired
patients.1, 5, 8-9,11
A new family of automated perimetry, the Swedish Interactive Threshold
Algorithms (SITA), was recently developed to shorten perimetric test time
without reducing data quality as compared with the full-threshold Humphrey
strategy.12 The SITA concept allows flexibility
of many test parameters. It updates threshold values and adjusts time between
stimulus presentation based on the patient's response. The SITA technique
has been shown to produce the same high-quality test results as the full-threshold
Humphrey strategy in glaucoma patients, but with considerably fewer stimulus
exposures.12-15
Furthermore, the SITA standard strategy has a considerably shorter test time
(50%) compared with the full-threshold Humphrey test.12
SITA Fast is another threshold strategy that is even more rapid than the SITA
standard strategy.16 It is based on the same
algorithms, and it has good reproducibility, even though it may be slightly
less sensitive than SITA standard in glaucoma patients.16-20
SITA Fast's shorter test time and flexibility of test parameters would be
expected to reduce visual fatigue, thereby improving cooperation in patients
with neurogenic visual field defects. Indeed, based on the patient's response,
the SITA strategy continuously updates threshold values during the test, and
it automatically adjusts the time between stimulus presentations in response
to the reaction time of the patient. In this study, we compared SITA Fast
computerized static perimetry with GVF in the detection and characterization
of visual field defects in neuro-ophthalmic practice.
PATIENTS AND METHODS
PATIENTS
We prospectively evaluated consecutive patients seen with either severe
neurological impairment or severe vision loss in the Neuro-Ophthalmology Unit
at Emory University (Atlanta, Ga) between September 2000 and April 2001 (Table 1 and Table 2). Severe neurological impairment was defined by a score
of 3 or 4 on the Modified Rankin Scale (MRS) (MRS 3 = moderate disability:
requires some help, but able to walk without assistance; MRS 4 = patient unable
to walk: requires permanent help).21 Severe
vision loss was defined by a visual acuity of 20/200 or worse in at least
one eye. Patient inclusion criteria consisted of age 18 years or older, the
ability to understand instructions, and the motor ability to carry out a visual
field examination (patient able to sit upright for at least half an hour and
to press a button in response to visual stimulation). Patients not willing
to have both GVF and SITA Fast perimetry on the same day were excluded.
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Table 1. Demographics and Visual Field Results of Patients With Severe
Neurological Deficits (MRS 3 or 4)*
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Table 2. Demographics and Visual Field Results of Patients With Severely
Decreased Vision in at Least 1 Eye*
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VISUAL FIELD TESTING
Visual field examinations were performed using the GVF and the Humphrey
automated static perimeter with the SITA Fast algorithm. Both tests on both
eyes were always performed on the same day, with the GVF examination performed
first. The GVF was performed by the same skilled technician. Patients were
seated before the Goldmann perimeter with the left eye occluded first. Each
patient's near refraction, with additional diopters adjusted for age, was
provided. The machine was calibrated according to the manufacturer's instructions,
and the background-target luminosity ratio was set at 1:33. The blind spot
was mapped using the I2e or I4e test object (depending on the patient's visual
acuity) at a distance of 300 mm to ensure patient reliability. Relative defects
in the visual field were detected by using standard test objects such as V4e,
I4e, I2e, I1e, with additional isopters plotted as indicated. To mark the
peripheral edge of an isopter, the test object was moved at a rate of 2°
to 3° per second from the far periphery toward fixation until it was seen.
For scotoma testing, the test object was presented inside the region of field
loss and moved radially in a straight line until it was seen. The left eye
was then tested in the same fashion.
SITA Fast perimetry was obtained for all patients after at least 1 hour
of rest. We used a Humphrey 740 perimeter with the standard settings of a
size III (4 mm2) test object at a distance of 333 mm, with a 200-millisecond
stimulus duration, and a bowl illumination of 31.5 apostilb (asb) as previously
described.12, 16 To perform the
fastest test, we chose the 24-2 strategy (exploring the central 24°) rather
than the 30-2 strategy. Each patient's fixation and position were checked
every 1 to 2 minutes on the video eye monitor, with adjustments made as necessary.
The right eye was tested prior to the left eye.
RELIABILITY OF VISUAL FIELDS
The GVF was considered unreliable if the technician performing the test
assessed the patient's cooperation and fixation to be too poor to plot an
adequate field, or if the blind spot could not be plotted. A SITA Fast visual
field was considered unreliable if fixation losses were 50% or more. We did
not use false-positive and false-negative catch trials.
COMPARISON OF GVF AND SITA FAST VISUAL FIELDS
The 3 investigators made an independent subjective assessment of the
pattern configuration, extent and depth of the visual field defects on the
hand-drawn Goldmann chart, and on the pattern SD and the graytone printout
from the SITA Fast perimeter. Direct comparison was made between the central
24° of the GVF as assessed by putting a template over that area, and with
the pattern SD and the graytone printout from SITA Fast (Figure 1).
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Figure 1. Comparison of Goldmann manual
kinetic perimetry (GVF) (A) and Swedish Interactive Thresholding Algorithm
(SITA) Fast perimetry (B) visual fields. The central 24° of the GVF were
assessed by putting a template over that area (dashed line). Goldmann perimetry
was then compared with the pattern deviation and the graytone printout from
the SITA Fast. The black spots on the pattern deviation and the dark areas
on the graytone printout of the SITA Fast correspond to areas with decreased
sensitivity. In this example, there was a relatively good correlation between
the GVF and SITA Fast, and these eyes were classified as group II.
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The results of the visual field comparison were classified into 1 of
9 groups, as previously suggested by others (Table 3).5, 9
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Table 3. Classification of Visual Field Comparison Into 9 Groups*
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OTHER OUTCOME MEASURES
The testing time required for each visual field strategy in each eye
was compared using the  2 test. The patient's functional status
was assessed with the MRS and the Barthel Index,21
on the day of the visual field tests. Patient preference was evaluated by
asking the patient which visual field test they would rather have on their
follow-up examination.
RESULTS
PATIENTS
A total of 64 patients was included in the study. There were 36 men
and 28 women with a mean age of 53 years (range, 18-92 years). Patients were
divided into 2 groups, depending on their neurological status and visual acuity.
Twenty-five patients (17 men, 8 women; mean age, 51 years [range, 18-86 years])
with severe neurological impairment (MRS 3 or 4) were included in the first
group (Table 1). All 25 patients
were able to perform both visual field tests with both eyes, and all 50 eyes
were included in the analysis. The mean MRS was 3.4 (range, 3-4), and the
mean Barthel index was 52.4 (range, 25-85). Five patients with neurological
deficits also had 8 eyes with poor visual acuity, ranging between 20/200 and
hand motions. The other 42 eyes had a mean visual acuity of 20/30 (range,
20/20-20/100). Thirty-nine patients with severe vision loss (19 men, 20 women;
mean age, 54 years [range, 18-92 years]) were included in the second group
(Table 2). Among these 39 patients
(representing 78 eyes), 3 patients had 1 eye with a visual acuity of no light
perception, and 25 patients had 1 eye with a visual acuity better than 20/200.
These 28 eyes were excluded from the study, and the analysis was performed
on the remaining 50 eyes. Visual acuity was extremely poor (20/400 or worse)
in 34 of 50 eyes.
Clinical characteristics of the patients and visual field description,
reliability, test time, and categorization of the visual field comparison
for each of the 100 eyes included in the study, are detailed in Table 1 and Table 2.
RELIABILITY OF VISUAL FIELDS
Visual field examinations with GVF were reliable in 77% of all eyes.
Visual fields obtained with the SITA Fast strategy were also estimated to
be reliable in 77% of all eyes. Among the 50 eyes of patients with severe
neurological deficits, 32 (64%) had a reliable GVF, and 36 (72%) had a reliable
SITA Fast visual field. Among the 50 eyes with severe vision loss, 45 (90%)
had a reliable GVF, and 41 eyes (82%) had a reliable SITA Fast visual field.
In 16% of all eyes (7 [14%] of 50 eyes in patients with severe neurological
deficits, and 9 [18%] of 50 eyes with severe vision loss), the GVF was reliable,
but the SITA Fast was not. In 14% of all eyes, (11 [22%] of 50 eyes of patients
with severe neurological deficits, and 3 [6%] of 50 eyes with severe vision
loss), the SITA Fast was reliable, but the GVF was not. In 7 (14%) of 50 eyes
of patients with neurological deficits, neither of the visual field tests
were reliable.
COMPARISON OF GVF AND SITA FAST VISUAL FIELDS
The distribution of the results of the visual field comparisons is demonstrated
in Figure 2. Overall, the 2 fields
were similar (groups 1, 2, 3, and 4) in 75% of all eyes. Among the eyes of
patients with neurological deficits, 35 (70%) of 50 eyes had similar visual
field tests on both strategies (Figure 3).
However, 11 (22%) of 50 eyes of patients with neurological deficits had normal
visual fields (group 4) (Figure 2).
Excluding these 11 healthy eyes from the analysis, 24 (61.5%) of 39 eyes of
patients with neurological deficits had similar visual field defects with
both tests. Among the eyes with vision loss, 40 (80%) of 50 had similar visual
field defects on both fields (Figure 4).
A few eyes were classified in groups 5 and 6, in which both visual field tests
were reliable, with one of the tests being abnormal and the other one being
healthy. In 8% of all eyes (6 of 43 eyes of patients with neurological deficits,
and 2 of 50 eyes with vision loss), GVF failed to show a defect demonstrated
by SITA Fast (group 7) (Figure 5).
In 9% of all eyes (3 of 43 eyes of patients with neurological deficits, and
6 of 50 eyes with vision loss), SITA Fast failed to show the visual field
changes demonstrated by GVF (group 8). In 4 of these patients categorized
as group 8, the visual field defect or the residual island of vision was located
at the edge or outside of the central 24° explored by automated perimetry
(Figure 6).
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Figure 2. Distribution of the results of
the visual field comparisons.
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Figure 3. Similar visual field results (group
I) in a patient with Parkinson disease and dyskinesia, who developed a right
homonymous hemianopia after a left pallidotomy. The discrepancy between Goldmann
manual kinetic perimetry (A) and Swedish Interactive Thresholding Algorithm
Fast perimetry (B) is less than 5°.
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Figure 4. Similar visual field results (group
II) in a patient with poor vision. The discrepancy between Goldmann manual
kinetic perimetry (GVF) (A) and Swedish Interactive Thresholding Algorithm
(SITA) Fast perimetry (B) is more than 5°, but the 2 fields are very similar,
with SITA Fast demonstrating a slightly larger defect than GVF in this patient
with bilateral central scotomas.
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Figure 5. Visual field results in a patient
in whom Goldmann manual kinetic perimetry (A) failed to show the right superior
homynomous defect demonstrated by Swedish Interactive Thresholding Algorithm
Fast perimetry (B) (group VII).
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Figure 6. Visual field results in a patient
with a left optic neuritis in whom Swedish Interactive Thresholding Algorithm
(SITA) Fast perimetry (B) failed to show the residual island of vision demonstrated
by Goldmann manual kinetic perimetry (A) (group VIII). The patient had a large
scotoma involving fixation, and the residual temporal island of vision was
located outside of the central 24° of the visual field tested with SITA
Fast.
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TEST TIME
The mean ± SD test time on the GVF perimeter was 7.97 ±
3.2 minutes per eye (range, 3-22 minutes). It was 8.04 ± 3.57 minutes
(range, 4-22 minutes) in the group of patients with neurological deficits,
and 7.9 ± 2.7 minutes (range, 3-15 minutes) in the group of patients
with poor vision. The mean ± SD test time on the SITA Fast perimeter
was 5.43 ± 1.41 minutes per eye (range, 3.03-11.4 minutes). It was
5.44 ± 1.54 minutes (range, 3.05-10.52 minutes) in the group of patients
with neurological deficits, and 5.79 ± 1.30 minutes (range, 3.40-11.73
minutes) in the group of patients with poor vision. The SITA Fast perimeter
reduced the test time by 2.54 minutes (47%) compared with the GVF perimeter
(P<.001). The amount of reduction of test time
with the SITA Fast perimeter was similar in the group of patients with neurological
deficits and in the group of patients with severe vision loss.
PATIENT PREFERENCE
When asked which visual field test they would rather have on their follow-up
examination, 58 (91%) of our 64 patients preferred GVF. The main reason given
by the patients who preferred GVF was the difficulty of maintaining concentration
during testing with the SITA Fast. Among the 6 patients who preferred SITA
Fast, one had severe neurologic deficits, and 5 had severe vision loss. They
all enjoyed the computerized aspect of the test.
COMMENT
Goldmann perimetry is the traditional method for evaluating visual field
defects in patients with severe neurological handicaps or severe vision loss.
With the development of more sophisticated, reliable, sensitive, affordable,
and easily performed automated perimetry programs, GVF performed by a skilled
technician has become less available. However, although the full-threshold
Humphrey analyzer has proven to be one of the most sensitive and reliable
automated perimetry strategies for more than 20 years, it is still only rarely
used by neurologists. Indeed, it does have drawbacks compared with GVF, such
as prolonged test time, the rapid appearance and disappearance of the light
stimulus, lack of human contact and reassurance, and continued testing despite
detection of poor fixation.1 Previous studies8-9 have shown that the full-threshold
Humphrey analyzer cannot overcome many of the major obstacles to accurate
visual field assessment, such as fixation losses, poor concentration, and
patient fatigue, which are all common findings in neurologically disabled
patients. The SITA family of automated perimetry uses the Humphrey perimeter
with different algorithms, making the visual field testing process much shorter
and easier for the patient.1, 12, 16
These automated perimetry programs have replaced the full-threshold Humphrey
analyzer in most glaucoma centers and will soon be readily available and accessible
in most ophthalmic and neuro-ophthalmic practices.
Our study shows that SITA Fast computerized static perimetry, a new
rapid perimetric threshold test, can be used to identify and localize visual
field defects in most patients with neuro-ophthalmic diseases. Previous studies16-17 have shown that SITA Fast is reliable
in healthy subjects and in glaucoma patients, in whom visual acuity is usually
relatively well preserved. We evaluated only patients with either severe vision
loss who may not be able to see the standard target used on the automated
perimeter, or those with a neurologic deficit that may compromise their ability
to perform a computer-driven test. We assumed from previous studies5, 8-9,11, 17
that patients with good visual acuity or mild neurological deficits would
not have trouble performing SITA Fast perimetry, and therefore, we excluded
such patients from our study.
The overall reliability of visual field testing in our study seemed
to be very good (77%) even in our disabled patient population. However, without
an accepted established definition of a "reliable visual field test" for both
GVF and SITA Fast perimetry, these results should be interpreted with caution.
Our estimation of a "reliable" GVF was based on the technician's subjective
assessment of the patient's cooperation. For SITA Fast perimetry, we used
a very high rate of fixation loss (>50% rather than >20%) to establish that
a visual field was not reliable. Sanabria et al22
showed that fixation losses result not only from subjects looking around,
but also from faulty initial localization of the blind spot and, therefore,
that these losses may be the result of technical artifacts. Using our criteria,
we observed similar reliabilities with both GVF and SITA Fast perimetry in
the group of patients with poor visual acuity. For the SITA Fast strategy,
we used the standard size III target provided by the Humphrey analyzer, which
corresponds to a 4-mm2 stimulus size (equivalent to a size III
target on GVF). This target allowed reliable evaluation of the visual field
of patients with visual acuities as poor as hand motions. Nevertheless, in
9 eyes with vision loss, and in 7 eyes of patients with neurological deficits,
GVF was reliable, but SITA Fast was not, according to the high percentage
of fixation losses. In this group of patients who had an unreliable SITA visual
field, most patients with vision loss had visual acuities worse than 20/400
or were older than 72 years. It is likely that a larger stimulus (such as
64 mm2, equivalent to the size V target on GVF) would have provided
more useful information in these patients.23
However, we selected the "standard" stimulus size provided by the standard
Humphrey package, as used by most community-based ophthalmologists, to simulate
common referral conditions. We felt it would be too taxing on the patients
who failed to perform a reliable SITA test to repeat perimetry with a larger
stimulus on the same day. Most patients with neurological deficits who were
not able to perform a reliable SITA Fast had either a cerebellar syndrome
compromising their coordination and their fixation, or frontal or occipital
lesions associated with spatial and cognitive disorders (Figure 7). Without the experience of the highly skilled technician
who performed all GVFs, it is likely that most of these patients would not
have been able to perform a reliable GVF. Nevertheless, in 22% of our patients
with neurological deficits, SITA was more reliable and provided better visual
field information than GVF (Figure 5). This may be explained by the short examination time of the 24-2 SITA Fast
perimetry, as well as the flexibility of the SITA Fast parameters.16
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Figure 7. Visual field results in a patient
with bilateral occipital infarctions in whom Swedish Interactive Thresholding
Algorithm Fast perimetry (B) failed to show the bilateral homonymous hemianopic
defects demonstrated by Goldmann manual kinetic perimetry (A) (group VIII).
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The results obtained with SITA Fast perimetry indicate a relatively
good correlation with Goldmann perimetry in the detection, characterization,
and quantification of visual field defects in this particular population.
We found that 75% of all eyes with abnormal visual fields had similar visual
field results with GVF and SITA Fast (70% of eyes in patients with neurological
deficits, and 80% of eyes with severe vision loss). Only a few previous studies
have compared GVF with automated perimetry in patients with neuro-ophthalmic
disorders. Various automated perimetric strategies were used, including the
Fieldmaster,7-8 the Octopus,5 and the Humphrey full-threshold analyzer.9-11 These studies showed
that automated perimetry was comparable to GVF in detecting visual field abnormalities
in neurologic diseases. For example, visual field defects were almost identical
with automated perimetry and GVF in 84% of the 25 patients studied by McCrary
and Feigon,5 and in 87% of the 69 eyes studied
by Beck et al.9 The purpose of these studies
was to evaluate the reliability of automated perimetry in identifying and
quantifying visual field defects from neuro-ophthalmic diseases such as nonglaucomatous
optic neuropathies and lesions involving the retrochiasmal visual pathways.
None of these studies specifically addressed the issue of severely decreased
vision in some patients with optic neuropathies, nor did they correlate their
results to the degree of a neurological handicap. Most of these studies5, 7-9 used
older-generation perimeters that are much slower and generate more visual
fatigue than the SITA Fast algorithm used in our study.
A quarter of all eyes, representing 25 (28%) of 89 eyes with abnormal
visual fields, were categorized into group 2, in which SITA Fast showed a
slightly larger visual field defect than GVF (Figure 4). It has been shown that automated perimetry is more sensitive
than GVF in the detection of visual field defects in patients with glaucoma.4, 6, 8-9 Indeed,
even in the hands of a skilled operator, GVF often underestimates the severity
of the visual field defects, especially when the defects are located in the
central part of the visual field.4, 6, 8-9
Another possible explanation is statokinetic dissociation, which has been
reported in various pathological cases involving the optic nerves as well
as the occipital lobes.24-25 Statokinetic
dissociation is a physiologic phenomenon related to the easier perception
of moving objects (as in Goldmann kinetic perimetry) than stable objects (as
in static automated perimetry), giving rise to a greater visual field defect
on automated perimetry compared with GVF.24-25
However, in 5 eyes with severe vision loss, GVF showed a slightly larger defect
than SITA Fast (group 3).
In 9 (10%) of 89 eyes with abnormal visual fields, SITA Fast failed
to show a visual field defect that was demonstrated by GVF (group 8). In 4
of these eyes, the visual field defects (or the residual island of vision)
were localized at the border or outside of the central 24° of visual field
evaluated by SITA Fast (Figure 6).
Goldmann perimetry tests the entire visual field (180°) and is hence the
obvious technique of choice in eyes with either residual eccentric islands
of vision or with visual field defects not involving the central 24° of
vision. The SITA software allows for the evaluation of the central 10°,
24°, or 30° of vision. We used the 24-2 instead of the 30-2 strategy
to reduce the duration of the test, thereby limiting visual fatigue. However,
it is unlikely that evaluation of the central 30° would have changed our
results.26 The full-threshold Humphrey analyzer
is able to test the central 60° of vision, but the length of the test
(as long as 30 minutes per eye) precludes easy usage. Development of a SITA
strategy testing the central 60° of visual field could potentially solve
this problem, with an acceptable minimal increase in test duration within
the SITA Fast algorithm. However, it is also possible that certain lesions
involving the retrochiasmal visual pathways may not be detected as well with
automated perimetry as with GVF, even if the defects fall within the central
visual field. For example, one of our patients with bilateral occipital infarctions
had a GVF perimetry that exquisitely delineated bilateral homonymous defects—findings
completely missed by SITA Fast perimetry, which was unreliable (Figure 7). Wong and Sharpe11 evaluated
12 patients with occipital lobe infarctions using tangent screen, GVF, and
the full-threshold Humphrey visual field, and correlated the findings with
magnetic resonance imaging of the causative lesions. They observed that even
though Humphrey automated perimetry was able to detect the visual field defects,
it incorrectly localized the defects to the proximal portion of the retrochiasmal
pathway in 2 patients, failed to detect sparing of the occipital pole in 4
patients, and overestimated the lesion size in 1 patient.11
The duration of visual field testing was significantly shorter for SITA
Fast than for GVF. Considering that SITA adjusts the time between stimuli
based on the patient's answers, and that our experienced Goldmann perimetrist
is faster than most, this difference is impressive. It helps explain why even
patients with cognitive disorders and poor concentration were able to reliably
perform a SITA Fast visual field test. Although the GVF was consistently performed
first in all patients, the GVF and SITA Fast techniques are extremely different;
it is therefore unlikely that a learning effect can explain the discrepancy
between the 2 visual fields observed in some patients, or the shorter SITA
Fast test duration.
Similar to previous studies,5-6
we found that nearly all our patients preferred GVF to SITA Fast perimetry.
Our patients noted that it was difficult to maintain concentration without
some communication with the examiner, and that the standard size III object
was hard to see on the SITA Fast. The 6 patients who preferred SITA Fast were,
in general, younger patients who seemed to enjoy the computerized method.
Our results suggest that SITA Fast perimetry could be ordered instead
of GVF in most patients with optic neuropathies or lesions involving the intracranial
visual pathways. Additionally, these findings may be applicable to younger
children, in whom the realization of a reliable visual field is often challenging.1 However, GVF may still be the test of choice in patients
with occipital lesions, in those with peripheral visual field defects, and
in those with large central defects of more than 30°. Furthermore, it
is likely that GVF performed by a skilled operator is preferable to SITA Fast
in patients with suspected nonorganic vision loss.
In conclusion, we believe that the SITA Fast strategy of automated perimetry
may be useful in the evaluation of central visual field defects associated
with neuro-ophthalmic disorders. The development of additional SITA software
that could test out to 60° might allow even better use of SITA strategies
in neuro-ophthalmic practice. Our results suggest that for the general ophthalmologist
or neurologist, visual field testing with SITA Fast perimetry might even be
preferable to GVF (especially if the GVF is performed by a marginally trained
technician) even in patients with severely decreased vision or who are neurologically
disabled.
AUTHOR INFORMATION
Submitted for publication October 11, 2001; final revision received
February 19, 2002; accepted April 30, 2002.
This study was supported in part by a departmental grant from Research
to Prevent Blindness Inc, New York, NY (Department of Ophthalmology). Dr Newman
is a recipient of a Research to Prevent Blindness Lew R. Wasserman Merit Award.
Presented at the 53rd Annual Meeting of the American Academy of Neurology,
Philadelphia, Pa, May 7, 2001.
We would like to thank Kathy B. Moore, OA, who performed Goldmann perimetry
on all the patients.
Corresponding author: Valérie Biousse, MD, Neuro-Ophthalmology
Unit, Emory Eye Center, 1365-B Clifton Rd NE, Atlanta, GA 30322 (e-mail: vbiouss{at}emory.edu).
From the Departments of Ophthalmology (Drs Szatmáry, Biousse,
and Newman), Neurology (Drs Biousse and Newman), and Neurological Surgery
(Dr Newman), Emory University School of Medicine, Atlanta, Ga.
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