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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_103_библиотеки_им_акад_М_И_Перельмана
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K. G. Pratinya et al.
(a) DeepGlaucoma: This AI uses quantita-
tive measurements of RNFL thickness,
optic disc morphology, and macular
thickness to predict the likelihood of
developing glaucoma.
(b) iWellnessScan: This AI provides a report
summarizing the results and compares the
patient’s measurements to a normative
database.
(c) Optovue: This AI platform includes the
“Ganglion Cell Complex Map,” which
displays the location of the ganglion cell
complex in a color-coded map.
(d) Topcon: This AI platform includes the
“Glaucoma Asymmetry Analysis,” which
compares the measurements of both eyes
to identify asymmetry.
20.6 Conclusion
OCT is an important imaging tool for generating high-resolution cross-sectional images.
Medicine and technology keep evolving handin-hand. New OCT variants, moving from timedomain acquisition to frequency domain
measurement of spectral interference, have
facilitated greater acquisition speed and tissue
contrast in the images. A patient can be followed
over time using their baseline values. Clinicians
should understand the limitations of this imaging technology and correlate clinically with
IOP, ONH, and RNFL appearance, visual eld
data, and quantitative data to detect glaucoma
and its progression. AI has the potential to revolutionize OCT imaging for glaucoma by improving the accuracy of diagnosis, monitoring
disease progression, and optimizing treatment
options. Further research is needed to develop
and validate AI algorithms for clinical use in
glaucoma.
Funding Hyderabad Eye Research Foundation.
Disclosure Nil.
References
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Visual Field
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AvikK.Roy , RamyashriShastry ,
andAparnaRao
21
21.1 Introduction
Visual eld testing is indispensable in diagnosing and managing glaucoma. Over the past
50years, computerized visual eld testing with
standard automated perimetry (SAP) has
become the standard method for assessing
visual function in glaucoma. SAP measures
threshold sensitivity at specic test locations
of the subject’s retina using white stimuli on a
white background and provides a method for
estimating visual eld abnormalities by comparing these to a normative database. This
chapter will briey describe the historical
development of the “eld test” and cover
important new advances in the technology,
technique, and clinical applications.
A. K. Roy
Mithu Tulsi Chanrai Campus, L V Prasad Eye
Institute, Bhubaneswar, India
e-mail: dravik@lvpei.org
R. Shastry
Drishti Eye Centre, Hyderabad, India
A. Rao (*)
Kallam Anji Reddy Campus, L V Prasad Eye
Institute, Hyderabad, India
e-mail: aparna@lvpei.org
21.2 History
The visual field test began with Aubert and
Forster developing the arc perimeter in the
1860s [1]. It helped map peripheral neurologic
and advanced glaucomatous visual field abnormalities. The first modern kinetic perimetry
was described in 1920 [2]. The tangent screen
kinetic perimetry was introduced by Traquair
a few years later [3]. The “bowl perimeter”
design by Goldmann was widely accepted by
ophthalmologists by 1945 [4]. The standardization of the background illumination and
varying degrees of test stimuli remained the
clinical benchmark. Since then, automated
perimetry has progressed rapidly over the past
few decades, courtesy the works of Fankhauser
[5], Heijl and Krakau [6], and Flammer
etal.[7].
21.3 Current Test
The Humphrey Visual Field Analyzer (HVFA) is
the current gold standard of visual eld testing
[8]. It includes varying test strategies like the
suprathreshold, full-threshold, efcient threshold, and the latest SITA (the Swedish Interactive
Thresholding Algorithm) [9].
The various test programs are 30-2, 24-2,
10-2, macular, and the most recent, 24-2C program.There are two numbers for the test; “30”
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024
T. Das, P. Satgunam (eds.), Ophthalmic Diagnostics, https://doi.org/10.1007/978-981-97-0138-4_21
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Fig. 21.1 The locations of the stimuli in the visual eld
analysis. Left: in the threshold test “1”, the stimuli are
placed 6° apart in the x- and y-axes. Right: in the thresh-
(or 24 and 10) refers to the visual eld 30°
extending from the xation; it is 30° in all four
directions. Thus, it is 60° of the subject’s visual
eld (similarly 48° for “24” and 20° for “10”).
The second number of the test is “2”, which
denotes the second pattern of the developed
threshold test. It varies from the rst pattern, “1”,
by the conguration of the stimuli in the x- and
y-axes. In “2”, the stimuli are 3° apart in contrast
to the 6° apart in “1” (Fig.21.1).
Thus a “30-2” eld means testing the eld 30°
from the xation point in all directions where the
stimuli are presented 3° apart. Appropriate
changes apply for the 24-2 and 10-2 tests. The
normal visual eld is widest horizontally, extending over 90° temporally, 60° nasally and superiorly, and 70° inferiorly.
old test “2”, the stimuli are placed 3° apart in the x- and
y-axes. (Source: http://www.healio.com)
21.4 Technique ofHumphry
Visual Field (HVF) Tests
A particular number (based on the “program”) of
(usually) white-colored stimuli of a standard size
(III or V) but with varying intensity (based on the
“strategy”) are presented on a white background
of a xed brightness. Each eye is tested one at a
time. The subject must click on a mouse to register a response as and when the subject sees the
stimulus. The 30-2, 24-2, 10-2, and macular programs test the central 30° (with 76 points locations), 24° (with 54 points locations), 10° (with
68 points locations), and 5° (with 16 points locations), respectively. The details of the procedures
and interpretation of ndings are elaborated in
manuals and textbooks (Fig.21.2) [8].
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Fig. 21.2 The subject sits comfortably facing the dome
of the device and places the chin on the chin rest. The
room is dimly illuminated (mesopic condition), with the
background illumination xed at 31.5 apostilbs. The average time taken for the SITA standard (most commonly
used) 24-2 test for one eye is approximately 8–10min
21.5 Technology
245
Fig. 21.3 Central Visual Field. The central most ring
(2° of eccentricity) was allotted a weight of 8.0, the second ring was assigned a weight of 2.5, and the outermost
ring was assigned a weight of 2.0
21.5.1.1 Clinical Application
VFI is an extremely useful tool in diagnosing
glaucoma and monitoring disease progression.
This is also less sensitive to cataract and its
removal.
21.5.1 Visual Field Index (VFI)
The HVFA provides the mean deviation (MD)
for the 24-2 and 10-2 programs as a global index
of the subject’s visual function. This is calculated
by averaging the age-corrected threshold sensitivities at all test locations after adjusting for the
variability of each test location and eccentricity
from the fovea. The MD is subject to alterations
secondary to any media opacity—most commonly, the senile cataract that might co-exist
with glaucoma. There is a signicant change in
MD after cataract surgery in the presence or
absence of glaucomatous damage. To address
this and other issues, Bengtsson and Heijl [10]
described a new global index for 24-2 and 30-2
programs, the Visual Field Index (VFI). It summarizes the visual eld information into a number (percentage) that measures the visual eld
status and changes over time. The VFI ranges
from 100 (normal) to 0 (perimetrically blind).
21.5.2 Central Field Index (CFI)
The VFI is a global measure of the subject’s
visual function in the 24 or 30° visual elds.
There was no similar analytic tool for the central
10° visual eld. The macula corresponds to only
10° of the visual eld, but it is represented a
much larger (approx. 60%) area of the visual cortex [11]. Central eld disturbances are signicantly related to deterioration in vision-related
quality of life [12]. de Moraes etal. [13] introduced a novel global index for the central 10° of
the visual eld, the Central Field Index (CFI). It
follows almost the same methodology as that of
Bengtsson and Heijl [10] but divides the 10-2
printout into three smaller concentric rings,
instead of ve for the VFI calculation, with
increasing weight from the center toward the
periphery (Fig.21.3).
These values were obtained from a study by
Qiu etal. [14] on estimating linear cortical mag-
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nication in the human primary visual cortex.
Finally, the weighted averages of the CFI value of
all 68 test locations of the 10-2 visual eld printout are calculated for each visual eld examination of each patient’s sequence of 5 or more
examinations. The result is a global index that
ranges from 0% (central blindness) to 100%
(normal central vision). The calculation is primarily based on the 10-2 pattern deviation probability plots, already adjusted for diffuse
sensitivity loss resulting from media opacities.
Hence the discrimination between glaucomatous
eld defects and those that result from media
opacity, mainly cataract, is relatively easy.
21.5.2.1 Clinical Application
CFI varies less than VFI in stable eyes. Hence,
incorporating CFI calculation for monitoring
advanced disease in eyes with central defects
could be valuable [15]. However, as of now, there
is no commercially available software designed
specically to detect and measure rates of progression in the central eld.
second check of points in which the test individual did not respond to a stimulus of maximum
intensity.
21.5.3.1 Clinical Application
Heijl etal. [16] reported that the SITA Faster test
time was 30.4% shorter the SITA Fast and 53.5%
shorter than the SITA Standard. Furthermore,
there were no differences in MD or VFI between
these strategies. However, on comparing the 24-2
SITA Standard and SITA Faster, Phu etal. [17]
reported that the latter was signicantly less reliable, mainly due to high false- positive rates and a
type of artifact the authors named as “seeding
point errors.” These are errors in determining
threshold sensitivity in the initial phase of the
visual eld when the four cardinal locations were
tested. Despite these shortcomings, SITA Faster
can be considered when frequent visual eld testing and more data are desired.
21.5.4 The 24-2C SITA Faster
Algorithm
21.5.3 Swedish Interactive
Thresholding Algorithm (SITA)
Faster
In the late 1990s, two modes of Swedish
Interactive Thresholding Algorithm (SITA) were
introduced: the SITA Standard and SITA Fast
(Fig.21.4) [9]. The SITA Faster (Fig.21.5) was
introduced in 2019 by Heijl etal. [16] to expedite
testing time without compromising the quality.
Seven adjustments were made to the SITA
Fast algorithm. These were: (1) the use of agecorrected normal threshold values for starting
stimulus intensity (without conventional staircase method for cardinal points), (2) requiring
only one staircase test reversal at primary test
points, (3) using the distribution of SITA Fast
normal values to determine when testing can stop
at each test point location, (4) performing no
false-negative catch trials, (5) rechecking the
physiologic blind spot, (6) accounting for the
delay in stimulus timing, and (7) performing a
An accumulating body of evidence demonstrates that the retinal ganglion cells residing in
the macula are lost, even in the early stages of
glaucoma, and this has important clinical implications [18]. Detection of central visual eld
loss is therefore important in the management
of glaucoma although it is unclear whether
patients should be evaluated with dedicated
10-2 visual eld tests instead of or in addition
to 24-2 visual eld tests. The 24-2 visual eld
test points are spaced 6° apart, with 13 points in
the central 10° when foveal sensitivity is
included. On the contrary, 10-2 visual eld test
points are spaced 2° apart, with 68 points in the
central 10°. Therefore, the 24-2 test may not
detect central damage that would have otherwise been detected with 10-2 visual elds [19].
Moraes etal. [20] found that 61.5% of glaucomatous eyes and 39.5% of glaucoma- suspect
eyes had depressed points on 10-2 tests, which
were earlier considered normal on cluster criteria on the 24-2 tests.
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Fig. 21.4 SITA Fast. An HVF single eld printout of a
25-year-old subject’s right eye, with reliable indices, with
the 24-2 program and the SITA Fast strategy showing sig-
21.5.5 Technology
Leveraging the time saved using the SITA
Faster algorithm, ten additional testing locations are added in the central 10° in the 24-2C
nicantly depressed points in both, the total deviation and
pattern deviation maps (the total duration of the test was
3min and 26s)
SITA Faster algorithm (Fig.21.6). Preliminary
studies have shown that the 24-2C SITA Faster
is 18.3% faster than the 24-2 SITA Fast, but
17.5% slower than the 24-2 SITA Faster in
glaucoma [21].
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Fig. 21.5 SITA FASTER. An HVF single eld printout
of a 25-year-old subject’s right eye, with reliable indices,
with the 24-2 program and the SITA Faster strategy showing signicantly depressed points in both, total deviation
21.5.5.1 Clinical Application
In a larger, prospective cross-sectional study, Phu
etal. [22] compared global visual eld indices,
test duration, and pattern standard deviation
and pattern deviation maps (more than the previously
demonstrated SITA Fast). The total duration of the test
was 3min and 29s
results of glaucoma patients and glaucoma suspects who underwent both, the 24-2 and 24-2C
SITA Faster tests. In their study, the 24-2C SITA
Faster and 24-2 SITA obtained similar global
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Fig. 21.6 The SITA Faster 24-2C HVF single eld printout of a 23-year-old subject’s right eye, with reliable indices, with the 24-2C program and SITA Faster strategy,
indexes, but the former test identied more clusters of central defects (though this was not
statistically signicant). Thus, the 24-2C SITA
showing few scattered non-signicantly depressed points
in both, total and pattern deviation maps. The total duration of the test was 2min and 38s
Faster may be a reasonable alternative when central defects are suspected. It can be done to avoid
performing 10-2 tests routinely.
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21.6 Recent Advances inOctopus
Perimetry
The rst automated static perimeter, the
Octopus 201, was developed by Franz
Fankauser and colleagues in 1974 [23]. Since
then, various improvements have been made to
the original test, such as the G program, M program, direct projection system, and different
testing strategies with software to analyze early
progression on visual elds, as elaborated in
the user manual (Octopus Digest, 8th Edition
[23]). Recent studies report that the HFA and
Octopus have similar efcacies and performance [24]. The newer Octopus 900 offers several technical advancements over the earlier
Octopus 600 model; it has static and kinetic
perimetry algorithms and seamless integration
with the patented EyeSuite Software for more
effective data analysis.
21.7 Home-Based Portable
Perimeter
Portable perimeters are visual eld-testing
devices that are lightweight, compact, and easily
transportable. These are ideal for use in remote
or underserved areas with limited access to specialized eye care equipment. Portable perimeters
are typically battery-powered and may use different stimuli, such as white or colored lights, to
test the patient’s visual eld. They may also use
different testing strategies, such as static or
kinetic perimetry. Portable perimeters offer several advantages over traditional tabletop perimeters, including greater exibility and portability,
reduced cost, and the ability to perform visual
eld testing in various settings. These are also
ideal for screening programs, where many
patients must be tested quickly and efciently.
The limitations of these include limited testing
range and the need for frequent calibration and
maintenance. Currently, three platforms are
available for portable perimeters, namely, tabletbased, laptop- based, and head-mounted virtual
reality.
A. K. Roy et al.
Fig. 21.7 This is a representative picture of a portable
perimeter that enables visual eld testing on portable tablet devices
21.7.1 Tablet-Based or iPad-Based
Perimetry
Tablet/iPad-based perimetry involves using a tablet or smartphone with a specialized application
to perform visual eld testing (Fig.21.7). While
these are portable, exible, and less expensive,
their limitations include reduced testing accuracy
and the need for frequent calibration and
maintenance.
Some examples of tablet-based/smartphone-
based perimeters used in glaucoma are:
(a) Visual Fields Easy (VFE) [25]: Designed
by Konan Medical, it uses a standardized
testing protocol and provides a range of testing options, including threshold and suprathreshold perimetry. The VFE runs on a small
smartphone screen (iPhone) which must be
held steady in the hands throughout the test.
The VFE is a reliable and effective tool for
glaucoma telescreening. The average testing
time is under 3min.
(b) Peristat [26] is an online visual eld test. It
is based on Adobe/Flash technology and runs
on a web browser.
(c) Melbourne Rapid Fields (MRF) [27]: This
iPad-based perimetry app is reportedly similar to the SITA Fast in speed, with an intraclass coefcient value of 0.7–0.88 over
6months of follow-up visits. The MRF tests
66 locations over 28° × 18° by having the
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