Neurocase
The Neural Basis of Cognition

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Visual field improvement in neglect after virtual
reality intervention: a single-case study
Michael Christian Leitner & Stefan Hawelka
To cite this article: Michael Christian Leitner & Stefan Hawelka (2021) Visual field improvement
in neglect after virtual reality intervention: a single-case study, Neurocase, 27:3, 308-318, DOI:
10.1080/13554794.2021.1951302
To link to this article: https://doi.org/10.1080/13554794.2021.1951302

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NEUROCASE
2021, VOL. 27, NO. 3, 308–318
https://doi.org/10.1080/13554794.2021.1951302

Visual field improvement in neglect after virtual reality intervention: a single-case
study
Michael Christian Leitner

a,b

and Stefan Hawelka

a,b

a

Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria; bDepartment of Psychology, University of Salzburg, Salzburg,
Austria
ABSTRACT

ARTICLE HISTORY

A patient suffering from visuo-spatial neglect was investigated as a special interest case during a study on
the effectiveness of “restorative approaches” after visual field loss. This patient trained with our newly
developed Virtual Reality (VR) system “Salzburg Visual Field Trainer” for 254 days. Perimetric results show
a visual field expansion of 48.8% (left eye) and 36.8% (right eye) translating to an improvement of
approximately 5.5° to 10.5° of visual angle. Further, subjective self-report shows improvements of up to
317% in visual field functionality. Our results indicate that patients suffering from visuo-spatial neglect
could benefit from a VR-based restorative intervention.

Received 10 May 2021
Accepted 27 June 2021
KEYWORDS

Neglect; visual field defect;
rehabilitation; stroke;
neuropsychology; virtual
reality

Introduction

Neuropsychological rehabilitation

Scientific background

There are two main approaches for patients suffering from
visual defects. “Visual Field Training” describes a methodology
that helps patients to learn strategies to compensate (thus also
known as “Compensatory therapies”) for visual field defects by
improvement of saccadic search patterns and increasing atten­
tion to blind areas. Conversely, “Visual Field Recovery” aims to
reactivate/restitute lesioned areas (in the visual cortex) by
repeated light stimulation which – supposedly – leads to neu­
ronal reconnection (thus also known as “Restitution therapies”).
While visual field defects originating from stroke or trauma are
classified in the scientific literature as “perception deficit,”
visuospatial neglect is widely described as “attention deficit”
(e.g., Halligan et al., 2003; Lunven & Bartolomeo, 2017). Despite
these differences in neurological location and neuropsycholo­
gical functionality, similar rehabilitation routines are conducted
in visual field defects and visuospatial neglect with both based
on methodologies of Visual Field Training (e.g., Kerkhoff et al.,
2021; Umarova et al., 2011). While Visual Field Training cur­
rently represents the “gold standard” in clinical rehabilitation,
the true effect sizes of Visual Field Recovery are subject to
discussion in the scientific community for years (e.g.,
Bouwmeester et al., 2007; Frolov et al., 2017). However,
researchers agree that the need for visual rehabilitation and
new approaches will further increase in the near future.
Trauzettel-Klosinski (2011) states that “suitable rehabilitative
measures chosen after the thorough diagnostic evaluation of
a visual impairment and analysis of its effects can usually restore
reading ability, improve orientation, and thereby enhance the
patient’s independence and quality of life. As the demand for
visual rehabilitation is increasing, steps will need to be taken to
make it more widely available.” (p. 871)

Worldwide over 13 million new cases of stroke are reported
annually, with stroke being the second major reason for dis­
ability (Lindsay et al., 2019). Approximately 50% of people
suffering from stroke report visual problems, ranging from
central visual issues to eye movement and perceptual disorders
(Rowe et al., 2019). Besides visual field defects stemming from
lesions in early/primary cortical areas, a widespread clinical
disorder after stroke or trauma is visuospatial neglect stemming
from lesions in higher cortical areas (Berti et al., 2015). Neglect
describes a multicomponent complex disease with neuropsy­
chological issues in the patients’ processing of spatial informa­
tion, resulting in decreased awareness for the spatial side
opposite to the lesioned cerebral area (e.g., Bisiach, 1996;
Kerkhoff et al., 2021). Literature distinguishes between ego­
centric and allocentric neglect, with egocentric neglect being
the more common form and left-sided neglect occurring twice
as frequent than right-sided neglect (Bowen et al., 1999;
Demeyere & Gillebert, 2019). Patients suffering from egocentric
neglect “[. . .] fail to attend to the contralesional side of space
(with reference to their own body midline) [while] allocentric
neglect is where [patients] fail to attend to the contralesional
side of an object in focus.” (Demeyere & Gillebert, 2019,
p. 491). Studies show prevalence of neglect in older stroke
patients (>60 years) ranging from 15% to 33.5% and 50% of
stroke patients of all ages suffer left-sided neglect (Chen et al.,
2015; Linden et al., 2005; Ten Brink et al., 2016). Visual field
assessment is usually conducted with kinetic perimetry (e.g.,
“Goldmann Perimetry”) and/or static perimetry (e.g.,
“Humphrey Field Analyzer”) (Kerkhoff et al., 2021; Kolling
et al., 2012).

CONTACT Michael Christian Leitner
michaelchristian.leitner@sbg.ac.at
Hellbrunnerstrasse 34/5020 Salzburg/Austria

University of Salzburg/Centre for Cognitive Neuroscience/Department of Psychology,

© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.

NEUROCASE

Controversy
Visual Field Recovery is based on the concept of “visual border
stimulation,” the activation of “residual vision capacities,” with
various proprietary developments from different research
groups and companies. What unites all the concepts, however,
is the hypothesis that – by stimulating the “border area”
between the intact and the damaged visual area – neurons in
the topographically corresponding area of the visual cortex can
be re-activated (e.g., Sabel et al., 2013). Sabel et al. (1997)
reported that patients sometimes detect visual stimuli in the
border to the intact visual field. The authors further suggest
that 15% of remaining, functionally intact neurons are sufficient
to stimulate activity in the affected area. This could, in turn, lead
to plastic cerebral changes and result in a partial restitution of
the visual field (Rosa et al., 2013).
Some studies reported considerable training effects with
border stimulation programs indicating neuroplasticity in the
visual cortex (Marshall et al., 2010; Mueller et al., 2007, 2003;
Poggel et al., 2004; Sabel et al., 2005, 2004; Zihl & von Cranon,
1985). Mueller et al. (2007), for example, reported that their
training restored up to 17.2% of the formerly blind visual field
of their patients. Marshall et al. (2010) reported an average
improvement rate of 12.5%.
Other studies, by contrast, did not find (significant) effects
(Balliet et al., 1985; Glisson, 2006; Horton, 2005; Reinhard, 2005)
and hence the effect of vision restoration is still controversially
discussed (e.g., Pollock et al., 2019; Sabel & Trauzettel-Klosinski,
2005). Frolov et al. (2017), for example, attest that there are
“remaining nagging questions as to the validity of [published
data] and the clinical benefit” (p. 40) and Kerkhoff et al. (2021)
states that “the overall evidence is unclear and thus restorative
visual field training cannot generally be recommended [. . .]”
(p. 196). Horton (2005) assumed in his review that those studies
which found beneficial effects of Visual Field Recovery reported
overly optimistic outcomes. The reason for this skepticism is the
imprecision of the diagnostic instruments which are tradition­
ally used to assess the extent of the visual field loss (e.g.,
Goldmann Perimetry and/or Humphrey Field Analyzer). Thus,
traditional diagnostics systems have major limitations in reli­
ably assessing the potential effects of Visual Field Recovery: i)
they lack a stringent fixation control; ii) they allow the patient
to (unconsciously) resort to compensation strategies (Schreiber
et al., 2006); and iii) – in case of manual perimetry – are prone to
a certain degree of subjectivity of the examiner.
Against this background, we developed an eye tracking
based-perimetric methodology for highly accurate pre-, post-,
and follow-up assessments, i.e., “Eye Tracking Based Visual Field
Analysis” (EFA) (Leitner, Hutzler et al., 2021). The EFA is based
on static automated perimetry while additionally taking indivi­
dual eye movements (with the help of an eye-tracker) in real
time into account and compensating for them. The EFA pro­
vides a standard error of measurement (SEM) of 0.44° of visual
angle. Based on participants’ individual results, the EFA pro­
vides disattenuated correlation (validity) with established peri­
metric instruments of 1.00. Results from patients suffering from
cortical lesions imply that the EFA is applicable for clinical use

309

and pre-post-assessment enabling the finding of small changes
(>0.5°) in patients’ visual fields.

Virtual reality
Recently, various research groups began developing and
studying perimetric and therapeutic procedures for patients
suffering from visual field defects based on virtual reality and
mobile concepts. The shared vision is to use so-called “Head
Mounted (Virtual Reality) Devices” (VR) and/or mobile applica­
tions (based on tablets or cell phones) as valid and reliable
tools for diagnostic and therapeutic purposes (e.g., Goh et al.,
2018; Leitner, Guetlin et al., 2021; Matsumoto et al., 2016;
Wroblewski et al., 2014). The goal is to ease and improve
both diagnostics and intervention for healthcare professionals
and patients alike. Different studies imply that VR and mobile
visual field assessment tools (e.g., implemented on iPads) are
indeed an alternative for established, stationary tools.
Anderson et al. (2017) showed that “Detecting rapid visual
field progression may be improved using a home-monitoring
strategy, even when compliance is imperfect.” (p. 1735). For
example, Schulz et al. (2017) state that iPad-based threshold
perimetry shows “[. . .] reasonable sensitivity/specificity [. . .]”
(p. 346) and Nesaratnam et al. (2017) envisage that “[. . .]
such a test having a role in assessing bed-bound patients in
hospital where access to formal visual field testing is difficult, or
indeed in rapid testing of visual fields at the bedside [. . .]” (p. 1).
This approach is particularly helpful for stroke patients who
are bedridden or immobile (Spofforth et al., 2017). Sand et al.
(2012) additionally emphasize that the focus in daily neurolo­
gical practice and rehabilitation is mainly on motor symptoms
and that visual impairments must receive more consideration
in order to improve patients’ independence and quality of life.
Because VR or tablets offer various protocols for connectivity
(e.g., 5 G, 4 G, 3 G, WIFI, Bluetooth, NFC, etc.), this hardware
can be implemented effortlessly in telemedical routines. In
this context, Johnson et al. (2017) showed that mobile peri­
metric applications produce valid and reliable results in areas
with limited medical care. This progress represents a major
opportunity for people in developing countries or medically
poorly served areas to receive orthoptic and neuropsycholo­
gical care and rehabilitation, prevent degenerative illnesses
and monitor therapeutic progress. In general, VR constitutes
an evolution that will continue to develop in stroke and
orthoptic research but also in various other academic fields
such as in traumatic brain injury, Parkinson disease, or autism
over the next few years (e.g., Canning et al., 2020;
Cortés-Pérez et al., 2020; Maggio et al., 2019; Qazi & Raza,
2020; Spreij et al., 2020).
In this light, we developed a portable VR solution for neu­
ropsychological rehabilitation to both investigate and enable
the effectiveness of therapeutic interventions on visual field
defects (Leitner, Guetlin et al., 2021). Results on the reliability
and validity of the device indicate that the “Salzburg Visual
Field Trainer” (SVFT) is highly accurate in displaying visual
stimuli in predefined areas of the users’ visual field, which is

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M. C. LEITNER AND S. HAWELKA

a fundamental requirement for the potential effects of rehabi­
litation approaches such as Visual Field Recovery. Specifically,
SVFT provides an overall accuracy of .990 (sensitivity of .982 and
specificity of .994). Concurrently, feedback from patients further
indicates that neurorehabilitative training with VR is practical,
easy, and comfortable to perform (in contrast to setups based
on classical “Head-Chin Rests” solutions).

Aim
In our current research project, we found indications that
patients suffering from neglect might significantly benefit
from Visual Field Recovery when training with SVFT. Due to
the scope of our research project, we originally excluded
patients suffering from visual neglect from our experimental
design and concentrated solely on patients suffering from
clearly definable defects in early visual cortex (e.g., infarct of
the arteria cerebri posterior). However, we later decided to
include one patient (i.e., “Patient 7”) – who suffers from visual
neglect after trauma (see below for details) – as a designated
special interest case. We hypothesized that the highly focused
and frequently repeated training situation in VR – due to its
closed design covering both eyes and, in this way, leading to
intense confrontation with the training task – could potentially
improve attentional mechanisms in neglect patients (Azouvi
et al., 2017; Kerkhoff et al., 2021; Kerkhoff & Schenk, 2012). In
the following case report, we present our findings.

Methods
Patient involvement, privacy, and ethical considerations
Patient 7 was not directly involved in the design of this study.
Her ID number is not known to anyone outside the research
group. Written informed consent (to report all amnestic, clin­
ical, and diagnostic details in this manuscript) was obtained
from Patient 7. The neuropsychological intervention, the
ophthalmologic assessment, and the concept of the study
was approved by the ethics committee of the University of
Salzburg. The present study is guided by the fundamental
principles of respect for the individual, the right to selfdetermination, and the right to make informed decisions, i.e.,
informed consent, as noted in the Declaration of Helsinki. The
study is registered in the ICMJE-approved registry “German
Clinical Trials Register” (DRKS00025205).

Patient characteristics
Patient 7 is a 40 to 45 years old woman who suffered traumatic
brain injury from an accident in the mid of 2018 with extensive
posterior medial infarct and posterior infarct on the right with
midline shift (ICD: I63.4) and posterior medial infarct on the left
and right cerebellar infarct in the AICA flow area resulting in
a visual field defect (quadrantanopia lower right and lower left)
with egocentric visual neglect symptomatic to the lower left
side.
From a neuropsychological perspective, Patient 7 is con­
scious, oriented in time, place, and situation. She is unobtrusive
in her general perception and attention, her concentration

capacity is undisturbed, there are no memory or retentive
disorders, and she shows no signs of anosognosia. Her speech
production is fluent and well articulated, her speech compre­
hension is undisturbed and requests from healthcare profes­
sionals are executed promptly and adequately. There are no
signs of meningismus, her pupillomotor functionality is undis­
turbed and pupils are bilaterally isochor and normal light reac­
tive. Patient 7 shows a slightly saccadic gaze sequence, but no
gaze paresis or indications of double vision with age adequate
accommodation. Patient 7 showed significant difficulties in the
“Clock Drawing Test”. Drawing from 12 to 6 o’clock was
uneventful; however, the patient did not know what to do
next and stopped the test. After some further questioning,
the patient first drew 8, 4, and 3 in the left half of the clock
face. After repeated questions and assistance, the patient was
able to complete the clock. In a second task, the (horizontally
performed) “Line Bisection Test,” Patient 7 showed no signifi­
cant abnormalities.

Design, assessment, and rehabilitation
Patient 7 was told that the effectiveness of the therapeutic
approach on her condition is unknown. Further, no outcomes
regarding perimetric results were communicated during the
study but fully discussed after the final assessment date.
The inner 10° of visual field of Patient 7 was diagnosed
monocularly in detail with the help of the EFA on July 14th,
2020 at the “Centre for Cognitive Neuroscience” of the
University of Salzburg. Patient 7’s vision was corrected for
acuity during all visual field tests. Based on these diagnostic
results, the SVFT was configured to present bright light stimuli
onto her visual border area, which is between the intact and
defect visual field of Patient 7 (see Figure 1). In a total training
duration of 254 days, the visual field of Patient 7 was assessed
in regular intervals (M = 51 days (SD = 17)) with the help of the
EFA (6 assessments in total). When significant changes in the
visual field (> 3°) after each assessment were found, the training
stimuli were rearranged accordingly.
Training stimuli had a size of 3° and a luminance of 1,000 cd/
m2, appearing for 750 ms in randomized order on a dark back­
ground. The presentation of each stimulus was delayed for
2000 ms (plus a randomized duration of up to 1500 ms) to
give Patient 7 time to react to the displayed stimulus via remote
control. This is necessary as the SVFT runs a “stimulus-location
adaptation process” during training sessions which is based on
user feedback by clicking (or not) the remote control during the
delay after every displayed stimulus. If the user detects the
stimulus peripherally, its location is moved for 0.8° toward
a custom reference point within the central area of the defect
visual area. This allows the system to automatically adapt to an
improving visual field or small inaccuracies from minor gaze
deviations from the fixation cross. On the contrary, if the stimu­
lus is not detected, it is moved away from the reference point
for 0.4° toward the center of the patient’s intact visual field,
balancing out the therapeutic process in case of inaccuracies,
misclicks, or loss of already gained training progress. Thus, this
behavioral procedure produces a steady approximation of the
“real” border across the intact and defect visual field and suc­
cessively compensates for potential minor gaze inaccuracies of

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311

Figure 1. Illustration of placement of 38 training stimuli (yellow-dotted circles) along the border area of the intact (green dots) and defect (red dots) inner 10° of the
binocular visual field of Patient 7, as assessed with the help of the “Eye Tracking Based Visual Field Analysis” (EFA). The illustration shows training stimuli arrangement
after the first visual field assessment with the EFA on July 14th, 2020.

the patient during the training session procedure (Leitner,
Guetlin et al., 2021). After 30 minutes of training, the SVFT
ends automatically.
Patient 7 was instructed to train twice a day for 6 days
a week and extensively informed about the procedure and
methodology of Visual Field Recovery and regarding the func­
tionality of the SVFT on the first assessment date (for details see
Leitner, Guetlin et al., 2021). At the end of the first appointment,
the SVFT was handed over to Patient 7 and an appointment
was made for the first interim measurement. The study called
for Patient 7 to come into our laboratory at the University of
Salzburg approximately every 2 months for visual field testing
with the EFA. However, this plan could not be fully adhered to
due to the COVID-19 pandemic, which is why some appoint­
ments had to be shifted back-and-forth by a few weeks over the
next months. Nonetheless, this led to a mean duration between
assessment appointments of 51 days (SD = 17).

Measures and analysis
Changes in the visual field of Patient 7 are calculated and
displayed in two different ways. These are as follows: 1)
Percentage change of visual field functionality is based on the
ratio of perceived (green dots) and unperceived stimuli (red
dots) between the first (0 days) and the last assessment day
(254 days), as well between assessment days (0, 64, 105, 182,
217, 254). Areas that were not assessed at the first appointment
were not considered for the calculation of indicated percent
change – even if these areas were additionally tested in later
assessment days due to significant changes in visual field func­
tionality. As a result, potential improvements tend to be under­
estimated rather than overestimated. 2) Apparently improved
regions in the visual field of Patient 7 are marked in the visual
field plots with yellow rectangles. Horizontal and vertical

changes of these areas are calculated and reported in degree
of visual angle (°). A prerequisite for this calculation is
a coherent image of the enhancement of larger contiguous –
former blind areas – of at least 3°. Areas that do not qualify for
calculation but tend to show apparent improvements are
reported but no specific calculation for degree of visual angle
is carried out.
In addition to the objective perimetric measurement of
potential improvements in the visual field functionality of
Patient 7 – which was done with the help of the EFA – we
were also especially interested in the subjective valuation of
Patient 7 regarding her visual capacities. Thus, before every EFA
assessment in our lab, Patient 7 was asked to rate the status of
her visual field on a continuum subjectively, ranging from “very
bad” to “very good.” In order not to influence Patient 7’s sub­
jective self-assessment performed before each EFA assessment;
the results of the visual field results were not reported to her
between appointments. After the last appointment, the visual
field results were communicated to Patient 7 and discussed in
detail.

Results
Visual field test results from the EFA after training for approxi­
mately 8 months with the SVFT show an expansion of Patient
7’s visual field of 48.8% (OS) and 36.8% (OD). This translates to
a horizontal expansion of approximately 7.25° and vertical
expansion of approximately 5.5° of visual angle for the upper
left area in OS and to a horizontal expansion of approximately
10.5° and vertical expansion of approximately 5.5° of visual
angle for the lower right area in OD (both marked as yellow
rectangles in Figure 2). Improvements marked by the lower
right rectangle in OS are too widespread and diffuse to be
translated into degree of visual angle, however reporting of

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M. C. LEITNER AND S. HAWELKA

overall improvement in this area appears worth noticing. In this
context, also the unsystematic improvements in the center of
the defect area, which are (naturally) not yet locatable during
baseline assessment, are remarkable. Because the EFA repeats
undetected stimuli – after displaying a random stimulus that is
not recorded – the probability of improvements by random
patient’s reaction is highly unlikely. Also, the EFA documents
if patients are “trigger happy”, which is not the case with this
patient (also see Figure 3). Dots in dark red represent stimuli
not detected the first time but detected the second time. These
stimuli usually occur near “visual border areas,” situated
between defect and functional visual field areasand are also
observable in the visual field results of Patient 7.
The behavior of Patient 7 during visual field assessment –
represented in the EFA’s test statistics – shows no abnormal­
ities, with false-negative and false-positive rates within usual
and similar ranges comparable to standard perimetric analysis
of Patient 7 with the Humphrey Field Analyzer (see Figure 3).
Analysis of the SVFT training log shows that Patient 7 trained
consistently at least twice for 30 minutes per day over the
entire period. Specifically, Patient 7 performed 136 training
sessions within the first 64 days, 88 training sessions within
the following 41 days, 171 training sessions within the follow­
ing 77 days, 104 training sessions within the following 35 days
and 111 training sessions within the last 37 days. This results in
an average of 2.1 training sessions per day for the first period,
2.1 training sessions per day for the second period, 2.2 training
sessions per day for the third period and 3.0 training sessions
per day for the fourth and fifth period. This translates to a total
mean of 2.5 training sessions per day with the SVFT for the
entire period of 254 days. Additional results show that the
perceptual improvements of Patient 7 – because of the training
with the SVFT – are not only objectively measurable via the EFA
but also reported by the patient herself (see Figure 4). These
results further indicate that Patient 7 feels that she is benefiting
from the rehabilitation program and that her visual (attentional) capabilities improve. We interpret the subjective
worsening at the last test time point as a reaction to the
preceding announcement of the research team to temporarily
stop the therapeutic intervention to evaluate the data of the
study and to plan further steps. According to her own state­
ments after assessment, the patient would have liked to con­
tinue training with the device.
Figure 5 illustrates visual field assessment of Patient 7 with
the Humphrey Field Analyzer and Goldmann Perimeter before
and after neuropsychological training with the “Salzburg Visual
Field Trainer” (SVFT). Initial results indicate a broad visual field
defect below the horizontal line. Test statistics (SITA-Fast) from
the Humphrey Field Analyzer show 10% false-positive errors,
11% false negative errors, 1 fixation loss and an assessment
duration of 6 minutes for the right eye. For the left eye there are
0% false-positive errors, 0% false negative errors, 0 fixation
losses and an assessment duration of 5 minutes 28 seconds.
After training with the SVFT, results from the Humphrey Field
Analyzer indicate no substantial changes in visual field func­
tionality. Test statistics (SITA-Fast) show 3% false-positive
errors, 10% false negative errors, 0 fixation losses and an

assessment duration of 5 minutes 24 seconds for the right
eye. For the left eye there are 0% false-positive errors, 0%
false negative errors, 0 fixation losses and an assessment dura­
tion of 6 minutes 1 second. However, results from Goldmann
perimetry indicate – following assessment results from the EFA
(see Figure 2) – that visual field functionality of Patient 7
increased considerably after neuropsychological training with
the SVFT. Especially, wide areas in the lower left quadrant
indicate improvement. In addition, lower areas within the
inner 10° of visual field appear to have improved for around
5° of visual angle. During both visual field-testing sessions with
the Goldmann Perimeter, Patient 7 was calm, concentrated and
acted consistently.
Patient 7 reported mild dizziness that occurred especially at
the beginning – after finishing training sessions with our virtual
reality device SVFT. After a few weeks, however, this no longer
occurred. Patient 7 also reported that the training sometimes
made her tired, especially in the evening. Otherwise, Patient 7
reported no unwanted or unpleasant side effects or adverse
events. Rather, she related that the compact and flexible design
of the training device greatly facilitated the rehabilitation mea­
sures, and that the device was comfortable to wear.

Discussion
Reliable and conclusive evidence on the effect of neuropsycho­
logical interventions to improve visual field defects is scarce
and still subject to debate in the scientific community. In our
current research project, we aim to test different clinical inter­
ventions for their effectiveness and strive to provide new,
evidence-based approaches to established methodologies. To
create the basic conditions for this we have developed two new
tools in the field of diagnosis as well as in the field of rehabilita­
tion. On the one hand, the perimetric tool “Eye tracking based
visual field analysis” (EFA) helps us to obtain reliable and accu­
rate assessment results on the patients' current visual field
status as well as regarding potential changes after intervention
(Leitner, Hutzler et al., 2021). On the other hand, the neuropsy­
chological tool “Salzburg Visual Field Trainer” (SVFT) creates the
virtual reality-based foundation for an accurate, controlled, and
immersive rehabilitation situation (Leitner, Guetlin et al., 2021).
We are currently concentrating on questions regarding “resti­
tutive procedures”, as utilized in so-called “Visual Field
Recovery” approaches. Since the findings in this context can
be described as controversial, we decided to pay strict atten­
tion to the neurological background of the respective indivi­
dual visual field defects when selecting patients. Therefore, we
focus mainly on clearly definable “classical” visual field defects
that originate in early cortical areas (e.g., stemming from insult
of the arteria cerebri posterior) and can be classified as pure
“perceptual disorder”. It is our suspicion that earlier studies –
besides inaccurate pre-, post-, and follow-up diagnostics, which
are due to compensatory eye movements in the course of
perimetric examinations – did not elaborate on the exact neu­
rological and neuropsychological background of the visual field
defects. Specifically, we suspect that i.a., patients with early and
higher cortical lesions were mixed in these studies. In addition,

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313

Figure 2. Illustration of visual field tests (inner 10°) – conducted with our perimetric “Eye Tracking Based Visual Field Analysis” (EFA) – after 217 days of therapy with our
“Salzburg Visual Field Trainer” (SVFT) of Patient 7 suffering from quadrantanopia and visual neglect symptomatic. Red dots represent stimuli not detected, green dots
represent stimuli detected during perimetric assessment. One stimulus stands for approximately 0.75° of visual angle. Note the obvious improvements in stimulus
detection – marked by the yellow rectangles – at both sides of the respective visual field defects. Data analysis (by total numbers of undetected stimuli based on
baseline assessment) shows total visual field enlargement of 48.8% (OS) and 36.8% (OD) and gradual improvement especially during the first 64 days of therapy (also
see Figure 3).

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M. C. LEITNER AND S. HAWELKA

Figure 3. Illustration of test statistics of “Eye Tracking Based Visual Field Analysis” (EFA) of the left eye (OS) and the right eye (OD) of Patient 7 after 0, 64, 105, 182, 217
and 254 days of neuropsychological training with the “Salzburg Visual Field Trainer” (SVFT) (x-axis) in absolute numbers of presented test stimuli (left y-axis). The ratio
between true positive and true negative stimuli shows improvements in visual functions (yellow line) due to repeated neuropsychological training with the SVFT (right
y-axis).

it is often difficult and time-consuming to differentiate
between scotomas that occur either due to perceptual issues
or attentional issues. This would explain the incoherent picture
that emerges from literature and textbooks. To further investi­
gate the results presented in this manuscript, advancing stu­
dies with a larger number of patients suffering from
visuospatial neglect is currently underway.

Interpretation
The results of the present case study suggest that patients
suffering from neglect could benefit from a virtual realitybased neuropsychological intervention based on restitutive
concepts. Interestingly, the Visual Field Recovery intervention
we used for Patient 7 was not originally intended for neglect
patients as they suffer from lesions in higher cortical regions.
The primary understanding of the scientific community and the
clinical gold standard here is the use of so-called “compensa­
tory procedures” (e.g., Kerkhoff et al., 2021). This means that in
the course of training, patients are encouraged to make con­
scious eye movements into the blind field to improve aware­
ness for this area. In contrast, “restitutive procedures” – as
utilized in the SVFT in this study – rely on continuous fixation
of a central point, thus forcing decentralized, peripheral aware­
ness of the training stimuli displayed between defect and intact

visual field. The background of this approach is – as mentioned
above – the hypothesis that these training stimuli reactivate
the respective lesioned, topographically equivalent regions in
early areas of the visual cortex. To date, we are not aware of any
other study that has treated patients with neglect symptoms
using an immersive procedure such as we did with a virtual
reality device, combined with a restitutive procedure.
Conversely, current literature reviews show mainly studies con­
centrating on visual scanning or pursuit trainings, neck-muscle
vibration therapy, prism adaptation, visuo-motor feedback or
other forms of attention training combined with magnetic or
current stimulation (Kerkhoff et al., 2021; Pollock et al., 2019)
We interpret the results of Patient 7 after intervention as
improvements in both the right lower quadrant and the left
lower quadrant. Based on perimetric analysis and changes after
therapy, we hypothesize that Patient 7 suffers from a quadrant
anopia to the right with primarily leftward (but also partially
rightward) neglect components. Results from Goldmann
Perimetry after intervention seem to support this hypothesis.
Further, these results from the Goldmann Perimeter addition­
ally hold another interesting component as they indicate that
areas outside the actual training area of the SVFT seem to have
improved during therapy. Because these areas are consistent
with the training direction of the presented stimuli in the SVFT,
we hypothesize that these ameliorations may represent an

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315

Figure 4. Illustration of subjective self-report (left y-axis) of visual field improvement of Patient 7 after 0, 64, 105, 182, 217 and 254 days of training (x-axis) with the
“Salzburg Visual Field Trainer” (SVFT). Results show improvements in self-evaluation (on a continuum (right y-axis) ranging from “very bad” (0%) to “very good” (100%))
of visual field functionality and confirms objective data from repeated perimetric assessment with the “Eye Tracking Based Visual Field Analysis” (EFA).

extension of Patient 7’s generally improved perceptual ability
to the (lower) left – ranging even into outer areas of her visual
field.
Regarding the results from the Humphrey Field Analyzer,
indicating no considerable changes in the visual field of Patient
7 we hypothesize that the diagnostics algorithm, the overall
accuracy and results illustration of this device are too imprecise
and coarsely. Additionally, some areas of improvement – as
indicated by results from the Goldmann Perimeter – lie outside
the assessment area of the Humphrey Field Analyzer (>30°). As
the Goldmann Perimeter is still considered as the “gold stan­
dard” in perimetric assessment, we interpret the results from
this device as confirmation of the results found with the EFA.

Another limitation of the present work relates to the func­
tional improvement of patient 7’s daily life during/after therapy
with the SVFT. In discussions after each assessment appoint­
ment, the patient’s general life situation and her coping with
the visual field defect were discussed. However, Patient 7 did
not report any conspicuous improvements in her daily life,
although she consistently rated her visual impairment as
improving over the training period. Thus, the present study
does not provide structured and objectified data on the prac­
tical implications of Patient 7’s life situation during/after train­
ing with the SVFT. This area will also be further investigated and
analyzed in continuing studies with larger numbers of
participants.

Limitations

Conclusion

Our findings are limiting due to the nature of a case study, but
concurrently indicate the potential of a virtual reality-based
neuropsychological intervention method that is based on
a restitutive concept. Thus, at this point no generalized state­
ments about the therapeutic effect size of our presented virtual
reality training are valid. However, our findings warrant further
and closer investigation (with a larger sample size) of the
potential effective factors of the neuropsychological interven­
tion that contributed to Patient 7 benefitting from an improved
visual field both objectively and subjectively.

Our findings suggest that a virtual reality supported neuropsy­
chological intervention based on restitutive concepts for
patients suffering from visual neglect could improve visual
field functionality and related visual perception after stroke or
trauma.

Acknowledgments
The authors sincerely thank Anja-Maria Ladek and Lydia Hell from the
University Hospital Salzburg for Ophthalmology and Optometry for their

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M. C. LEITNER AND S. HAWELKA

Figure 5. Illustration of visual field test with Humphrey Field Analyzer and Goldmann Perimetry before and after training with the “Salzburg Visual Field Trainer” (SVFT).
While the results of the Humphrey Field Analyzer do not suggest any significant changes in the visual field of Patient 7, the results of Goldmann Perimetry indicate
noticeable improvements. Particularly in areas on the lower left and in lower areas of the inner 10° of visual angle, apparent improvements can be observed. Note: To
increase visibility and interpretability of the Goldmann Perimetry plot, the red and blue markers were digitally redrawn. Blue lines represent Goldmann marker size
I and red lines size III, both with a relative intensity of 1.00.

NEUROCASE

medical and orthoptic support and Sarah Schuster for proof-reading and
critical comment on the work.

Ethics approval
The following study was reviewed and approved by the ethics commission
of the University of Salzburg (Reference No. 39/2018)

Competing interests
All authors declare that they have no conflict of interest and approve the
manuscript.
The sponsor or funding organization had no role in the design or
conduct of this research.

Contribution
All authors contributed equally to this work.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Data availability statement
Data is available from the corresponding author upon reasonable request.

Funding
The present study is based on the funded project “Advanced Perimetry for
the Evaluation of Neuroplasticity in the Visual Cortex” by the Austrian
Science Fund (FWF) (Reference No. P31299)

ORCID
Michael Christian Leitner
http://orcid.org/0000-0002-9341-854X
Stefan Hawelka
http://orcid.org/0000-0002-5304-8521

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