Posts Tagged visual field defects

[Abstract + References] Perspectives: Hemianopia—Toward Novel Treatment Options Based on Oscillatory Activity?

Stroke has become one of the main causes of visual impairment, with more than 15 million incidences of first-time strokes, per year, worldwide. One-third of stroke survivors exhibit visual impairment, and most of them will not fully recover. Some recovery is possible, but this usually happens in the first few weeks after a stroke.

Most of the rehabilitation options that are offered to patients are compensatory, such as optical aids or eye training. However, these techniques do not seem to provide a sufficient amount of improvement transferable to everyday life.

Based on the relatively recent idea that the visual system can actually recover from a chronic lesion, visual retraining protocols have emerged, sometimes even in combination with noninvasive brain stimulation (NIBS), to further boost plastic changes in the residual visual tracts and network.

The present article reviews the underlying mechanisms supporting visual retraining and describes the first clinical trials that applied NIBS combined with visual retraining. As a further perspective, it gathers the scientific evidence demonstrating the relevance of interregional functional synchronization of brain networks for visual field recovery, especially the causal role of α and γ oscillations in parieto-occipital regions.

Because transcranial alternating current stimulation (tACS) can induce frequency-specific entrainment and modulate spike timing–dependent plasticity, we present a new promising interventional approach, consisting of applying physiologically motivated tACS protocols based on multifocal cross-frequency brain stimulation of the visuoattentional network for visual field recovery.

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via Perspectives: Hemianopia—Toward Novel Treatment Options Based on Oscillatory Activity? – Estelle Raffin, Roberto F. Salamanca-Giron, Friedhelm Christoph Hummel,

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[ARTICLE] Segregation of Spontaneous and Training Induced Recovery from Visual Field Defects in Subacute Stroke Patients – Full Text

Whether rehabilitation after stroke profits from an early start is difficult to establish as the contributions of spontaneous recovery and treatment are difficult to tease apart. Here, we use a novel training design to dissociate these components for visual rehabilitation of subacute stroke patients with visual field defects such as hemianopia. Visual discrimination training was started within 6 weeks after stroke in 17 patients. Spontaneous and training-induced recoveries were distinguished by training one-half of the defect for 8 weeks, while monitoring spontaneous recovery in the other (control) half of the defect. Next, trained and control regions were swapped, and training continued for another 8 weeks. The same paradigm was also applied to seven chronic patients for whom spontaneous recovery can be excluded and changes in the control half of the defect point to a spillover effect of training. In both groups, field stability was assessed during a no-intervention period. Defect reduction was significantly greater in the trained part of the defect than in the simultaneously untrained part of the defect irrespective of training onset (p = 0.001). In subacute patients, training contributed about twice as much to their defect reduction as the spontaneous recovery. Goal Attainment Scores were significantly and positively correlated with the total defect reduction (p = 0.01), percentage increase reading speed was significantly and positively correlated with the defect reduction induced by training (epoch 1: p = 0.0044; epoch 2: p = 0.023). Visual training adds significantly to the spontaneous recovery of visual field defects, both during training in the early and the chronic stroke phase. However, field recovery as a result of training in this subacute phase was as large as in the chronic phase. This suggests that patients benefited primarily of early onset training by gaining access to a larger visual field sooner.

Introduction

Loss of up to one-half of the visual field (hemianopia) as result of post-chiasmatic stroke in one hemisphere occurs in about 30% of all stroke patients. Following a period of spontaneous recovery in the first 3–6 months (12), the patient enters the chronic phase of hemianopia.

Rehabilitation treatment most often involves eye movement training to compensate for the visual field defect (3) rather than visual restitution training, which reduces the defect itself. The latter has long been controversial (4). However, a recent series of investigations (512) have argued for the more balanced view that visual training of the defect may provide an additional and valuable approach to rehabilitation of occipital stroke patients.

Brain plasticity is believed to be greater in the acute stage after stroke when there is a window for relatively quick and extensive synaptic reorganization (13). Recommendations that rehabilitation should begin “as soon as possible” or “early” are therefore common in clinical guidelines (1415). However, many of these recommendations are based on limited data (16), and there are no agreed definitions of what constitutes early rehabilitation (17). Thus far, visual restitution training is generally applied in the chronic phase after stroke, so that spontaneous recovery can be excluded, and changes in the visual field can be attributed to training. In this way, one can obtain an accurate estimate of the effect of the training itself (811). Yet, we wondered if visual restitution training would profit from an early start as suggested in the rehabilitation literature.

The effect of visual perceptual learning in normally sighted subjects is often restricted to the trained region of the visual field (1820) and specific to the trained task (2122). This raises the question whether the visual recovery that is induced by visual restitution training is also limited to just the trained region and task. Several studies have shown that recovered vision after restitution training transfers to untrained visual tasks (1011) but only to a limited extent to untrained regions. For example, the defect reduction induced by training of the intact visual hemifield was significantly smaller than the reduction induced by training the affected hemifield itself, and it was not significantly different from the defect reduction following a non-intervention period (11). Because spontaneous recovery could be excluded in that study, any improvement during intact training could point to a spillover effect of training between the two hemispheres. That is, the defect reduces—albeit to limited extent—even when another part of the visual field is trained.

Following the practice of general rehabilitation medicine, one would preferably train patients in the early phase of stroke. To do so, we applied a method that builds on the observation that visual training carries over to neighboring areas only to a limited extent. That is, we used two training rounds, which targeted complementary parts of the defect [regions of interest (ROIs)], while monitoring in both training rounds the trained and the untrained half of the defect. The untrained half of the defect, which serves as an internal control for the trained half, will show spontaneous recovery and a potential spillover from the neighboring trained region. To assess that spill over, we used data from seven patients who were trained in the chronic phase of stroke using the same method. The differences between the defect reductions for the subacute phase of stroke and the chronic phase of stroke in the trained and untrained parts of the defect should allow us to distinguish between spillover, spontaneous recovery and training-induced recovery. This allows us to test the hypothesis that training in the early phase leads to a larger defect reduction than training in the chronic phase.

Materials and Methods

The study was approved by the ethical committee CMO Arnhem–Nijmegen in correspondence with the 1964 Declaration of Helsinki.

20 Subacute stroke patients and 10 chronic stroke patients with visual field defects due to post-geniculate damage were included following written informed consent. Subacute stroke patients were screened for participation in four neurology departments of Dutch hospitals: UMC in Utrecht, St. Elisabeth Hospital in Tilburg, CWZ in Nijmegen and St. Antonius Hospital in Nieuwegein (screening; eight patients). Patients could also sign up for the study by filling out a form on our website (www.hemianopsie.nl; 12 patients), to be screened at a regional office by the first author. Chronic stroke patients all applied through the website.

Patients inclusion criteria as follows:

∗ age between 18 and 75 years;

∗ presence of homonymous visual field defect.

Patient exclusion criteria as follows:

∗ visual neglect (as assessed by line bisection test);

∗ cardiac or other implants (for the chronic patients only: MRI scans were made; to be presented elsewhere).

The intake procedure included a Goldmann perimetry measurement. Patient demographics can be found in Table S2 in Supplementary Material.

For the 30 included patients, we had to exclude the data of 3 subacute and 3 chronic patients from further analysis. In the three subacute patients, the training was not applied as intended because the defect was not divided in two equal halves (n = 2), or for unequal duration of the training rounds (n = 1). In the chronic patients, absence of an absolute defect (n = 1), inability to cope with training demands (n = 1), and anxiety for fMRI scanner measurements (n = 1) were reasons to exclude their data. Thus, in total, we analyzed 17 subacute and 7 chronic data sets.

The 20 subacute patients were trained by DB for this study, the 10 chronic patients were trained by JE in a parallel study using the same training paradigm.

Study Design

Before the training, baseline values were established for visual field size (Goldmann perimetry), reading speed and Goal Attainment Scaling (GAS: personally customized and realistic goals).

Following these baseline measurements, the visual field defect was divided in equal halves using the following procedure. First, meridional angles through the defect were established that were farthest apart. Then, the average of these two outer meridional angles formed the border between the two training regions (in the case of SA15, the division was along the vertical midline). One-half of the visual field defect was trained for 8 weeks, while the other half was untrained. After this period, intermediate measurements were carried out (perimetry and reading speed tests) during the course of one week. Then, a second training period of 8 weeks was started, in which the training was applied to the other half of the defect, while the first half received no further training. Post-measurements were carried out as during baseline measurements (Figure 1). Finally, we collected follow-up perimetry data in the subacute group. The period without training, in-between the final training session and the follow-up perimetry of the subacute group, is denominated “No Intervention.”

Figure 1. Study design and time line for subacute patients. The defect was divided into two training regions [region of interest (ROI) 1, ROI 2] of equal size. In this example, the left upper quarter field was trained first, followed by the lower left quadrant. This order was randomized between patients. For chronic patients, the study design was similar, except that the first training started at least 10 months after the stroke (and about 2 months after intake), and no follow-up measurements were taken.

Continue —>  Frontiers | Segregation of Spontaneous and Training Induced Recovery from Visual Field Defects in Subacute Stroke Patients | Neurology

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[ARTICLE] Development and Implementation of a New Telerehabilitation System for Audiovisual Stimulation Training in Hemianopia – Full Text

Telerehabilitation, defined as the method by which communication technologies are used to provide remote rehabilitation, although still underused, could be as efficient and effective as the conventional clinical rehabilitation practices. In the literature, there are descriptions of the use of telerehabilitation in adult patients with various diseases, whereas it is seldom used in clinical practice with child and adolescent patients. We have developed a new audiovisual telerehabilitation (AVT) system, based on the multisensory capabilities of the human brain, to provide a new tool for adults and children with visual field defects in order to improve ocular movements toward the blind hemifield. The apparatus consists of a semicircular structure in which visual and acoustic stimuli are positioned. A camera is integrated into the mechanical structure in the center of the panel to control eye and head movements. Patients can use this training system with a customized software on a tablet. From hospital, the therapist has complete control over the training process, and the results of the training sessions are automatically available within a few minutes on the hospital website. In this paper, we report the AVT system protocol and the preliminary results on its use by three adult patients. All three showed improvements in visual detection abilities with long-term effects. In the future, we will test this apparatus with children and their families. Since interventions for impairments in the visual field have a substantial cost for individuals and for the welfare system, we expect that our research could have a profound socio-economic impact avoiding prolonged and intensive hospital stays.

Introduction

Telerehabilitation, defined as the method by which communication technologies are used to provide remote rehabilitation, although still underused, could be as efficient and effective as the conventional clinical rehabilitation practices (1). In the literature, we can find some descriptions of the use of telerehabilitation in adult patients for various types of disorder, whereas it is seldom used in clinical practice with children and adolescents (2).

The development and use of telerehabilitation program are slow because they are affected by many logistical factors, such as regional economic resources, medical technical support systems, and population quality, but their potential is very high, as they are conceived and studied to improve patients’ ability to perform activities from daily life, thereby increasing their independence (3). For example, for adult post-stroke patients, telerehabilitation is widely used with the main goal of giving disabled people the same quality of motor, cognitive, and neuropsychological rehabilitation at home as they would have in-home visit and day-care rehabilitation (457).

So far, the application of telerehabilitation during childhood has been primarily limited to preterm babies (8) and children with hemiplegia (910), with autism spectrum disorders (11), with speech and language disorders (1213), and with learning difficulties (1416). Despite the well-known impact of visual defects on cognitive functioning and neurological recovery (17), no study has yet investigated the application of telerehabilitation with children with visual impairments.

Here, we describe an innovative telerehabilitation platform, which consists in an audiovisual telerehabilitation (AVT) system, developed for children and adults with visual field defects caused by post-chiasmatic brain lesions. The AVT system allows patients to exercise independently, in an intensive, active, and functional way and in a familiar environment, under remote supervision; it consists of a mobile device platform with remote control, which is accessible directly from home and suitable both for adults, adolescents, and children from the age of 8.

The AVT system is based on a very promising multisensory audiovisual therapy, originally developed for the treatment of adults and children with visual field defects caused by brain lesions (1819). Basically, this training aims to stimulate multisensory integration mechanisms in order to reinforce visual and spatial compensatory functions (i.e., implementation of oculomotor strategies). In this first phase of the study, we tested the feasibility and efficacy of AVT in three adult patients with chronic visual field defects, in order to explore how the apparatus can be implemented at home.[…]

Continue —>  Frontiers | Development and Implementation of a New Telerehabilitation System for Audiovisual Stimulation Training in Hemianopia | Neurology

Figure 1. Magnetic resonance imaging of the brain and visual field campimetry of S1, S2, and S3.

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[Abstract] Impaired visual competition in patients with homonymous visual field defects.

Highlights

    Humphrey perimetry shows partial field recovery in patients with homonymous visual field defects after post-chiasmatic lesions.Visual decision-making is deviating from healthy controls, even in the ipsilateral, assumed ’intact’ visual field.Patients, however, do show a slight hint of primacy as healthy controls, but these effects are disrupted by their tendency to guess.Rehabilitation methods may profit from training focused on improving visual decision-making of the defective and the intact visual field.

Abstract

Intense visual training can lead to partial recovery of visual field defects caused by lesions of the primary visual cortex. However, the standard visual detection and discrimination tasks, used to assess this recovery process tend to ignore the complexity of the natural visual environment, where multiple stimuli continuously interact. Visual competition is an essential component for natural search tasks and detecting unexpected events.

Our study focused on visual decision-making and to what extent the recovered visual field can compete for attention with the ’intact’ visual field. Nine patients with visual field defects who had previously received visual discrimination training, were compared to healthy age-matched controls using a saccade target-selection paradigm, in which participants actively make a saccade towards the brighter of two flashed targets. To further investigate the nature of competition (feed-forward or feedback inhibition), we presented two flashes that reversed their intensity difference during the flash. Both competition between recovered visual field and intact visual field, as well as competition within the intact visual field, were assessed.

Healthy controls showed the expected primacy effect; they preferred the initially brighter target. Surprisingly, choice behaviour, even in the patients’ supposedly ‘intact’ visual field, was significantly different from the control group for all but one. In the latter patient, competition was comparable to the controls. All other patients showed a significantly reduced preference to the brighter target, but still showed a small hint of primacy in the reversal conditions.

The present results indicate that patients and controls have similar decision-making mechanisms but patients’ choices are affected by a strong tendency to guess, even in the intact visual field. This tendency likely reveals slower integration of information, paired with a lower threshold. Current rehabilitation should therefore also include training focused on improving visual decision-making of the defective and the intact visual field.

Source: Impaired visual competition in patients with homonymous visual field defects.

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[Abstract] Combined tDCS and Vision Restoration Training in Subacute Stroke Rehabilitation: A Pilot Study

Abstract

Background

Visual field defects after posterior cerebral artery stroke can be improved by vision restoration training (VRT), but when combined with transcranial direct current stimulation (tDCS) which alters brain excitability, vision recovery can be potentiated in the chronic stage. To date the combination of VRT and tDCS has not been evaluated in post-acute stroke rehabilitation.

Objective

To determine whether combined tDCS and VRT can be effectively implemented in the early recovery phase following a stroke, we wished to explore the feasibility, safety and efficacy of an early intervention.

Design

Open-label pilot study including a case series of seven tDCS/VRT versus a convenience sample of seven control patients (clinicalTrials.gov ID: NCT02935413).

Setting

Rehabilitation center

Subjects

Patients with homonymous visual field defects following a posterior cerebral artery stroke.

Methods

Seven homonymous hemianopia patients were prospectively treated with 10 sessions of combined tDCS (2mA, 10 daily sessions of 20 min) and VRT at 66 (±50) days on average post-stroke. Visual field recovery was compared with retrospective data of 7 controls, whose defect sizes and age of lesions were matched to the experimental subjects and who had received standard rehabilitation with compensatory eye movement and exploration training.

Results

All seven patients of the treatment group completed the treatment protocol. Safety and acceptance were excellent, and patients reported occasional skin itching beneath the electrodes as the only minor side effect. Irrespective of their treatment, both groups (treatment and control) showed improved visual fields as documented by an increased mean sensitivity threshold in dB (decibel) in standard static perimetry. Recovery was significantly greater (p<.05) in tDCS/VRT patients (36.73 ± 37.0%) than in controls (10.74 ± 8.86).

Conclusion

In this open-label pilot study, tDCS/VRT in sub-acute stroke was safe, with excellent applicability and acceptance of the treatment. Preliminary effectiveness calculations show that tDCS/VRT may be superior to standard vision training procedures. A confirmatory, larger-sample, controlled, randomized and double-blind trial is now underway to compare real- vs. sham-tDCS supported visual field training in the early vision rehabilitation phase.

This study was supported by the ERA-net neuron network “Restoration of Vision after Stroke (REVIS)”, (BMBF grant nr: 01EW1210).
clinicalTrials.gov ID: NCT02935413

Source: Combined tDCS and Vision Restoration Training in Subacute Stroke Rehabilitation: A Pilot Study

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[ARTICLE] Assessment of visual space recognition of patients with unilateral spatial neglect and visual field defects using a head mounted display system – Full Text PDF

Abstract

[Purpose] The purpose of this study was the development of a method for presenting diverse visual information and assessing visual space recognition using a new head mounted display (HMD) system.

[Subjects] Eight patients: four with unilateral spatial neglect (USN) and four with visual field defects (VFD).

[Methods] A test sheet was placed on a desk, and its image was projected on the display of the HMD. Then, space recognition assessment was conducted using a cancellation test and motion analysis of the eyeballs and head under four conditions with images reduced in size and shifted.

[Results] Leftward visual search was dominant in VFD patients, while rightward visual search was dominant in USN patients. The angular velocity of leftward eye movement during visual search of the right sheet decreased in both patient types. Motion analysis revealed a tendency of VFD patients to rotate the head in the affected direction under the left reduction condition, whereas USN patients rotated it in the opposite direction of the neglect.

[Conclusion] A new HMD system was developed for presenting diverse visual information and assessing visual space recognition which identified the differences in the disturbance of visual space recognition of VFD and USN patients were indicated.

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Source: Assessment of visual space recognition of patients with unilateral spatial neglect and visual field defects using a head mounted display system

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[Dissertation] Effects of homonymous visual field defects on visuo-spatial perception and performance – Full Text PDF

General Abstract

Homonymous visual field defects are typically associated with three distinct types of visual disorders beyond the field cut: (i) a visual exploration or scanning deficit, (ii) reading disturbances (“hemianopic alexia”), and (iii) a contralesional visuospatial bias towards the blind field in localizing the midline position (“hemianopic line bisection error”, HLBE). While the exploration and reading disorder are well explored and their causes often analysed, the origin of the HLBE – although already known for more than 100 years – have remained largely unclear and are still a matter of debate. The present Ph.D. thesis addresses several unresolved issues of the HLBE in three subsequent, already published studies.

First, it was investigated, whether and to what extent patients with homonymous quadrantranopia display a contralesional visuospatial error when indicating the visual midline. Interestingly, in earlier studies the HLBE was almost exclusively found in horizontal (left or right) or vertical (altitudinal) hemianopia. All 15 tested patients with quadranopia showed distinct and large shifts towards their blind quadrant when estimating their visual subjective straight ahead in a bowl perimeter. Moreover, patients with dorsal lesions respectively lower quadrantanopia showed the largest errors.

Second, the matter of eccentric fixation as a possible cause of the HLBE was analysed in this study and in the subsequent study with patients showing horizontal hemianopia by using the technique of perimetric blind spot mapping. The results revealed in both studies that static fixation as measured by the position of the blind spot(s) was completely normal in nearly all subjects and was neither (cor)related to shifts of the visual straight ahead nor the HLBE. In addition, it was found that the capacity to scan the blind field with saccadic eye movements (“saccadic search field”) was not related to the HLBE, thus ruling out visual scanning deficits as a possible cause of the HLBE.

The last issue that was analysed in this thesis was the question of attention in relation to the HLBE. Deficits in line bisection are a frequent finding in patients with visual neglect. Many studies in this context have shown that manipulations of visuospatial General Abstract IV attention, i.e. via attentional cueing to one side of space, significantly modulate the ipsilesional spatial error in patients with visual neglect.

In a similar logic, we evaluated in the second and third study of this thesis, whether attentional cueing to the left or right side of the horizontal line that had to be bisected modulated the HLBE in hemianopic patients. Surprisingly, cueing had virtually no effect on the HLBE in hemianopic subjects while the very same manipulation clearly modulated bisection in a small group of patients with left visual neglect, thus showing the principal efficacy of the attentional manipulation.

In summary, this thesis reports novel evidence of an oblique contralesional spatial error in homonymous quadrantanopia akin to the HLBE in horizontal hemianopia. Moreover, the present results in chronic patients with hemianopia do neither support the notion of eccentric fixation nor of hypo-/hyperattention to one side of space as possible determinants of the HLBE. Furthermore, gross visual exploration deficits do not seem to contribute to the HLBE either. Finally, possible limitations of the present studies are mentioned and alternative theoretical accounts shortly discussed.

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[ARTICLE] Homonymous hemianopia: challenges and solutions – Full Text PDF

Abstract:

Stroke is the most common cause of homonymous hemianopia (HH) in adults, followed by trauma and tumors. Associated signs and symptoms, as well as visual field characteristics such as location and congruity, can help determine the location of the causative brain lesion.

HH can have a significant effect on quality of life, including problems with driving, reading, or navigation. This can result in decreased independence, inability to enjoy leisure activities, and injuries. Understanding these restrictions, as well as the management options, can aid in making the best use of remaining vision.

Treatment options include prismatic correction to expand the remaining visual field, compensatory training to improve visual search abilities, and vision restoration therapy to improve the vision itself. Spontaneous recovery can occur within the first months. However, because spontaneous recovery does not always occur, methods of reducing visual disability play an important role in the rehabilitation of patients with HH.

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via Homonymous hemianopia: challenges and solutions | OPTH.

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