Posts Tagged homonymous hemianopia

[ARTICLE] Driving with Hemianopia V: Do Individuals with Hemianopia Spontaneously Adapt Their Gaze Scanning to Differing Hazard Detection Demands?

Abstract

Purpose: We investigated whether people with homonymous hemianopia (HH) were able to spontaneously (without training or instructions) adapt their blind-side scan magnitudes in response to differing scanning requirements for detection of pedestrians in a driving simulator when differing cues about pedestrian eccentricities and movement behaviors were available in the seeing hemifield.

Methods: Twelve HH participants completed two sessions in a driving simulator pressing the horn when they detected a pedestrian. Stationary pedestrians outside the driving lane were presented in one session and approaching pedestrians on a collision course in the other. Gaze data were analyzed for pedestrians initially appearing at approximately 14° in the blind hemifield. No instructions were given regarding scanning.

Results: After appearing, the stationary pedestrians’ eccentricity increased rapidly to a median of 31° after 2.5 seconds, requiring increasingly larger blind-side gaze scans for detection, while the approaching pedestrians’ eccentricity remained constant at approximately 14°, requiring a more moderate scan (∼14°) for detection. Although median scan magnitudes did not differ between the two conditions (approaching: 14° [IQR 9°–15°]; stationary: 13° [IQR 9°–20°]; P= 0.43), three participants showed evidence of adapting (increasing) their blind-side scan magnitudes in the stationary condition.

Conclusions: Three participants (25%) appeared to be able to apply voluntary cognitive control to modify their blind-side gaze scanning in response to the differing scanning requirements of the two conditions without explicit training.

Translational Relevance: Our results suggest that only a minority of people with hemianopia are likely to be able to spontaneously adapt their blind-side scanning in response to rapidly changing and unpredictable situations in on-road driving.

 

Introduction
Homonymous hemianopia (HH) is the loss of half the field of vision on the same side in both eyes. It is caused by lesions in the postchiasmal visual pathways, primarily due to strokes and, to a lesser extent, trauma and tumors.1 People with HH may compensate for their hemifield loss by scanning using eye and/or head movements toward the blind hemifield. However, there is accumulating evidence2 that many do not compensate well leading to impaired hazard detection in simulated driving,38 in on-road driving,9 and in walking tasks.10
In order to see an object in the blind hemifield, people with complete HH need to scan at least as far into the blind hemifield as the location of the object. However, they receive no visual cues from peripheral vision as to when to scan or how far to scan into the blind hemifield. People with HH are usually aware of their visual field loss (unless they have spatial neglect) and could use voluntary, cognitive control to guide their blind-side scanning. For example, patients with HH may be trained or told to scan to the blind side in order to detect potential hazards.11 However, relatively little is known about the extent to which people with HH use such strategies in real world situations (e.g., driving2) or whether they are able to adapt their scanning patterns in response to differing conditions (e.g., a busy city-center street with frequent hazards versus a quiet rural road with infrequent hazards).
Only a limited number of studies have addressed the question of whether people with HH adapt their scanning strategies. A recent study using a gaze-contingent simulation of HH concluded that efficient search strategies were not spontaneously adopted by the majority of participants; however, a minority (4/20) did modify their search strategy in response to changing task demands. In general, a strategy of searching the seeing side before the blind side was adopted both for difficult search tasks in which each item needed to be viewed in a serial fashion as well as easier tasks in which the target was clearly visible in the periphery and a large saccade toward the blind side would have been the more efficient strategy. Only four participants modified their search to start from the blind field when the task was easy. In another study, Schuett et al.12reported that normally sighted participants with simulated HH became more efficient at a dot-counting task (an irregular array of dots) and a reading task after a short period of practice (∼15 minutes) on each of the tasks. However, in follow-up studies they found no evidence of transfer of learning (modification of gaze behaviors) between the two tasks, either for simulated HH13 or real HH13 (i.e., participants who practiced the dot-couting task did not demonstrate improvements on the reading task and vice versa).
In a study involving detection of peripherally presented moving basketballs within a virtual environment, participants with HH scanned less extensively in the horizontal plane and spent more time looking toward the ground when performing the task while walking than when seated.10 Thus, when walking, it appears that they modified their gaze behaviors in favor of walking, at the expense of peripheral target detection. In a driving simulator study3 involving detection of stationary pedestrians on the blind and seeing sides, no improvement in blind-side detection rates was found between two simulator sessions, approximately 1 week apart. These results suggested that no learning had occurred, despite 60 minutes of test drives at each session. Moreover, information was available in the seeing hemifield about pedestrian eccentricity, which could have been used as a guide for the scanning behaviors that were needed for detection of blind-side pedestrians. However, gaze movements were not recorded so it was unknown whether there were any changes in gaze behaviors.
In this paper, we report an analysis of gaze behaviors from a driving simulator study5 in which we evaluated detection performance of people with HH for pedestrians that were stationary to the side of the driving lane and pedestrians that approached the driving lane, walking or running on a collision course (detection rates and reaction time results were reported previously5). The scanning requirements for successful detection of blind-side pedestrians differed for the two pedestrian conditions, providing an opportunity to examine whether participants adapted their scanning behaviors. In the stationary condition the pedestrians did not move after appearing.3,5 Thus, their eccentricity increased rapidly as the car progressed, moving them farther into the blind hemifield, requiring increasingly larger gaze movements for detection. On the other hand, in the approaching condition, the pedestrians were on a collision course,5,14 so their eccentricity remained approximately constant as the car progressed. Thus, the magnitude of the gaze scan needed for detection would also have remained approximately constant, and smaller than the gaze scan needed in the stationary condition.
Herein, we address two main questions: (1) did participants with HH adapt their blind-side scan magnitudes (without training or instructions) to match the differing scanning requirements (pedestrian eccentricities) for successful blind-side detection in the stationary and approaching conditions; and (2) were the previously reported5 differences in blind-side detection rates between the two conditions accounted for by differences in the scanning requirements? We quantified the magnitudes of scans after the appearance of pedestrians in the blind hemifield and tested the hypothesis that blind-side scans would be larger in the stationary than the approaching condition. We expected to find greater evidence of within-session learning in the stationary condition (where scanning requirements were higher) than in the approaching condition. In addition, we tested the hypothesis that more time would be available after the pedestrian appearance for a moderate-sized gaze scan to reach the pedestrian in the approaching than the stationary condition, resulting in better detection rates but longer response times.[…]

Continue —> Driving with Hemianopia V: Do Individuals with Hemianopia Spontaneously Adapt Their Gaze Scanning to Differing Hazard Detection Demands? | TVST | ARVO Journals

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[VIDEO] Homonymous hemianopia – YouTube

Published on Jul 3, 2017

This project was created with Explain Everything ™ Interactive Whiteboard for iPad.

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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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[Abstract] A pilot randomized controlled trial comparing effectiveness of prism glasses, visual search training and standard care in hemianopia

Abstract

Objective

Pilot trial to compare prism therapy and visual search training, for homonymous hemianopia, to standard care (information only).

Methods

Prospective, multicentre, parallel, single-blind, three-arm RCT across fifteen UK acute stroke units.

Participants

Stroke survivors with homonymous hemianopia.

Interventions

Arm a (Fresnel prisms) for minimum 2 hours, 5 days per week over 6 weeks. Arm b (visual search training) for minimum 30 minutes, 5 days per week over 6 weeks. Arm c (standard care—information only).

Inclusion criteria

Adult stroke survivors (>18 years), stable hemianopia, visual acuity better than 0.5 logMAR, refractive error within ±5 dioptres, ability to read/understand English and provide consent.

Outcomes

Primary outcomes were change in visual field area from baseline to 26 weeks and calculation of sample size for a definitive trial. Secondary measures included Rivermead Mobility Index, Visual Function Questionnaire 25/10, Nottingham Extended Activities of Daily Living, Euro Qual, Short Form-12 questionnaires and Radner reading ability. Measures were post-randomization at baseline and 6, 12 and 26 weeks.

Randomization

Randomization block lists stratified by site and partial/complete hemianopia.

Blinding

Allocations disclosed to patients. Primary outcome assessor blind to treatment allocation.

Results

Eighty-seven patients were recruited: 27—Fresnel prisms, 30—visual search training and 30—standard care; 69% male; mean age 69 years (SD 12). At 26 weeks, full results for 24, 24 and 22 patients, respectively, were compared to baseline. Sample size calculation for a definitive trial determined as 269 participants per arm for a 200 degree2 visual field area change at 90% power. Non-significant relative change in area of visual field was 5%, 8% and 3.5%, respectively, for the three groups. Visual Function Questionnaire responses improved significantly from baseline to 26 weeks with visual search training (60 [SD 19] to 68.4 [SD 20]) compared to Fresnel prisms (68.5 [SD 16.4] to 68.2 [18.4]: 7% difference) and standard care (63.7 [SD 19.4] to 59.8 [SD 22.7]: 10% difference), P=.05. Related adverse events were common with Fresnel prisms (69.2%; typically headaches).

Conclusions

No significant change occurred for area of visual field area across arms over follow-up. Visual search training had significant improvement in vision-related quality of life. Prism therapy produced adverse events in 69%. Visual search training results warrant further investigation.

Source: A pilot randomized controlled trial comparing effectiveness of prism glasses, visual search training and standard care in hemianopia – Rowe – 2016 – Acta Neurologica Scandinavica – Wiley Online Library

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[ARTICLE] Behavioural consequences and cortical reorganization in homonymous hemianopia – Full Text

Abstract

The most common visual defect to follow a lesion of the retrochiasmal pathways is homonymous hemianopia (HH), whereby, in each eye, patients are blind to the contralesional visual field. From a behavioral perspective, in addition to exhibiting a severe deficit in their contralesional visual field, hemianopic patients can also present implicit residual capacities, now usually referred to collectively as blindsight. It was recently demonstrated that HH patients can also suffer from a subtle deficit in their ipsilesional visual field, called sightblindness (the reverse case of blindsight). Furthermore, the nature of the visual deficit in the contralesional and ipsilesional visual fields, as well as the pattern of functional reorganization in the occipital lobe of HH patients after stroke, all appear to depend on the lesion side. In addition to their contralesional and ipsilesional visual deficits, and to their residual capacities, HH patients can also experience visual hallucinations in their blind field, the physiopathological mechanisms of which remain poorly understood. Herein we review blindsight in terms of its better-known aspects as well as its less-studied clinical signs such as sightblindness, hemispheric specialization and visual hallucinations. We also discuss the implications of recent experimental findings for rehabilitation of visual field defects in hemianopic patients.

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Source: Frontiers | Behavioural consequences and cortical reorganization in homonymous hemianopia | Frontiers in Systems Neuroscience

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[ARTICLE] A Randomised Controlled Trial of Treatment for Post-Stroke Homonymous Hemianopia: Screening and Recruitment – Full Text

ABSTRACT

The authors report the screening process and recruitment figures for the VISION (Visual Impairment in Stroke; Intervention Or Not) trial. This is a prospective, randomised, single-blinded, three-arm controlled trial in 14 UK acute hospital stroke units. Stroke teams identified stroke survivors suspected as having homonymous hemianopia.
Interventions included Fresnel prisms versus visual search training versus standard care (information only). Primary outcome was change in visual field assessment from baseline to 26 weeks. Secondary measures included change in quality-of-life questionnaires.
Recruitment opened in May 2011. A total of 1171 patients were screened by the local principal investigators. Of 1171 patients, 178 (15.2%) were eligible for recruitment: 87 patients (7.4%) provided consent and were recruited; 91 patients (7.8%) did not provide consent, and 993 of 1171 patients (84.8%) failed to meet the eligibility criteria. Almost half were excluded due to complete/partial recovery of hemianopia (43.6%; n = 511).
The most common ineligibility reason was recovery of hemianopia. When designing future trials in this area, changes in eligibility criteria/outcome selection to allow more patients to be recruited should be considered, e.g., less stringent levels of visual acuity/refractive error. Alternative outcomes measurable in the home environment, rather than requiring hospital attendance for follow-up, could facilitate increased recruitment.

Continue —> A Randomised Controlled Trial of Treatment for Post-Stroke Homonymous Hemianopia: Screening and Recruitment – Neuro-Ophthalmology – Volume 40, Issue 1

Figure 1. Flow chart of recruitment figures.

 

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[ARTICLE] Vision problems in ischaemic stroke patients: effects on life quality and disability – European Journal of Neurology – Full Text HTML

Abstract

Background and purpose Vision problems after cerebral infarction are an increasingly acknowledged problem. Our aim was to investigate the effect on quality of life and post-stroke disability.

Methods Patients admitted to the Stroke Unit, Department of Neurology, Haukeland University Hospital, between February 2006 and July 2008 with acute cerebral infarction were prospectively registered in the NORSTROKE Registry. Patients received a postal questionnaire at least 6 months after stroke. The questionnaire included 15D©, EuroQol 5D (EQ-5D™), the Hospital Anxiety and Depression Scale (HADS), the Fatigue Severity Scale (FSS) and the Barthel Index (BI).

Results Of 328 responders, 83 (25.4%) reported a vision problem. Vision problems were associated with older age (71.8 years vs. 66.5 years, P = 0.001), higher National Institutes of Health Stroke Scale score on admission (5.9 vs. 3.8, P < 0.001), higher modified Rankin Scale day 7 (2.0 vs. 1.4, P < 0.001) and lower BI day 7 (85.7 vs. 93.9, P = 0.002). Patients with vision problems had lower median EQ-5D utility score (0.62 vs. 0.80, P < 0.001), lower median 15D utility score (0.73 vs. 0.89, P < 0.001), higher median HADS score (12 vs. 5, P < 0.001), higher median FSS score (5.6 vs. 4.3, P < 0.001) and lower median BI (95 vs. 100, P < 0.001) on long-term follow-up. Patients with self-reported vision problems scored lower on all sub-scores of BI on follow-up (all P < 0.001).

Conclusion One in four patients reported a vision problem on follow-up after cerebral infarction. Vision problems after cerebral infarction reduce quality of life and are associated with increased disability. Thorough diagnostic evaluation and targeted rehabilitation is important.

Continue: —>  Vision problems in ischaemic stroke patients: effects on life quality and disability – Sand – 2015 – European Journal of Neurology – Wiley Online Library

 

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[ARTICLE] Non-invasive electric current stimulation for restoration of vision after unilateral occipital stroke

Abstract

Occipital stroke often leads to visual field loss, for which no effective treatment exists. Little is known about the potential of non-invasive electric current stimulation to ameliorate visual functions in patients suffering from unilateral occipital stroke. One reason is the traditional thinking that visual field loss after brain lesions is permanent. Since evidence is available documenting vision restoration by means of vision training or non-invasive electric current stimulation future studies should also consider investigating recovery processes after visual cortical strokes. Here, protocols of repetitive transorbital alternating current stimulation (rtACS) and transcranial direct current stimulation (tDCS) are presented and the European consortium for restoration of vision (REVIS) is introduced. Within the consortium different stimulation approaches will be applied to patients with unilateral occipital strokes resulting in homonymous hemianopic visual field defects. One goal is to evaluate effects of the stimulation on vision parameters, vision-related quality of life, and physiological parameters that allow conclude about the mechanisms of vision restoration as induced by electrical current stimulation. These include EEG-spectra and coherence measures, and visual evoked potentials. The design of stimulation protocols involves an appropriate sham-stimulation condition and sufficient follow-up periods to test whether the effects are stable.

This is the first application of non-invasive current stimulation for vision rehabilitation in stroke-related visual field deficits. Positive results of the trials could have far-reaching implications for clinical practice. The ability of non-invasive electrical current brain stimulation to modulate the activity of neuronal networks may have implications for stroke rehabilitation also in the visual domain.

 

via Non-invasive electric current stimulation for restoration of vision after unilateral occipital stroke.

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[WEB SITE] Hemianopia – Lighthouse International

What Is Hemianopia?

Hemianopia is a blindness or reduction in vision in one half of the visual field due to damage of the optic pathways in the brain. This damage can result from acquired brain injuries caused by stroke, tumor or trauma.

A graphic simulation of Hemianopia comparing a normal street scene, and the same street scene viewed under the simulated effects of Hemianopia

Stroke occurs when there is damage to a group of nerve cells in the brain often due to interrupted blood flow, caused by a blood clot or blood vessel leaking. Depending on the area of the brain that is damaged, a stroke can result in coma, paralysis of one side of the body, speech and vision problems, and dementia.

What Are the Different Types of Hemianopia?

The most common defect, right homonymous hemianopia, occurs in corresponding halves of the right field of vision. It can also occur in corresponding halves of the left field of vision (left homonymous hemianopia), in the upper half of the field (superior hemianopia), the lower half (inferior hemianopia), or both outer halves of the field (bitemporal hemianopia). In hemianopia, half of the field is blanked out on both eyes.

Symptoms

  • Loss of half of the field of vision
  • Decreased night vision
  • Need for more light

Risk Factors

Whoever may be at risk for stroke is also at risk for hemianopia. People with high blood pressure or those with an abnormal heart rhythm, which is associated with blood clots in the heart, may be at risk for stroke.

Age is also a risk factor, as the majority of people who experience stroke are over the age of 55.

What You Can Do to Reduce Risk

Reducing the risk of stroke will reduce the risk of hemianopia. For more information on how to reduce your stroke risk, visit the National Stroke Association.

Treatment

Though there is no specific medical or surgical treatment for hemianopia, one’s effective use of vision may improve over time. In addition, there are optical devices that may be helpful in increasing the field of vision. Some examples include field-expanding prism lenses and magnifiers.

Following diagnosis of hemianopia, it is also important to receive a careful evaluation by a low vision specialist who can prescribe optical prism glasses and other devices, as well as recommend vision rehabilitation services. Vision rehabilitation specialists can teach people with hemianopia to maximize their existing sight by increasing lighting or using adaptive devices, for example.

via Lighthouse International – Hemianopia.

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[ARTICLE] Difficulties in Daily Life Reported by Patients With Homonymous Visual Field Defects.Visual Fields

Abstract

Background: Homonymous visual field defects (HVFD) are common after postchiasmatic acquired brain injury and may have a significant impact on independent living and participation in society. Vision-related difficulties experienced in daily life are usually assessed using questionnaires. The current study 1) links the content of 3 of these questionnaires to the International Classification of Functioning, Disability and Health (ICF) and 2) provides analyses of vision-related difficulties reported by patients with HVFD and minimal comorbidities.

Methods: Fifty-four patients with homonymous hemianopia or quadrantanopia were asked about difficulties experienced in daily life because of their HVFD. This was performed during a structured interview including 3 standardized questionnaires: National Eye Institute Visual Functioning Questionnaire, Independent Mobility Questionnaire, and Cerebral Visual Disorders Questionnaire. The reported difficulties were linked to the ICF according to the ICF linking rules. Main outcome measures were presence or absence of experienced difficulties.

Results: The ICF linking procedure resulted in a classification table that can be used in future studies of vision-related difficulties. Besides well-known difficulties related to reading, orientation, and mobility, a high proportion of patients with HVFD reported problems that previously have not been documented in the literature, such as impaired light sensitivity, color vision, and perception of depth.

Conclusions: A systematic inventory of difficulties experienced in daily life by patients with HVFD was performed using the ICF. These findings have implications for future study, assessment and rehabilitation of patients with HVFD.

via Difficulties in Daily Life Reported by Patients With Homonym… : Journal of Neuro-Ophthalmology.

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