Posts Tagged Hemianopia
[Case Study] Transcranial direct current stimulation (tDCS) combined with blindsight rehabilitation for the treatment of homonymous hemianopia: a report of two-cases – Full Text PDF
[Purpose] Homonymous hemianopia is one of the most common symptoms following neurologic damage leading to impairments of functional abilities and activities of daily living. There are two main types of restorative
rehabilitation in hemianopia: “border training” which involves exercising vision at the edge of the damaged visual field, and “blindsight training,” which is based on exercising the unconscious perceptual functions deep
inside the blind hemifield. Only border effects have been shown to be facilitated by transcranial direct current stimulation (tDCS). This pilot study represents the first attempt to associate the modulatory effects of tDCS over
the parieto-occipital cortex to blindsight treatment in the rehabilitation of the homonymous hemianopia.
[Subjects and Methods] Patients TA and MR both had chronic hemianopia. TA underwent blindsight treatment which was combined with tDCS followed by blindsight training alone. MR underwent the two training rounds in reverse order.
[Results] The patients showed better scores in clinical-instrumental, functional, and ecological assessments after tDCS combined with blindsight rehabilitation rather than rehabilitation alone. [Conclusion] In this two-case report parietal-occipital tDCS modulate the effects induced by blindsight treatment on hemianopia.
[Conclusion] In this two-case report parietal-occipital tDCS modulate the effects induced by blindsight treatment on hemianopia.
[Abstract] From cortical blindness to conscious visual perception: Theories on neuronal networks and visual training strategies
Homonymous hemianopia (HH) is the most common cortical visual impairment leading to blindness in the contralateral hemifield. It is associated with many inconveniences and daily restrictions such as exploration and visual orientation difficulties. However, patients with HH can preserve the remarkable ability to unconsciously perceive visual stimuli presented in their blindfield, a phenomenon known as blindsight. Unfortunately, the nature of this captivating residual ability is still misunderstood and the rehabilitation strategies have been insufficiently exploited. This paper discusses type I and type II blindsight in a neuronal framework of altered global workspace, resulting from inefficient perception, attention and conscious networks. To enhance synchronisation and create global availability for residual abilities to reach visual consciousness, rehabilitation tools need to stimulate subcortical extrastriate pathways through V5/MT. Multisensory bottom-up compensation combined with top-down restitution training could target pre-existing and new neuronal mechanisms to recreate a framework for potential functionality.
[Abstract] Review of rehabilitation and habilitation strategies for children and young people with homonymous visual field loss caused by cerebral vision impairment
Partial and homonymous visual field loss (HVFL) is a common consequence of post-chiasmatic injury to the primary visual pathway or injury to the primary visual cortex. Different approaches to rehabilitation have been reported for older adults with HVFL and there is evidence to support the use of compensatory training over other proposed therapies. We reviewed the literature to investigate the current state of the art of rehabilitation and habilitation strategies for children and young people with HVFL, and whether there is enough evidence to support the use of these strategies in the paediatric population. We have provided an overview of the existing literature on children and young people with HVFL, a brief overview of rehabilitation strategies for adults with HVFL, and evidence on whether these different interventions have been applied with children and young people effectively. We found that there have been very few studies to investigate these strategies with children and young people, and the quality of evidence is currently low. New research is required to evaluate which strategies are effective for children and young people with HVFL and whether new strategies need to be developed.
Hemianopia explained and simulated using an eye-tracker
Strategies for adapting a computer for use by people with visual field deficits.
Hemianopia leads to severe impairment of spatial orientation and mobility. In cases without macular sparing an additional reading disorder occurs. Persistent visual deficits require rehabilitation. The goal is to compensate for the deficits to regain independence and to maintain the patient’s quality of life. Spontaneous adaptive mechanisms, such as shifting the field defect towards the hemianopic side by eye movements or eccentric fixation, are beneficial, but often insufficient. They can be enhanced by training, e.g., saccadic training to utilize the full field of gaze in order to improve mobility and by special training methods to improve reading performance. At present only compensatory interventions are evidence-based.
Objectives: More than 50% of human cerebral activity is related to vision. Visual impairments are therefore common after acquired brain injury, although they are often overlooked. In order to evaluate the prevalence of visual deficits in our Out-patient Brain Injury Program, a structured screening questionnaire, the Visual Interview, was administered.
Methods: A total of 170 patients with acquired brain injury, mean age 47 years, who were enrolled in the programme during 2010–12, underwent the Visual Interview. The interview consists of 18 questions concerning visual impairment and was performed on admission. The different types of visual impairment were compared with regard to sex and diagnosis.
Results: Fifty-four percent of the patients reported visual changes, mainly reading difficulties, photosensitivity, blurred vision and disorders of the visual field. Sixteen patients who did not experience visual changes also reported visual symptoms in 4–9 questions. Only slight differences were noted in the occurrence of visual symptoms when correlated with sex or diagnosis.
Conclusion: Visual impairments are common after acquired brain injury, but some patients do not define their problems as vision-related. A structured questionnaire, covering the most common visual symptoms, is helpful for the rehabilitation team to facilitate assessment of visual changes.
The visual system is widely distributed in the brain. It is integrated in more than 50% of human cerebral activity and is fundamental for interpretation of, and interaction with, the environment (1, 2).
A pyramidal hierarchical model of visual perceptual function was presented by Warren in 1993 (3). In this model, visual cognition forms the top level, followed by, in descending order: visual memory, pattern recognition, scanning, attention and a base level holding acuity, visual fields, and ocular motor control. The model illustrates how higher visual skills evolve from integration and interaction with lower skills and how visual cognition depends on well-functioning lower levels of visual perception.
Base level disturbances, such as visual field defects (VFDs), visual acuity changes, diplopia, strabismus, photophobia and different types of binocular disorders, are common after acquired brain injury (ABI) (4, 5), and lead to chronic headache, fatigue, dizziness, reading problems, and difficulties navigating the environment (6, 7). Although a complete VFD or manifest diplopia seldom escapes notice, disturbances of ocular motor abilities and photophobia are likely to be overlooked. Examinations of convergence and accommodation are not customary in standard ophthalmological assessments. Ordinary short examinations are unable to reveal declining attention ability and fatigue. Thus, the true problems may remain hidden.
Several reports of prevalence and quality of visual deficits after ABI document visual dysfunctions in approximately 50–75% of patients (8–13). The occurrence of different visual symptoms differs between the studies, including reading disturbances, VFD, diplopia, ocular motor dysfunction and photophobia. Nevertheless, visual symptoms are often overlooked in neurorehabilitation. The observations of Sand et al. (14) are noteworthy, i.e. that 1 of 4 stroke patients with VFD, 6 months after onset of stroke, considered that their visual problems reduced quality of life and increased their disability.
Visual disturbances after ABI are common and lead to reduced quality of life. An important question is why they are so often overlooked in neurorehabilitation? A possible explanation is the difficulty for different professionals to co-operate. Vision disturbances are complex and many different professionals operate in the field. An ability to co-operate is needed for a high-quality assessment. Another explanation could be the patients’ difficulty describing their shortcomings. They experience decreased reading speed, fatigue and dizziness, but do not recognize these problems as expressions of visual deficits. A structured questionnaire at admission would help the clinician to obtain informative answers.
In 1990, Kerkhoff et al (15). compiled an “Interview Questionnaire” in order to capture visual disorders after ABI. This interview was used by Wilhelmsen 2003 (12). Jacobsson & Hamelius translated it from Norwegian to Swedish in 2010 (16). During the last 5 years we have used this questionnaire, slightly modified, termed the Vision Interview (TVI), as an aid to discover visual deficits in our Out-patient Brain Injury Program.
The aim of the present study was to examine and analyse the occurrence of self-reported visual changes in a Swedish out-patient group with medium to severe ABI, based on TVI.
Strokes, or cerebrovascular accidents (CVA) are common, particularly in older people. The problems of motor function and speech are well known. This article explains the common visual problems which can occur with a stroke and gives information about diagnosis and management.
What is a stroke?
A stroke occurs when there is an interruption to blood flow to the brain either because of a blood clot blocking the blood vessel or a haemorrhage in the brain.1 Strokes can cause signs which are obvious, such as loss of speech, drooping of one side of their face, or weakness or paralysis of the arm and/or leg on one side of the body.1 The vision is affected in about two thirds of people who have had a stroke, but this is often not obvious to the patient or their carers. For example, someone who has weakness down one side may bump into things or not eat all the food on their plate, not realising that this may also be because they have visual field loss.2
What causes a stroke?
A stroke or cerebrovascular accident, (CVA) is the result of a blocked blood vessel in the brain (thrombosis or embolus), or haemorrhage into the brain.1 Strokes are more likely in the elderly, and those who have high blood pressure, diabetes or cardiovascular disease.
Types of visual loss in people who have had a stroke
There are four ways in which vision can be affected following a stroke:
- Loss of central vision
- Visual field loss
- Visual perceptual abnormalities
- Eye movement abnormalities
These may occur in isolation but more frequently occur in combination.3 Problems with central vision are quite common after a stroke. The symptoms include blurred or altered vision. In many the vision improves, but the visual loss can be permanent.
Visual field loss occurs in up to half of people with a stroke, with the commonest defect being homonymous hemianopia in which vision is lost in the right or the left visual fields (Figure 1).4 Patients may not be aware of this, and bump into door frames or trip over things on the affected side. Reading can also be difficult (Figure 2).
Visual perceptual deficits are many and varied affecting about a third of people with a stroke. Problems that may develop include neglect one side of their body; difficulty recognising faces or objects, or difficulties with colour vision, depth perception and motion.5 Eye movement abnormalities can also be varied, including strabismus (misaligned eyes), difficulty in converging the eyes to look at near objects, or double vision due to the cranial nerves which control eye movement being affected.6 Typical symptoms include double vision, or jumbled, blurred and/or juddery vision (Figure 2).
Blurred vision, double vision and lossand loss of visual field are significant symptoms that impair daily functioning.7 The patient or their close relatives may report that they frequently bump into objects such as door frames; have difficulty finding things on surfaces; are unsure of their footing while walking and stumble; may leave food uneaten on one side of the plate and have difficulty with reading. Other impacts on the quality of life include loss of confidence, fear of falling, fear of going out alone, social isolation and loss of independence.8
How to assess visual function in someone who has had a stroke
Examination for visual loss is essential for stroke survivors.9 There are various assessment tools which can be used to examine visual function after a stroke:
- UK National Clinical Guidelines for Stroke
- UK stroke/vision resources and factsheets
- UK Stroke Association stroke/vision factsheet
- UK Royal National Institute for the Blind stroke/vision factsheet
Treatment options aim to restore visual function to as normal as possible.10 For eye movement abnormalities,prisms and patching one eye can be effective in reducing double vision.6 For visual field loss a Cochrane systematic review reports favourable evidence of visual scanning training which aims to compensate for the visual field loss.11 It is available as a paper training option (www.strokevision.org.uk) or through computer training (www.eyesearch.ucl.ac.uk; www.readright.ucl.ac.uk.
Stroke survivors with persistent impairment of central vision may be helped by low vision services which can include magnifiers, reading aids, computerised adaptations and improved lighting.12 Furthermore, simple adaptations can be made by stroke survivors such as using large print, ensuring good lighting at home, putting labels or coloured stickers on cooking equipment, decluttering areas and having a companion when going out, particularly in busy, crowded places.10
Post-stroke difficulties in visual function are an under-recognised problem that cause significant impact to the quality of life of stroke survivors. Carers and health workers need to be aware that problems with vision are a common consequence of stroke that is not outwardly obvious. Assessment including visual functioning is best provided as part of a multi-disciplinary team on acute stroke units, or in neuro-rehabilitation units. A careful history about visual problems from the patient and carers followed by examination of visual acuity, eye movements and visual field are important in understanding the difficulties in visual functioning.
Management should be tailored to each individual, their visual difficulties and visual needs. With about one quarter of stroke survivors being of working age, rehabilitation in the conext of adaptation of the work place environment is vital if younger people are to return to work after stroke. Rehabilitation requires patience and perseverance on the side of the client, relatives and the health provider.
Despite improvement in stroke prevention and acute stroke management, the increasing ageing population will result in more stroke survivors requiring rehabilitation. Policy makers need to understand the importance of providing post-stroke rehabilitation services including visual functioning.
All webpages accessed 30th January 2017
1 World Health Organization. Stroke and cerebrovascular accident. 2017. http://www.who.int/topics/cerebrovascular_accident/en/
2 Hepworth LR, Rowe FJ, Walker MF, Rockliffe J, Noonan C, Howard C, Currie J. Post-stroke Visual Impairment: A Systematic Literature Review of Types and Recovery of Visual Conditions. Ophthalmology Research: An International Journal. 2015; 5(1). ISSN: 2321-7227
3 Rowe FJ, VIS group. Visual impairment following stroke. Do stroke patients require vision assessment? Age and Ageing. 2009; 38: 188-193
4 Rowe FJ, VIS UK. A Prospective Profile of Visual Field Loss following Stroke: Prevalence, Type, Rehabilitation, and Outcome. BioMed Research International, vol. 2013, Article ID 719096, 1-12, 2013. doi:10.1155/2013/719096.
5 Rowe FJ, VIS group. Visual perceptual consequences of stroke. Strabismus 2009; 17: 24-28
6 Rowe FJ, VIS group. The profile of strabismus in stroke survivors. Eye 2010; 24: 682-5
7 Rowe FJ, VIS Group. Symptoms of stroke related visual impairment. Strabismus, 2013; 21: 150-4
8 Hepworth L, Rowe FJ. Visual impairment following stroke – the impact on quality of life: a systematic review. Ophthalmology Research: an international journal. 2016; 5(2): 1-15
9 Rowe FJ. The importance of accurate visual assessment after stroke: Editorial. Expert Reviews in Ophthalmology. 2011: 6; 133-6
10 Rowe FJ. Care provision and unmet need for post stroke visual impairment; Final report. 2013. http://www.stroke.org.uk/sites/ default/files/final_report_unmet_need_2013.pdf?
11 Pollock A, Hazelton C, Henderson CA, Angilley J, Dhillon B, Langhorne P, Livingstone K, Munro FA, Orr H, Rowe FJ, Shahani U. Interventions for visual field defects in patients with stroke. Cochrane Database of Systematic Reviews 2011, Issue 10. Art. No.: CD008388. DOI: 10.1002/14651858.CD008388.pub2.
12 Virgili G, Rubin G. Orientation and mobility training for adults with low vision. Cochrane Database of Systematic Reviews 2010, Issue 5. Art. No.: CD003925. DOI: 10.1002/14651858.CD003925.pub3