Posts Tagged visual field
This video outlines the fitting and training process for The Peli Lens for Homonymous Hemianopsia
[Abstract] A qualitative exploration of the effect of visual field loss on daily life in home-dwelling stroke survivors
To explore the effect of visual field loss on the daily life of community-dwelling stroke survivors.
Semi-structured interviews were conducted with a non-purposive sample of 12 stroke survivors in their own homes. These were recorded, transcribed verbatim and analyzed with the framework method, using an inductive approach.
Two key analytical themes emerged. ‘Perception, experience and knowledge’ describes participant’s conflicted experience of having knowledge of their impaired vision but lacking perception of that visual field loss and operating under the assumption that they were viewing an intact visual scene when engaged in activities. Inability to recognize and deal with visual difficulties, and experiencing the consequences, contributed to their fear and loss of self-confidence. ‘Avoidance and adaptation’ were two typologies of participant response to visual field loss. Initially, all participants consciously avoided activities. Some later adapted to vision loss using self-directed head and eye scanning techniques.
via A qualitative exploration of the effect of visual field loss on daily life in home-dwelling stroke survivors – Christine Hazelton, Alex Pollock, Anne Taylor, Bridget Davis, Glyn Walsh, Marian C Brady, 2019
Watch a demonstration of assessing visual fields.
Read FREE related article: https://www.medbridgeeducation.com/h/…
Visual Deficits:Now You See It, Now You Don’t- A Clinical Pearl by Diane Powers Dirette, PhD, OTL
Visual deficits match many diagnoses and, if undetected, can be mistaken for other problems – e.g. sensory, motor, balance and cognitive deficits. It’s critical, therefore, that therapists know how to complete a basic visual screening and to interpret the results. For example, how can you tell homonymous hemianopia apart from unilateral inattention? The screening tools are virtually the same, but the screening results differ subtly.
This is an attempt to show people how I see the world since my brain injury 8 years ago. This is what I see when I’m going shopping… I hate going shopping… I rarely go full shopping….. My left side of vision is missing, it’s not really black, it’s just not there, but I can’t explain it… and what I have left, is what you see here… My camera caught it all perfectly, sun glare as well… So if I don’t recognise you in the street, it’s really because I can’t see your face. If I need to see your face, I look for the right side edge of your face and look above you… that helps me see more of your features. But to be honest, I’ve kind of got used to not seeing people’s faces. I look at the floor a lot so I can see people’s feet, so I can sort of work out where they are if they are too close to me. Gradually, over 8 years I have adapted to doing things, walking, etc on the right. I stop in mid walking sometimes because I saw a person in front of me, then they vanished to my left and I wasn’t sure how close to me they were and I didn’t want to bump into them…. I cope better in wider spaces. Narrow corridors look even more narrow. I discreetly use my hands to touch anything that might be too close, so that I know to move myself away. I still walk into things and get hurt. If I turn my head too quickly, then I go off balance and sometimes fall over. It is very frightening when you can’t see properly, but look normal to everyone else. I’m not too bad if I’m with someone else. I constantly rely on touch… Hence doing Papiér Maché instead of drawing or painting. Also, I still get lost and wonder where I am, even sometimes going past my own house… I haven’t read a book in years, and I used to like reading… I couldn’t work out why I couldn’t see the words properly, and they kept vanishing, and the bits that I could see were double vision – then I had prisms fitted in my glasses lenses, which helped with the double vision, but I still couldn’t work out why I couldn’t see properly. I was officially diagnosed in January 2017. The Neurologist said despite all that, I had made some very good ways of trying to cope… It still is a struggle, but I do my best.
Every year, nearly 800,000 Americans suffer a stroke, according to the Internet Stroke Center.
Strokes are a leading cause of death and disability, but what many people don’t realize is that two out of three stroke survivors will also experience visual impairments related to their stroke (Rowe). These can include diminished central or peripheral vision, eye movement abnormalities or visual perceptual defects.
Sadly, it is not uncommon for me to see patients who are still struggling with undiagnosed vision problems months or even years after a stroke. There are a number of reasons for this. In the immediate days and weeks after a stroke, patients and their families and doctors are often most concerned about preventing brain hemorrhages and addressing motor and language deficits. After that, patients may have difficulty articulating their symptoms or may not be aware that balance issues are connected to vision. In some cases, they may have been examined and incorrectly told that nothing can be done.
Given the prevalence of post-stroke visual impairment, anyone who suffers a stroke should be seen by an eye care specialist as soon as possible and, ideally, be referred to a neuro-optometric rehabilitation optometrist. Visual rehabilitation can lead to greater independence and improved quality of life and can accelerate the success of other therapies. In fact, most stroke survivors need more than one type of rehabilitation, so it is not unusual for me to work with a team of speech, occupational or physical therapists to help the stroke survivor learn new ways of performing tasks to circumvent or compensate for any residual disabilities.
The most common visual complication of stroke is a homonymous hemianopsia, or a visual field defect on the same side in each eye, resulting from damage to the occipital lobe, where the majority of visual processing takes place. This type of stroke-related field loss is often accompanied by a visual midline shift, which occurs when there is a mismatch between visual spatial information and the patient’s proprioceptive base of support.
A shift in the visual midline can directly affect posture, balance and spatial orientation, and it significantly increases the risk of falls. It is relatively easy to diagnose: Just ask a patient to walk down the hall and observe whether they drift to one side or tip backwards or forwards. In a study that I co-authored with Dr. William Padula, we showed that intervention with yoked prisms can restore the visual midline, thereby improving balance and reducing the risk of falls and subsequent injury.
Strokes that affect other parts of the brain may result in cranial nerve damage-associated diplopia or the rare but fascinating phenomenon of visual neglect, in which the patient completely loses awareness of one side of the body. In less severe cases, there can also be subtle effects on eye tracking and teaming, leading to impaired saccades and pursuits or convergence insufficiency. These impairments can be improved with vision rehabilitation and prism lenses.
Vision rehabilitation may not always be able to fully restore patients to the same degree of visual function they had before the stroke, but we can go a long way towards improving quality of life and helping patients maximize the vision they have.
Internet Stroke Center. U.S. Stroke Statistics. http://www.strokecenter.org/patients/about-stroke/stroke-statistics/. Accessed January 16, 2019.
Padula WV, et al. NeuroRehabilitation. 2015;doi:10.3233/NRE-151263.
Rowe FJ. Brain Behav. 2017;doi:10.1002/brb3.778.
A new University of Liverpool study, published in Wiley Brain and Behaviour, examines the factors that influence how a person adapts to visual field loss following stroke.
Approximately 65% of acute stroke survivors have visual impairment which typically relates to impaired central or peripheral vision, eye movement abnormalities, or visual perceptual defects.
Symptoms can include blurred or altered vision, double or jumbled vision, loss of visual field, reading difficulty, inability to recognize familiar objects or people and glare. The factors that influence how a person adapts to a Post stroke visual impairment (PSVI) is currently an under researched area.
Compensate and adapt
In order to profile the full range of influencing factors researchers from the University’s Department of Health Services Research, led by Dr Fiona Rowe, systematically reviewed data pertaining to PSVI produced between 1861 and 2016. This data included randomized controlled trials, controlled trials, cohort studies, observational studies, and case controlled studies.
The researchers identified 47 studies which involved a total of 2,900 participants and categorised them into two sections. Section one included seventeen studies where the reviewers were able to identify a factor they considered as likely to be important for the process of adaptation to post stroke visual field loss.
Section two included thirty studies detailing interventions for visual field loss that the reviewers deemed likely to have an influence on the adaptation process.
The study highlighted a substantial amount of evidence showing patients can be supported to compensate and adapt to visual field loss following stroke using a range of strategies and methods.
Valuable starting point
Dr Rowe, said: “This is an area that must be addressed in the interest of equality for those with visual impairment. It is vital that the factors important for adaptation be identified to allow clinicians to recognise which people are likely to have difficulty adapting and target interventions specifically within these areas, as well as to develop methods for assessing adaptation and monitoring change over time.
“Our review also highlights the fact that many unanswered questions remain: what does adaptation to visual field loss mean to the patient, carer, and clinician? How can adaptation be measured over time? Why do some people adapt more effectively and at a quicker rate than others, despite seemingly similar rehabilitation opportunities and experiences? If these questions can be answered through high quality observations and assessments then this would be a valuable starting point for understanding adaptation.”
Materials provided by University of Liverpool. Note: Content may be edited for style and length.
- Claire Howard, Fiona J. Rowe. Adaptation to poststroke visual field loss: A systematic review. Brain and Behavior, 2018; 8 (8): e01041 DOI: 10.1002/brb3.1041
New study highlights the role of attention as a component of vision restoration training in hemianopia
- About one-third of patients who have suffered a stroke end up with low vision, losing up to half of their visual field. This partial blindness was long considered irreversible, but recent studies have shown that vision training after optic nerve and brain damage can help restore or improve vision. A new study reports on key mechanisms of vision restoration: attention.
About one third of patients who have suffered a stroke end up with low vision, losing up to half of their visual field. This partial blindness was long considered irreversible, but recent studies have shown that vision training after optic nerve and brain damage can help restore or improve vision. A new study published in the journal Clinical Neurophysiology reports on key mechanisms of vision restoration: attention.
Hemianopia is a decreased vision or blindness in half the visual field, usually as a consequence of stroke or trauma to the brain. It greatly reduces quality of life, affecting patients’ reading, driving and spatial navigation.
“Knowledge in this field is still rather fragmentary, but recent studies have shown that vision can be partially restored by vision training, which improves the deficient visual field sectors,” explains Prof. Bernhard Sabel, PhD, Director of the Institute of Medical Psychology at Magdeburg University, Germany, co-investigator of the study. “Neuroimaging evidence supports a possible role of attention in this vision restoration.”
The study confirmed this hypothesis by obtaining evidence from functional magnetic resonance imaging (fMRI) that visual training led to functional connectivity reorganization of the brain´s attentional network.
Seven chronic hemianopic patients with lesions of the visual cortex took part in vision rehabilitation training for five weeks. After the pre-tests all received training sessions lasting one and a half hours per day for six days per week for five weeks. Each training session, lasting about 60 minutes, was composed of six blocks with 120 training trials each, during which participants had to respond to specially designed visual stimuli on a computer monitor. The pre- and post-test included perimetry testing, contrast sensitivity testing and fMRI scanning one or two days before and after training, respectively. Each contrast sensitivity test consisted of 420 trials in six blocks. The visual rehabilitation training was performed with one eye open, which was randomly chosen, while the non-trained eye was covered with an opaque eye patch.
After training, the patients had significantly improved visual function at the training location, and fMRI showed that the training led to a strengthening of the cortical attentional network connections between the brain region of the right temporoparietal junction (rTPJ) and the insula and the anterior cingulate cortex (ACC).
“Our MRI results highlight the role of attention and the right TPJ activation as a component of vision restoration training in hemianopia,” notes lead investigator Yifeng Zhou, DSc, of the Hefei National Laboratory for Physical Sciences at Microscale and School of Life Science, University of Science and Technology of China, Hefei, P.R. China, and State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, P.R. China. “However, it is unclear whether the rehabilitation of attentional networks is the direct result of training or the result of the rebalancing of bottom-up sensory streams, which should be investigated in future studies.”
“This discovery that the brain´s attention network is a key mechanism in partially reversing blindness is an exciting advance in the field of restoring vision in the blind, and it opens up new avenues to design new therapies that are even more effective than current methods to help people with low vision or blindness,” concludes Prof. Sabel.
Materials provided by Institute for Medical Psychology, Otto-v.-Guericke University Magdeburg. Note: Content may be edited for style and length.
- Qilin Lu, Xiaoxiao Wang, Lin Li, Bensheng Qiu, Shihui Wei, Bernhard A. Sabel, Yifeng Zhou. Visual rehabilitation training alters attentional networks in hemianopia: An fMRI study. Clinical Neurophysiology, 2018; 129 (9): 1832 DOI: 10.1016/j.clinph.2018.05.027
Cite This Page:
- Therapy restores visual field lost to brain injury in some patients
- At-home visual therapy system targets stroke, TBI patients
- Homonymous hemianopia and vision loss progress after gunshot wound, decompressive craniectomy
- Rehab program improved neural activity in patients with stroke-, trauma-related vision loss
An educational video regarding homonymous hemianopia, homonymous hemianopsia, the Peli Lens, and prisms for stroke related visual field cuts.
[WEB SITE] High-power prismatic devices may further expand visual fields for patients with hemianopia – ScienceDaily
Series of novel optical designs may address some limitations of existing prism technology, which can expand visual fields by up to 30 degrees
Summary: Three new eyeglasses have now been designedusing high-power prisms to optimally expand the visual fields of patients with hemianopia, a condition in which the visual fields of both eyes are cut by half. The new designs address some limitations of existing prism correction available to this population.
Researchers from the Schepens Eye Research Institute of Massachusetts Eye and Ear and Harvard Medical School have designed three new eyeglasses using high-power prisms to optimally expand the visual fields of patients with hemianopia, a condition in which the visual fields of both eyes are cut by half. The new designs, described in Optometry and Vision Science, address some limitations of existing prism correction available to this population.
Impairing either the left or right halves of the visual fields in both eyes, hemianopia affects more than one million Americans and is most commonly caused by stroke, brain tumors and head trauma. Hemianopia reduces the natural visual field of about 180 degrees to a mere 90 degrees. People with hemianopia have difficulty detecting hazards on their blind sides, leading to collisions, falls and other accidents. Patients with hemianopia cannot legally drive in Massachusetts, where a visual field of 120 degrees is required.
One method of treatment for hemianopia is to expand the visual field with prisms mounted on or embedded in eyeglasses. A research team led by Eli Peli, M.Sc., O.D., FAAO, Professor of Ophthalmology at Harvard Medical School and the Moakley Scholar in Aging Eye Research at the Schepens Eye Research Institute of Mass. Eye and Ear, has been developing prism devices to expand the visual field for these patients for more than 15 years. Their most recent commercially available device introduced in 2013, the peripheral prism glasses, has been shown to expand the visual fields of patients with hemianopia by as much as 30 degrees, optically shifting objects from the blind side of the visual field to the seeing side.
With the goal of expanding the visual field on the blind side even farther, the researchers explored new optical techniques to create higher power image shifting devices designed to bend the light farther than the 30-degree limit of conventional prisms. In conventional prisms, increasing the angle eventually results in the light bending back into the prism, trapped by what is called “total internal reflection.”
“It’s not just that we need a device with a higher angle of light shifting to let them see farther,” said Dr. Peli (pictured right). “We also want the new devices to provide the additional range of vision when the patient scans their eyes in both directions. The current prism devices support such flexibility only when scanning into the seeing side.”
The authors introduced three new high-power prism concept devices in the Optometry and Vision Science paper:
Yoked Prisms in the Carrier Lens
By embedding the current prism in a spectacle lens that has prismatic power in the opposite direction, the image shifting effect is increased by the summation of the power of both prism types. This design allows for up to 36 degrees of expansion to the visual field on the patient’s blind side. This design permits 5 degrees of scanning range to the blind side with full effect.
Bi-Part Double Fresnel Prism
To increase the power of the peripheral prism, the bi-part double Fresnel prism combines two prism segments angled to each other. This design allows for up to 43 degrees of expansion to the visual field on the patient’s blind side and an increase to 14 degrees scanning range into the blind side.
Mirror-Based Periscopic Prism
The third approach — not yet fully manufactured — uses a pair of angled mirrors to deflect the image from the blind side to the seeing side — not unlike prism correction. Due to the mirror-based design, this device is distortion-free and does not suffer from the color splitting effect of prisms, which reduces image clarity. It may allow for up to 40 degrees of expansion to the visual field on the patient’s blind side with much wider scanning range permitted.
The researchers intend to fully design and implement the mirror-based periscopic prism and also begin testing all three designs in patients with hemianopia.
“The new optical devices can improve the functionality of the current prism devices used for visual field expansion and may find use in various other field expansion applications such as a mobility aid for patients with tunnel vision,” Dr. Peli said.
Materials provided by Massachusetts Eye and Ear Infirmary. Note: Content may be edited for style and length.
Eli Peli, Alex R. Bowers, Karen Keeney, Jae-Hyun Jung. High-Power Prismatic Devices for Oblique Peripheral Prisms. Optometry and Vision Science, 2016; 93 (5): 521 DOI: 10.1097/OPX.0000000000000820
via High-power prismatic devices may further expand visual fields for patients with hemianopia: Series of novel optical designs may address some limitations of existing prism technology, which can expand visual fields by up to 30 degrees — ScienceDaily