Homonymous hemianopsia
Encyclopedia
Hemianopsia or hemianopia is visual field loss that respects the vertical midline, and usually affects both eyes, but can involve one eye only. Homonymous hemianopsia, or homonymous hemianopia occurs when there is hemianopic visual field loss on the same side of both eyes. Hemianopias occur because the right half of the brain has visual pathways for the left hemifield of both eyes, and the left half of the brain has visual pathways for the right hemifield of both eyes.
Vascular
and neoplastic (malignant or benign tumours) lesions from the optic tract
, to visual cortex
can cause a contralateral homonymous hemianopsia. Injury to the right side of the brain will affect the left visual fields of each eye. The more posterior the cerebral lesion, the more symmetric (congruous) the homonymous hemianopsia will be. For example, a person who has a lesion of the right optic tract
will no longer see objects on his left side. Similarly, a person who has a stroke to the right occipital lobe
will have the same visual field defect, usually more congruent between the two eyes, and there may be macular sparing.
A stroke on the right side of the brain (especially parietal lobe), in addition to producing a homonymous hemianopsia, may also lead to the syndrome of hemispatial neglect
.
Transient homonymous hemianopsia does not necessarily mean stroke. For instance, it can constitute the aura phase of migraine. Concomitant presence of a moving scintillating scotoma
is suggestive of migraine, but has been seen in cerebral cancer as well.. Computed tomography
(CT scan) or MRI can be used to investigate if stroke, tumor,structural lesion, or demyelination is the cause of homonymous hemianopsia.
Mobility can be difficult for people with homonymous hemianopia. “Patients frequently complain of bumping into obstacles on the side of the field loss, thereby bruising their arms and legs.”3
People with homonymous hemianopia often experience discomfort in crowds. “A patient with this condition may be unaware of what he or she cannot see and frequently bumps into walls, trips over objects or walks into people on the side where the visual field is missing.”5
Peripheral prism spectacles expand the visual field of patients with hemifield visual defects and have the potential to improve visual function and mobility.4 Prism spectacles incorporate higher power prisms, with variable shapes and designs. The Gottlieb button prism, and the Peli superior and inferior horizontal bands are some proprietary examples of prism glasses. These high power prisms "create" artificial peripheral vision into the blind field for obstacle avoidance and motion detection.
Proponents of the Peli lens have provided the information below: "The Peli Lens was developed as a mobility aid for homonymous hemianopia by Dr. Eli Peli of the Schepens Eye Research Institute (SERI), an affiliate of Harvard University 3 and is manufactured by Chadwick Optical, Inc.. Dr. Peli’s technique provides a measurable 20º expansion of the visual field while leaving central field unobstructed. More information is available and pictures can be viewed at www.Hemianopia.org. Results of clinical trials using this technique were published in 2008 and reported a 74% patient acceptance rate.4 The Peli company cites a paper entitled “Rehabilitation of hemianopia”. which suggests that “given the relatively low cost of these lenses, perhaps a test pair of adaptive glasses should be offered to suitable patients on a two month trial basis.“ 2 An improved version of the Peli Lens expanding the visual field by 30 degrees is available. Clinical trial results are pending."
Homonymous hemianopsia is also called Homonymous hemianopia.
Causes
Homonymous hemianopsa can be congenital, but is usually caused by brain injury such as from stroke, trauma, tumors, infection, or following surgery.Vascular
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
and neoplastic (malignant or benign tumours) lesions from the optic tract
Optic tract
The optic tract is a part of the visual system in the brain.It is a continuation of the optic nerve and runs from the optic chiasm to the lateral geniculate nucleus....
, to visual cortex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
can cause a contralateral homonymous hemianopsia. Injury to the right side of the brain will affect the left visual fields of each eye. The more posterior the cerebral lesion, the more symmetric (congruous) the homonymous hemianopsia will be. For example, a person who has a lesion of the right optic tract
Optic tract
The optic tract is a part of the visual system in the brain.It is a continuation of the optic nerve and runs from the optic chiasm to the lateral geniculate nucleus....
will no longer see objects on his left side. Similarly, a person who has a stroke to the right occipital lobe
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
will have the same visual field defect, usually more congruent between the two eyes, and there may be macular sparing.
A stroke on the right side of the brain (especially parietal lobe), in addition to producing a homonymous hemianopsia, may also lead to the syndrome of hemispatial neglect
Hemispatial neglect
Hemispatial neglect, also called hemiagnosia, hemineglect, unilateral neglect, spatial neglect, unilateral visual inattention, hemi-inattention or neglect syndrome is a neuropsychological condition in which, after damage to one hemisphere of the brain, a deficit in attention to and awareness of...
.
Transient homonymous hemianopsia does not necessarily mean stroke. For instance, it can constitute the aura phase of migraine. Concomitant presence of a moving scintillating scotoma
Scintillating scotoma
Scintillating scotoma is the most common visual aura preceding migraine and was first described by 19th century physician Hubert Airy . It is often confused with ocular migraine which originates in the eyeball or socket.-Presentation:...
is suggestive of migraine, but has been seen in cerebral cancer as well.. Computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
(CT scan) or MRI can be used to investigate if stroke, tumor,structural lesion, or demyelination is the cause of homonymous hemianopsia.
Effects
People with homonymous hemianopia often experience discomfort in crowds. “A patient with this condition may be unaware of what he or she cannot see and frequently bumps into walls, trips over objects or walks into people on the side where the visual field is missing.”5
Vision Restitution Therapy
If hemianopsia has not improved by 6-12 months, it is unlikely to improve. The restoration of peripheral vision by "visual stimulation" is difficult. Many researchers feel that vision restitution therapy helps more with adaptive eye movements in to the blind hemifield, rather than restoration of the lost peripheral vision. Products such as NovaVision and VisioCoach are commercially available.Help With Mobility
Prisms or "field expanders" that bend light have been described for decades in patients with hemianopsia. Higher power Fresnel ("stick-on") prisms are commonly employed because they are thin and light weight, and can be cut and placed in different positions on a spectacle lens.Peripheral prism spectacles expand the visual field of patients with hemifield visual defects and have the potential to improve visual function and mobility.4 Prism spectacles incorporate higher power prisms, with variable shapes and designs. The Gottlieb button prism, and the Peli superior and inferior horizontal bands are some proprietary examples of prism glasses. These high power prisms "create" artificial peripheral vision into the blind field for obstacle avoidance and motion detection.
Proponents of the Peli lens have provided the information below: "The Peli Lens was developed as a mobility aid for homonymous hemianopia by Dr. Eli Peli of the Schepens Eye Research Institute (SERI), an affiliate of Harvard University 3 and is manufactured by Chadwick Optical, Inc.. Dr. Peli’s technique provides a measurable 20º expansion of the visual field while leaving central field unobstructed. More information is available and pictures can be viewed at www.Hemianopia.org. Results of clinical trials using this technique were published in 2008 and reported a 74% patient acceptance rate.4 The Peli company cites a paper entitled “Rehabilitation of hemianopia”. which suggests that “given the relatively low cost of these lenses, perhaps a test pair of adaptive glasses should be offered to suitable patients on a two month trial basis.“ 2 An improved version of the Peli Lens expanding the visual field by 30 degrees is available. Clinical trial results are pending."
Etymology
Homonymous hemianopsia can be broken down as follows:- Homonymous: having the same name
- hemi: half
- anopsia: blindness
Homonymous hemianopsia is also called Homonymous hemianopia.
See also
- Binasal hemianopsiaBinasal hemianopsiathumb|Paris as seen with full visual fieldsthumb|Binasal hemianopsia is the medical description of a type of partial blindness where vision is missing in the inner half of both the right and left visual field...
- Bitemporal hemianopsiaBitemporal hemianopsiaBitemporal hemianopsia is the medical description of a type of partial blindness where vision is missing in the outer half of both the right and left visual field...
- British Columbia (Superintendent of Motor Vehicles) v. British Columbia (Council of Human Rights)British Columbia (Superintendent of Motor Vehicles) v. British Columbia (Council of Human Rights)British Columbia v. British Columbia , [1999] 3 S.C.R. 868, known as the Grismer Estate case, is a leading Supreme Court of Canada decision on human rights law...
- Vision restoration therapyVision restoration therapyVision Restoration Therapy is a noninvasive, nonsurgical form of Vision therapy provided by NovaVision. This therapy was developed by Bernhard Sabel, Ph.D...