Hemianopsia, or hemianopia, is a loss of vision or blindness ( anopsia) in half the

visual field The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a poin ...

, usually on one side of the vertical midline. The most common causes of this damage are

stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...

brain tumor A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and seco ...

, and trauma. This article deals only with permanent hemianopsia, and not with transitory or temporary hemianopsia, as identified by William Wollaston PRS in 1824. Temporary hemianopsia can occur in the aura phase of

migraine Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...

Etymology

The word ''hemianopsia'' is from Greek origins, where: * ''hemi'' means "half", * ''an'' means "without", and * ''opsia'' means "seeing".

Types

When the pathology involves both eyes, it is either homonymous or heteronymous.

Homonymous hemianopsia

Paris as seen with left homonymous hemianopsia. A

homonymous hemianopsia Hemianopsia, or hemianopia, is a visual field loss on the left or right side of the vertical midline. It can affect one eye but usually affects both eyes. Homonymous hemianopsia (or homonymous hemianopia) is hemianopic visual field loss on the s ...

is the loss of half of the visual field on the same side in both eyes. The visual images that we see to the right side travel from both eyes to the left side of the brain, while the visual images we see to the left side in each eye travel to the right side of the brain. Therefore, damage to the right side of the posterior portion of the brain or right optic tract can cause a loss of the left field of view in both eyes. Likewise, damage to the left posterior brain or left optic radiation can cause a loss of the right field of vision. Paris as seen with binasal hemianopsia.

Heteronymous hemianopsia

Paris as seen with bitemporal hemianopsia. A heteronymous hemianopsia is the loss of half of the

on different sides in both eyes. It is separated into two categories: *

Binasal hemianopsia 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. It is associated with certain lesions of the eye and of the central nervous system, ...

– the loss of the fields surrounding the nose; *

Bitemporal hemianopsia Bitemporal 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. It is usually associated with lesions of the optic chiasm, the area where the opt ...

– the loss of the fields closest to the temples.

Other forms

* Superior hemianopsia – the upper half of the field of vision is affected, possibly because of a tumor beginning to compress the lower part of the chiasma, typically one from the hypophysis. *

Inferior hemianopsia Inferior may refer to: * Inferiority complex * An anatomical term of location * Inferior angle of the scapula, in the human skeleton * ''Inferior'' (book), by Angela Saini * '' The Inferior'', a 2007 novel by Peadar Ó Guilín See also * Junio ...

– the lower half of the field of vision is affected, possibly because of a tumor beginning to compress the upper part of the chiasma, typically a

craniopharyngioma A craniopharyngioma is a rare type of brain tumor derived from pituitary gland embryonic tissue that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidence ...

Quadrantanopia

Quadrantanopia Quadrantanopia, quadrantanopsia, refers to an anopia (loss of vision) affecting a quarter of the visual field. It can be associated with a lesion of an optic radiation. While quadrantanopia can be caused by lesions in the temporal and parie ...

(quadrantanopsia or quadrantic hemianopsia) is decreased vision or blindness in one quarter of the visual field. The particular quarter of vision missing depends on whether the location of the brain damage is temporal or parietal, and the side of the lesion. For example, a lesion to the right temporal lobe with damage specifically to

Meyer's loop In neuroanatomy, the optic radiation (also known as the geniculocalcarine tract, the geniculostriate pathway, and posterior thalamic radiation) are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex. The optic ...

will give rise to a left upper (superior) quadrantanopsia, while a lesion to the right parietal radiation with damage specifically to Baum's loop will result in a left lower (inferior) quadrantanopsia.

Visual neglect

Visual neglect (also called hemispatial neglect or unilateral spatial neglect) differs from hemianopsia in that it is an attentional deficit rather than a visual one. Unlike patients with hemianopsia who actually don't see, those with visual neglect have no trouble seeing but are impaired in attending to and processing the visual information they receive. Whereas hemianopsia can be assuaged by allowing patients to move their eyes around a visual scene (ensuring that the entire scene makes it into their intact visual field), neglect cannot. Neglect can also apply to auditory or tactile stimuli and can even leave a patient unaware of one side of his or her own body. Ellis and Young (1998) showed that neglect can also affect patients' mental maps such that if they are asked to picture themselves standing in a familiar location and name the buildings around them, they will neglect to name the buildings on their impaired side but will be able to name them when asked to mentally face the opposite direction. Some patients with neglect also have hemianopsia, however the two often occur independent of one another.

Management

Some forms of hemianopia can be treated through repeated presentations of multisensory stimuli due to the process of

multisensory integration Multisensory integration, also known as multimodal integration, is the study of how information from the different sensory modalities (such as sight, sound, touch, smell, self-motion, and taste) may be integrated by the nervous system. A coherent ...

occurring in the

superior colliculus In neuroanatomy, the superior colliculus () is a structure lying on the roof of the mammalian midbrain. In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe. The adjective form '' tectal'' is common ...

. Surgical interventions have also been shown to ameliorate certain forms of hemianopia due to counterbalancing brain lesions due to a process known as the Sprague effect.

Notes

References

*O'Neill, E., O'Connor, J., Brady, J., Reid, I., and Logan, P. Prism Therapy and Visual Rehabilitation in Homonymous Visual Field Loss. 2011 Optometry and Vision Science, Vol. 88, No 2 February 2011. *Giorgi, RG., Woods, RI., Peli, E. Clinical and Laboratory Evaluation of Peripheral Prism Glasses for hemianopsia. Optometry and Vision Science 2009; 86: 492-502.

External links

{{Use dmy dates, date=April 2017 Blindness Brain disorders Visual perception