View source for Visual field defects

<section begin="neuro 1" />Vision is a complex process which involves many neurological structures. Different parts of the vision depends on different structures. As such, a great variety of '''visual field defects''' (areas of the visual field with defective or absent vision) can occur depending on which structure is affected.

Homonymous vision loss = same side is lost on both eyes. E. g. temporal half on left eye and nasal half on right eye

Heteronymous vision loss = opposing regions are lost. E. g. temporal half on left eye and temporal half on right eye

Hemianopia = loss of half the vision field

Quadrantanopia = loss of one quarter of the vision field

== Types ==

* Complete unilateral vision loss
** Due to pre-chiasmal lesion (retina or optic nerve)
* Bitemporal heteronymous hemianopia
** = bilateral loss of temporal visual field
** Due to lesion of the middle part of the optic chiasm
** Fibres transmitting the nasal part of the visual field crosses in the optic chiasm
** Fibres transmitting the temporal part of the visual field does not cross
* Ipsilateral nasal hemianopia
** = ipsilateral loss of nasal visual field
** Due to lesion of the lateral part of the optic chiasm
* Binasal heteronymous hemianopia
** = bilateral loss of nasal visual field
** Due to lesion of both lateral parts of the optic chiasm
* Contralateral homonymous hemianopia
** = loss of the ipsilateral nasal and contralateral temporal visual fields
** Due to lesion of the optic tract
** The optic tract transmits information from the ipsilateral nasal visual field and the contralateral temporal visual field
* Contralateral homonymous upper quadrantanopia
** = loss of ipsilateral upper nasal quadrant and contralateral upper temporal quadrant
** Due to lesion of
*** Anterior part of optic radiation
*** Lower part of calcarine fissure
* Contralateral homonymous lower quadrantanopia
** = loss of ipsilateral lower nasal quadrant and contralateral lower temporal quadrant
** Due to lesion of
*** Posterior part of optic radiation
*** Upper part of calcarine fissure
* Contralateral homonymous hemianopia with central sparing
** = loss of the ipsilateral nasal and contralateral temporal visual fields, but the central vision remains intact
** Due to lesion of the occipital lobe
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[[Category:Neurology]]