• Clinical science

Disorders of the visual pathway

Overview

The visual pathways transmit signals from the retina to the visual cortex (striate cortex, brodmann area 17).

Structure Characteristics Lesions Causes
Retina
  • Cones and rods transform light into visual signals, which are projected to the brain via the optic nerve.
Optic nerve
  • Transmits visual information from the ipsilateral retina to the brain
  • Afferent limb of pupillary reflex and accomodation reflex
Optic chiasm
  • Fibers from nasal part of the retina cross to contralateral side
  • Fibers from the temporal part of the retina do not cross to the contralateral side
Optic tract

Lateral geniculate nucleus (LGN)

  • Transmits information of the
    • ipsilateral, nasal visual field
    • contralateral, temporal visual field
  • Projects to primary visual cortex via optic radiations
  • MCA infarction
Optic radiations
  • Anterior/lateral bundle in Meyer loop
    • Passes through the temporal lobe in close proximity to the inferior horn of the lateral ventricle
    • Transmits information of the superior visual field from the lower retina
    • Projects to the lingual gyrus
  • Posterior/medial bundle
    • Located in the parietal lobe, passes through the internal capsule
    • Transmits information of the inferior visual field infromation from the upper retina
    • Projects to the cuneus gyrus
Visual cortex

Unilateral visual field loss → pathology mainly in front of the optic chiasm. Bilateral visual field loss → pathology mainly in or behind the optic chiasm

References:[1][2]

Prechiasmal visual pathway damage

Prechiasmal damage to the visual pathway mainly involves the optic nerve.For retinal diseases see table above.

Optic nerve

Optic neuritis

Multiple sclerosis is the most common cause of optic neuritis!

Optic atrophy

Anterior ischemic optic neuropathy (AION)

  • Definition: segmental or generalized infarction of the anterior part of the optic nerve
  • Etiology
  • Clinical features
    • Sudden unilateral loss of vision
    • Wedge-shaped and altitudinal visual field defects
    • AAION: other symptoms of giant cell arteritis
  • Diagnostics
    • Fundoscopy
    • Laboratory findings
    • AAION: temporal artery biopsy
  • Treatment
  • Prognosis
    • Typically poor: permanent loss of vision
    • Involvement of the other eye is common during the course of the disease.

Immediate high-dose glucocorticoid treatment is essential in AAION!

Papilledema

Damage in the region of the optic chiasm

Retrochiasmal visual pathway damage

last updated 08/12/2019
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