Optic radiations - Definition and Overview

Right superior quadrantanopia. The areas of the visual field lost in each eye are shown as black areas. This visual field defect is characteristic of damage to Meyer's loop on the left side of the brain.

The optic radiations consist of axons of relay neurons in the lateral geniculate nucleus (LGN) which run from the LGN to the visual cortex.

A distinctive feature of the optic radiations is the fact that they split into two parts on each side.

The fibers which run more inferiorly must loop around the inferior horn of the lateral ventricle. These fibers, which carry information from the superior part of the visual world, are called Meyer's loop or Archambault's loop.

The fibers which run more superiorly travel straight back in the retrolenticular limb of the internal capsule to the visual cortex. They carry information from the inferior part of the visual world and, taking the shorter path, are less susceptible to damage.

Damage to Meyer's loop causes a characteristic visual field defect, as shown.