Quadrantanopia, quadrantanopsia, or quadrant anopia refers to an anopia affecting a quarter of the field of vision.

It can be associated with a lesion of an optic radiation

Optic radiation

The optic radiation is a collection of axons from relay neurons in the lateral geniculate nucleus of the thalamus carrying visual information to the visual cortex along the calcarine fissure.There is one such tract on each side of the brain.-Parts:A distinctive...

. If Meyer's loop (temporal pathway) is lesioned, the vision loss is superior (colloquially referred to as "pie in the sky"); if Baum's loop (parietal pathway) is lesioned, the vision loss is inferior.