Anatomy of the visual system and the types of visual field defects

1. Big picture

For the exam, this topic is mainly a localization topic. A visual field defect tells you where the lesion is in the visual pathway:

• Monocular defect → retina or optic nerve, before the chiasm.

• Bitemporal defect → optic chiasm.

• Homonymous defect → retrochiasmal lesion: optic tract, lateral geniculate body, optic radiation, or occipital cortex.

• Quadrantanopia → usually optic radiation or partial occipital cortex lesion.

• Cortical blindness → bilateral occipital cortex lesion, classically with preserved pupillary reflexes.

Always examine CN II by checking visual acuity, visual field, and optic fundus.