Chapter contents
Overview
Sensory transduction
Central course
Primary visual cortex
Retinal deficits
Optic nerve damage
Chiasm damage
Damage posterior to chiasm
| Cranial Nerve II - Optic Nerve | Page 6 of 11 |
Retinal Projections to the Primary Visual Cortex
Because fibers from different quadrants of the retina project to the primary visual cortex via predictable portions of the optic nerves, chiasm, and tracts it is convenient and clinically useful to divide the retina (and therefore the visual field) of each eye into nasal and temporal halves as well as superior and inferior halves yielding four quadrants.
The regions of the retina are referenced to the midline. The nasal hemiretina lies medial to the fovea, while the temporal hemiretina lies lateral to the fovea. The superior and inferior halves of the retina are also referenced to the fovea.
Axons of ganglion cells from the nasal hemiretina (lateral visual field) decussate at the optic chiasm and project to the contralateral lateral geniculate nucleus and midbrain.
Axons from the temporal hemiretina (medial visual field) remain ipsilateral throughout their course.
Axons from the inferior half of the retina (upper visual field) project via the Meyer's loop/temporal lobe portion of the optic radiation to the primary visual cortex below the calcarine fissure.
Axons from the superior half of the retina (lower visual field) project via the parietal lobe portion of the optic radiation to the primary visual cortex above the calcarine fissure.
Ganglion cells from the center of the retina (fovea) project to the tip of the occipital pole.
