Synsbanen

Synsbanen, or the visual pathway, is the neural route that transmits visual information from the retina to the primary visual cortex. It includes the optic nerve, the optic chiasm where nasal retinal fibers cross to the opposite side, the optic tract, the lateral geniculate nucleus of the thalamus, the optic radiations, and the primary visual cortex in the occipital lobe.

Anatomy and organization: signals originate in retinal ganglion cells and travel via the optic nerve from each eye. At the chiasm, nasal fibers cross while temporal fibers stay on the same side. After the chiasm, fibers form the optic tracts and relay to the LGN. From the LGN, the pathways project through the optic radiations to the calcarine sulcus of the occipital cortex. Within the visual cortex, dorsal and ventral streams process motion/space and form/color, respectively.

Development and function: the synsbanen develops from the retina and diencephalon during embryogenesis and is essential for conscious vision, depth perception, color discrimination, and motion detection. It integrates with higher-order visual areas to interpret complex scenes.

Clinical significance: lesions at different points produce characteristic visual field defects. Optic nerve damage causes monocular vision loss; chiasm lesions lead to bitemporal hemianopia; post-chiasmatic tract lesions cause contralateral homonymous hemianopia or quadrantanopia, depending on location. Conditions affecting the pathway include optic neuritis, glaucoma, stroke, tumors, and demyelinating diseases.

See also: optic nerve, visual cortex, visual field, and visual pathways.