Home > Optic nerve

1 Anatomy

The nerve is the second of twelve paired cranial nerves but is usually considered to be part of the central nervous system as it is derived from an outpouching of the diencephalon during embryonic development. Its nerve fibers mainly extend from the retina to the primary visual cortex.

The optic nerve arises from ganglionic cell s of the eye's retina. It leaves the orbit (eye) via the optic canal , running postero-medially towards the optic chiasm where there is a decussation (crossing) of fibres from the temporal visual fields of both eyes. Its axons terminate in the lateral geniculate nucleus from where information is relayed to the visual cortex and superior colliculus from where spinotectal reflexes are mediated.

From the lateral geniculate body, fibers of the optic radiation pass to the visual cortexThe visual cortex is the part of the cerebral cortex that is responsible for processing visual stimuli. It is located at the back of the brain in the occipital lobe. It is highly specialized for processing information about static and moving objects and i in the occipital lobeThe occipital lobes are the visual processing center of mammalian brains. The primary visual area is Brodmann area 17, located in the interior portion of the occipital lobe at the calcarine sulcus and sometimes continuing onto the surface of the lobe. of the brain. More specifically, fibers carrying information from the contralateral superior visual field traverse Meyer's loop to terminate in the lingual gyrus below the calcarine fissure in the occipital lobe, and fibers carrying information from the contralateral inferior visual field terminate more superiorly.

2 Physiology

The optic nerve contains roughly one million nerve fibers. This number is low compared to the roughly 130 million receptors in the retina, and implies that substantial pre-processing takes place in the retina before the signals are sent to the brain through the optic nerve.

The blind spotThe term blind spot has several meanings. All are related to an inability to perceive, usually in a visual sense. In anatomy, one's blind spot is the region of the retina where the optic nerve and blood vessels pass through to connect to the back of the e of the eye lies in the part of the retina where the optic nerve leaves the eye. This is because there are no photoreceptorPhotoreceptors are light-sensitive proteins involved in the function of photoreceptor cells. Some examples are rhodopsin in our retina, phytochrome in plants, and bacteriorhodopsin in some bacteria. Photoreceptor can also refer to the cells found in ommats in this area.

3 Role in disease

Damage to the optic nerve typically causes an abnormal pupillary reflexIn medicine, pupil constriction (also known as the pupillary reflex is reduction of pupil size. It is the normal response of the pupil of the eye to light and dependent on the function of the optic nerves and oculomotor nerves. It is also important in acc and loss of visionVision can refer to: Visual perception is one of the senses. vision (religion) "Vision" can mean an imagined picturing originating with not-so-divine sources: politicians, business planners and change gurus play on this sense of the word. A company vision. The type of visual field loss will depend on which optic nerve was damaged and where the damage occurred:

• Damage before the optic chiasm affect vision in one eye only.
• Damage in the chiasm causes loss of vision laterally in both eyes (bitemporal hemianopia). It may occur in large pituitary adenomata.
• Damage after the chiasm causes loss of vision on one side but affecting both eyes: the visual field affected is located on the opposite side of the lesion.