Optic nerve

The optic nerve (2° cranial nerve) is the “electric wire” that connects our camera (ie the eye) to the brain. In fact carries sensory nerve impulses from more than one million ganglion cells (for more information about the central vision) of the retina to the visual centers of the occipital cortex. The head of the optic nerve, placed in the posterior pole, can be observed by looking at the fundus (optic disc or optical disc ), has a diameter of about 1,5 mm and is classically described "Sharp margins and a pink. The optic nerve is formed by axons ganglion cell. The cells of the retina are stratified into cellshorizontal, bipolar, amacrine and ganglion. The axons of the latter, we said, form the optic nerve which continues behind the bulb, in orbital stretch and in tract intracranial. At this point the optic nerve of each eye meets with each other giving rise to a structure in the shape of "X" said optic chiasm. At this crossroads of nerve fibers, located just above the pituitary gland, about half of the optical fibers of each eye decussano (ie intersect) and then reach a particular nucleus (the lateral geniculate body) and continue in the visual radiation (optical radiation ) the opposite side to reach the occipital lobes in the back of the brain (calcarine area). This particular course of the optical fibers allows the vision binocular. The area occupied by the retinal optic nerve, is obviously lacks photoreceptors and is known as"Blind spot" to the visual field and is a small area in which we do not see, but that in the performance of daily activities is never perceived. The retina, the optic disc, the optic nerve, the optic chiasm, the optic tract, optical radiation and the visual centers of the brain are topographically organized to allow the perception of binocular field of vision. Therefore, damage or compression involving these structures results, symptomatically, a specific deficit in the visual field (provided that being completely painless can not be recognized by the patient). Tai campimetrici deficits occur in glaucoma, where increased pressure in the eye slowly and directly damage nerve fibers and in various vascular diseases, inflammatory and toxic substances that may involve the optic nerve (this Optic neuritis). Direct and indirect damage to the optic nerve is irreversible because as mentioned, consists of nerve fibers that have very little capacity for regeneration.