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Over many years, glaucoma has been defined by an intraocular pressure of more than 20 mm Hg. Incompatible with this (now obsolete) definition of glaucoma was the ever larger number of cases that have been reported in medical literature in the 1980s and 1990s who had the typical signs of glaucomatous damage, like optic nerve head excavation and thinning of the retinal nerve fiber layer, while ...
Conversely, optic nerve damage may occur with normal pressure, known as normal-tension glaucoma. [27] In case of above-normal intraocular pressure, the mechanism of open-angle glaucoma is believed to be the impeded exit of aqueous humor through the trabecular meshwork, while in closed-angle glaucoma, the iris blocks the trabecular meshwork. [ 2 ]
The optic nerve contains axons of nerve cells that emerge from the retina, leave the eye at the optic disc, and go to the visual cortex where input from the eye is processed into vision. There are 1.2 million optic nerve fibers that derive from the retinal ganglion cells of the inner retina. [2] Damage to the optic nerve can have different causes:
The optic disc can be flat or it can have a certain amount of normal cupping. But glaucoma, which is in most cases associated with an increase in intraocular pressure, often produces additional pathological cupping of the optic disc. The pink rim of disc contains nerve fibers. The white cup is a pit with no nerve fibers.
The blockage leads to greater-than-normal elevated intraocular pressure [2] which, in turn, can damage the optic nerve. [7] The eye produces a clear fluid called the aqueous humor which subsequently drains such that there is a constant level of safe pressure within the eye, but glaucoma can result if this normal outflow of fluid is blocked.
The ophthalmic nerve (CN V 1) is a sensory nerve of the head. It is one of three divisions of the trigeminal nerve (CN V) , a cranial nerve . It has three major branches which provide sensory innervation to the eye , and the skin of the upper face and anterior scalp , as well as other structures of the head.
RNFL asymmetry has been proposed as a strong indicator of optic neuritis, [7] [8] with one small study proposing that asymmetry of 5–6μm was "a robust structural threshold for identifying the presence of a unilateral optic nerve lesion in MS." [9] Optic neuritis is often associated with multiple sclerosis, and RNFL data may indicate the pace ...
The fibers from the retina run along the optic nerve to nine primary visual nuclei in the brain, from which a major relay inputs into the primary visual cortex. A fundus photograph showing the back of the retina. The white circle is the beginning of the optic nerve. The optic nerve is composed of retinal ganglion cell axons and glia.