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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 ...
Ocular hypertension is the presence of elevated fluid pressure inside the eye (intraocular pressure), usually with no optic nerve damage or visual field loss. [1] [2]For most individuals, the normal range of intraocular pressure is between 10 mmHg and 21 mmHg. [3]
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]
Ocular hypertension (OHT) is defined by intraocular pressure being higher than normal, in the absence of optic nerve damage or visual field loss. [13] [14] Ocular hypotension, hypotony, or ocular hypotony, is typically defined as intraocular pressure equal to or less than 5 mmHg.
Intra-ocular pressure ISNT: Inferior, Superior, Nasal, Temporal ... Normal retinal correspondence NV ... Optic nerve head Oph Ophthalmoscopy OS
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.
Hence the pressure is asymmetrical and this causes a pinching and protrusion of the optic nerve at its head. The fibers of the retinal ganglion cells of the optic disc become engorged and bulge anteriorly. Persistent and extensive optic nerve head swelling, or optic disc edema, can lead to loss of these fibers and permanent visual impairment.
[7] [8] The facial nerve (seventh cranial nerve) is affected occasionally – the result is total or partial weakness of the muscles of facial expression on one or both sides of the face. [5] The increased pressure leads to papilledema, which is swelling of the optic disc, the spot where the optic nerve enters the eyeball. This occurs in ...