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The optic nerve can be damaged when exposed to direct or indirect injury. Direct optic nerve injuries are caused by trauma to the head or orbit that crosses normal tissue planes and disrupts the anatomy and function of the optic nerve; e.g., a bullet or forceps that physically injures the optic nerve.
The optic nerve is the bundle of axons that carry the visual signals from the eye to the brain. This optic nerve must penetrate through the wall of the eye, and the hole to accommodate this is usually 20-30% larger than the nerve diameter. In some patients the optic nerve is nearly as large as the opening in the back of the eye, and the optic ...
Here, 2% xylocaine is introduced into the muscle cone behind the eyeball. The injection is usually given through the inferior fornix of the skin of the outer part of the lower lid when the eye is in primary gaze. The ciliary nerves, ciliary ganglion, oculomotor nerve and abducens nerve are anesthetized in retrobulbar block. [2]
The most common cause is multiple sclerosis (MS) or ischemic optic neuropathy due to thrombosis or embolism of the vessel that supplies the optic nerve. [ 13 ] [ 14 ] Up to 50% of patients with MS will develop an episode of optic neuritis, and 20–30% of the time optic neuritis is the presenting sign of MS .
The exact mechanism of optic nerve ischemia in these cases remains unclear, but contributing factors may include hypotension, anemia, hypoxia, and changes in the autoregulation of optic nerve arterial blood flow. The incidence of ischemic optic neuropathy leading to vision loss following general surgeries ranges between 0.1% and 0.002%.
The optic tract is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus. [14] The optic tract represents the first stage in the visual pathway in which visual information is transferred in a homonymous nature. [ 15 ]
The anterior optic nerve receives blood primarily from the posterior ciliary arteries. The anterior optic nerve, a.k.a. the optic nerve head, is surrounded by the scleral canal, and is vulnerable to crowding of nerve fibers. The portion of the optic nerve head that is visible by looking into the eye with an ophthalmoscope is called the optic disc.
The optic disc may appear mildly hyperemic with small splinter hemorrhages on or around the disc, or may appear nearly normal. Optic atrophy typically develops later and may appear mild. In later stages the optic atrophy can become severe, which indicates less opportunity for recovery. [3]
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