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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 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 ...
Ischemic optic neuropathy (ION) is the loss of structure and function of a portion of the optic nerve due to obstruction of blood flow to the nerve (i.e. ischemia).Ischemic forms of optic neuropathy are typically classified as either anterior ischemic optic neuropathy or posterior ischemic optic neuropathy according to the part of the optic nerve that is affected.
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.
Temporal arteritis is an inflammatory disease of medium-sized blood vessels that happens especially with advancing age. AAION occurs in about 15-20 percent of patients with temporal arteritis. Damage to the blood vessels supplying the optic nerves leads to insufficient blood supply to the nerve and subsequent optic nerve fiber death. Most cases ...
Unilateral or bilateral optic disc edema may occur. The exact etiology, pathogenesis and mechanism of the disc edema is unknown. [1] [2] Theories suggest that the dis edema is due to retinal vascular leakage into and surrounding the optic nerve and disruption of axoplasmic flow resulting from microvascular disease of the optic nerve head. [2]
However, the anterior end of the optic nerve stops abruptly at the eye. 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 ...