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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 ]
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.
Retrobulbar neuritis, an inflamed optic nerve, but with a normal-appearing nerve head, is associated with pain and the other findings of papillitis. Pseudopapilledema is a normal variant of the optic disk , in which the disk appears elevated, with indistinct margins and a normal vascular pattern.
NAION is believed to be caused by reduced blood flow to the optic nerve head. It can lead to permanent visual loss in one eye that may develop painlessly and suddenly or over several days before ...
On medical examination the head of the optic nerve can easily be visualized by a slit lamp with a high positive lens or by using direct ophthalmoscopy; however, frequently there is no abnormal appearance of the nerve head in optic neuritis (in cases of retrobulbar optic neuritis), though it may be swollen in some patients (anterior papillitis ...
The term "disc-at-risk" refers to an optic nerve head characterized by a small cup-to-disc ratio and a crowding of optic nerve fibers. This anatomical feature is a significant factor in the development of NAION. [4] [5] Individuals predisposed to this condition typically have smaller optic discs with minimal or no cupping. This anatomical ...
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.
[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 ...