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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 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] Edema is seen in and around the optic nerve head also ...
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 ...
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.
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 ...
Schematic diagram of the human eye, with the optic disc, or blind spot, at the lower left. Shown is a horizontal cross section of the right eye, viewed from above. A normal optic disc is orange to pink in colour and may vary based on ethnicity. [3] A pale disc is an optic disc which varies in colour from a pale pink or orange colour to white. A ...
The test is a dye tracing method. The fluorescein dye also reappears in the patient urine, causing the urine to appear darker, and sometimes orange. [2] It can also cause discolouration of the saliva. Fluorescein angiography is one of several health care applications of this dye, all of which have a risk of severe adverse effects.
There was no evidence of disc edema in the left eye or choroidal folds in either eye (Figure 13). MRI of the brain and eyes days postflight revealed bilateral flattening of the posterior globe, right greater than left, and a mildly distended right optic nerve sheath. There was also evidence of optic-disc edema in the right eye.