ISCHEMIC OPTIC NEUROPATHY
Ischemia
Ischemia of the optic nerve results in ischemic optic neuropathy [17, 24, 36, 49, 57, 74]. Ischemia is a decrease in the blood supply to a tissue in the body which in turn decreases oxygen and nutrition. Without sufficient oxygen and nutrition, nerves cannot function properly and will eventually die. As an example, placing a tight rubber band around the wrist causes the fingers to begin to tingle and then lose the sensation of touch because the rubber band cuts off the blood supply, starving the nerves of oxygen and nutrients. If the blood supply to the optic nerve is interrupted, it produces ischemia of the optic nerve (technical name, "ischemic optic neuropathy"), and a loss of vision develops. The blood supply of the anterior (Fig. 1-A) of the optic nerve (also called the optic nerve head) is mainly by the posterior ciliary arteries, while the blood supply to the posterior part (back part of Fig. 1-B) is from several quite different sources but not the posterior ciliary arteries [4-6, 8, 9, 13, 18, 25, 30, 35, 36, 49, 52, 74].
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Fig. 1: Schematic
representation of blood supply of: (A) the optic nerve head and (B) the
optic nerve. Abbreviations: A = arachnoid; C = choroid; CRA = central retinal artery; Col. Br. = Collateral branches; CRV = central retinal vein; D = dura; LC = lamina cribrosa; NFL = surface nerve fiber layer of the disc; OD = optic disc; ON = optic nerve; P = pia; PCA = posterior ciliary artery; PR and PLR = prelaminar region; R = retina; RA = retinal arteriole; S = sclera; SAS = subarachnoid space. |
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Design