Lebers Hereditary Optic Neuropathy Definition

Leber's hereditary optic neuropathy (LHON) is a mito-chondrially inherited, severe, initially monocular but within weeks binocular visual loss, most commonly in young men.

The visual acuity in LHON is reduced to 20/200 or worse. The visual field shows a large, central or cecocentral sco-toma, and color perception is badly damaged. The acute phase is marked by a peripapillary microangiopathy with irregular areas of microvascular dilation, tortuosity, and variations in caliber sometimes described as telangiecta-sias. The next stage (within a few weeks) is marked by increasing optic disc pallor and a disappearance of the initial microangiopathy. It is notable that the microangiopathy can be found in asymptomatic carriers of the maternally inherited deficit.

The diagnosis can be confirmed by identification of the causative mutations in the mitochondrial DNA (point mutations, usually at nucleotide positions of 3460, 11778, or 14484, and much less commonly, other sites). There is no specific or effective therapy. Patients and their families should be told to avoid sources of trace cyanide (secondary exposure to cigarette smoke and cyanide-carrying foods such as bitter almonds, apricot pits, pear or apple seeds, and white lima beans).

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