[Posterior ischaemic optic neuropathy].

Here one case report of the posterior ischaemic optic neuropathy, a rare and underdiagnosed form of the non arteritic ischaemic optic neuropathy is presented, to underline the value of the MRI in the diagnosis. The ischaemic optic neuropathy is the infarction of the optic nerve. Depending on the affected segment of optic nerve (optic nerve head or retrobulbar segment) two subclasses exist: the anterior (AION) and the posterior (PION) ischaemic optic neuropathy. Ischaemic optic neuropathy characterized by sudden, painless, mononuclear loss of vision, and/or visual field defect, that is accompanied by a diagnostic picture of the optic disc fundus only in the case of the AION. The diagnosis of the PION is based on a diagnosis of exclusion described by Hayreh in 1981. The macular and retinal lesions, the etiological role of toxic agent, the compression and the inflammation of the optic nerve all have to be excluded. The differential diagnosis between the PION and the retrobulbar neuritis is more difficult. Nowadays, in addition to the case history and the clinical data the diagnosis of the PION could be confirmed with help of VEP (visual evoked potential) and MRI. In the case of an old woman who had a sudden, painless visual loss of left eye we confirmed the diagnosis of PION with MRI which was presumed after had excluding other etiological factors.