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9: Neuro-ophthalmic look-alikes using .net vs 2010 tobuild data matrix ecc200 on web,windows application QR Codes is a thickened app .net vs 2010 Data Matrix ECC200 earance of the nerve ber layer, termed pseudo-edema . This characteristic fundus appearance may be present prior to the onset of visual loss and can also be seen in about half of unaffected family members, many of whom never progress to visual loss.

In about one-third of patients with symptomatic LHON, the disc has a completely normal appearance at the time of initial visual loss. Hence, a normal fundus appearance in no way rules out a diagnosis of LHON. In some cases, optic atrophy has already developed by the time the patient is evaluated.

LHON is a maternally inherited disorder due to a point mutation in the mitochondrial DNA complex I genes. Four mutations (11778, 3460, 14484 and 14459) are considered primary and account for approximately 95% of cases, with the 11778 mutation alone accounting for about 50%. A fth, 15257, may be another primary LHON mutation but is also found in low frequency in control groups.

Genetic testing is strongly recommended, not only for diagnostic con rmation, but also for prognostic value. In most patients with symptomatic LHON, visual loss is usually profound and permanent. Yet an occasional patient experiences some degree of spontaneous improvement and the likelihood of such recovery is related to the speci c mutation.

Only 4% of patients with the common 11778 mutation experience visual improvement, whereas the other mutations are associated with a higher percentage of spontaneous visual recovery. The onset of visual recovery, when it does occur, can be surprisingly delayed, occurring from three months to several years after initial visual loss. There is currently no effective treatment for visual loss due to LHON.

Exogenous factors such as systemic infection, nutritional de ciency, medications and exposure to toxins have been explored as possible triggers that may provoke the onset or increase the risk of phenotypic expression, but no de nite causal relationship has been con rmed for any of these. Nonetheless, patients who harbor a LHON mutation are strongly advised to discontinue smoking, avoid exposure to solvents and other fumes and take daily vitamin supplements..

Genetic counsellin g is an important aspect of management in patients with LHON. Phenotypic penetrance of the LHON mutation is notably incomplete; many individuals carry the mutation but never suffer visual loss. Because all mitochondria are maternally inherited, men with the LHON mutation never pass on the disorder and male patients should be assured of this fact.

However, all female relatives of a male proband are obligatory carriers, and will necessarily transmit the mutation to all their children. In addition to being carriers, 5 to 20% of females with a primary LHON mutation will eventually experience visual loss. In contrast, male carriers have a much greater lifetime risk of visual loss, ranging from 25 to 60%.

The basis for this genderspeci c susceptibility is unknown. Since the availability of genetic testing for this disorder, our understanding of the clinical features has greatly expanded, including con rmed cases of LHON occurring in young children and in individuals over age 65 years. Atypical temporal patterns have also been described, including sudden bilateral blindness and protracted visual deterioration over years.

These variations in the phenotype serve as reminders that LHON should be included in the differential diagnosis of any patient with an acute painless optic neuropathy, regardless of age and gender. The clinical scenario: Acute monocular optic neuropathy with central visual loss in a young adult The look-alikes: Idiopathic optic neuritis vs. Leber s hereditary optic neuropathy Tip: Absence of pain, male gender and normal MRI strongly suggest the possibility of Leber s hereditary optic neuropathy.

. Acute tonic pupil vs. pharmacologic mydriasis Case: A 40-year-ol d oncology nurse accidently splashed disinfecting solution in his right eye while cleaning a countertop. He immediately experienced a burning sensation and copiously lavaged his eye..

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