Hydroxocobalamin in the treatment of Leber's hereditary optic atrophy

Leber Hereditary Optic Neuropathy: Review of Treatment and Management

Leber hereditary optic neuropathy (LHON) is a maternally inherited mitochondrial disease that specifically targets the retinal ganglion cells by reducing their ability to produce enough energy to sustain. The mutations of the mitochondrial DNA that cause LHON are silent until an unknown trigger causes bilateral central visual scotoma. After the onset of loss of vision, most patients experience progressive worsening within the following months. Few of them regain some vision after a period of ~1 year. Management of LHON patients has been focused on understanding the triggers of the disease and its pathophysiology to prevent the onset of visual loss in a carrier. Medical treatment is recommended once visual loss has started in at least one eye. Research evaluated drugs that are thought to be able to restore the mitochondrial electron transport chain of the retinal ganglion cells. Significant advances were made in evaluating free radical cell scavengers and gene therapy as potential treatments for LHON. Although encouraging the results of clinical trial have been mixed in stopping the worsening of visual loss. In patients with chronic disease of over 1 year, efficient treatment that restores vision is yet to be discovered. In this review, we summarize the management strategies for patients with LHON before, during, and after the loss of vision, explain the rationale and effectiveness of previous and current treatments, and report findings about emerging treatments.

Gene-Based Therapies for Leber Hereditary Optic Neuropathy. Hype or Hope?

Leber hereditary optic neuropathy has now joined Leber congenital amaurosis in the list of genetic eye diseases undergoing gene therapy clinical trials. Although a dramatic response to treatment would be welcome, a minor improvement in vision is a major challenge in efficacy assessment, given this may occur spontaneously as part of the natural history of minor recovery in some patients. Thus, we must await the outcome of adequately powered clinical trials to know if the treatment is effective, particularly given the likely high cost of such therapeutic interventions in the future. We need global cooperation to ensure that the most suitable patients are enrolled in these trials and that support is provided for participants who need to travel from the Asia-Pacific region to Europe or North America if there are no local arms of these trials.

Clinical, biochemical and molecular genetic features of Leber's hereditary optic neuropathy

Leber's hereditary optic neuropathy (LHON) has traditionally been considered a disease causing severe and permanent visual loss in young adult males. In nearly all families with LHON it is associated with one of three pathogenic mitochondrial DNA (mtDNA) mutations, at bp 11778, 3460 or 14484. The availability of mtDNA confirmation of a diagnosis of LHON has demonstrated that LHON occurs with a wider range of age at onset and more commonly in females than previously recognised. In addition, analysis of patients grouped according to mtDNA mutation has demonstrated differences both in the clinical features of visual failure and in recurrence risks to relatives associated with each of the pathogenic mtDNA mutations. Whilst pathogenic mtDNA mutations are required for the development of LHON, other factors must be reponsible for the variable penetrance and male predominance of this condition. Available data on a number of hypotheses including the role of an additional X-linked visual loss susceptibility locus, impaired mitochondrial respiratory chain activity, mtDNA heteroplasmy, environmental factors and autoimmunity are discussed. Subacute visual failure is seen in association with all three pathogenic LHON mutations. However, the clinical and experimental data reviewed suggest differences in the phenotype associated with each of the three mutations which may reflect variation in the disease mechanisms resulting in this common end-point.

Progressive visual loss associated with peculiar disc swelling

A patient with progressive visual loss associated with swelling of the disc presented the classic clinical picture of Leber's optic neuropathy. The hereditary patterns, diagnostic characteristics and natural history of the disease are discussed. Although there is no efficacious treatment for Leber's optic neuropathy available at this time, correct diagnosis is important for purposes of genetic counseling and avoidance of unnecessary neuroradiologic and surgical procedures.

Tobacco amblyopia: the effect of treatment on the electroretinogram

In seven recently diagnosed and untreated patients with tobacco amblyopia the light and dark adapted electroretionograms were recorded together with visual acuity, central fields and the Farnsworth-Munsell 100-Hue test. After 3 months treatment with injections of hydroxocobalamin all these tests were repeated. An improvement in visual acuity resulted in all cases. A significant reduction in the Farnsworth-Munsell total error score of the seven patients was noted (p less than 0.01). A significant increase in the amplitude of the light adapted b-wave of the ERG was found (0.01 less than p less than 0.02) following the course of hydroxocobalamin injections. No other significant changes in the ERG were demonstrated. It is suggested that the ERG changes demonstrated an improvement in an abnormal biochemical state in those bipolar and perhaps Müller cell of the inner nuclear layer of the retina which make electrophysiological connnections chiefly with foveal cones.

Role of vegetarianism, smoking, and hydroxocobalamin in optic neuritis

Only 20 patients with optic neuritis of unknown aetiology could be collected in Bombay over a period of two and a half years. Only six of them were smokers and only three (one a non-smoker) had bilateral centrocaecal scotomata similar to those found in tobacco amblyopia. In 11 untreated patients the serum vitamin B(12) and plasma thiocyanate levels were estimated and found to show no significant differences from those in normal control subjects. Treatment with hydroxocobalamin in the majority of cases and with cyanocobalamin, corticotrophin, or prednisolone in the rest showed equally good results; spontaneous improvement was seen in one case.No significant role could be assigned to smoking (cyanide) or to vegetarianism in the production of optic neuritis in these patients; nor was there any evidence of depletion of total (cyanide-extracted) B(12) or of an increase in the proportion of non-cyanide-extracted B(12) in the serum.