Optic Atrophy 1

Alternative Names

  • OPA1
  • Optic Atrophy, Juvenile
  • Kjer-Type Optic Atrophy
  • Optic Atrophy, Kjer Type
  • OAK
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WHO-ICD-10 version:2010

Diseases of the eye and adnexa

Disorders of optic nerve and visual pathways

OMIM Number

165500

Mode of Inheritance

Autosomal dominant

Gene Map Locus

3q29

Description

Optic neuropathy, better known as optic atrophy, is a group of clinically and genetically heterogenous diseases resulting from ganglion cell degeneration of the optic nerve. Autosomal dominant optic atrophy (ADOA) is the most common form of hereditary optic neuropathy, and OPA1, in turn is the most commonly found variant of ADOA. Although there is considerable variation in the clinical spectrum, the disease is typically characterized by optic nerve pallor and bilateral subnormal visual acuity. The visual impairment ranges from mild to severe. Other features include visual field defects, typically centrocecal, central, or paracentral, and color vision defects, most notably a blue-yellow loss (tritanopia). The condition may present as early as within the first year of birth. However, it usually has an onset between 4 and 6-years of age, in some cases, remaining subclinical till early adulthood. Apart from isolated cases, OPA1 may also be seen in conjunction with other conditions such as deafness (ADOAD), or in some cases is seen as part of multi-systemic syndromes involving neurological and neuromuscular manifestations (ADOA Plus).

The incidence of OPA1 has been calculated to be 1:50,000 worldwide. However, some populations, like the Danes demonstrate a higher prevalence.

A diagnosis of OPA1 depends upon the clinical examination, electrophysiologic studies, and molecular genetic studies. Affected patients can be seen to have delayed or absent visual evoked potentials, abnormal N95:P50 ratio on the pattern electroretinogram, tritanopia, and a temporal or diffuse pallor of the optic discs. Molecular genetic testing of the OPA1 gene is now available for suspected families. As is the case with most hereditary optic defects, no treatment is available for OPA1. The condition can be managed with the help of low-vision aids for improving visual acuity. Annual ophthalmologic and hearing evaluations of affected patients might be necessary.

OPA1 is inherited in an autosomal dominant fashion. Most cases are familial, although some de novo mutations have also been reported. The gene responsible has been identified as the OPA1 gene, located on chromosome 3q29. The disease shows incomplete penetrance, which complicates genetic counseling efforts.

The OPA1 gene codes for a mitochondrial dynamin related GTPase, which is implicated in the formation and maintenance of the mitochondrial network. More than 60 mutations have been identified in this gene and linked to optic atrophy. It is interesting to note that the other major form of hereditary optic atrophy, Leber Optic Neuropathy, is also caused due to defects in a protein integral to mitochondrial function.

Epidemiology in the Arab World

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Subject IDCountrySexFamily HistoryParental ConsanguinityHPO TermsVariantZygosityMode of InheritanceReferenceRemarks
165500.1United Arab EmiratesMaleNoNo Optic atrophyNM_130837.3:c.1189A>GHeterozygousAutosomal, DominantMu et al. 2019

Other Reports

Kuwait

Al-Merjan et al. (2005) presented the causes and incidence rates of disorders leading to blindness and low vision in Kuwait, based on the data collected by the Visual Disability Committee in a 5-year period from 2000 to 2004. Of the 826,083 people (407,871 males) registered with blindness and low vision, 39% were below the age of 20-years, 32% were between the ages of 21 and 40-years, while only about 10% were over 60-years of age. Optic Atrophy was found to be the second most common cause of disability, occurring with an overall incidence rate of 1.88 per 100,000 individuals. The incidence varied between males (2.45) and females (1.33). Optic Atrophy was also found to be the leading cause of disability in the under 20-years age group.

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