Optic Atrophy Type 1
Optic atrophy type 1 is an inherited eye condition characterized by a progressive loss of vision, tunnel vision, and color vision deficiencies that typically begin in childhood.
Overview
Optic atrophy type 1 is a condition that often causes slowly worsening vision, usually beginning in childhood. Both eyes are typically affected equally, but the severity of the vision loss varies widely, even among affected members of the same family, ranging from nearly normal vision to complete blindness.
Symptoms & Clinical Features
People with this condition experience a progressive decline in visual function, which is characterized by several distinct features:
- Tunnel vision: Affected individuals typically experience a narrowing of their field of vision. They gradually lose their sight as their field of vision becomes smaller.
- Color vision deficiency: In addition to vision loss, affected individuals frequently have problems with color vision that make it difficult or impossible to distinguish between shades of blue and green.
- Retinal cell loss: In the early stages of the condition, individuals experience a progressive loss of retinal ganglion cells, which are specialized light-sensitive cells within the retina at the back of the eye.
- Optic nerve degeneration: The loss of retinal ganglion cells is followed by the degeneration (atrophy) of the optic nerves, which relay visual information from the eye to the brain.
- Optic nerve pallor: Atrophy causes these nerves to have an abnormally pale appearance (pallor), which can be observed during an eye examination.
Frequency
Optic atrophy type 1 is estimated to affect 1 in 35,000 people worldwide. This condition is more common in Denmark, where it affects approximately 1 in 10,000 people.
Causes & Genetics
Optic atrophy type 1 is caused by mutations in the OPA1 gene. The protein produced from this gene is active in cells and tissues throughout the body and is located within the mitochondria, the energy-producing centers of cells.
The OPA1 protein plays a key role in:
- Organizing the shape and structure of the mitochondria.
- Regulating controlled cell death (apoptosis).
- Supporting oxidative phosphorylation, the process by which cells derive much of their energy.
- Maintaining mitochondrial DNA (mtDNA).
Mutations in the OPA1 gene lead to poorly functioning, misshapen, and disorganized mitochondria with reduced energy-producing capabilities. Cells with high energy demands, such as retinal ganglion cells, become highly susceptible to apoptosis and die over time. Because the specialized extensions (axons) of these cells form the optic nerves, the death of retinal ganglion cells leads to optic nerve atrophy and the loss of visual transmission to the brain.
Inheritance Pattern
This condition is inherited in an autosomal dominant pattern, meaning one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person inherits the mutation from an affected parent. Other cases result from new mutations and occur in people with no history of the disorder in their family. In rare cases, individuals with an OPA1 gene mutation do not develop the condition, a phenomenon known as reduced penetrance.
Other Names for This Condition
- ADOA
- Autosomal dominant optic atrophy
- Autosomal dominant optic atrophy Kjer type
- DOA
- Dominant optic atrophy
- Kjer type optic atrophy
- Kjer's optic atrophy
- Optic atrophy, autosomal dominant
- Optic atrophy, hereditary, autosomal dominant
- Optic atrophy, juvenile
- Optic atrophy, Kjer type