This condition affects the vision but could also include additional features. The vision problems normally become apparent within the first decade of the individual’s life and the severity of the condition appears to vary greatly among the cases ranging from normal vision to complete blindness. These individuals have a problem with the color vision which can make it almost impossible to distinguish the different shades of blue and green. Other problems can include tunnel vision, pale appearance of the optic nerve and the neurological problems. This disorder is estimated to affect around 1 in 50,000 people globally and appears to be more prevalent in Denmark.
Causes
Optic atrophy 1 develops because of the mutations in the gene OPA1 and the protein produced by this gene is made in several cells and tissues of the body. The OPA1 protein is important for the organization of shape and structure of the mitochondria which are the energy-producing parts of the cells. In addition, the OPA1 proteins are also involved in the self-destruction of cells (apoptosis), oxidative phosphorylation and the maintenance of the mitochondrial DNA (mtDNA). The genetic mutation results in the structural disorganization of mitochondria and the cells become more susceptible to self-destruction, the energy-producing capabilities of the mitochondria becomes reduced and mtDNA mutations occur. This causes the breakdown of structures that transmits visual details from the eyes to the brain, progressive loss of nerve cells within the retina and the degeneration of the optic nerve. This condition is inherited in an autosomal dominant pattern meaning a single copy of the defective gene in each cell can cause the disorder. In some cases, it can also develop because of a new genetic mutation with no history of the condition among the family members.
Symptoms
Optic atrophy 1 can have early childhood onset but in some case, the symptoms may not become evident until the child reaches the second decade of life. The vision loss appears to progress slowly presenting problems with color vision, tunnel vision and an abnormally pale appearance of the optic nerve. Less common problems include sensorineural hearing loss, ataxia, muscle disease (myopathy) and other neurological findings. Some of the affected individuals also appear to have drooping of the eyelids, difficulty moving the eyes in all directions and unsteadiness.
Diagnosis
The diagnosis of the disorder is usually identified by an ophthalmologist or a neurologist. The examination includes visual acuity, color vision, pupillary reflexes and visual field check. The visual acuity is not always affected as the central vision appears to be spared initially. The assessment of color vision can detect the differences between the eyes with the red color desaturation as a common indication. The optic atrophy can be diagnosed based on a fundoscopy and confirmed with an optical coherence tomography. The genetic testing can detect the gene responsible for the development of the disorder.
Treatment
There is no effective treatment available for the disorder. When the nerve fibers in the optic nerve become damaged, they cannot heal or grow back. Hence, early detection can help prevent further damage from the condition.
References
http://www.umkelloggeye.org/conditions-treatments/optic-atrophy
http://disorders.eyes.arizona.edu/handouts/optic-atrophy-1
https://ghr.nlm.nih.gov/condition/optic-atrophy-type-1#inheritance
https://rarediseases.info.nih.gov/diseases/9890/optic-atrophy-1
