In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision. As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon. Onset of symptoms is generally gradual and often begins in childhood.
Leber's hereditary optic neuropathy (LHON) is a mitochondrially inherited degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision; it predominantly affects young adult males. LHON is transmitted only through the mother, as it is primarily due to mutations in the mitochondrial genome, and only the egg contributes mitochondria to the embryo. Men cannot pass on the disease to their offspring. LHON is usually due to one of three pathogenic mitochondrial DNA (mtDNA) point mutations. These mutations are at nucleotide positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunit genes of complex I of the oxidative phosphorylation chain in mitochondria.
Anterior ischemic optic neuropathy (AION) is a medical condition involving loss of vision caused by damage to the optic nerve as a result of insufficient blood supply (ischemia). This form of ischemic optic neuropathy is generally categorized as two types: arteritic AION, in which the loss of vision is the result of an inflammatory disease of arteries in the head called temporal arteritis, and non-arteritic AION, which is due to non-inflammatory disease of small blood vessels.
Posterior ischemic optic neuropathy (PION) is a medical condition characterized by damage to the retrobulbar portion of the optic nerve due to inadequate blood flow (ischemia) to the optic nerve. Despite the term posterior, this form of damage to the eye's optic nerve due to poor blood flow also includes cases where the cause of inadequate blood flow to the nerve is anterior, as the condition describes a particular mechanism of visual loss as much as the location of damage in the optic nerve. In contrast, anterior ischemic optic neuropathy (AION) is distinguished from PION by the fact that AION occurs spontaneously and on one side in affected individuals with predisposing anatomic or cardiovascular risk factors.
Mitochondrial myopathies are types of myopathies associated with mitochondrial disease. Adenosine triphosphate (ATP), the chemical used to provide energy for the cell, cannot be produced sufficiently by oxidative phosphorylation when the mitochondrion is either damaged or missing necessary enzymes or transport proteins. With ATP production deficient in mitochondria, there is an over-reliance on anaerobic glycolysis which leads to lactic acidosis either at rest or exercise-induced.
Behr syndrome is characterized by the association of early-onset optic atrophy with spinocerebellar degeneration resulting in ataxia, pyramidal signs, peripheral neuropathy and developmental delay.
Ischemic optic neuropathy (ION) is the loss of structure and function of a portion of the optic nerve due to obstruction of blood flow to the nerve. Ischemic forms of optic neuropathy are typically classified as either anterior ischemic optic neuropathy or posterior ischemic optic neuropathy according to the part of the optic nerve that is affected. People affected will often complain of a loss of visual acuity and a visual field, the latter of which is usually in the superior or inferior field.
Toxic and nutritional optic neuropathy is a group of medical disorders defined by visual impairment due to optic nerve damage secondary to a toxic substance and/or nutritional deficiency. The causes of these disorders are various, but they are linked by shared signs and symptoms, which this article will describe. In several of these disorders, both toxic and nutritional factors play a role, acting synergistically.
Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain.
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.
Costeff syndrome, or 3-methylglutaconic aciduria type III, is a genetic disorder caused by mutations in the OPA3 gene. It is typically associated with the onset of visual deterioration in early childhood followed by the development of movement problems and motor disability in later childhood, occasionally along with mild cases of cognitive deficiency. The disorder is named after Hanan Costeff, the doctor who first described the syndrome in 1989.
Dynamin-like 120 kDa protein, mitochondrial is a protein that in humans is encoded by the OPA1 gene. This protein regulates mitochondrial fusion and cristae structure in the inner mitochondrial membrane (IMM) and contributes to ATP synthesis and apoptosis, and small, round mitochondria. Mutations in this gene have been implicated in dominant optic atrophy (DOA), leading to loss in vision, hearing, muscle contraction, and related dysfunctions.
Paul Kjer is a Danish ophthalmologist who studied a condition in nineteen families that was characterized by infantile optic atrophy along with a dominant inheritance mode. In 1959, the condition was named Kjer's optic neuropathy in his honor.
Behçet's disease (BD) is a type of inflammatory disorder which affects multiple parts of the body. The most common symptoms include painful sores on the mucous membranes of the mouth and other parts of the body, inflammation of parts of the eye, and arthritis. The sores can last from a few days, up to a week or more. Less commonly there may be inflammation of the brain or spinal cord, blood clots, aneurysms, or blindness. Often, the symptoms come and go.
Mitochondrial optic neuropathies are a heterogenous group of disorders that present with visual disturbances resultant from mitochondrial dysfunction within the anatomy of the Retinal Ganglion Cells (RGC), optic nerve, optic chiasm, and optic tract. These disturbances are multifactorial, their aetiology consisting of metabolic and/or structural damage as a consequence of genetic mutations, environmental stressors, or both. The three most common neuro-ophthalmic abnormalities seen in mitochondrial disorders are bilateral optic neuropathy, ophthalmoplegia with ptosis, and pigmentary retinopathy.
Chronic relapsing inflammatory optic neuropathy (CRION) is a form of recurrent optic neuritis that is steroid responsive and dependent. Patients typically present with pain associated with visual loss. CRION is a clinical diagnosis of exclusion, and other demyelinating, autoimmune, and systemic causes should be ruled out. An accurate antibody test which became available commercially in 2017 has allowed most patients previously diagnosed with CRION to be re-identified as having MOG antibody disease, which is not a diagnosis of exclusion. Early recognition is crucial given risks for severe visual loss and because it is treatable with immunosuppressive treatment such as steroids or B-cell depleting therapy. Relapse that occurs after reducing or stopping steroids is a characteristic feature.
Occult macular dystrophy (OMD) is a rare inherited degradation of the retina, characterized by progressive loss of function in the most sensitive part of the central retina (macula), the location of the highest concentration of light-sensitive cells (photoreceptors) but presenting no visible abnormality. "Occult" refers to the degradation in the fundus being difficult to discern. The disorder is called "dystrophy" instead of "degradation" to distinguish its genetic origin from other causes, such as age. OMD was first reported by Y. Miyake et al. in 1989.
Alfredo Arrigo Sadun is an American ophthalmologist, academic, author and researcher. He holds the Flora L. Thornton Endowed Chair at Doheny Eye Centers-UCLA and is Vice-Chair of Ophthalmology at UCLA.
Wolfram-like syndrome is a rare autosomal dominant genetic disorder that shares some of the features shown by those affected with the autosomal recessive Wolfram syndrome. It is a type of WFS1-related disorder.
