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.
This is a partial list of human eye diseases and disorders.
The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction";in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”.
The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc,it corresponds to a small blind spot in each eye.
Homoplasmy is a term used in genetics to describe a eukaryotic cell whose copies of mitochondrial DNA are all identical. In normal and healthy tissues,all cells are homoplasmic. Homoplasmic mitochondrial DNA copies may be normal or mutated;however,most mutations are heteroplasmic. It has been discovered,though,that homoplasmic mitochondrial DNA mutations may be found in human tumors.
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 adult males,and onset is more likely in younger adults. 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.
Neuro-ophthalmology is an academically-oriented subspecialty that merges the fields of neurology and ophthalmology,often dealing with complex systemic diseases that have manifestations in the visual system. Neuro-ophthalmologists initially complete a residency in either neurology or ophthalmology,then do a fellowship in the complementary field. Since diagnostic studies can be normal in patients with significant neuro-ophthalmic disease,a detailed medical history and physical exam is essential,and neuro-ophthalmologists often spend a significant amount of time with their patients.
Anterior ischemic optic neuropathy (AION) is a medical condition involving loss of vision caused by damage to the anterior portion of 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. It is in contrast to posterior ischemic optic neuropathy,which affects the retrobulbar portion of the optic nerve.
Dominant optic atrophy (DOA),or autosomal dominant optic atrophy (ADOA),(Kjer's type) is an autosomally inherited disease that affects the optic nerves,causing reduced visual acuity and blindness beginning in childhood. However,the disease can seem to re-present a second time with further vision loss due to the early onset of presbyopia symptoms (i.e.,difficulty in viewing objects up close). DOA is characterized as affecting neurons called retinal ganglion cells (RGCs). This condition is due to mitochondrial dysfunction mediating the death of optic nerve fibers. The RGCs axons form the optic nerve. Therefore,the disease can be considered of the central nervous system. Dominant optic atrophy was first described clinically by Batten in 1896 and named Kjer’s optic neuropathy in 1959 after Danish ophthalmologist Poul Kjer,who studied 19 families with the disease. Although dominant optic atrophy is the most common autosomally inherited optic neuropathy (i.e.,disease of the optic nerves),it is often misdiagnosed.
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. 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.
Allotopic expression (AE) refers to expression of genes in the cell nucleus that normally are expressed only from the mitochondrial genome. Biomedically engineered AE has been suggested as a possible future tool in gene therapy of certain mitochondria-related diseases,however this view is controversial. While this type of expression has been successfully carried out in yeast,the results in mammals have been conflicting.
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.
MT-ND6 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 6 protein (ND6). The ND6 protein is a subunit of NADH dehydrogenase (ubiquinone),which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Variations in the human MT-ND6 gene are associated with Leigh's syndrome,Leber's hereditary optic neuropathy (LHON) and dystonia.
MT-ND4 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 4 (ND4) protein. The ND4 protein is a subunit of NADH dehydrogenase (ubiquinone),which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Variations in the MT-ND4 gene are associated with age-related macular degeneration (AMD),Leber's hereditary optic neuropathy (LHON),mesial temporal lobe epilepsy (MTLE) and cystic fibrosis.
José-Alain Sahel is a French ophthalmologist and scientist. He is currently the Chair of the Department of Ophthalmology at the University of Pittsburgh School of Medicine,Director of the UPMC Vision Institute,and the Eye and Ear Foundation Chair of Ophthalmology. Dr. Sahel previously led the Vision Institute in Paris,a research center associated with one of the oldest eye hospitals of Europe,Quinze-Vingts National Eye Hospital in Paris,founded in 1260. He is a pioneer in the field of artificial retina and eye regenerative therapies. He is a member of the French Academy of Sciences.
The Vision Institute is a research center in the Quinze-Vingts National Eye Hospital in Paris,France. It is one of several such centers in Europe on eye diseases.
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.
Intravitreal injection is the method of administration of drugs into the eye by injection with a fine needle. The medication will be directly applied into the vitreous humor. It is used to treat various eye diseases,such as age-related macular degeneration (AMD),diabetic retinopathy,and infections inside the eye such as endophthalmitis. As compared to topical administration,this method is beneficial for a more localized delivery of medications to the targeted site,as the needle can directly pass through the anatomical eye barrier and dynamic barrier. It could also minimize adverse drug effects on other body tissues via the systemic circulation,which could be a possible risk for intravenous injection of medications. Although there are risks of infections or other complications,with suitable precautions throughout the injection process,chances for these complications could be lowered.
