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 on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”.
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.
Idebenone is a drug that was initially developed by Takeda Pharmaceutical Company for the treatment of Alzheimer's disease and other cognitive defects. This has been met with limited success. The Swiss company Santhera Pharmaceuticals has started to investigate it for the treatment of neuromuscular diseases. In 2010,early clinical trials for the treatment of Friedreich's ataxia and Duchenne muscular dystrophy have been completed. As of December 2013 the drug is not approved for these indications in North America or Europe. It is approved by the European Medicines Agency (EMA) for use in Leber's hereditary optic neuropathy (LHON) and was designated an orphan drug in 2007.
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.
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 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.
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,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. [1].
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.
Blurred vision is an ocular symptom where vision becomes less precise and there is added difficulty to resolve fine details.
Sohan Singh Hayreh was an ophthalmologist,clinical scientist,and professor emeritus of ophthalmology at the University of Iowa. As one of the pioneers in the field of fluorescein angiography,he was generally acknowledged to be a leading authority in vascular diseases of the eye and the optic nerve. For over 60 years,Hayreh was actively involved in basic,experimental,and clinical research in ophthalmology,publishing over 400 original peer-reviewed articles in various international ophthalmic journals,six classical monographs and books in his field of research,and more than 50 chapters in ophthalmic books. He made many seminal observations dealing with the ocular circulation in health and disease,the optic disc and the optic nerve,retinal and choroidal vascular disorders,glaucomatous optic neuropathy,fundus changes in malignant arterial hypertension,ocular neovascularization,rheumatologic disorders of the eye,and nocturnal arterial hypotension. He was an elected fellow of the National Academy of Medical 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.
Mitohondrial 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.
Robert E. MacLaren FMedSci FRCOphth FRCS FACS VR is a British ophthalmologist who has led pioneering work in the treatment of blindness caused by diseases of the retina. He is Professor of Ophthalmology at the University of Oxford and Honorary Professor of Ophthalmology at the UCL Institute of Ophthalmology. He is a Consultant Ophthalmologist at the Oxford Eye Hospital. He is also an Honorary Consultant Vitreo-retinal Surgeon at the Moorfields Eye Hospital. MacLaren is an NIHR Senior Investigator,or lead researcher,for the speciality of Ophthalmology. In addition,he is a member of the research committee of Euretina:the European Society of Retina specialists,Fellow of Merton College,in Oxford and a Fellow of the Higher Education Academy.
