The X-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes.
The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.
The paired caudal parts of the PROSENCEPHALON from which the THALAMUS; HYPOTHALAMUS; EPITHALAMUS; and SUBTHALAMUS are derived.
An eph family receptor found primarily in the nervous system. In the embryonic BRAIN EphB1 receptor expression occurs in the mantle layer and increases with the progression of embryogenesis. In adult brain it is found in the several regions including the CEREBELLUM; CEREBRAL CORTEX; and CAUDATE NUCLEUS; and PUTAMEN.
Atrophy of the optic disk which may be congenital or acquired. This condition indicates a deficiency in the number of nerve fibers which arise in the RETINA and converge to form the OPTIC DISK; OPTIC NERVE; OPTIC CHIASM; and optic tracts. GLAUCOMA; ISCHEMIA; inflammation, a chronic elevation of intracranial pressure, toxins, optic nerve compression, and inherited conditions (see OPTIC ATROPHIES, HEREDITARY) are relatively common causes of this condition.
Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.
Set of cell bodies and nerve fibers conducting impulses from the eyes to the cerebral cortex. It includes the RETINA; OPTIC NERVE; optic tract; and geniculocalcarine tract.
Partial or complete loss of vision in one half of the visual field(s) of one or both eyes. Subtypes include altitudinal hemianopsia, characterized by a visual defect above or below the horizontal meridian of the visual field. Homonymous hemianopsia refers to a visual defect that affects both eyes equally, and occurs either to the left or right of the midline of the visual field. Binasal hemianopsia consists of loss of vision in the nasal hemifields of both eyes. Bitemporal hemianopsia is the bilateral loss of vision in the temporal fields. Quadrantanopsia refers to loss of vision in one quarter of the visual field in one or both eyes.
General term for a number of inherited defects of amino acid metabolism in which there is a deficiency or absence of pigment in the eyes, skin, or hair.
Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.
Benign and malignant neoplasms that arise from the optic nerve or its sheath. OPTIC NERVE GLIOMA is the most common histologic type. Optic nerve neoplasms tend to cause unilateral visual loss and an afferent pupillary defect and may spread via neural pathways to the brain.
The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.
The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve.
In invertebrate zoology, a lateral lobe of the FOREBRAIN in certain ARTHROPODS. In vertebrate zoology, either of the corpora bigemina of non-mammalian VERTEBRATES. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1329)
Inflammation of the optic nerve. Commonly associated conditions include autoimmune disorders such as MULTIPLE SCLEROSIS, infections, and granulomatous diseases. Clinical features include retro-orbital pain that is aggravated by eye movement, loss of color vision, and contrast sensitivity that may progress to severe visual loss, an afferent pupillary defect (Marcus-Gunn pupil), and in some instances optic disc hyperemia and swelling. Inflammation may occur in the portion of the nerve within the globe (neuropapillitis or anterior optic neuritis) or the portion behind the globe (retrobulbar neuritis or posterior optic neuritis).
Congenital absence of the eye or eyes.
An eph family receptor found widely expressed in embryonic and adult tissues. High levels of EphB2 receptor are observed in growing AXONS and NERVE FIBERS. Several isoforms of the protein exist due to multiple alternative mRNA splicing.
The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.
A transmembrane domain containing ephrin that binds with high affinity to EPHB1 RECEPTOR; EPHB3 RECEPTOR; and EPHB4 RECEPTOR. Expression of ephrin-B2 occurs in a variety of adult tissues. During embryogenesis, high levels of ephrin-B2 is seen in the PROSENCEPHALON; RHOMBENCEPHALON; developing SOMITES; LIMB BUD; and bronchial arches.
Part of the DIENCEPHALON inferior to the caudal end of the dorsal THALAMUS. Includes the lateral geniculate body which relays visual impulses from the OPTIC TRACT to the calcarine cortex, and the medial geniculate body which relays auditory impulses from the lateral lemniscus to the AUDITORY CORTEX.
Conditions which produce injury or dysfunction of the second cranial or optic nerve, which is generally considered a component of the central nervous system. Damage to optic nerve fibers may occur at or near their origin in the retina, at the optic disk, or in the nerve, optic chiasm, optic tract, or lateral geniculate nuclei. Clinical manifestations may include decreased visual acuity and contrast sensitivity, impaired color vision, and an afferent pupillary defect.
Injuries to the optic nerve induced by a trauma to the face or head. These may occur with closed or penetrating injuries. Relatively minor compression of the superior aspect of orbit may also result in trauma to the optic nerve. Clinical manifestations may include visual loss, PAPILLEDEMA, and an afferent pupillary defect.
Neoplasms which arise from or metastasize to the PITUITARY GLAND. The majority of pituitary neoplasms are adenomas, which are divided into non-secreting and secreting forms. Hormone producing forms are further classified by the type of hormone they secrete. Pituitary adenomas may also be characterized by their staining properties (see ADENOMA, BASOPHIL; ADENOMA, ACIDOPHIL; and ADENOMA, CHROMOPHOBE). Pituitary tumors may compress adjacent structures, including the HYPOTHALAMUS, several CRANIAL NERVES, and the OPTIC CHIASM. Chiasmal compression may result in bitemporal HEMIANOPSIA.
The reciprocal exchange of segments at corresponding positions along pairs of homologous CHROMOSOMES by symmetrical breakage and crosswise rejoining forming cross-over sites (HOLLIDAY JUNCTIONS) that are resolved during CHROMOSOME SEGREGATION. Crossing-over typically occurs during MEIOSIS but it may also occur in the absence of meiosis, for example, with bacterial chromosomes, organelle chromosomes, or somatic cell nuclear chromosomes.
The sudden loss of blood supply to the PITUITARY GLAND, leading to tissue NECROSIS and loss of function (PANHYPOPITUITARISM). The most common cause is hemorrhage or INFARCTION of a PITUITARY ADENOMA. It can also result from acute hemorrhage into SELLA TURCICA due to HEAD TRAUMA; INTRACRANIAL HYPERTENSION; or other acute effects of central nervous system hemorrhage. Clinical signs include severe HEADACHE; HYPOTENSION; bilateral visual disturbances; UNCONSCIOUSNESS; and COMA.
Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.
A bony prominence situated on the upper surface of the body of the sphenoid bone. It houses the PITUITARY GLAND.
The surgical removal of the eyeball leaving the eye muscles and remaining orbital contents intact.
Compounds that contain three methine groups. They are frequently used as cationic dyes used for differential staining of biological materials.
The total area or space visible in a person's peripheral vision with the eye looking straightforward.
Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.

Temporal and spatial profile of apoptotic cells after focal cerebral ischemia in rats. (1/277)

The significance of apoptosis in focal ischemia was investigated in the spatial and temporal profiles of apoptotic cells caused by permanent and transient focal ischemia induced in male Wistar rats by intraluminal vascular occlusion. Animals were sacrificed at various times and coronal sections of the brain at the level of the optic chiasm were examined histologically by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling. Animals in both groups showed apoptotic cells in the infarcted area, particularly in the border zone. Animals with permanent ischemia showed more extensive infarct and more rapid appearance of apoptotic cells. Activation of apoptosis might depend on the severity of the ischemic insult. Apoptotic cells were observed at 7 days after the ischemic insult in animals with transient ischemia, suggesting apoptosis is involved in the developments of delayed infarct.  (+info)

Cavernous angioma of the optic chiasm--case report. (2/277)

A 31-year-old female presented with cavernous angioma originating from the optic chiasm manifesting as sudden onset of right retroorbital pain and right visual disturbance. She had a psychomotor seizure 10 years ago. Cavernous angioma at the right basal ganglia had been partially removed at that time. After the operation, the patient had left hemiparesis, but gradually improved. Neurological examination revealed decreased right visual acuity, left homonymous hemianopsia, and left hemiparesis. Magnetic resonance imaging revealed a mixed signal intensity mass at the right optic nerve to the optic chiasm with a low signal intensity rim on T2-weighted imaging, situated at the right basal ganglia where the cavernous angioma had been partially resected. Right frontotemporal craniotomy was performed by the pterional approach. A subpial hematoma was situated at the right optic nerve to the optic chiasm. The hematoma with an angiomatous component was completely resected from the surrounding structure. Histological examination of the specimens confirmed cavernous angioma. Postoperatively, her right visual acuity was slightly improved, but the visual field defect was unchanged. We emphasize the importance of correct diagnosis by magnetic resonance imaging and subsequent resection for preserving and improving the visual function of patients with cavernous angiomas of the optic chiasm.  (+info)

Chunk versus point sampling: visual imaging in a small insect. (3/277)

The eyes of strepsipteran insects are very unusual among living insects. In their anatomical organization they may form a modern counterpart to the structural plan proposed for the eyes of some trilobites. Externally they differ from the usual "insect plan" by presenting far fewer but much larger lenses. Beneath each lens is its own independent retina. Anatomical and optical measurements indicate that each of these units is image-forming, so that the visual field is subdivided into and represented by "chunks," unlike the conventional insect compound eye that decomposes the visual image in a pointwise manner. This results in profound changes in the neural centers for vision and implies major evolutionary changes.  (+info)

Altered midline axon pathways and ectopic neurons in the developing hypothalamus of netrin-1- and DCC-deficient mice. (4/277)

Optic nerve formation in mouse involves interactions between netrin-1 at the optic disk and the netrin-1 receptor DCC (deleted in colorectal cancer) expressed on retinal ganglion cell (RGC) axons. Deficiency in either protein causes RGC pathfinding defects at the disk leading to optic nerve hypoplasia (). Here we show that further along the visual pathway, RGC axons in netrin-1- or DCC-deficient mice grow in unusually angular trajectories within the ventral hypothalamus. In heterozygous Sey(neu) mice that also have a small optic nerve, RGC axon trajectories appear normal, indicating that the altered RGC axon trajectories in netrin-1 and DCC mutants are not secondarily caused by optic nerve hypoplasia. Intrinsic hypothalamic patterning is also affected in netrin-1 and DCC mutants, including a severe reduction in the posterior axon projections of gonadotropin-releasing hormone neurons. In addition to axon pathway defects, antidiuretic hormone and oxytocin neurons are found ectopically in the ventromedial hypothalamus, apparently no longer confined to the supraoptic nucleus in mutants. In summary, netrin-1 and DCC, presumably via direct interactions, govern both axon pathway formation and neuronal position during hypothalamic development, and loss of netrin-1 or DCC function affects both visual and neuroendocrine systems. Netrin protein localization also indicates that unlike in more caudal CNS, guidance about the hypothalamic ventral midline does not require midline expression of netrin.  (+info)

Asymmetric connections, duplicate layers, and a vertically inverted map in the primary visual system. (5/277)

The achiasmatic mutation is a remarkable and rare visual system mutation carried in a line of black sheepdogs. In affected animals, the optic chiasm is missing, and each retina projects entirely to the ipsilateral hemisphere. As a result of this navigational error, maps of visual space in the lateral geniculate nucleus (LGN) have a unique structure with mirror reversals of field position across the A-A1 border. Animals also have a persistent and severe congenital nystagmus. In this report we analyze a novel variant of the achiasmatic mutation, one in which retinal axons from only one eye successfully cross midline and in which the great majority of fibers from both eyes terminate in a single lateral geniculate nucleus. The dominant optic tract contains four times as many axons as the other tract. The hyperinnervated LGN has a lamination pattern consisting of duplicate and partly interwoven layers. A multiunit mapping study of visual cortex (primarily area 17 along the marginal gyrus) shows that receptive field topography and orientation selectivity are normal. The size of central binocular visual space is nearly normal and is flanked by monocular domains in the periphery. However, there is an inexplicable vertical inversion in the orientation of the cortical representation: superior fields are located rostrally, and inferior fields are located caudally. Despite a host of drastic abnormalities at all level of the visual system, from retina to cortex, this animal was behaviorally indistinguishable from normal dogs and did not have any detectable oculomotor abnormalities.  (+info)

The homeodomain protein vax1 is required for axon guidance and major tract formation in the developing forebrain. (6/277)

The homeodomain protein Vax1 is expressed in a highly circumscribed set of cells at the ventral anterior midline of the embryonic CNS. These cells populate the choroid fissure of the optic disk, the body of the optic stalk and nerve, the optic chiasm and ventral diencephalon, and the anterior midline zones that abut developing commissural tracts. We have generated mutant mice that lack Vax1. In these mice (1) the optic disks fail to close, leading to coloboma and loss of the eye-nerve boundary; (2) optic nerve glia fail to associate with and appear to repulse ingrowing retinal axons, resulting in a fascicle of axons that are completely segregated from optic nerve astrocytes; (3) retinal axons fail to penetrate the brain in significant numbers and fail to form an optic chiasm; and (4) axons in multiple commissural tracts of the anterior CNS, including the corpus callosum and the hippocampal and anterior commissures, fail to cross the midline. These axon guidance defects do not result from the death of normally Vax1(+) midline cells but, instead, correlate with markedly diminished expression of attractive guidance cues in these cells. Vax1 therefore regulates the guidance properties of a set of anterior midline cells that orchestrate axon trajectories in the developing mammalian forebrain.  (+info)

Visual function and brain organization in non-decussating retinal-fugal fibre syndrome. (7/277)

Functional neuroimaging, psychophysical and electrophysiological investigations were performed in a patient with non-decussating retinal-fugal fibre syndrome, an inborn achiasmatic state in which the retinal projections of each eye map entirely to the ipsilateral primary visual cortex. Functional magnetic resonance imaging (fMRI) studies showed that for monocularly presented simple visual stimuli, only the ipsilateral striate cortex was activated. Within each hemisphere's striate cortex, the representation of the two hemifields overlapped extensively. Despite this gross miswiring, visual functions that require precise geometrical information (such as vernier acuity) were normal, and there was no evidence for the confounding of visual information between the overlapping ipsi-lateral and contralateral representations. Contrast sensitivity and velocity judgments were abnormal, but their dependence on the orientation and velocity of the targets suggests that this deficit was due to ocular instabilities, rather than the miswiring per se. There were no asymmetries in performance observed in visual search, visual naming or illusory contour perception. fMRI analysis of the latter two tasks under monocular viewing conditions indicated extensive bilateral activation of striate and prestriate areas. Thus, the remarkably normal visual behavior achieved by this patient is a result of both the plasticity of visual pathways, and efficient transfer of information between the hemispheres.  (+info)

Morphometric comparison of the human optic nerve fiber with various other human nerve fibers. (8/277)

The morphometric characteristics of nerve fibers of the human optic nerve in the chiasmatic region were measured with the combination of an image analyzer and a computer, using the Luxol fast blue-periodic acid-Schiff-hematoxylin discriminative staining method. The mean axonal transverse area of the human optic nerve fibers was 0.644 +/- 0.361 micron 2. Comparison of the size of the axon of the human optic nerve fiber with that of various other human nerves showed optic nerve fibers were definitely thinner than the other nerve fibers, and were surrounded by a thinner myelin sheath. Optic nerves may be more liable to mechanical damage at surgery that previously believed.  (+info)

The optic chiasm is a structure in the brain where the optic nerves from each eye meet and cross. This allows for the integration of visual information from both eyes into the brain's visual cortex, creating a single, combined image of the visual world. The optic chiasm plays an important role in the processing of visual information and helps to facilitate depth perception and other complex visual tasks. Damage to the optic chiasm can result in various visual field deficits, such as bitemporal hemianopsia, where there is a loss of vision in the outer halves (temporal fields) of both eyes' visual fields.

The optic nerve, also known as the second cranial nerve, is the nerve that transmits visual information from the retina to the brain. It is composed of approximately one million nerve fibers that carry signals related to vision, such as light intensity and color, from the eye's photoreceptor cells (rods and cones) to the visual cortex in the brain. The optic nerve is responsible for carrying this visual information so that it can be processed and interpreted by the brain, allowing us to see and perceive our surroundings. Damage to the optic nerve can result in vision loss or impairment.

The diencephalon is a term used in anatomy to refer to the part of the brain that lies between the cerebrum and the midbrain. It includes several important structures, such as the thalamus, hypothalamus, epithalamus, and subthalamus.

The thalamus is a major relay station for sensory information, receiving input from all senses except smell and sending it to the appropriate areas of the cerebral cortex. The hypothalamus plays a crucial role in regulating various bodily functions, including hunger, thirst, body temperature, and sleep-wake cycles. It also produces hormones that regulate mood, growth, and development.

The epithalamus contains the pineal gland, which produces melatonin, a hormone that helps regulate sleep-wake cycles. The subthalamus is involved in motor control and coordination.

Overall, the diencephalon plays a critical role in integrating sensory information, regulating autonomic functions, and modulating behavior and emotion.

EphB1 is a type of receptor tyrosine kinase (RTK) that belongs to the Eph family of receptors. It is a single-pass transmembrane protein that contains an extracellular domain with a binding site for its ligand, ephrin-Bs, and an intracellular domain with tyrosine kinase activity.

EphB1 receptors are primarily expressed in the nervous system, where they play important roles in various developmental processes, including axon guidance, neuronal migration, and synaptic plasticity. They also have been implicated in tumorigenesis and cancer progression, as well as in the regulation of immune responses.

The binding of ephrin-Bs to EphB1 receptors triggers a variety of intracellular signaling pathways that can lead to both forward and reverse signaling. Forward signaling occurs when the activated EphB1 receptor phosphorylates downstream effector proteins, leading to changes in cell behavior such as repulsion or adhesion. Reverse signaling occurs when ephrin-Bs, which are also transmembrane proteins, activate their own intracellular signaling pathways upon binding to EphB1 receptors.

Overall, the EphB1 receptor is a crucial component of the Eph/ephrin signaling system that plays important roles in various biological processes and has potential implications for disease treatment and diagnosis.

Optic atrophy is a medical term that refers to the degeneration and shrinkage (atrophy) of the optic nerve, which transmits visual information from the eye to the brain. This condition can result in various vision abnormalities, including loss of visual acuity, color vision deficiencies, and peripheral vision loss.

Optic atrophy can occur due to a variety of causes, such as:

* Traumatic injuries to the eye or optic nerve
* Glaucoma
* Optic neuritis (inflammation of the optic nerve)
* Ischemic optic neuropathy (reduced blood flow to the optic nerve)
* Compression or swelling of the optic nerve
* Hereditary or congenital conditions affecting the optic nerve
* Toxins and certain medications that can damage the optic nerve.

The diagnosis of optic atrophy typically involves a comprehensive eye examination, including visual acuity testing, refraction assessment, slit-lamp examination, and dilated funduscopic examination to evaluate the health of the optic nerve. In some cases, additional diagnostic tests such as visual field testing, optical coherence tomography (OCT), or magnetic resonance imaging (MRI) may be necessary to confirm the diagnosis and determine the underlying cause.

There is no specific treatment for optic atrophy, but addressing the underlying cause can help prevent further damage to the optic nerve. In some cases, vision rehabilitation may be recommended to help patients adapt to their visual impairment.

Retinal Ganglion Cells (RGCs) are a type of neuron located in the innermost layer of the retina, the light-sensitive tissue at the back of the eye. These cells receive visual information from photoreceptors (rods and cones) via intermediate cells called bipolar cells. RGCs then send this visual information through their long axons to form the optic nerve, which transmits the signals to the brain for processing and interpretation as vision.

There are several types of RGCs, each with distinct morphological and functional characteristics. Some RGCs are specialized in detecting specific features of the visual scene, such as motion, contrast, color, or brightness. The diversity of RGCs allows for a rich and complex representation of the visual world in the brain.

Damage to RGCs can lead to various visual impairments, including loss of vision, reduced visual acuity, and altered visual fields. Conditions associated with RGC damage or degeneration include glaucoma, optic neuritis, ischemic optic neuropathy, and some inherited retinal diseases.

Visual pathways, also known as the visual system or the optic pathway, refer to the series of specialized neurons in the nervous system that transmit visual information from the eyes to the brain. This complex network includes the retina, optic nerve, optic chiasma, optic tract, lateral geniculate nucleus, pulvinar, and the primary and secondary visual cortices located in the occipital lobe of the brain.

The process begins when light enters the eye and strikes the photoreceptor cells (rods and cones) in the retina, converting the light energy into electrical signals. These signals are then transmitted to bipolar cells and subsequently to ganglion cells, whose axons form the optic nerve. The fibers from each eye's nasal hemiretina cross at the optic chiasma, while those from the temporal hemiretina continue without crossing. This results in the formation of the optic tract, which carries visual information from both eyes to the opposite side of the brain.

The majority of fibers in the optic tract synapse with neurons in the lateral geniculate nucleus (LGN), a part of the thalamus. The LGN sends this information to the primary visual cortex, also known as V1 or Brodmann area 17, located in the occipital lobe. Here, simple features like lines and edges are initially processed. Further processing occurs in secondary (V2) and tertiary (V3-V5) visual cortices, where more complex features such as shape, motion, and depth are analyzed. Ultimately, this information is integrated to form our perception of the visual world.

Hemianopsia is a medical term that refers to a loss of vision in half of the visual field in one or both eyes. It can be either homonymous (the same side in both eyes) or heteronymous (different sides in each eye). Hemianopsia usually results from damage to the optic radiations or occipital cortex in the brain, often due to stroke, trauma, tumor, or other neurological conditions. It can significantly impact a person's daily functioning and may require visual rehabilitation to help compensate for the vision loss.

Albinism is a group of genetic disorders that result in little or no production of melanin, the pigment responsible for coloring skin, hair, and eyes. It is caused by mutations in genes involved in the production of melanin. There are several types of albinism, including oculocutaneous albinism (OCA) and ocular albinism (OA). OCA affects the skin, hair, and eyes, while OA primarily affects the eyes.

People with albinism typically have very pale skin, white or light-colored hair, and light-colored eyes. They may also have vision problems, such as sensitivity to light (photophobia), rapid eye movements (nystagmus), and decreased visual acuity. The severity of these symptoms can vary depending on the type and extent of albinism.

Albinism is inherited in an autosomal recessive manner, which means that an individual must inherit two copies of the mutated gene, one from each parent, in order to have the condition. If both parents are carriers of a mutated gene for albinism, they have a 25% chance with each pregnancy of having a child with albinism.

There is no cure for albinism, but individuals with the condition can take steps to protect their skin and eyes from the sun and use visual aids to help with vision problems. It is important for people with albinism to undergo regular eye examinations and to use sun protection, such as sunscreen, hats, and sunglasses, to prevent skin damage and skin cancer.

An axon is a long, slender extension of a neuron (a type of nerve cell) that conducts electrical impulses (nerve impulses) away from the cell body to target cells, such as other neurons or muscle cells. Axons can vary in length from a few micrometers to over a meter long and are typically surrounded by a myelin sheath, which helps to insulate and protect the axon and allows for faster transmission of nerve impulses.

Axons play a critical role in the functioning of the nervous system, as they provide the means by which neurons communicate with one another and with other cells in the body. Damage to axons can result in serious neurological problems, such as those seen in spinal cord injuries or neurodegenerative diseases like multiple sclerosis.

Optic nerve neoplasms refer to abnormal growths or tumors that develop within or near the optic nerve. These tumors can be benign (non-cancerous) or malignant (cancerous).

Benign optic nerve neoplasms include optic nerve meningiomas and schwannomas, which originate from the sheaths surrounding the optic nerve. They usually grow slowly and may not cause significant vision loss, but they can lead to compression of the optic nerve, resulting in visual field defects or optic disc swelling (papilledema).

Malignant optic nerve neoplasms are rare but more aggressive. The most common type is optic nerve glioma, which arises from the glial cells within the optic nerve. These tumors can quickly damage the optic nerve and cause severe vision loss.

It's important to note that any optic nerve neoplasm requires prompt medical evaluation and treatment, as they can potentially lead to significant visual impairment or even blindness if left untreated.

The retina is the innermost, light-sensitive layer of tissue in the eye of many vertebrates and some cephalopods. It receives light that has been focused by the cornea and lens, converts it into neural signals, and sends these to the brain via the optic nerve. The retina contains several types of photoreceptor cells including rods (which handle vision in low light) and cones (which are active in bright light and are capable of color vision).

In medical terms, any pathological changes or diseases affecting the retinal structure and function can lead to visual impairment or blindness. Examples include age-related macular degeneration, diabetic retinopathy, retinal detachment, and retinitis pigmentosa among others.

The optic disk, also known as the optic nerve head, is the point where the optic nerve fibers exit the eye and transmit visual information to the brain. It appears as a pale, circular area in the back of the eye, near the center of the retina. The optic disk has no photoreceptor cells (rods and cones), so it is insensitive to light. It is an important structure to observe during eye examinations because changes in its appearance can indicate various ocular diseases or conditions, such as glaucoma, optic neuritis, or papilledema.

The optic lobe in non-mammals refers to a specific region of the brain that is responsible for processing visual information. It is a part of the protocerebrum in the insect brain and is analogous to the mammalian visual cortex. The optic lobes receive input directly from the eyes via the optic nerves and are involved in the interpretation and integration of visual stimuli, enabling non-mammals to perceive and respond to their environment. In some invertebrates, like insects, the optic lobe is further divided into subregions, including the lamina, medulla, and lobula, each with distinct functions in visual processing.

Optic neuritis is a medical condition characterized by inflammation and damage to the optic nerve, which transmits visual information from the eye to the brain. This condition can result in various symptoms such as vision loss, pain with eye movement, color vision disturbances, and pupillary abnormalities. Optic neuritis may occur in isolation or be associated with other underlying medical conditions, including multiple sclerosis, neuromyelitis optica, and autoimmune disorders. The diagnosis typically involves a comprehensive eye examination, including visual acuity testing, dilated funduscopic examination, and possibly imaging studies like MRI to evaluate the optic nerve and brain. Treatment options may include corticosteroids or other immunomodulatory therapies to reduce inflammation and prevent further damage to the optic nerve.

Anophthalmos is a medical condition where an individual is born without one or both eyes. It is a congenital disorder, which means it is present at birth. In cases where only one eye is affected, it is called unilateral anophthalmos, and when both eyes are missing, it is referred to as bilateral anophthalmos.

Anophthalmos is different from microphthalmia, another congenital condition where the eye is present but abnormally small. In some cases, anophthalmos may be accompanied by other developmental anomalies or syndromes. The exact cause of anophthalmos is not always known, but it can be associated with genetic mutations or environmental factors that affect fetal development.

Individuals with anophthalmos require specialized medical care and management to ensure proper eye socket development, visual rehabilitation, and overall well-being. This may include the use of prosthetic eyes, orthoptic therapy, and other supportive measures.

EphB2 is a type of receptor tyrosine kinase (RTK) that belongs to the Eph family of receptors. These receptors are involved in bidirectional communication between cells and are important in the development and function of the nervous system. Specifically, EphB2 receptors are expressed on the surface of certain types of neurons and bind to ephrin-B ligands on nearby cells. This binding triggers a cascade of intracellular signaling events that can regulate various cellular processes, including cell migration, adhesion, and axon guidance.

EphB2 receptors have also been implicated in the pathology of several diseases, including cancer. For example, abnormal activation of EphB2 has been linked to tumor growth, progression, and metastasis in certain types of cancer. Therefore, EphB2 is an important target for the development of new therapies for cancer and other diseases.

The eye is the organ of sight, primarily responsible for detecting and focusing on visual stimuli. It is a complex structure composed of various parts that work together to enable vision. Here are some of the main components of the eye:

1. Cornea: The clear front part of the eye that refracts light entering the eye and protects the eye from harmful particles and microorganisms.
2. Iris: The colored part of the eye that controls the amount of light reaching the retina by adjusting the size of the pupil.
3. Pupil: The opening in the center of the iris that allows light to enter the eye.
4. Lens: A biconvex structure located behind the iris that further refracts light and focuses it onto the retina.
5. Retina: A layer of light-sensitive cells (rods and cones) at the back of the eye that convert light into electrical signals, which are then transmitted to the brain via the optic nerve.
6. Optic Nerve: The nerve that carries visual information from the retina to the brain.
7. Vitreous: A clear, gel-like substance that fills the space between the lens and the retina, providing structural support to the eye.
8. Conjunctiva: A thin, transparent membrane that covers the front of the eye and the inner surface of the eyelids.
9. Extraocular Muscles: Six muscles that control the movement of the eye, allowing for proper alignment and focus.

The eye is a remarkable organ that allows us to perceive and interact with our surroundings. Various medical specialties, such as ophthalmology and optometry, are dedicated to the diagnosis, treatment, and management of various eye conditions and diseases.

Ephrin-B2 is a type of protein that belongs to the ephrin family and is primarily involved in the development and function of the nervous system. It is a membrane-bound ligand for Eph receptor tyrosine kinases, and their interactions play crucial roles in cell-cell communication during embryogenesis and adult tissue homeostasis.

Ephrin-B2 is specifically a glycosylphosphatidylinositol (GPI)-anchored protein that is expressed on the cell membrane of various cell types, including endothelial cells, neurons, and some immune cells. Its interactions with Eph receptors, which are transmembrane proteins, lead to bidirectional signaling across the contacting cell membranes. This process regulates various aspects of cell behavior, such as adhesion, migration, repulsion, and proliferation.

In the context of the cardiovascular system, ephrin-B2 is essential for the development and maintenance of blood vessels. It is involved in the formation of arterial-venous boundaries, vascular branching, and remodeling. Mutations or dysregulation of ephrin-B2 have been implicated in various diseases, including cancer, where it can contribute to tumor angiogenesis and metastasis.

The geniculate bodies are part of the auditory pathway in the brainstem. They are two small, rounded eminences located on the lateral side of the upper pons, near the junction with the midbrain. The geniculate bodies are divided into an anterior and a posterior portion, known as the anterior and posterior geniculate bodies, respectively.

The anterior geniculate body receives inputs from the contralateral cochlear nucleus via the trapezoid body, and it is involved in the processing of sound localization. The posterior geniculate body receives inputs from the inferior colliculus via the lateral lemniscus and is involved in the processing of auditory information for conscious perception.

Overall, the geniculate bodies play a critical role in the processing and transmission of auditory information to higher brain areas for further analysis and interpretation.

Optic nerve diseases refer to a group of conditions that affect the optic nerve, which transmits visual information from the eye to the brain. These diseases can cause various symptoms such as vision loss, decreased visual acuity, changes in color vision, and visual field defects. Examples of optic nerve diseases include optic neuritis (inflammation of the optic nerve), glaucoma (damage to the optic nerve due to high eye pressure), optic nerve damage from trauma or injury, ischemic optic neuropathy (lack of blood flow to the optic nerve), and optic nerve tumors. Treatment for optic nerve diseases varies depending on the specific condition and may include medications, surgery, or lifestyle changes.

Optic nerve injuries refer to damages or trauma inflicted on the optic nerve, which is a crucial component of the visual system. The optic nerve transmits visual information from the retina to the brain, enabling us to see. Injuries to the optic nerve can result in various visual impairments, including partial or complete vision loss, decreased visual acuity, changes in color perception, and reduced field of view.

These injuries may occur due to several reasons, such as:

1. Direct trauma to the eye or head
2. Increased pressure inside the eye (glaucoma)
3. Optic neuritis, an inflammation of the optic nerve
4. Ischemia, or insufficient blood supply to the optic nerve
5. Compression from tumors or other space-occupying lesions
6. Intrinsic degenerative conditions affecting the optic nerve
7. Toxic exposure to certain chemicals or medications

Optic nerve injuries are diagnosed through a comprehensive eye examination, including visual acuity testing, slit-lamp examination, dilated fundus exam, and additional diagnostic tests like optical coherence tomography (OCT) and visual field testing. Treatment options vary depending on the cause and severity of the injury but may include medications, surgery, or vision rehabilitation.

Pituitary neoplasms refer to abnormal growths or tumors in the pituitary gland, a small endocrine gland located at the base of the brain. These neoplasms can be benign (non-cancerous) or malignant (cancerous), with most being benign. They can vary in size and may cause various symptoms depending on their location, size, and hormonal activity.

Pituitary neoplasms can produce and secrete excess hormones, leading to a variety of endocrine disorders such as Cushing's disease (caused by excessive ACTH production), acromegaly (caused by excessive GH production), or prolactinoma (caused by excessive PRL production). They can also cause local compression symptoms due to their size, leading to headaches, vision problems, and cranial nerve palsies.

The exact causes of pituitary neoplasms are not fully understood, but genetic factors, radiation exposure, and certain inherited conditions may increase the risk of developing these tumors. Treatment options for pituitary neoplasms include surgical removal, radiation therapy, and medical management with drugs that can help control hormonal imbalances.

Crossing over, genetic is a process that occurs during meiosis, where homologous chromosomes exchange genetic material with each other. It is a crucial mechanism for generating genetic diversity in sexually reproducing organisms.

Here's a more detailed explanation:

During meiosis, homologous chromosomes pair up and align closely with each other. At this point, sections of the chromosomes can break off and reattach to the corresponding section on the homologous chromosome. This exchange of genetic material is called crossing over or genetic recombination.

The result of crossing over is that the two resulting chromosomes are no longer identical to each other or to the original chromosomes. Instead, they contain a unique combination of genetic material from both parents. Crossing over can lead to new combinations of alleles (different forms of the same gene) and can increase genetic diversity in the population.

Crossing over is a random process, so the location and frequency of crossover events vary between individuals and between chromosomes. The number and position of crossovers can affect the likelihood that certain genes will be inherited together or separated, which is an important consideration in genetic mapping and breeding studies.

Pituitary apoplexy is a medical emergency that involves bleeding into the pituitary gland (a small gland at the base of the brain) and/or sudden swelling of the pituitary gland. This can lead to compression of nearby structures, such as the optic nerves and the hypothalamus, causing symptoms like severe headache, visual disturbances, hormonal imbalances, and altered mental status. It is often associated with a pre-existing pituitary tumor (such as a pituitary adenoma), but can also occur in individuals without any known pituitary abnormalities. Immediate medical attention is required to manage this condition, which may include surgical intervention, hormone replacement therapy, and supportive care.

Nerve fibers are specialized structures that constitute the long, slender processes (axons) of neurons (nerve cells). They are responsible for conducting electrical impulses, known as action potentials, away from the cell body and transmitting them to other neurons or effector organs such as muscles and glands. Nerve fibers are often surrounded by supportive cells called glial cells and are grouped together to form nerve bundles or nerves. These fibers can be myelinated (covered with a fatty insulating sheath called myelin) or unmyelinated, which influences the speed of impulse transmission.

The Sella Turcica, also known as the Turkish saddle, is a depression or fossa in the sphenoid bone located at the base of the skull. It forms a housing for the pituitary gland, which is a small endocrine gland often referred to as the "master gland" because it controls other glands and makes several essential hormones. The Sella Turcica has a saddle-like shape, with its anterior and posterior clinoids forming the front and back of the saddle, respectively. This region is of significant interest in neuroimaging and clinical settings, as various conditions such as pituitary tumors or other abnormalities may affect the size, shape, and integrity of the Sella Turcica.

Eye enucleation is a surgical procedure that involves the removal of the entire eyeball, leaving the eye muscles, eyelids, and orbital structures intact. This procedure is typically performed to treat severe eye conditions or injuries, such as uncontrollable pain, blindness, cancer, or trauma. After the eyeball is removed, an implant may be placed in the socket to help maintain its shape and appearance. The optic nerve and other surrounding tissues are cut during the enucleation procedure, which means that vision cannot be restored in the affected eye. However, the remaining eye structures can still function normally, allowing for regular blinking, tear production, and eyelid movement.

Carbocyanines are a class of organic compounds that contain a polymethine chain, which is a type of carbon-based structure with alternating single and double bonds, and one or more cyanine groups. A cyanine group is a functional group consisting of a nitrogen atom connected to two carbon atoms by double bonds, with the remaining valences on the carbon atoms being satisfied by other groups.

Carbocyanines are known for their strong absorption and fluorescence properties in the visible and near-infrared regions of the electromagnetic spectrum. These properties make them useful as dyes and fluorescent labels in various applications, including biomedical research, clinical diagnostics, and material science.

In medicine, carbocyanines are sometimes used as fluorescent contrast agents for imaging purposes. They can be injected into the body and accumulate in certain tissues or organs, where they emit light when excited by a specific wavelength of light. This allows doctors to visualize the distribution of the agent and potentially detect abnormalities such as tumors or inflammation.

It is important to note that while carbocyanines have potential medical applications, they are not themselves medications or drugs. They are tools used in various medical procedures and research.

Visual fields refer to the total area in which objects can be seen while keeping the eyes focused on a central point. It is the entire area that can be observed using peripheral (side) vision while the eye gazes at a fixed point. A visual field test is used to detect blind spots or gaps (scotomas) in a person's vision, which could indicate various medical conditions such as glaucoma, retinal damage, optic nerve disease, brain tumors, or strokes. The test measures both the central and peripheral vision and maps the entire area that can be seen when focusing on a single point.

Medical Definition:

Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic imaging technique that uses a strong magnetic field and radio waves to create detailed cross-sectional or three-dimensional images of the internal structures of the body. The patient lies within a large, cylindrical magnet, and the scanner detects changes in the direction of the magnetic field caused by protons in the body. These changes are then converted into detailed images that help medical professionals to diagnose and monitor various medical conditions, such as tumors, injuries, or diseases affecting the brain, spinal cord, heart, blood vessels, joints, and other internal organs. MRI does not use radiation like computed tomography (CT) scans.

Beyond the optic chiasm, with crossed and uncrossed fibers, the optic nerves are called optic tracts. The optic tract inserts ... the two optic nerves merge in the optic chiasm. In such a merged optic chiasm, part of the nerve fibres do not cross the ... In neuroanatomy, the optic chiasm, or optic chiasma ( /ɒptɪk kaɪæzəm/; from Greek χίασμα 'crossing', from Ancient Greek χιάζω ' ... This article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a ...
Optic chiasm; C=Visual (and motor) cortex; M, S=Decussating pathways; R, G: Sensory nerves, motor ganglia. Purkinje cell of the ... Structure of the Chiasma opticum and general theory of the crossing of nerve tracks)" [Die Structur des Chiasma opticum nebst ... 1905 Drawing of a section through the optic tectum of a sparrow, from "Estructura de los centros nerviosos de las aves", Madrid ...
The eye, especially the retina The optic nerve The optic chiasma The optic tract The lateral geniculate body The optic ... The optic nerve then carries these pulses through the optic canal. Upon reaching the optic chiasm the nerve fibers decussate ( ... "Optic Chiasma." Optic Chiasm Function, Anatomy & Definition. Healthline Medical Team, 9 March 2015. Web. 27 March 2016. ... The optic nerves from both eyes meet and cross at the optic chiasm, at the base of the hypothalamus of the brain. At this point ...
The optic chiasm has abnormal uncrossed wiring; many early Siamese were cross-eyed to compensate, but like the kinked tails, ...
... it extends to the optic chiasm. The cistern communicates superiorly with the chiasmatic cistern, and inferiorly with the ...
The optic chiasm is the primary cause of decussation; nasal fibers of the optic nerve cross (so each cerebral hemisphere ...
Two of the cranial nerves show chiasmas: (1) the chiasm of the optic tract (i.e., cranial nerve II), which originates from the ... possess an optic chiasm, and even the skull impressions of early vertebrates from the Ordovician show the presence of an optic ... the thalamus does not retrieve a branch from the optic tract but only from the contralateral optic tectum, so that the optic ... de Lussanet, M.H.E.; Osse, J.W.M. (2012). "An ancestral axial twist explains the contralateral forebain and the optic chiasm in ...
The optic nerve is sensory and crosses the midline in the optic chiasm. The oculomotor nerve, trochlear nerve, and abducens ... and the pancreas Optic chiasm chiasm of the trochlear nerve Non-crossed olfactory tract Aurofacial asymmetry Yakovlevian torque ... The optic nerve inserts on the optic tectum of the midbrain. In tetrapods and bony fish it also branches off to the LGN of the ... The olfactory tracts run parallel to the optic tract but do not form a chiasm. Accordingly, each olfactory bulb connects to the ...
The optic chiasm is formed by the union of the two optic nerves. The nasal fibers of each optic nerve decussate (cross) across ... Clinically, no optic field deficits have been observed in a small series of optic nerve sections at the optic nerve-chiasm ... The optic nerves consist of the axons from the retinal ganglion of each eye. At the chiasm, 53% of the axons from the nasal ... Gliomas of the optic chiasm are usually derived from astrocytes. These tumors are slow growing and more often found children. ...
These axons form the optic nerve, optic chiasm, and optic tract. A small percentage of retinal ganglion cells contribute little ... and it may also be secreted to control chiasm formation. When RGCs approach the optic chiasm, the point at which the two optic ... Once out of the optic chiasm, RGCs will extend dorsocaudally along the ventral diencephalic surface making the optic tract, ... Petros TJ, Rebsam A, Mason CA (2008-01-01). "Retinal axon growth at the optic chiasm: to cross or not to cross". Annual Review ...
Foxd1 is also required for proper formation of optic chiasm. During the formation of optic chiasm, Foxd1 is expressed in VT ... axons leave the retina via optic disc until they reach the optic chiasm. Foxg1 and Foxd1 are expressed in adjacent domains in ... It is determined that Foxd1 is essential for the correct formation of optic chiasm. FOX D1 expressed and function in Glioma ... and it also functions in the development of the retina and optic chiasm. It may also regulate inflammatory reactions and ...
The major example in the human brain is the Optic chiasm. A decussation (from Latin decussis 'ten', written as a capital X) ... where nerve fibres from one side cross over to the next The optic chiasm in the human brain, showing pathways conveying ... Specific terms are also used to describe the route of a nerve or nerve fibre: A chiasm (from Greek Chi) is used to describe ... The difference between a chiasm and a decussation is that the first refers to peripheral nerves whereas the latter refers to ...
Elofsson, R., & E. Dahl., (1970). The optic neuropiles and chiasmata of Crustacea. Zeitschrift für Zellforschung und ...
Above: optic tract, optic chiasma, internal carotid artery. Inferiorly: foramen lacerum, and the junction of the body and ... The optic nerve lies just above and outside the cavernous sinus, superior and lateral to the pituitary gland on each side, and ... enters the orbital apex via the optic canal. As a venous sinus, the cavernous sinus receives blood from the superior and ...
In vertebrates three of the cranial nerves show a chiasm. The Optic chiasm of the optic tract (type I or II) The chiasm of the ... in the optic tract between the optic chiasm and the optic tectum. Another example is the optic radiation which rotates the ... The optic chiasm in vertebrates can be of type I or II. However, an optic chiasm of type III is found in many insects and in ... A chiasm is thus not a nervous processing centre. By far the most widely known chiasm is the optic chiasm in vertebrate animals ...
Optic gliomas are usually pilocytic tumors, and can involve the optic nerve or optic chiasm. Optic gliomas are usually ... Optic nerve glioma (or optic glioma), a form of glioma which affects the optic nerve, is often one of the central nervous ... Once the optic chiasm is involved, the prognosis for life & vision worsens. Huson, Susan Mary; Hughes, Richard Anthony Cranmer ... Enlargement of the optic nerve along with a downward kink in the mid-orbit is usually observed. While CT scans allow for optic ...
EFNB2 has been shown to interact with EPHA3 and EPHB1 in optic chiasm development. EFNB2 has also been shown to serve as a ... "Ephrin-B2 and EphB1 mediate retinal axon divergence at the optic chiasm". Neuron. 39 (6): 919-35. doi:10.1016/j.neuron.2003.08. ...
Those lateral retinal nerve fibers do not cross in the optic chiasm. Calcification of the internal carotid arteries can impinge ...
When the neurons pass from the retina to the brain and reach the optic chiasma, some cross and some do not, so that visual ... The abnormality is that there is a disruption in the optic chiasm. The examination of Moni's brain suggested the disruption is ... Because of the visual pathway abnormality, by which some optic nerves are routed to the wrong side of the brain, white tigers ...
The optic chiasm, which is crucial to the visual system, was discovered around 100 C.E. by Marinus. Circa 1000, Al-Zahrawi, ... Jeffery G (October 2001). "Architecture of the optic chiasm and the mechanisms that sculpt its development". Physiological ... In the same year, Bartolomeo Eustachi studied the optic nerve, mainly focusing on its origin in the brain. In 1564, Giulio ...
Williams, SE; Mann, F; Erskine, L (2003). "Ephrin-B2 and EphB1 mediate retinal axon divergence at the optic chiasm". Neuron. 39 ...
Jeffery, G. (2001). Architecture of the optic chiasm and the mechanisms that sculpt its development. Physiological Reviews, 81( ... while information from the right visual field received by the left eye will not cross at the optic chiasm, and will remain on ... cells in the left eye that receive information from the left visual field cross to the right hemisphere at the optic chiasm; ...
... she has also investigated the role of ephrins in axon growth and the formation of the optic chiasm. In addition, her studies ... "Ephrin-B2 and EphB1 Mediate Retinal Axon Divergence at the Optic Chiasm, Neuron". Neuron. 39 (6): 919-935. doi:10.1016/j.neuron ...
These adenomas also have the potential to compress the hypothalamus and optic chiasm. POMC produced from the melanotropes of ...
Horton JC (1997). "Wilbrand's knee of the primate optic chiasm is an artefact of monocular enucleation". Transactions of the ... Wilbrand's knee: Inferonasal fibres of the optic nerve which go into the contralateral optic nerve 4 mm before crossing over to ... A lesion here produces a junctional scotoma in the superior temporal field of the optic nerve opposite the site of injury. Shin ... v t e (Optic nerve, All stub articles, Eye stubs). ...
Primates also have an optic chiasm (OC), with 45 percent made up of uncrossed nerves.[citation needed] The traditional idea is ... Larsson, M. (2013). The optic chiasm: a turning point in the evolution of eye/hand coordination. Front. zool. 10, 41. doi: ... Larsson M, Binocular vision, the optic chiasm, and their associations with vertebrate motor behavior. Frontiers in Ecol. Evol. ... Optic ataxia has been often confused with Balint's syndrome, but recent research has shown that optic ataxia can occur ...
... occurs in the upper nasal cavity, near the optic nerves and optic chiasm. Thus, tumor growth can impinge ... Craniofacial resection can help preserve the optic nerves and brain while removing the cribriform plate, olfactory bulb, dura ...
"An ancestral axial twist explains the contralateral forebrain and the optic chiasm in vertebrates". Animal Biology. 62 (2): 193 ...
"An ancestral axial twist explains the contralateral forebrain and the optic chiasm in vertebrates". Animal Biology. 62 (2): 193 ...
de Lussanet, M.H.E.; Osse, J.W.M. (2012). "An ancestral axial twist explains the contralateral forebain and the optic chiasm in ...
Beyond the optic chiasm, with crossed and uncrossed fibers, the optic nerves are called optic tracts. The optic tract inserts ... the two optic nerves merge in the optic chiasm. In such a merged optic chiasm, part of the nerve fibres do not cross the ... In neuroanatomy, the optic chiasm, or optic chiasma ( /ɒptɪk kaɪæzəm/; from Greek χίασμα crossing, from Ancient Greek χιάζω ... This article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a ...
The meaning of OPTIC CHIASMA is the X-shaped partial decussation on the undersurface of the hypothalamus through which the ... optic nerves are continuous with the brain -called also optic chiasm. ... The first known use of optic chiasma was in 1872 See more words from the same year ... "Optic chiasma." Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/optic%20chiasma. ...
... J Anat. 1956 Oct;90(4):486-93. ...
The fact that the CNN recognition of the optic chiasm fails for chiasm abnormalities in PWA underlines the fundamental ... The fact that the CNN recognition of the optic chiasm fails for chiasm abnormalities in PWA underlines the fundamental ... Here, we tested whether CNN trained to segment normal optic chiasms from the T1w magnetic resonance imaging (MRI) image can be ... The quality of outcome segmentation was assessed via the comparison to manually defined optic chiasm masks using the Dice ...
Optic Chiasma. Synaptic transmission of impulses from retinal cells follows the optic nerve to the optic chiasma, an x-shaped ... Damage to the optic pathway or visual cortex in the left brain-perhaps from a stroke-can cause complete loss of the right ... Optic pathway, Visual field, Accommodation, Common visual problems, Amblyopia, Other common visual problems ...
The crossed and uncrossed fibres of the optic chiasma differ not only anatomically in the areas of retina in which they arise ... The gross anatomy of the optic nerves and chiasma has been studied, and differences in the tension in the crossed and uncrossed ... Binasal hemianopia results from compression of the uncrossed fibres in the optic nerve or chiasma by the anterior cerebral or ... The chiasma has been dissected under low power microscopy and a three dimensional picture of it developed. Bitemporal ...
PATHWAY OF CENTRIFUGAL FIBRES IN THE HUMAN OPTIC NERVE, CHIASM, AND TRACT ... PATHWAY OF CENTRIFUGAL FIBRES IN THE HUMAN OPTIC NERVE, CHIASM, AND TRACT ...
An X-shaped structure in the brain where the optic nerves cross. It is an essential structure that aids in binocular vision and ... An X-shaped structure in the brain where the optic nerves cross. It is an essential structure that aids in binocular vision and ...
The acuity of central vision (at the optic disc) was explained by the concentration of visual spirit where the optic nerve met ... During the Renaissance, the organ of vision was transferred from the lens to the optic nerve, which was generally believed to ... Greek and Roman humoral physiology needed a hollow optic nerve, the obstruction of which prevented the flow of visual spirit to ... Medieval physicians understood that the presence of a fixed dilated pupil indicated optic nerve obstruction, preventing the ...
Diagram showing relative position of pituitary gland and optic chiasm; pituitary tumors may cause visual problems, labeled ... Pituitary gland and optic chiasm, labeled. Diagram showing relative position of pituitary gland and optic chiasm; pituitary ...
Optic chiasm stimulation. EPSCs were evoked by electrical stimulation of the optic chiasm with a Grass S88 stimulator (Grass ... Stimulation of the optic chiasm with trains of 25 stimuli at 0.08- to 25-Hz frequencies (A-F). The amplitude of each subsequent ... Dependence of eEPSC amplitude (pA) on the strength of stimulus (V) applied to the optic chiasm in WT and Opn4Cre/+ mice (A-F). ... Stimulation of the optic chiasm at 0.08 Hz does not induce synaptic depression at RHT-SCN synapses, and the eEPSC amplitude is ...
They are the most common astrocytic tumors in children, accounting for 80-85% of cerebellar astrocytomas and 60% of optic ... Optic nerve and optic chiasm hypothalamic juvenile pilocytic astrocytomas. Optic chiasm hypothalamic gliomas cannot be ... These tumors may involve the optic nerves, the optic chiasm, and the optic tracts. Most are juvenile pilocytic astrocytomas, ... Optic nerve and optic chiasm hypothalamic juvenile pilocytic astrocytomas. A subset of astrocytic tumors occurs in patients ...
Arachnoiditis involving the optic nerves and chiasm has been reported previously by Heuer and Vail4 (1931), Craig and Lillie1 ( ... Arachnoiditis involving the optic nerves and chiasm has been reported previously by Heuer and Vail4 (1931), Craig and Lillie1 ( ... Subdural Membrane with Arachnoiditis of the Optic Chiasm: A Clinical and Pathological Report. AMA Arch Ophthalmol. 1959;62(3): ... The occurrence of a free subdural membrane with arachnoiditis of the optic nerves and chiasm after spinal anesthesia and ...
OC, Optic chiasm; 3V, third ventricle.. ER-β expression in PVN: selective effect of osmolality on MNCs. One of the areas that ...
The optic nerve is located in the back of the eye. It is also called the second cranial nerve or cranial nerve II. It is the ... Optic chiasma. Medically reviewed by the Healthline Medical Network. The optic chiasm or optic chiasma is an X-shaped space, ... It is referred to as atrophy of the optic nerve.. Although the optic nerve is part of the eye, it is considered part of the ... The optic nerve is located in the back of the eye. It is also called the second cranial nerve or cranial nerve II. It is the ...
Carolinas Perfect Solution® Sheep Brain, Dura Mater Removed, Optic Chiasma Intact, Plain, Pail Item #228703 ... Microscopes & Optics Microscopes & Optics. Carolinas extensive assortment of compound and stereomicroscopes span virtually all ...
Cavernous sinus, optic chiasm area, or pituitary fossa. Other indications for nasal surgery include cancers, nasal valve ...
Compression of the optic chiasm, usually by a tumour of the pituitary fossa, may result in the "blinkers" effect. At the optic ...
Optic chiasm! Too cool for school.. Rigamarole February 1, 2012, 6:43am 13 ...
optic chiasm. OFS. orbitofrontal sulcus. OLS. olfactory sulcus. OLT. olfactory tubercle. OlT. olfactory tract. ...
Signals from each Retina follow the Optic Nerve to the Optic Chiasm, in the region of the Pituitary Gland. *Left Visual Field ... Localizes lesions to the Optic Radiations between the Lateral Geniculate Body and the visual cortex (Occipital Lobe). *Parietal ... Right Lateral Geniculate Body signals follow right Optic Radiations. *Upper Visual Fields through the Temporal Lobe ... Left Visual Field signals follow the Optic Nerve to the right Lateral Geniculate Body ...
Cover all of hippocampi, from optic chiasm to splenium of corpus callosum.. ...
Optic chiasm 5 . Amygdaloid nucleus 6 . Hippocampus 7 . Superior cerebellar artery right ...
Optic commissure. *. Optic fibers extend to optic chiasma. *. Brain: Inferior colliculus (in ...
Suprasellar: Vision problems due to compression of the optic nerves/chiasm.. *Posterior Fossa: Facial symptoms or loss of ... If the tumor grows large enough, vision problems may occur due to compression of the optic nerve. ... swelling of the optic nerve head in the back of the eye), the first step should be a thorough neurological evaluation, followed ...
Optic chiasm 5 . Amygdaloid nucleus 6 . Hippocampus 7 . Superior cerebellar artery right ...
  • Pituitary gland and optic chiasm, labeled. (alilamedicalmedia.com)
  • The optic chiasm lies in close proximity to the pituitary gland and can be compressed by tumors leading to visual disturbances (bitemporal hemianopsia) [6]. (bvsalud.org)
  • Arachnoiditis involving the optic nerves and chiasm has been reported previously by Heuer and Vail 4 (1931), Craig and Lillie 1 (1931), and Ryan 7 (1943). (jamanetwork.com)
  • The occurrence of a free subdural membrane with arachnoiditis of the optic nerves and chiasm after spinal anesthesia and meningitis has not been previously noted. (jamanetwork.com)
  • One patient had rudimentary optic nerves and chiasm on imaging. (bvsalud.org)
  • Retinal ganglion cell (RGC) axons leaving the eye through the optic nerve are blocked from exiting the developing pathway by Slit2 and Sema5A inhibition, expressed bordering the optic nerve pathway. (wikipedia.org)
  • Beyond the optic chiasm, with crossed and uncrossed fibers, the optic nerves are called optic tracts. (wikipedia.org)
  • The gross anatomy of the optic nerves and chiasma has been studied, and differences in the tension in the crossed and uncrossed fibres after chiasmal displacement have been investigated. (bmj.com)
  • The crossed and uncrossed fibres of the optic chiasma differ not only anatomically in the areas of retina in which they arise but also physically. (bmj.com)
  • In the case of such partial decussation, the optic nerve fibres on the medial sides of each retina (which correspond to the lateral side of each visual hemifield, because the image is inverted) cross over to the opposite side of the body midline. (wikipedia.org)
  • The inferonasal retina are related to the anterior portion of the optic chiasm whereas superonasal retinal fibers are related to the posterior portion of the optic chiasm. (wikipedia.org)
  • Ephrin-B2 is expressed at the chiasm midline by radial glia and acts as a repulsive signal to axons originating from the ventrotemporal retina expressing EphB1 receptor protein, giving rise to the ipsilateral, or uncrossed, projection. (wikipedia.org)
  • The optic chiasm is a key structure in the visual system, where the fate of axons from the retina is decided, such that axons carrying information from the right visual hemifield are guided to the left hemisphere and vice versa. (frontiersin.org)
  • The acuity of central vision (at the optic disc) was explained by the concentration of visual spirit where the optic nerve met the retina. (nature.com)
  • The job of the optic nerve is to transfer visual information from the retina to the vision centers of the brain via electrical impulses. (healthline.com)
  • Our blind spot is caused by the absence of specialized photosensitive (light-sensitive) cells, or photoreceptors, in the part of the retina where the optic nerve exits the eye. (healthline.com)
  • In such a merged optic chiasm, part of the nerve fibres do not cross the midline, but continue towards the optic tract of the ipsilateral side. (wikipedia.org)
  • The optic tract inserts on the optic tectum (in mammals known as superior colliculus) of the midbrain. (wikipedia.org)
  • Contralateral axons cross the chiasm midline as they progress from the optic nerve to the optic tract. (umontreal.ca)
  • In contrast, ipsilateral axons deviate from the chiasm and continue in the ipsilateral optic tract. (umontreal.ca)
  • Synaptic transmission of impulses from retinal cells follows the optic nerve to the optic chiasma , an x-shaped junction in the brain where half the fibers from each eye cross to the other side of the brain. (jrank.org)
  • All patients had absence of the optic nerve and retinal vessels in the affected eye or eyes. (bvsalud.org)
  • Cover all of hippocampi, from optic chiasm to splenium of corpus callosum. (ohsu.edu)
  • Interocular transfer of visual form discrimination habit in cats after section of the optic chiasm and corpus callosum. (bvsalud.org)
  • A-Transverse image at the level of the optic chiasm (black arrowhead). (avma.org)
  • Transverse images were obtained just rostral to the level of the optic chiasm. (avma.org)
  • H) Encephalitis (inflammation of the brain) in an infected ferret, showing perivascular cuffing (arrows) at the level of the optic chiasma. (cdc.gov)
  • In all vertebrates, the optic nerves of the left and the right eye meet in the body midline, ventral to the brain. (wikipedia.org)
  • Ssh expressed at the central nervous system midline inhibits crossing prior to the chiasm, where it is downregulated. (wikipedia.org)
  • RGC axons that do cross at the optic chiasm are guided by the vascular endothelial growth factor, VEGF-A, expressed at the midline, which signals through the receptor Neuropilin-1 (NRP1) expressed on RGC axons. (wikipedia.org)
  • Chiasm crossing is also promoted by Nr-CAM (Ng-CAM-related cell adhesion molecule) and Semaphorin6D (Sema6D) expressed at the midline, which form a complex that signals to Nr-CAM/Plexin-A1 receptors on crossing RGC axons. (wikipedia.org)
  • Together with the presence of Shh at the midline, this complementary expression pattern led us to hypothesize that Shh might repel ipsilateral RGC axons at the chiasm. (umontreal.ca)
  • additionally reporting thinner optic nerves and wider angles between optic tracts. (frontiersin.org)
  • Brain tumor and its treatment can affect the visual system at different levels, from the optic nerves (through compression or infiltration), to subcortical structures like the superior colliculus (SC) and lateral geniculate nuclei (LGN) to optic tracts, optic radiations, and visual cortices ( 1 - 4 ). (frontiersin.org)
  • The lateral surface is contiguous with the thalamus and subthalamus and is bordered by the internal capsule and optic tracts. (medscape.com)
  • The optic chiasm or optic chiasma is an X-shaped space, located in the forebrain, directly in front of the hypothalamus. (healthline.com)
  • 2] Rostrally, the hypothalamus extends from the anterior commissure, lamina terminalis, and optic chiasm. (medscape.com)
  • Septo-optic dysplasia (SOD) , also known as de Morsier syndrome , is a condition characterized by optic nerve hypoplasia and absence of the septum pellucidum and, in two-thirds of patients hypothalamic-pituitary dysfunction . (radiopaedia.org)
  • Rudimentary optic nerve on neuroimaging in one case suggests that ONA is on the continuum of optic nerve hypoplasia. (bvsalud.org)
  • In addition to enlarged lateral ventricles with an absent septum pellucidum, CT may demonstrate small optic apparatus (best seen with volumetric scanning and coronal reformats) and associated small bony optic foramina. (radiopaedia.org)
  • We will trace the history of ideas about optic nerve anatomy and function in the Western world from the ancient Greeks to the early 20th century and show how these influenced causal theories of optic nerve diseases. (nature.com)
  • The partial crossing over of optic nerve fibres at the optic chiasm allows the visual cortex to receive the same hemispheric visual field from both eyes. (wikipedia.org)
  • Bitemporal hemianopia, as well as associated or independent hemianopic scotomata, results from stretching of the crossing fibres in the chiasma. (bmj.com)
  • Binasal hemianopia results from compression of the uncrossed fibres in the optic nerve or chiasma by the anterior cerebral or internal carotid arteries. (bmj.com)
  • The organization of RGC axons changes from retinotopic to a flat sheet-like orientation as they approach the chiasm site. (wikipedia.org)
  • The first step of this integration is possible anatomically with the segregation of contralateral and ipsilateral axons at the optic chiasm. (umontreal.ca)
  • In vivo, we show that Boc is required for the normal segregation of ipsilateral axons at the optic chiasm and, conversely, that Boc expression in contralateral RGCs prevents their axons from crossing the optic chiasm. (umontreal.ca)
  • The fact that the CNN recognition of the optic chiasm fails for chiasm abnormalities in PWA underlines the fundamental differences in their spatial features. (frontiersin.org)
  • The researchers found significant abnormalities within the visual system brain structures of Parkinson's disease patients, including alterations of optic radiations, a reduction of white matter concentration and a reduction of optic chiasm volume. (eurekalert.org)
  • from Greek χίασμα 'crossing', from Ancient Greek χιάζω 'to mark with an X'), is the part of the brain where the optic nerves cross. (wikipedia.org)
  • The optic chiasm is found in all vertebrates, although in cyclostomes (lampreys and hagfishes), it is located within the brain. (wikipedia.org)
  • Damage to the optic pathway or visual cortex in the left brain-perhaps from a stroke-can cause complete loss of the right visual field. (jrank.org)
  • An X-shaped structure in the brain where the optic nerves cross. (eyepatient.net)
  • Greek and Roman humoral physiology needed a hollow optic nerve, the obstruction of which prevented the flow of visual spirit to and from the brain and resulted in blindness. (nature.com)
  • Specifically, Ibn Isa illustrated the optic chiasm and brain. (muslimheritage.com)
  • The optic chiasm is the part of the brain where the left and right optic nerves intersect. (eurekalert.org)
  • Optic neuritis is an inflammatory injury of the optic nerve that causes vision loss, which is common in MS and other CNS inflammatory disorders. (medscape.com)
  • Clinical presentation of septo-optic dysplasia is varied and mostly dependent on whether or not it is associated with schizencephaly (~50% of cases). (radiopaedia.org)
  • In vertebrates with a large overlap of the visual fields of the two eyes, i.e., most mammals and birds, but also amphibians, reptiles such as chameleons, the two optic nerves merge in the optic chiasm. (wikipedia.org)
  • Medieval physicians understood that the presence of a fixed dilated pupil indicated optic nerve obstruction, preventing the passage of visual spirit, and that cataract surgery in such cases would not restore sight. (nature.com)
  • Sudden visual loss (or worsening of vision) can occur if the optic chiasm becomes (more) compressed. (uclahealth.org)
  • The neurological symptoms are due to compression or invasion of adjacent structures, such as the optic nerve, causing visual involvement [10]. (bvsalud.org)
  • Juvenile pilocytic astrocytomas usually arise in the cerebellum, brainstem, hypothalamic region, or optic pathways, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord. (medscape.com)
  • a) Is found between the optic nerve and the medial rectus * b) Contains sympathetic nerve that supplies the sphincter pupillae * c) Is a parasympathetic relay ganglion for fibers from the Edinger-Westphal Nucleus? (globalguideline.com)
  • After collecting behavioral data, hypothalamic slices were prepared and evoked EPSCs (eEPSCs) were recorded from SCN neurons by stimulating the optic chiasm. (eneuro.org)
  • Glaucoma is one of the most common illnesses affecting the optic nerve. (healthline.com)
  • The optic chiasm volume differed significantly between the control and advanced NTG groups ( p = 0.0003) and between early and advanced glaucoma patients ( p = 0.004). (mdpi.com)
  • All imaging modalities that can visualize the septum pellucidum (ultrasound, CT and MRI) will detect its absence in septo-optic dysplasia. (radiopaedia.org)
  • Since all vertebrates, even the earliest fossils and modern jawless ones, possess an optic chiasm, it is not known how it evolved. (wikipedia.org)
  • 3 He admitted that cobweb-thin nerves might not possess a lumen but those in the optic nerves ( poroi optikoi -optic channels) were large enough to be visible and to be probed with a hog bristle. (nature.com)
  • A number of theories have been proposed for the function of the optic chiasm in vertebrates (see theories). (wikipedia.org)
  • Effectively, it is unknown which anatomical features of the chiasm may be employed in an individualized detection of malformations or whether such a detection is possible in the first place. (frontiersin.org)
  • A median protuberance, the tuber cinereum lies between the optic chiasm (rostrally) and mammillary bodies (caudally) and is continuous anteriorly with the lamina terminalis. (medscape.com)
  • Here, we tested whether CNN trained to segment normal optic chiasms from the T1w magnetic resonance imaging (MRI) image can be also applied to abnormal chiasms, specifically with optic nerve misrouting as typical for human albinism. (frontiersin.org)
  • Specifically, both studies provided significant evidence of reductions in the width of optic nerves and optic chiasm in PWA, with Schmitz et al. (frontiersin.org)
  • Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/optic%20chiasma. (merriam-webster.com)
  • In many vertebrates the left optic nerve crosses over the right one without fusing with it. (wikipedia.org)
  • image: Left and right optic radiation (OR) image in a representative subject overlaid onto a T1-weighted axial volume image of the same subject. (eurekalert.org)
  • 1. Sener R. Septo-Optic Dysplasia Associated with Cerebral Cortical Dysplasia (Cortico-Septo-Optic Dysplasia). (radiopaedia.org)
  • Although the optic nerve is part of the eye, it is considered part of the central nervous system. (healthline.com)
  • We performed supervised training of the CNN on the T1w images of control participants ( n = 1049) from the Human Connectome Project (HCP) repository and automatically generated algorithm-based optic chiasm masks. (frontiersin.org)
  • During the Renaissance, the organ of vision was transferred from the lens to the optic nerve, which was generally believed to be on the axis of the eye. (nature.com)
  • Both the microscope and the ophthalmoscope allowed visualisation of the optic nerve, but problems of interpretation persisted until conceptual transformations in medical science were made. (nature.com)