All articles starting with O
9,097 articles
Optic disc swelling
Optic disc swelling (disc edema, papilledema when from raised intracranial pressure) is axoplasmic-stasis swelling of the optic nerve head, distinguished from pseudoedema such as optic disc drusen by OCT and fundus findings.
OpTic Gaming
OpTic Gaming: American esports organization founded 2006 as a Call of Duty team, famous for the GreenWall fanbase, the Scump-FormaL-Karma-Crimsix dynasty, Halo World Championship titles, and the 2021 Envy merger.
Optic nerve
Optic nerve (cranial nerve II, nervus opticus): the CNS white-matter tract of about 1.2 million retinal ganglion cell axons carrying vision from retina to chiasm and brain; myelinated by oligodendrocytes, afferent limb of the light reflex, limited regeneration.
Optic nerve avulsion
Optic nerve avulsion (ONA, Evulsio nervi optici) is traumatic disinsertion of optic nerve fibers at the lamina cribrosa after blunt ocular trauma; rare, causes permanent severe vision loss, no effective treatment.
Optic neuritis
Optic neuritis, inflammatory optic neuropathy causing subacute vision loss and eye pain in young adults; typical (idiopathic or MS) versus atypical AQP4-IgG NMOSD and MOGAD forms, diagnosed clinically with OCT and MRI support.
Optic pathway glioma
Optic pathway glioma (visual pathway glioma) is a rare, slow-growing, usually WHO grade I pilocytic astrocytoma of the optic nerve, chiasm, or tract, mostly in children under 10, often linked to NF1, treated by observation, chemotherapy, or targeted MEK inhibitors.
Optica (society)
Optica, formerly the Optical Society of America, is an international optics and photonics society founded in 1916, headquartered in Washington, DC, with more than 24,000 members.
Optical
Optical is the alias of Matt Quinn, a London drum and bass producer and DJ who forms half of Ed Rush & Optical and co-founded Virus Recordings.
Optical aberration
Optical aberration, also called lens aberration, is a departure of a real optical system's image from the ideal of simple lens theory, arising as monochromatic or chromatic types.
Optical activity
Optical activity is the rotation of the plane of polarized light as it passes through a chiral material such as quartz or sugar, a phenomenon discovered by François Arago in 1811.
Optical add-drop multiplexer
An optical add-drop multiplexer (OADM) is a wavelength-selective device in WDM fiber systems that drops and adds wavelength channels at a site while other wavelengths pass through untouched.
Optical amplifier
An optical amplifier, also called a laser amplifier, is a device that boosts light signals directly without converting them to electricity, enabling long-haul fiber-optic transmission and dense wavelength-division multiplexing.
Optical antenna
An optical antenna, also called a nanoantenna, is a nanoscale metallic or dielectric structure that converts light into localized energy and back, beating the diffraction limit.
Optical attenuator
An optical attenuator is a passive device that reduces the power of an optical signal by a specified amount in decibels, existing as fixed or adjustable variable types.
Optical axis
The optical axis is the line of rotational symmetry of an optical system: a ray traveling along it meets each surface at normal incidence and leaves undeviated.
Optical binding
Optical binding is a laser-induced inter-particle force between particles illuminated by off-resonant light, first predicted in 1980 and able to self-organize particles into optical matter.
Optical biometry
Optical biometry is a non-contact ophthalmic technique that uses infrared light to measure the eye's axial length, replacing ultrasound for intraocular lens power calculation before cataract surgery.
Optical bistability
Optical bistability is a nonlinear optical effect where a device has two stable output states for the same input light intensity, enabling all-optical switching and memory.
Optical black hole
An optical black hole is a laboratory structure reproducing a black hole's event horizon or omnidirectional light absorption, built to study Hawking radiation in the lab.
Optical breakdown
Optical breakdown is the rapid ionization of a medium by an intense laser pulse, first observed in 1964, which forms a luminous plasma that limits light transmission through transparent materials.
Optical brightener
Optical brighteners, also called fluorescent whitening agents, are compounds that absorb ultraviolet light and re-emit it as blue fluorescence, making textiles, paper, and plastics look whiter.
Optical buffering
Optical buffering is the temporary storage of optical packets as light, without electrical conversion, using fiber delay lines that add fixed delays, since optical switches lack random-access memory.
Optical burst switching
Optical burst switching is a switching technique for optical networks in which edge nodes aggregate packets into bursts that intermediate nodes switch entirely in the optical domain, proposed in 1999.
Optical bypass
Optical bypass is a fiber network design principle in which transit traffic at an intermediate node is forwarded directly between fibers in the optical domain, avoiding costly electronic processing.
Optical cavity
An optical cavity, also called an optical resonator or laser resonator, is an arrangement of mirrors in which light circulates repeatedly, selecting laser frequencies and enhancing light-matter interactions.
Optical center (optics)
The optical center of a lens is the point where light passes through without deviation, with zero prismatic effect; in a thin lens it lies on the optical axis.
Optical channel monitoring
Optical channel monitoring measures the physical parameters of individual wavelength channels in WDM systems, such as power, wavelength, and OSNR, and impairments like chromatic dispersion.
Optical character recognition
Optical character recognition (OCR), also known as an optical character reader, is a technology that converts images of text, such as scans and image-only PDFs, into searchable, editable machine-readable text.
Optical circuit switch
An optical circuit switch (OCS) is a device that steers whole light paths between fiber ports with movable mirrors, without converting signals to electrical form or inspecting packets.
Optical circulator
An optical circulator is a non-reciprocal device with three or four ports that routes entering light to the next port in fixed cyclic order, used in full-duplex fiber communication.