25,729 articles
Orthoptics
Orthoptics is an allied health discipline concerned with the assessment, diagnosis, and non-surgical treatment of binocular vision, eye movement, and eye alignment disorders, including amblyopia and strabismus.
Orthorexia nervosa
Orthorexia nervosa (ON), coined by Steven Bratman in 1997, is a proposed disorder of obsessive healthy eating, not in DSM-5 or ICD-11, with prevalence estimates from 1% to 90% and no validated clinical diagnostic tool.
Orthostatic hypertension
Orthostatic hypertension: a sustained systolic blood pressure rise of at least 20 mmHg on standing with standing SBP at least 140 mmHg, per the American Autonomic Society and Japanese Society of Hypertension consensus definition; linked to sympathetic overactivity and hypertension.
Orthostatic hypotension
Orthostatic hypotension (postural hypotension): a fall of ≥20 mm Hg systolic or ≥10 mm Hg diastolic within 3 minutes of standing. Neurogenic (autonomic failure, synucleinopathies) versus non-neurogenic (drugs, hypovolemia) forms; treated with fluids, salt, compression, midodrine, droxidopa.
Orthostatic intolerance
Orthostatic intolerance: symptoms of cerebral hypoperfusion or sympathetic activation while standing, relieved by lying down. Covers orthostatic hypotension, vasovagal syncope, and POTS (heart rate rise ≥30 bpm without blood pressure fall).
Orthostatic proteinuria
Orthostatic (postural) proteinuria: excess urinary protein only when upright, normal when supine; benign condition affecting 2-5% of adolescents, diagnosed by first-morning urine testing, requiring no treatment.
Orthotic Devices
Orthotic devices, or orthoses, are braces, slings, and supports worn outside the body to align or stabilize weak body parts, unlike prostheses, which replace missing parts.
Orthotics
Orthotics, also known as orthopedic or orthopedic braces, is the branch of healthcare concerned with orthoses, externally applied devices that support joints, correct alignment, and relieve pain.
Orthotopic xenograft model
The orthotopic xenograft model transplants human tumor cells or tissue into the organ of origin in an immunodeficient mouse, so tumors grow in their native microenvironment.
OSB Digital
OSB Digital, LLC is a process-engineering consultancy founded in 2018 in Spring, Texas, by Osvaldo A. Bascur, a metallurgical engineer elected to the National Academy of Engineering in 2025.
Oscillococcinum
Oscillococcinum (Anas barbariae 200CK) is Boiron's homeopathic flu remedy made from diluted wild duck heart and liver; Cochrane finds low-quality evidence with no proven preventive effect.
Oscillopsia
Oscillopsia is the illusion that the visual world moves when it is still, caused by nystagmus, saccadic intrusions, or vestibulo-ocular reflex failure, most often in bilateral vestibulopathy, Ménière's disease, or neurological disease.
Oseltamivir
Oseltamivir (Tamiflu) is an oral neuraminidase inhibitor antiviral against influenza A and B, developed by Roche, licensed 1999, used for treatment and prophylaxis, with H275Y as its key resistance marker.
Osemitamab
Osemitamab (TST001) is Transcenta's humanized, fucose-reduced anti-Claudin18.2 IgG1 monoclonal antibody for CLDN18.2-expressing solid tumors, in phase III first-line G/GEJ gastric cancer development with FDA orphan drug designation.
Osemozotan
Osemozotan (MKC-242) is a selective 5-HT1A receptor agonist developed by Mitsubishi Chemical and characterized at Osaka University, showing antianxiety and antidepressant effects in animal studies.
OSGA trial
OSGA trial (NCT02619214), a phase 4 randomized Barcelona trial comparing 30% vs 60% inspired oxygen during one hour of sevoflurane general anesthesia, measuring malondialdehyde and other oxidative stress markers in healthy surgical patients.
Osgood–Schlatter disease
Osgood-Schlatter disease (Lannelongue disease) is a traction apophysitis of the tibial tuberosity where the patellar tendon attaches, first described in 1903, affecting about 10% of adolescent athletes and usually resolving with conservative care.
Osilodrostat
Osilodrostat (Isturisa, LCI699) is an oral cortisol synthesis inhibitor blocking CYP11B1 (and CYP11B2), FDA-approved in 2020 and expanded in 2025 for endogenous hypercortisolemia in adult Cushing's syndrome; dosing starts at 2 mg twice daily up to 30 mg twice daily.
Osimertinib
Osimertinib (Tagrisso) is a third-generation irreversible EGFR-TKI for EGFR-mutated NSCLC, binding Cys797, targeting T790M, penetrating the blood-brain barrier, with approvals in first-line, adjuvant, and combination settings.
Osimertinib regimen
The osimertinib regimen is an oral treatment plan for EGFR-mutated non-small cell lung cancer, built around osimertinib (Tagrisso), a third-generation EGFR inhibitor taken as an 80 mg tablet once daily.
Oskar Bernhard
Oskar Bernhard (1861–1939) was a Swiss surgeon and general physician in the Engadin valley, regarded as the first modern heliotherapist for treating wounds and tuberculosis with sunlight from 1902.
Oslo University Hospital
Oslo University Hospital (Oslo universitetssykehus) is Norway's largest hospital, a university hospital created in 2008 by merging Aker, Rikshospitalet, and Ullevål, with roots tracing to 1826.
Osmotherapy
Osmotherapy is the intravenous use of osmotic agents, principally mannitol and hypertonic saline, to draw water from brain tissue and lower intracranial pressure in cerebral edema.
Osmotic Fragility
Osmotic fragility (erythrocyte osmotic fragility test, OFT, NESTROFT, AGLT) measures red blood cell resistance to lysis in hypotonic saline; spherocytes in hereditary spherocytosis lyse at higher NaCl, thalassemia cells resist, and the test lacks specificity for autoimmune hemolytic anemia.
Ospemifene
Ospemifene (Osphena, Senshio) is an oral SERM, 60 mg daily with food, for moderate to severe vulvar and vaginal atrophy, dryness, and dyspareunia in postmenopausal women; FDA-approved 2013, EU 2015.
OSS study
OSS study (NCT07453901): The Multicentre Prospective Observational Study on the Management of Septic Shock, a 5,000-patient prospective cohort led by Xavier Monnet at Bicetre Hospital, describing real-world septic shock treatment, monitoring practices, and guideline adherence from October 2026.
Osseointegrated prosthetic limb
An osseointegrated prosthetic limb is an artificial arm or leg attached directly to the skeleton by a titanium implant passing through the skin, replacing the socket.
Ossicles
Ossicles (auditory ossicles): the malleus, incus, and stapes, three tiny chained bones of the mammalian middle ear that carry and amplify eardrum vibrations to the oval window; smallest bones in the body.
Ossicular Prosthesis
Ossicular prosthesis: an implant replacing one or more middle ear ossicles, made as PORP (drum-to-stapes) or TORP (drum-to-footplate) devices in titanium, hydroxyapatite, or autologous material for conductive hearing loss.
Ossicular replacement
Ossicular replacement, or ossiculoplasty, is a middle-ear operation that implants a prosthesis to rebuild the ossicular chain, restoring sound conduction between the tympanic membrane and the oval window.