1,527 articles
Ocular pain
Ocular pain (eye pain, ICD-10 H57.1, ICD-11 MC18) is pain in or around the eye, from corneal abrasion to glaucoma, uveitis, scleritis, referred headache, or neuropathic ocular pain; red flags include vision loss and proptosis.
Ocular siderosis
Ocular siderosis (siderosis bulbi): iron deposition in eye tissues from a retained iron-containing intraocular foreign body, usually after hammering trauma; causes heterochromia, cataract, retinal degeneration; treated by foreign body removal.
Ocular tilt reaction
Ocular tilt reaction (OTR): triad of skew deviation, ocular torsion, and head tilt toward the lower eye, from otolithic pathway imbalance; coined by Westheimer and Blair, 1975.
Oculocerebrocutaneous syndrome
Oculocerebrocutaneous syndrome, also called Delleman-Oorthuys syndrome, is a rare congenital disorder combining eye, brain, and skin malformations, first described in 1981 in around 40 reported cases, mostly in boys.
Oculocutaneous albinism type 7
Oculocutaneous albinism type 7 (OCA7, OMIM 615179) is a very rare autosomal recessive albinism caused by LRMDA (C10orf11) variants on 10q22.2-q22.3, with predominantly ocular features; 18 patients described, proposed rename ocular albinism type 2.
Oculoskeletodental syndrome
Oculoskeletodental syndrome (OCSKD, OMIM 618440) is an extremely rare autosomal recessive ciliopathy caused by PIK3C2A loss-of-function variants, causing congenital cataract, glaucoma, skeletal and dental anomalies, developmental delay, and stroke.
Oguchi disease
Oguchi disease is a rare autosomal recessive retinal disorder causing congenital stationary night blindness and the Mizuo-Nakamura phenomenon, first described by Chuta Oguchi in Japan in 1907.
Oligoastrocytoma, dual genotype
Oligoastrocytoma, dual genotype (ORPHA:251656), also called mixed oligoastrocytoma, is a rare low-grade mixed glioma containing both astrocytoma-type (TP53/ATRX) and oligodendroglioma-type (1p/19q codeleted) genotypes; fewer than 10 cases reported, term deleted in WHO 2021.
Oligocone trichromacy
Oligocone trichromacy (oligocone syndrome, ORPHA:75378) is a rare congenital cone dysfunction disorder with reduced visual acuity, absent or reduced cone ERG, normal fundus and rod responses, and preserved color vision; some cases involve CNGA3, CNGB3, or PDE6C mutations.
Oligodendroglioma grade 3
Oligodendroglioma grade 3 (formerly anaplastic oligodendroglioma) is a malignant IDH-mutant, 1p/19q-codeleted brain tumor; standard care is radiotherapy plus PCV chemotherapy, with temozolomide as a toxicity-sparing alternative.
Ophthalmoparesis
Ophthalmoparesis, also called ophthalmoplegia when complete, is weakness of the extraocular muscles causing diplopia and ptosis; causes span brain, cranial nerve, neuromuscular junction (myasthenia gravis), and muscle (thyroid eye disease, CPEO).
Opisthotonos
Opisthotonus (opisthotonos): severe backward arching of the neck and trunk from involuntary extensor paraspinal muscle contraction; symptom of tetanus, strychnine poisoning, dystonia, seizures, or functional disorders; described since Hippocrates.
Opsoclonus-myoclonus syndrome
Opsoclonus-myoclonus syndrome (Kinsbourne syndrome, dancing eye syndrome) is a rare neuroinflammatory disorder with opsoclonus, myoclonus, ataxia, and sleep and behavioral disturbance, usually paraneoplastic from neuroblastoma in children and lung or breast cancer in adults.
Optic atrophy
Optic atrophy, better termed optic neuropathy, is death of retinal ganglion cell axons causing a pale optic disc and vision loss; causes include glaucoma, compression, ischemia, toxins, and inherited mitochondrial disorders like LHON and OPA1-related dominant optic atrophy.
Optic atrophy-intellectual disability syndrome
Optic atrophy-intellectual disability syndrome, or Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS, OMIM 615722), is a rare autosomal dominant NR2F1 disorder with developmental delay, intellectual disability, optic atrophy, hypotonia, and seizures.
Optic disc dysplasia
Optic disc dysplasia (ICD-11 LA13.73) is a congenital malformation in which the optic disc is deformed and fits no recognized diagnostic category; related excavated anomalies include morning glory disc anomaly, optic disc pit, and coloboma, with risks of retinal detachment and systemic associations such as papillorenal syndrome.
Optic disc pit
Optic disc pit (ODP, optic nerve pit): rare congenital optic nerve head excavation, about 1 in 11,000, usually inferotemporal and unilateral; causes maculopathy with retinal fluid in 25–75% of eyes, treated mainly by vitrectomy.
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.
Orbital cyst
Orbital cyst (ICD-11 9A23): an epithelium- or tissue-lined cystic lesion in the orbit, congenital or acquired. Dermoid cysts dominate, 3-9% of orbital masses; diagnosis by CT/MRI, treatment by intact excision.
Orbital inflammation
Orbital inflammation (nonspecific orbital inflammation, idiopathic orbital inflammation, orbital pseudotumor) is benign noninfectious inflammation of orbital tissues, diagnosed by exclusion, third commonest after thyroid eye disease and lymphoma, treated first with corticosteroids.
Orbital leiomyoma
Orbital leiomyoma (ORPHA:52994) is a rare benign smooth muscle tumor of the eye socket, arising from orbital vessel walls or Müller's muscle, slow-growing, encapsulated, causing painless proptosis, treated by complete excision with excellent prognosis.
Orbital subperiosteal abscess
Orbital subperiosteal abscess (SPA), Chandler stage III orbital infection: pus between the orbital wall and periorbita, usually medial, complicating ethmoid or frontal sinusitis; managed medically in selected young patients, drained otherwise.
Oromandibular dystonia
Oromandibular dystonia is a focal dystonia in which involuntary contractions of the jaw, tongue, and facial muscles disrupt chewing, speaking, and swallowing, typically beginning in the 50s.
Other peripheral vertigo
Other peripheral vertigo, ICD-11 code AB34.1 (also indexed as otogenic, auditory, or aural vertigo and Lermoyez syndrome), is the residual WHO category for peripheral vestibular vertigo not classified under a named disorder such as BPPV, vestibular neuritis, or Ménière's disease.
Ototoxic hearing loss
Ototoxic hearing loss: irreversible sensorineural hearing loss from ototoxic drugs (aminoglycosides, cisplatin, loop diuretics, salicylates) or workplace chemicals (solvents, lead, carbon monoxide), detected by baseline and serial high-frequency audiometry.
Pachymeningitis
Pachymeningitis, also called hypertrophic pachymeningitis in its fibrotic form, is inflammation and thickening of the dura mater (ICD-11 8E41) caused by infection, autoimmune disease including ANCA and IgG4-related disease, or cancer, diagnosed by MRI and dural biopsy.
Pain
Pain: unpleasant sensory and emotional experience (IASP); acute vs chronic (>3 months, ICD-11 disease). Covers nociceptive, neuropathic, nociplastic mechanisms, gate control theory, measurement scales, ~20-30% prevalence, $500-600 billion US cost, 2025 suzetrigine approval.
Pain disorders
Pain disorders are conditions in which pain is the central clinical problem, coded 8E43 in ICD-11's nervous system chapter and classified broadly under chronic pain (MG30) as primary or secondary pain lasting over three months.
Palatal myoclonus
Palatal myoclonus, also called palatal tremor, is a rare movement disorder with rhythmic 0.5-5 Hz contractions of the soft palate. Two forms: essential (tensor veli palatini, ear clicks, no lesion) and symptomatic (Guillain-Mollaret triangle lesion, often post-stroke).