497 articles
Martinique crinkled retinal pigment epitheliopathy
Martinique crinkled retinal pigment epitheliopathy (MCRPE, MDPT3, patterned macular dystrophy 3) is an ultra-rare autosomal dominant retinal dystrophy from MAPKAPK3 mutations, first described in Martinique, with a dry-desert-land fundus pattern, adult onset, and PCV or CNV complications.
Mastoiditis
Mastoiditis is a bacterial infection of the mastoid air cells, usually complicating acute otitis media in young children. Key signs are postauricular swelling with pinna displacement; treated with IV ceftriaxone, sometimes mastoidectomy.
Mechanical lagophthalmos
Mechanical lagophthalmos is incomplete eyelid closure caused by physical obstruction such as proptosis, scarring, ectropion, or symblepharon, distinct from paralytic lagophthalmos; ICD-10 code H02.22, treated with lubricants, taping, tarsorrhaphy, and scar release.
Mechanoreceptor
Mechanoreceptors are sensory receptors converting touch, pressure, vibration, and stretch into neural signals. Key cutaneous types include Merkel, Meissner, Pacinian, and Ruffini receptors, with PIEZO2 as the principal mechanotransducer ion channel.
Meibomian gland
Meibomian gland (tarsal gland): large modified sebaceous gland in the eyelid tarsal plate, described by Heinrich Meibom in 1666, secreting meibum holocrinely to form the tear film's lipid layer; its dysfunction (MGD) causes most evaporative dry eye.
Ménière's disease
Ménière's disease, an inner ear disorder with episodic vertigo, fluctuating hearing loss, tinnitus, and aural fullness, linked to endolymphatic hydrops; cause unknown, treated with diet, drugs, injections, or surgery.
Merkel cell
Merkel cell (Tastzelle), an epidermal mechanosensory cell in the basal skin layer, forming the Merkel cell-neurite complex with Aβ SA1 fibers for light touch; PIEZO2-dependent, ATOH1-specified, epidermal origin; linked to Merkel cell carcinoma.
Microtia
Microtia is a congenital underdevelopment of the external ear, ranging from a small malformed auricle to anotia; about 1 in 3,800 US births, usually unilateral, treated by rib cartilage or porous polyethylene reconstruction and bone conduction hearing devices.
Middle ear
The middle ear (tympanic cavity) is the air-filled space behind the eardrum holding the malleus, incus, and stapes, which transmit and amplify sound to the inner ear, ventilated by the eustachian tube.
Middle ear neuroendocrine tumor
Middle ear neuroendocrine tumor (MeNET), formerly called middle ear adenoma, is a rare tumor of the middle ear causing hearing loss and tinnitus, treated by surgical excision.
Middle Ear Ventilation
Middle ear ventilation, also called tympanostomy or grommet insertion, treats glue ear by inserting tiny tubes through the eardrum to drain fluid and let air in.
Mirror-touch synesthesia
Mirror-touch synesthesia is a synesthesia variant in which seeing another person touched produces a felt touch on one's own body; prevalence about 1.6%, explained by threshold and self-other theories, and linked variably to empathy.
Misophonia
Misophonia is a disorder of intense anger or disgust triggered by specific sounds like chewing or breathing, first named in 2001, defined by a 2022 Delphi consensus, and treatable with cognitive behavioral therapy.
Mitomycin C
Mitomycin C (MMC, NSC 26980) is an antitumor antibiotic activated by quinone reduction into a DNA-cross-linking bis-electrophile; FDA-approved 1974 for cancers and widely used off-label as an antiscarring agent in glaucoma trabeculectomy surgery.
Morning glory disc anomaly
Morning glory disc anomaly (MGDA) is a rare congenital optic nerve malformation with a funnel-shaped, flower-like optic disc, usually affecting one eye and impairing vision.
Moro reflex
Moro reflex, also called the startle or embrace reflex (Umklammerungsreflex), is a primitive newborn reflex elicited by sudden head drop, with arm extension-abduction then flexion; it disappears by 2–5 months and signals clavicle fracture, brachial plexus palsy, or brain injury when absent or asymmetric.
Motion sickness
Motion sickness (seasickness, car sickness) is nausea, vomiting, dizziness, pallor, and cold sweating from real or perceived motion conflicting vestibular, visual, and proprioceptive inputs; treated with habituation, scopolamine, and sedating antihistamines.
Mucopurulent conjunctivitis
Mucopurulent conjunctivitis (ICD-11 9A60.3, ICD-10 H10.0), bacterial conjunctival infection with mucus-and-pus discharge and matted eyelids; usually self-limited, antibiotics modestly speed cure.
Multifocal Intraocular Lenses
Multifocal intraocular lenses (MIOLs), including bifocal, trifocal, refractive, and diffractive designs, are implanted IOLs giving near, intermediate, and distance vision after cataract surgery, trading reduced contrast sensitivity and halos for spectacle independence.
Multifocal pattern dystrophy simulating fundus flavimaculatus
Multifocal pattern dystrophy simulating fundus flavimaculatus (MPDSFF), also called pseudo-Stargardt pattern dystrophy, is a rare autosomal dominant PRPH2-related retinal pigment epithelium dystrophy with adult-onset yellow flecks, hyperautofluorescence, no dark choroid, and a better prognosis than Stargardt disease.
Multiple evanescent white dot syndrome
Multiple evanescent white dot syndrome (MEWDS) is a rare, acute, usually unilateral, self-limiting outer retinal inflammatory disease of young women, first described by Jampol in 1984, diagnosed by ICGA/FAF/OCT imaging and resolving within weeks.
Muscle spindle
Muscle spindle (Muskelspindeln): encapsulated stretch receptor in skeletal muscle, built of intrafusal bag and chain fibers with Ia and II afferents and gamma motor innervation; signals muscle length and stretch velocity for proprioception and the stretch reflex.
Mydriasis
Mydriasis is abnormal pupil dilation, caused by iris dilator stimulation, sphincter paralysis, trauma, third nerve palsy, Adie tonic pupil, or pharmacologic agents; dilute pilocarpine testing distinguishes pharmacologic from neurologic causes.
Myokymia
Myokymia is involuntary, fine, rippling muscle contraction from repetitive motor-unit discharges; eyelid myokymia, the commonest form, is a benign eyelid twitch triggered by fatigue, stress, and caffeine, treated with botulinum toxin if persistent.
Myringotomy
Myringotomy, or tympanotomy, is a surgical incision in the eardrum to drain middle ear fluid or ventilate the ear, often with a tympanostomy tube (grommet). First recorded in 1649; reintroduced by Schwartze and Politzer in the 19th century.
NAION trial
Clinical trials for non-arteritic anterior ischemic optic neuropathy (NAION): the IONDT surgical trial and small citicoline (CDP-choline) studies; no treatment has demonstrated proven efficacy.
Near-sightedness
Near-sightedness (myopia) is a refractive error in which light focuses in front of the retina, blurring distance vision. Onset is typically ages 6–14; atropine drops, multifocal lenses, and orthokeratology slow childhood progression.
Neurotrophic keratopathy
Neurotrophic keratopathy (neurotrophic keratitis) is a rare degenerative corneal disease from trigeminal nerve damage causing loss of corneal sensation, poor healing, and ulceration; treated with cenegermin, serum drops, amniotic membrane, tarsorrhaphy, or neurotization.
Night vision
Night vision: low-light seeing mediated by rod photoreceptors and rhodopsin, restored through slow dark adaptation and the RPE visual cycle; vitamin A deficiency, Oguchi disease, and AMD delay it.
Nociceptor
A nociceptor, also called a pain receptor, is a sensory neuron that responds to noxious, tissue-damaging stimuli, triggering pain signals in the spinal cord and brain.