Miosis 949670 225112684 2008-07-11T22:59:01Z SieBot 4005189 robot Adding: [[he:מיוזיס]] {{dablink| Miosis should not be confused with [[meiosis]], the cellular division process involved in sexual reproduction, or [[mitosis]], the cellular division of somatic body cells.}} '''Miosis''' is [[constriction]] of the [[pupil]] of the [[eye]]. This is a normal response to an increase in light but can also be associated with certain [[pathological conditions]], [[microwave]] radiation exposure and certain [[drugs]]. The opposite, [[Mydriasis]], is the dilation of the pupil. {{Infobox_Disease | Name = {{PAGENAME}} | Image = Miosis.jpg | Caption = Miosis of the left eye | DiseasesDB = 8243 | ICD10 = {{ICD10|H|57|0|h55}} | ICD9 = {{ICD9|379.42}} | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | MeshID = D015877 | }} ==Physiology of the photomotor reflex== Light entering the eye strikes three different photoreceptors in the retina, the familiar [[Rod cell|rods]] and [[Cone cell|cones]] used in image-forming and the more newly discovered [[photosensitive ganglion cell]]s. These give information about ambient light levels, and react sluggishly compared to the rods and cones. Signals from these intrinsically photosensitive cells have three functions: acute suppression of the hormone [[melatonin]], [[Entrainment (chronobiology)|entrainment]] of the body's [[circadian rhythm]]s and regulation of the size of the pupil. The retinal photoceptors convert light stimuli into electric impulses. Nerves pertaining to the resizing of the pupil connect to the pretectal nucleus of the high midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex. From the pretectal nucleus neurons send axons to neurons of the [[Edinger-Westphal nucleus]] whose visceromotor axons run along both the left and right oculomotor nerves. Visceromotor nerve axons (which constitute a portion of [[cranial nerve]] III, along with the somatomotor portion derived from the Edinger-Westphal nucleus) synapse on ciliary ganglion neurons, whose [[parasympathetic]] axons innervate the constrictor muscle of the iris, producing '''[[miosis]]'''. This occurs because sympathetic activity from the ciliary ganglion is ''lost'' thus parasympathetics are not inhibited. [http://www.coldbacon.com/mdtruth/pics/netter/fn-oculomotor.jpg] ==Causes== === Age === The likelihood of suffering miosis increases with age. === Diseases === * [[Horner syndrome]] (a set of abnormalities in the nervous supply of the face due to damage to the [[sympathetic nervous system]]). * [[Pancoast tumor]] (a [[lung cancer|tumor]] of the apical [[lung]]), due to damage to the ascending sympathetic tract that would normally cause the pupil to dilate. * [[Hemorrhage]] into [[pons]] ([[intracranial hemorrhage]]) * [[Cluster Headaches]] with [[ptosis]] === Drugs === * [[Opioid]]s such as [[tramadol]], [[codeine]], [[fentanyl]], [[morphine]], [[heroin]] and [[methadone]] * [[Antipsychotics]], including [[haloperidol]], [[thorazine]], [[olanzapine]], [[quetiapine]] and others * [[Cholinergic]] agents such as those used to treat [[Alzheimer's disease]] and [[nerve gas]]es; cholinergic drugs such as [[pilocarpine]], [[carbachol]] (Miostat) and [[neostigmine]] * Some cancer [[chemotherapy]] drugs, including [[camptothecin]] derivatives * [[Mirtazapine]], a [[noradrenergic and specific serotonergic antidepressant]] ([[NaSSA]]) * [[Trazodone]] * Some [[MAO_inhibitor|MAO Inhibitors]]. * In some rare cases, when exposed to [[mustard gas]]. ===Miotics=== A '''miotic''' substance causes the constriction of the [[pupil]] of the eye (or [[miosis]]). It is the opposite of a [[Mydriatic]] substance, which causes [[dilation]] of the pupil. ==External links== * [http://www.fpnotebook.com/EYE35.htm FP Notebook] * {{GPnotebook|-1254817782}} {{Antiglaucoma preparations and miotics}} {{Eye pathology}} [[Category:Medical signs]] [[Category:Ophthalmology]] {{med-sign-stub}} [[bg:Миоза]] [[de:Miosis]] [[es:Miosis]] [[fr:Myosis]] [[it:Miosi]] [[he:מיוזיס]] [[nl:Miosis]] [[ja:縮瞳]] [[no:Miosis]] [[pl:Mioza]] [[pt:Miose]] [[ru:Миоз]] [[sk:Mióza]] [[sv:Mios]]