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Encyclopedia > Mydriasis
Mydriasis
Classification & external resources
An abnormally dilated pupil.
ICD-10 H57.0
ICD-9 379.43
OMIM 159420 159410 106240
DiseasesDB 8603

Mydriasis is an excessive dilation of the pupil due to disease or drugs. Normally, pupil dilates in the dark and constricts in the light. A mydriatic pupil will remain excessively large, even in a bright environment. It is occasionally referred to as a "blown pupil." Image File history File linksMetadata Download high resolution version (1704x2272, 1194 KB) Summary Dilated pupils after an optometrist appointment. ... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) is a coding of diseases and signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or diseases, as classified by the World Health Organization (WHO). ... // H00-H59 - Diseases of the eye and adnexa (H00-H06) Disorders of eyelid, lacrimal system and orbit (H00) Hordeolum and chalazion (H000) Hordeolum and other deep inflammation of eyelid (H001) Chalazion (H01) Other inflammation of eyelid (H010) Blepharitis (H011) Noninfectious dermatoses of eyelid (H02) Other disorders of eyelid (H020) Entropion... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... The Mendelian Inheritance in Man project is a database that catalogues all the known diseases with a genetic component, and - when possible - links them to the relevant genes in the human genome. ... The Disease Bold textDatabase is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... The human eye The pupil is the central transparent area (showing as black). ... This article is about the medical term. ... An assortment of psychoactive drugs A psychoactive drug or psychotropic substance is a chemical substance that acts primarily upon the central nervous system where it alters brain function, resulting in temporary changes in perception, mood, consciousness and behavior. ... Pupil dilated using anaesthetic and muscle relaxant. ...


The opposite, constriction of the pupil, is called miosis. Miosis should not be confused with meiosis, the cellular division process involved in sexual reproduction. ...

Contents

Mechanism

There are two types of muscle that control the size of the iris: circular muscle and radial muscle. The former is innervated by the parasympathetic nervous system, the latter by the sympathetic nervous system. Sympathetic stimulation of α1 adrenergic receptors causes the contraction of the radial muscle, and subsequent dilation of the iris. Conversely, parasympathetic stimulation cause contraction of the circular muscle and constriction of the iris. The Iris sphincter muscle is a muscle of the human body. ... The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a muscle of the eye. ... Autonomic nervous system innervation, showing the sympathetic and parasympathetic (craniosacral) systems, in red and blue, respectively The parasympathetic nervous system is one of three divisions of the autonomic nervous system. ... Grays FIG. 838– The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses. ... The adrenergic receptors (or adrenoceptors) are a class of G_protein coupled receptors that is the target of catecholamines. ...


The mechanism of mydriasis depends on the agent being used. It usually involves either a disruption of the parasympathetic nerve supply to the eye (which causes contraction of the pupil), or over activity of the sympathetic nervous system (SNS). The parasympathetic nervous system is one of two divisions of the autonomic nervous system. ... Grays FIG. 838– The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses. ...


Causes

Pathological

The parasympathetic nervous supply which causes constriction of the pupil, or miosis, is supplied by cranial nerve III, the oculomotor nerve. Damage to this nerve typically manifests itself as mydriasis, because the sympathetic supply to the pupil which causes mydriasis remains unaffected, and therefore unopposed. Anatomy and Physiology of the A.N.S. In contrast to the voluntary nervous system, the involuntary or autonomic nervous system is responsible for homeostasis, maintaining a relatively constant internal environment by controlling such involuntary functions as digestion, respiration, and metabolism, and by modulating blood pressure. ... Miosis should not be confused with meiosis, the cellular division process involved in sexual reproduction. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The word sympathetic means different things in different contexts. ...


Drugs

Atropine blocks muscarinic acetylcholine receptors. Acetylcholine (ACh) is the neurotransmitter of the parasympathetic nervous system and blocking its action means the pupil cannot constrict. Atropine is a tropane alkaloid extracted from the deadly nightshade (Atropa belladonna) and other plants of the family Solanaceae. ... Amanita muscaria from which muscarine was isolated Acetylcholine - natural agonist of muscarinic and nicotinic receptors. ... Chemical structure of D-aspartic acid, a common amino acid neurotransmitter. ... Autonomic nervous system innervation, showing the sympathetic and parasympathetic (craniosacral) systems, in red and blue, respectively The parasympathetic nervous system is one of three divisions of the autonomic nervous system. ...


Cocaine inhibits the reuptake of noradrenaline (aka norepinephrine) within a nerve synapse. When a solution of cocaine is dropped into the eye, noradrenaline is no longer reabsorbed by neurons, and its levels increase. Noradrenaline, the neurotransmitter for the SNS, causes dilation of the pupil. Mydriasis is used as a diagnostic test for Horner's Syndrome, in which it is initiated using a similar mechanism, though cocaine is not usually used in this procedure. Many other drugs such as amphetamines and psychedelic drugs (LSD, psychedelic mushrooms, mescaline, MDMA, Datura stramonium) are also known to cause mydriasis. Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. ... Norepinephrine, known as noradrenaline outside the USA, is a catecholamine and a phenethylamine with chemical formula C8H11NO3. ... Illustration of the major elements in a prototypical synapse. ... Horners syndrome is a clinical syndrome caused by damage to the sympathetic nervous system. ... Amphetamine or Amfetamine (Alpha-Methyl-PHenEThylAMINE), also known as, beta-phenyl-isopropylamine, and benzedrine, is a prescription stimulant commonly used to treat Attention-deficit hyperactivity disorder (ADHD) in adults and children. ... Lysergic acid diethylamide, commonly called LSD, LSD-25, or acid. ... Magic mushrooms are also known as sacred mushrooms, psychedelic mushrooms, and, more generally, hallucinogenic mushrooms. ... This article does not cite any references or sources. ... ecstasy and religious ecstasy MDMA, most commonly known today by the street name ecstasy, is a synthetic entactogen of the phenethylamine family whose primary effect is to stimulate the brain to rapidly secrete large amounts of serotonin, causing a general sense of openness, empathy, energy, euphoria, and well-being. ... Binomial name L. Datura stramonium, also called Jimson Weed, Gypsum Weed, Loco Weed, Jamestown Weed, Thorn Apple, Angels Trumpet, Devils Trumpet, Devils Snare, Mad Hatter, Crazy Tea, Malpitte and Zombies Cucumber is a common weed in the Nightshade Family. ...


Opiate withdrawal can cause dilated pupils in some people. [1] Scoring the poppy pod. ...


Antihistamines and tricyclic antidepressants may cause mydriasis. An antihistamine is a drug which serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions, through action at the histamine receptor. ... Chemical structure of the tricyclic antidepressant amitriptyline. ...


Mydriatic drops

Pupil dilated using anaesthetic and muscle relaxant.
Pupil dilated using anaesthetic and muscle relaxant.

A mydriatic is an agent which induces dilation of the pupil. Drugs such as tropicamide are used in medicine to permit examination of the retina and other deep structures of the eye, and also to reduce painful ciliary muscle spasm (see cycloplegia). One effect of administration of a mydriatic is intolerance to bright light and is or was sometimes called "drops in eyes". Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (3072 × 2048 pixel, file size: 3. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (3072 × 2048 pixel, file size: 3. ... Dilation in physiological context may mean: pupil dilation (mydriasis) dilation of blood vessels (vasodilation) cervical dilation (or dilation of the cervix) in childbirth Dilation and curettage (surgical dilation) In mathematics: Dilation This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same... The human eye The pupil is the central transparent area (showing as black). ... Tropicamide (troe-PIK-a-mide) is an acetylcholine receptor blocker. ... Cycloplegia is the paralysis of the ciliary muscle, resulting in a loss of accommodation. ...


See also


  Results from FactBites:
 
Mydriasis and Anisocoria: Autonomic Dysfunction - Neurology and Neurosurgery Forum (0 words)
Pupil size is determined among other things, by adrenergic tone and in my case the mydriasis and anisocoria are likely to be the result of a disruption in parasympathetic innervation.
One potential danger of drug-induced mydriasis is the exacerbation of acute angle glaucoma in patients over 50 years old.
However, in case reports from the literature the mydriasis should resolve with discontinuation of the drug and at 2 months, the medication should already be out of your system.
Reference.com/Encyclopedia/Mydriasis (419 words)
Mydriasis is an excessive dilation of the pupil due to disease or drugs.
Damage to this nerve typically manifests itself as mydriasis, because the sympathetic supply to the pupil which causes mydriasis remains unaffected, and therefore unopposed.
The mydriasis caused by cocaine is used as a diagnostic test for Horner's Syndrome, in which the pupil is not dilated by cocaine.
  More results at FactBites »


 

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