Editing Mydriasis (section)

{{short description|Excessive dilation of the pupil}}
{{Infobox medical condition (new)
| name          = Mydriasis
| synonyms      = Blown pupil<ref name=AANS>{{cite web|title=Traumatic Brain Injury|url=http://www.aans.org/Patient%20Information/Conditions%20and%20Treatments/Traumatic%20Brain%20Injury.aspx|publisher=American Association of Neurological Surgeons|access-date=27 March 2012}}</ref>
| image         = Dilated pupils 2006 (cropped 2).jpg
| caption       = Dilated pupils caused by mydriatic drops instilled for a [[dilated fundus examination]]
| pronounce     = {{IPAc-en|m|ɪ|ˈ|d|r|aɪ|.|ə|s|ɪ|s|,_|m|aɪ|-}}<ref>{{cite Dictionary.com|mydriasis}}</ref>
| field         = [[Ophthalmology]], [[neurology]]
| symptoms      = 
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'''Mydriasis''' is the [[Pupillary dilation|dilation]] of the [[pupil]], usually having a non-physiological cause,<ref>[http://medical-dictionary.thefreedictionary.com/mydriasis Mydriasis] in Farlex medical dictionary. In turn citing:
* The American Heritage Medical Dictionary (2007)
* Mosby's Dental Dictionary, 2nd edition.</ref> or sometimes a physiological [[pupillary response]].<ref>[http://medical-dictionary.thefreedictionary.com/mydriasis Mydriasis] in Farlex medical dictionary. In turn citing: Mosby's Medical Dictionary, 8th edition.</ref> Non-physiological causes of mydriasis include [[disease]], [[Physical trauma|trauma]], or the use of certain types of [[drug|drugs]]. It may also be of unknown cause.

Normally, as part of the [[pupillary light reflex]], the pupil dilates in the [[dark]] and [[miosis|constricts]] in the [[light]] to respectively improve vividity at night and to protect the [[retina]] from sunlight damage during the day. A ''mydriatic'' pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation. Mydriasis is frequently induced by drugs for certain [[Ophthalmology|ophthalmic]] examinations and procedures, particularly those requiring visual access to the [[retina]].

Fixed, unilateral mydriasis could be a symptom of raised [[intracranial pressure]]. The opposite, constriction of the pupil, is referred to as [[miosis]]. Both mydriasis and miosis can be physiological. [[Anisocoria]] is the condition of one pupil being more dilated than the other.