Editing Conjunctivitis (section)

== Signs and symptoms ==
[[File:Bloodshot eye.jpg|thumb|Bloodshot eyes]]

[[Red eye (medicine)|Red eye]], [[chemosis|swelling of the conjunctiva]], and [[epiphora (medical)|watering]] of the eyes are symptoms common to all forms of conjunctivitis. However, the pupils should be normally reactive, and the visual acuity normal.<ref>{{cite book | vauthors = Hashmi MF, Gurnani B, Benson S | chapter = Conjunctivitis |date=2023 | title = StatPearls | chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK541034/ |access-date=2023-05-23 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=31082078 }}</ref>

Conjunctivitis is identified by inflammation of the conjunctiva, manifested by irritation and redness. Examination using a [[slit lamp]] (biomicroscope) may improve diagnostic accuracy. Examination of the palpebral conjunctiva, that overlying the inner aspects of the eyelids, is usually more diagnostic than examination of the bulbal conjunctiva, that overlying the sclera.<ref>{{Cite web |date=2017-10-19 |title=Conjunctivitis |url=https://www.nhs.uk/conditions/conjunctivitis/ |access-date=2025-02-13 |website=nhs.uk |language=en}}</ref>

=== Viral ===
[[File:Conjunctivitis disease.jpg|thumb|Viral conjunctivitis]]
Approximately 80% of cases of conjunctivitis in adults and less than 20% in children are due to viruses, with 65% to 90% of these cases being attributed to adenoviruses.<ref name="Az2013"/><ref name="Durand 2023" />
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Other associated signs may include [[Preauricular deep parotid lymph nodes|pre-auricular]] lymph node swelling and contact with another person with a red eye.<ref name="Durand 2023" /> Eye pain may be present if the cornea is also involved.<ref name="Durand 2023" /> Its symptoms include excessive watering and itching. The discharge in viral conjunctivitis is usually (but not always) watery in nature.<ref name="Durand 2023" /> The infection usually begins in one eye but may spread easily to the other eye.{{citation needed|date=February 2023}}

Viral conjunctivitis manifests as a fine, diffuse pinkness of the conjunctiva which may be mistaken for [[iritis]], but corroborative signs on [[microscopy]], particularly numerous [[Lymph follicle|lymphoid follicle]]s on the [[Tarsus (eyelids)|tarsal]] conjunctiva, and sometimes a [[punctate keratitis]] are seen.{{citation needed|date=February 2023}}

=== Allergic ===
[[File:Allergicconjunctivitis.jpg|thumb|right|An eye with [[allergic conjunctivitis]] showing conjunctival edema]]
[[Allergic conjunctivitis]] is [[Allergic Inflammation|inflammation]] of the conjunctiva due to allergy.<ref name="Bielory">{{cite journal | vauthors = Bielory L, Friedlaender MH | title = Allergic conjunctivitis | journal = Immunology and Allergy Clinics of North America | volume = 28 | issue = 1 | pages = 43–58, vi | date = February 2008 | pmid = 18282545 | doi = 10.1016/j.iac.2007.12.005 | s2cid = 34371872 }}</ref> The specific [[allergen]]s may differ among patients. Symptoms result from the release of [[histamine]] and other active substances by [[mast cell]]s, and consist of redness (mainly due to [[vasodilation]] of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased production of tears.{{citation needed|date=September 2022}}

=== Bacterial ===

[[File:Swollen eye with conjunctivitis.jpg|thumb|right|An eye with bacterial conjunctivitis]]
Bacteria are responsible for approximately 70% of conjunctivitis in children and less than 20% of cases in adults.<ref name="Durand 2023" /> Common bacteria responsible for bacterial conjunctivitis are ''[[Staphylococcus]]'' including [[Staph aureus]], ''[[Streptococcus]]'' such as [[strep pneumoniae]],<ref>{{Cite web |title=Pink Eye (Conjunctivitis) |url=http://www.medicinenet.com/pink_eye/article.htm |url-status=live |archive-url=https://web.archive.org/web/20130622062209/http://www.medicinenet.com/pink_eye/article.htm |archive-date=22 June 2013 |publisher=MedicineNet |df=dmy-all}}</ref> ''[[Haemophilus]]'' species and [[Moraxella catarrhalis]].<ref name="Durand 2023" /> Less commonly, ''Chlamydia'' spp. and Niesseria species ([[Neisseria gonorrhoeae]] and [[Neisseria meningitidis]]) may be the cause.<ref name="Durand 2023" /><ref name="merck">{{Cite web |title=Acute Bacterial Conjunctivitis – Eye Disorders |url=http://www.merckmanuals.com/professional/eye-disorders/conjunctival-and-scleral-disorders/acute-bacterial-conjunctivitis |url-status=live |archive-url=https://web.archive.org/web/20161228184316/http://www.merckmanuals.com/professional/eye-disorders/conjunctival-and-scleral-disorders/acute-bacterial-conjunctivitis |archive-date=28 December 2016 |access-date=31 December 2016 |website=Merck Manuals Professional Edition |df=dmy-all}}</ref> Infection with ''[[Escherichia coli]]'' may also cause conjunctivitis, particularly in the [[Infant|neonatal]] subtype [[ophthalmia neonatorum]].<ref>{{cite journal | vauthors = Saadeh-Jackson S, Rodriguez L, Leffler CT, Freymiller C, Wolf E, Wijesooriya N, Couser NL | title = Ophthalmia neonatorum due to ''Escherichia coli'': A rare cause or an emerging bacterial etiology of neonatal conjunctivitis? | journal = Clinical Case Reports | volume = 10 | issue = 8 | pages = e6201 | date = August 2022 | pmid = 35949413 | pmc = 9354094 | doi = 10.1002/ccr3.6201 }}</ref> Bacterial conjunctivitis usually causes a rapid onset of conjunctival redness, swelling of the eyelid, and a sticky discharge. Typically, symptoms develop first in one eye, but may spread to the other eye within 2–5 days.  Conjunctivitis due to common [[pyogenic|pus-producing]] bacteria causes marked grittiness or irritation and a stringy, opaque, greyish or yellowish [[mucopurulent discharge|discharge]] that may cause the lids to stick together, especially after sleep.  Severe crusting of the infected eye and the surrounding skin may also occur.  The gritty or scratchy feeling is sometimes localized enough that patients may insist that they have a foreign body in the eye.{{citation needed|date=September 2022}}

[[File:Membranous conjunctivitis.jpg|thumb|right|Typical membranous conjunctivitis]]

Bacteria such as ''[[Chlamydia trachomatis]]'' or ''[[Moraxella]]'' spp. can cause a nonexudative but persistent conjunctivitis without much redness.  Bacterial conjunctivitis may cause the production of membranes or pseudomembranes that cover the conjunctiva.  Pseudomembranes consist of a combination of [[inflammatory cell]]s and exudates and adhere loosely to the conjunctiva, while true membranes are more tightly adherent and cannot be easily peeled away.  Cases of bacterial conjunctivitis that involve the production of membranes or pseudomembranes are associated with ''[[Neisseria gonorrhoeae]]'', β-hemolytic streptococci, and ''[[Corynebacterium diphtheriae]]''.  ''C. diphtheriae'' causes membrane formation in conjunctiva of unimmunized children.<ref>{{Cite book |title=Epidemiology and Prevention of Vaccine-Preventable Diseases |publisher=U.S. Dept. of Health & Human Services, Centers for Disease Control and Prevention |year=2015 |isbn=978-0-9904491-1-9 |veditors=Hamborsky J, Kroger A, Wolfe C |pages=112}}</ref>

=== Chemical ===
Chemical eye injury may result when an [[acidic]] or [[alkali]]ne substance gets in the eye.<ref name="Bet09">{{cite journal | vauthors = Zentani A, Burslem J | title = Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. BET 4: use of litmus paper in chemical eye injury | journal = Emergency Medicine Journal | volume = 26 | issue = 12 | pages = 887 | date = December 2009 | pmid = 19934140 | doi = 10.1136/emj.2009.086124 | s2cid = 38124735 }}</ref> Alkali burns are typically worse than acidic burns.<ref name=AFP08/> Mild burns produce conjunctivitis, while more severe burns may cause the [[cornea]] to turn white.<ref name=AFP08/> [[Litmus|Litmus paper]] may be used to test for chemical causes.<ref name=Bet09/> When a chemical cause has been confirmed, the eye or eyes should be flushed until the [[pH]] is in the range 6–8.<ref name="AFP08">{{cite journal | vauthors = Hodge C, Lawless M | title = Ocular emergencies | journal = Australian Family Physician | volume = 37 | issue = 7 | pages = 506–509 | date = July 2008 | pmid = 18592066 }}</ref> Anaesthetic eye drops can be used to decrease the pain.<ref name=AFP08/>

Irritant or toxic conjunctivitis is primarily marked by redness. If due to a chemical splash, it is often present in only the lower conjunctival sac.  With some chemicals, above all with caustic alkalis such as [[sodium hydroxide]], [[necrosis]] of the conjunctiva marked by a deceptively white eye due to vascular closure may occur, followed by sloughing off of the dead [[epithelium]]. A slit lamp examination is likely to show evidence of [[iritis|anterior uveitis]].<ref>{{Cite web |title=Diagnosing Conjunctivitis |url=https://nyulangone.org/conditions/conjunctivitis/diagnosis |access-date=2025-02-13 |website=nyulangone.org |language=en}}</ref>

=== Biomarkers ===
Omics technologies have been used to identify biomarkers that inform on the emergence and progression of conjunctivitis. For example, in chronic inflammatory cicatrizing conjunctivitis, active [[oxylipins]], [[lysophospholipid]]s, [[fatty acid]]s, and [[endocannabinoid]]s alterations, from which potential biomarkers linked to inflammatory processes were identified.<ref>{{cite journal | vauthors = Di Zazzo A, Yang W, Coassin M, Micera A, Antonini M, Piccinni F, De Piano M, Kohler I, Harms AC, Hankemeier T, Boinini S, Mashaghi A | title = Signaling lipids as diagnostic biomarkers for ocular surface cicatrizing conjunctivitis | journal = Journal of Molecular Medicine | volume = 98 | issue = 5 | pages = 751–760 | date = May 2020 | pmid = 32313985 | pmc = 7220886 | doi = 10.1007/s00109-020-01907-w }}</ref>

=== Other ===

[[File:Chlamydial-conjunctivitis.jpg|thumb|right|An eye with chlamydial conjunctivitis]]
Inclusion conjunctivitis of the newborn is a conjunctivitis that may be caused by the bacterium ''Chlamydia trachomatis'', and may lead to acute, [[purulent]] conjunctivitis.<ref name="Microbiology">{{Cite book | vauthors =  Fisher B, Harvey RP, Champe PC |title=Lippincott's Illustrated Reviews: Microbiology (Lippincott's Illustrated Reviews Series) |publisher=Lippincott Williams & Wilkins |year=2007 |isbn=978-0-7817-8215-9 |location=Hagerstown MD}}</ref> However, it is usually self-healing.<ref name=Microbiology/>