• Clinical science



Conjunctivitis (pinkeye) is a very common inflammation of the conjunctiva (the mucus membrane that lines the inside of the eyelids and the sclera). It is most commonly caused by viruses or bacteria but can also have noninfectious (e.g., allergic) causes. It is also commonly associated with corneal inflammation (then referred to as keratoconjunctivitis). Conjunctivitis is the most common cause of ocular hyperemia. Other classic features are burning, foreign body sensation, excessive tearing, and photophobia. Additionally, in infectious conjunctivitis, general signs of viral or bacterial infection (e.g., fever) may be seen, while itching is particularly common in allergic conjunctivitis. Dry eye is a hallmark feature of keratoconjunctivitis sicca. In most cases, local pharmacologic therapy with anti-infective, anti-inflammatory and/or antiallergic agents is sufficient. However, bacterial conjunctivitis can lead to blindness in newborns; therefore, strict and rapid treatment and prevention is vital. Surgical intervention is only rarely useful or necessary (e.g., correction of eyelids). An important differential diagnosis of conjunctivitis is subconjunctival hemorrhage, which is a collection of blood between the conjunctiva and the sclera that typically appears as a focal, red region on the surface of the eye.

Clinical features

General signs and symptoms of conjunctivitis

Bacterial vs viral conjunctivitis

Bacterial Viral
  • Usually unilateral
  • Thick purulent discharge (yellow, white or green)
  • Reduced vision and risk of blindness (if cornea is involved)
  • Extraocular signs of bacterial infection
  • See additional features of certain causes below
  • Bilateral (usually begins with one eye and spreads to the other within a few days)
  • Clear, watery discharge (with mucoid component) .
  • Increased lacrimation (epiphora)
  • Usually normal vision
  • Conjunctival follicles
    • Small raised, yellowish-white hyperplasia of lymphatic tissue, usually with peripheral (rather than central) vascularization
    • Particularly on the palpebral and bulbar conjunctiva
  • Extraocular/general signs of viral infection : e.g., fever, lymphadenopathy (e.g., preauricular node), pharyngitis
  • See additional features of certain causes below


Viral conjunctivitis

Patient education regarding proper hygiene is essential to prevent an outbreak!


Bacterial conjunctivitis


Neisserial conjunctivitis

  • Etiology
    • Pathogen: Neisseria gonorrhoeae
    • Route of infection (highly contagious)
      • Young, sexually active adults: direct contact to contaminated secretions (e.g., from the genitalia to the hand to the eye)
      • Newborns: perinatally
  • Clinical features
    • See “Clinical features” above; hyperacute conjunctivitis with marked eye swelling and profuse purulent discharge
    • Also preauricular lymphadenopathy
  • Diagnosis: gram stain shows intracellular gram negative diplococci
  • Treatment: IV or IM ceftriaxone plus oral azithromycin with saline irrigation (topical antibiotics may also be considered)

N.gonorrhoeae infection is an ocular emergency that can lead to keratitis, perforation, and blindess without prompt treatment!

Trachoma (Granular conjunctivitis)

  • Etiology
    • Infection with Chlamydia trachomatis type A-C
    • Route of infection: direct (human-to-human contact with eyes or nose) or indirect (flies or towels) contact
  • Epidemiology
    • Most common cause of blindness due to chronic scarring worldwide
    • Predominantly affects young children and women
  • Clinical features: see “Clinical features” above
  • Diagnosis: clinical diagnosis
  • Treatment/Prevention
    • Antibiotics
    • Surgical intervention (eyelid correction in trichiasis)
    • Hygienic measures (particularly facial cleanliness) and environmental improvement (e.g., supply of clean water)
  • Prognosis: good (if treated early)

SAFE strategy (WHO) - Surgery, Antibiotics, Facial cleanliness, Environmental improvement

Inclusion conjunctivitis (paratrachoma)


Newborn conjunctivitis

Chemical conjunctivitis Neonatal gonococcal conjunctivitis Chlamydial conjunctivitis Viral conjunctivitis
Underlying cause
  • Usually due to silver nitrate exposure
Onset after birth
  • Usually first day
  • 2–7 days
  • 5–14 days
  • Within 14 days
Clinical features
  • Watery/mucopurulent ocular discharge, eyelid swelling
  • Nonpurulent ocular discharge, corneal ulceration, periocular vesicles
  • Flush eye with saline
  • Systemic acyclovir plus topical drugs (e.g., vidarabine) for 14–21 days
  • Prenatal maternal screening and systemic antibiotic treatment
  • Proper hygiene

Gonococcal conjunctivitis is an emergency! Suspect and treat for gonococcal infection in newborns with conjunctivitis unless proven otherwise!


Non-infectious conjunctivitis

Allergic conjunctivitis

Keratoconjunctivitis sicca (dry eye disease)


Differential diagnoses

Subconjunctival hemorrhage (SCH) [27][28]

The differential diagnoses listed here are not exhaustive.