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Conjunctivitis

Medicine > Infection

Background knowledge 🧠

Definition

  • Conjunctivitis, also known as pink eye, is inflammation of the conjunctiva, the clear membrane covering the white part of the eye and the inner eyelids.
  • Can be caused by infections (bacterial, viral), allergies, or irritants.
  • Highly contagious if infectious.

Epidemiology

  • Common condition affecting all age groups.
  • Infectious conjunctivitis is more common in children.
  • Allergic conjunctivitis is more frequent in individuals with atopic conditions.
  • Bacterial conjunctivitis peaks in the winter and early spring.

Aetiology and Pathophysiology

  • Viral: Adenovirus is the most common cause.
  • Bacterial: Common pathogens include Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae.
  • Allergic: Triggered by allergens such as pollen, dust mites, and animal dander.
  • Irritant: Caused by chemicals, smoke, or foreign bodies.

Types

  • Viral Conjunctivitis.
  • Bacterial Conjunctivitis.
  • Allergic Conjunctivitis.
  • Irritant Conjunctivitis.

Clinical Features 🌡️

Symptoms

  • Redness in the white of the eye or inner eyelid.
  • Increased amount of tears.
  • Thick yellow discharge that crusts over the eyelashes, especially after sleep (bacterial).
  • Itchy eyes (allergic).
  • Burning eyes.
  • Blurred vision.

Signs

  • Conjunctival hyperaemia.
  • Chemosis (swelling of the conjunctiva).
  • Palpebral follicles or papillae.
  • Preauricular lymphadenopathy (viral).
  • Purulent discharge (bacterial).
  • Watery discharge (viral or allergic).

Investigations 🧪

Tests

  • Clinical diagnosis primarily based on history and examination.
  • Swabs for bacterial culture in severe or refractory cases.
  • PCR testing for viral pathogens if necessary.
  • Allergy testing if allergic conjunctivitis is suspected.
  • Fluorescein staining to check for corneal involvement.

Management 🥼

Management

  • Viral: Usually self-limiting, supportive care (e.g., artificial tears).
  • Bacterial: Topical antibiotics (e.g., chloramphenicol).
  • Allergic: Antihistamines and mast cell stabilizers (e.g., olopatadine).
  • Avoid contact lenses during infection.
  • Maintain good hygiene to prevent spread.
  • Refer to ophthalmologist if symptoms persist or if there is corneal involvement.

Complications

  • Keratitis.
  • Chronic conjunctivitis.
  • Preseptal or orbital cellulitis.
  • Corneal ulcers (bacterial).
  • Visual impairment if severe and untreated.

Key points

  • Conjunctivitis can be viral, bacterial, allergic, or irritant in origin.
  • Diagnosis is primarily clinical, based on history and examination.
  • Management depends on the cause; most cases are self-limiting.
  • Prevent spread by maintaining good hygiene and avoiding contact lenses during infection.
  • Refer to ophthalmology if symptoms persist or worsen.

References

  • NICE Clinical Knowledge Summary on Conjunctivitis (https://cks.nice.org.uk/topics/conjunctivitis-infective/).
  • BNF – British National Formulary (https://bnf.nice.org.uk/).
  • NHS Inform – Conjunctivitis (https://www.nhsinform.scot/illnesses-and-conditions/eyes/conjunctivitis).

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Infection