What is conjunctivitis?
The conjunctiva is the semi-transparent membrane that covers the white part of the eye (the sclera) and lines the inside of the eyelids.
When the conjunctiva is inflamed, the white of the eye appears red. Conjunctivitis is the most likely diagnosis when a patient has a red eye and discharge.
What causes conjunctivitis?
Acute conjunctivitis can be either infectious or non-infectious. Conjunctivitis due to infectious causes is highly contagious: spread is by direct contact with the patient, their secretions or contaminated surfaces.
- Allergic or atopic/vernal conjunctivitis
- Irritant or traumatic conjunctivitis
- Stevens-Johnson syndrome-toxic epidermal necrolysis
- Ocular cicatricial pemphigoid: a chronic autoimmune disease causing conjunctival contraction and secondary corneal damage
- Superior limbic keratoconjunctivitis: associated with dysthyroid eye disease
What are the symptoms and signs of conjunctivitis?
Conjunctivitis is a diagnosis of exclusion. All forms of conjunctivitis are characterised by:
- Redness and discharge in one or both eyes.
- Diffuse redness around the globe including the underside of the upper and lower lids.
- Adhesion of the upper and lower eyelids on waking.
- Normal vision
- Absence of focal pathology (eg stye or blepharitis).
The following "red flags" point to other more serious diagnoses, such as keratitis (inflammation of the cornea), iritis, or angle closure glaucoma:
- Changes in visual acuity
- Ciliary flush: A pattern of injection in which the redness is most pronounced in a ring at the limbus.
- Photophobia (light sensitivity)
- Severe foreign body sensation that prevents the patient from keeping the eye open
- Corneal opacity
- Fixed pupil
- Severe headache with nausea
What are the complications of conjunctivitis?
Most forms of conjunctivitis are self-limiting but in certain cases, severe complications may occur. Pain, loss of vision or photophobia require immediate referal to an opthalmologist.
Complications from conjunctivitis include:
- Chronic redness, discharge and irritation
Conjunctivitis caused by Neisseria meningitidis (meningococcus) can precede meningitis.
How is conjunctivitis treated?
Many cases of infectious conjunctivitis resolve spontaneously within 14 days. Treatment in mild cases is mainly symptomatic with patient education regarding hygiene to prevent its spread.
Glucocorticoids should only be used under specialist advice to avoid sight-threatening complications.