Conjunctivitis

Definition/diagnostic criteria Conjunctivitis is an inflammation of the conjunctiva, resulting in redness in one or both eyes, discharge (watery, purulent, or mucopurulent), irritation and a gritty feeling.

Epidemiology Conjunctivitis is one of the most common ocular conditions encountered in primary care in the UK. It can affect individuals of all ages but is particularly prevalent in children and the elderly. The condition can be viral, bacterial, or allergic in origin, with viral conjunctivitis being the most common.

Diagnosis
Clinical features: Conjunctivitis typically presents with redness of the eye, tearing, and a sensation of a foreign body in the eye. Itching is more associated with allergic conjunctivitis, while a purulent discharge is more indicative of a bacterial cause.

• Viral conjunctivitis often accompanies upper respiratory tract infection symptoms and presents with watery discharge.
• Typical findings on examination include conjunctival hyperaemia, swollen eyelids and, depending on the cause, either a watery, purulent or mucopurulent discharge.
• Follicles may be seen on the conjunctiva in viral conjunctivitis, while papillae are more common in allergic conjunctivitis.

Note that conjunctivitis occurring within the first four weeks of life is ophthalmia neonatorum, which can be caused by Neisseria gonorrhoeae or Chlamydia trachomatis

Investigations: In most cases, conjunctivitis is diagnosed clinically without the need for laboratory tests. However, swabbing for bacterial culture and sensitivity may be considered in severe, persistent, or atypical cases. Slit-lamp examination can be used to exclude other causes of red eye if the diagnosis is uncertain.

Treatment The treatment of conjunctivitis depends on its aetiology:

• Viral conjunctivitis: Typically self-limiting and treated with supportive care, such as cold compresses and lubricating eye drops.
• Bacterial conjunctivitis: Treated with topical antibiotics, such as chloramphenicol or fusidic acid.
• Allergic conjunctivitis: Managed with antihistamine or mast cell stabiliser eye drops, such as sodium cromoglicate. Oral antihistamines may also be helpful.
• Ophthalmia neonatorum: this requires immediate specialist referral.

Prognosis The prognosis for conjunctivitis is generally good. Viral and bacterial conjunctivitis are usually self-limiting conditions, resolving within 1-2 weeks. Allergic conjunctivitis may persist longer or recur, depending on exposure to allergens. Complications are rare but can include keratitis and, in severe cases, vision loss, necessitating prompt referral to an ophthalmologist. Ophthalmia neonatorum is associated with serious complications if not treated promptly.