Mohd Alhalki
West Middlesex University Hospital, London
Overview
The conjunctiva is a thin, transparent membrane underlying the inner lid surfaces and the anterior sclera, and it is important in maintaining a suitable environment for the cornea and as defence against infection and trauma. Conjunctivitis is the inflammation of the conjunctiva and is characterized by dilation of the conjunctival vessels, resulting in hyperaemia and oedema of the conjunctiva, typically with associated discharge. However, visual acuity is usually not affected.
Aetiology
Conjunctivitis can be divided into non-infectious and infectious causes.
The most common cause of Non-infectious conjunctivitis is allergy and is seen more frequently in the spring and summer. Other causes of non-infectious conjunctivitis are Trauma and systemic diseases.
Viruses are the most common causes of Infectious conjunctivitis followed by bacterial infections.
Risk Factors
Conjunctivitis can be precipitated by several risk factors depending on the aetiology.
History of atopy such as eczema, hay fever and asthma are the most common risk factors for allergic conjunctivitis.
Viral and bacterial conjunctivitis can be precipitated by direct contact with contaminated fingers or personal items from an infected person.
Pathophysiology
Allergic conjunctivitis is an inflammation of the conjunctiva in response to a transient allergen (e.g. pollen in seasonal allergic conjunctivitis), or a persistent allergen (e.g. house dust mite in perennial allergic conjunctivitis).
Adenoviruses accounts towards 65-90% of cases of viral conjunctivitis, and they produce two of the common clinical entities associated with viral conjunctivitis: pharyngoconjunctival fever, and epidemic keratoconjunctivitis.
* Pharyngoconjunctival fever presents with high fever, pharyngitis, bilateral conjunctivitis, and periauricular lymphadenopathy.
* Epidemic keratoconjunctivitis presents with watery discharge, conjunctival injection and swelling, and ipsilateral periauricular lymphadenopathy.
Herpes simplex virus (HSV) comprises 1.3-4.8% of all cases of acute conjunctivitis and is usually unilateral.
The most common causes of bacterial conjunctivitis in adults are Staphylococcal species, followed by Streptococcus pneumoniae and Haemophilus influenzae.
Hyperacute bacterial conjunctivitis is often caused by Neisseria gonorrhoeae.
Signs and symptoms
Allergic conjunctivitis
usually presents with eye redness, watering, discharge, and discomfort, and most importantly, ocular itching.
Many patients with allergic conjunctivitis will have a history of atopic conditions.
Viral conjunctivitis
Adenoviral conjunctivitis is highly contagious. Patients commonly report contact with an individual with a red eye, or they may have a history of recent symptoms of an upper respiratory tract infection.
Symptoms usually begins in one eye and may spread to the other eye within days
Discharge from the eye is usually watery
Bacterial conjunctivitis
Signs and symptoms include red eye, eye discharge which can be severe copious purulent discharge which can lead to eyelids sticking together. There is often accompanying eyelid swelling and eye pain on palpation.
Management
The management of allergic conjunctivitis is usually supportive such as avoiding allergens and contact lenses. Cold compresses and topical normal saline or lubricants (artificial tears) can help reducing symptoms. Topical or oral antihistamines can be used.
Most cases of viral and bacterial conjunctivitis are mild and self-limiting within 7-14 days.
Avoiding spread is essential by frequent hand washing, avoiding sharing personal care objects such as towels, and avoiding contact with eyes
Topical antibiotics should be avoided.
Herpes virus conjunctivitis can be treated with topical and oral antivirals to shorten the course of the disease.
Differential diagnosis
Many diseases can present with eye redness and discomfort which should be suspected such as Uveitis, Glaucoma, Herpes zoster ophthalmicus, Keratitis, Scleritis and episcleritis