Inflammation of the conjunctiva is a common cause of a diffusely red, uncomfortable eye. The main differential diagnosis often rests between infectious causes and allergy.
Bacterial Conjunctivitis
Acute bacterial conjunctivitis is relatively common and tends to present with a red, gritty eye and a sticky discharge. Everting the upper eyelid may reveal a papillary reaction on the tarsal conjunctiva. Papillae are small raised areas on the conjunctival surface due to dilated conjunctival capillaries surrounded by oedema and inflammatory infiltrates. The eyelids are frequently stuck together on waking.
Common causative organisms are staphylococcus, haemophilus and streptococcus species. Bacterial conjunctivitis can be unilateral or bilateral and usually resolves fairly quickly with a broad spectrum topical antibiotic.
Acute bacterial conjunctivitis left eye: Note the mucopurulent discharge with clumping of the eyelashes.
Gonococcal bacterial conjunctivitis is much rarer and characterised by an acute purulent conjunctivitis with associated pre-auricular lymphadenopathy. It is a venereal disease resulting from direct genital-hand-ocular transmission. Gonococci can cause corneal ulceration and prompt treatment should be with systemic and topical antibiotics.
Viral Conjunctivitis
Viral conjunctivitis usually presents with red, sore eyes and a watery discharge. Conjunctival follicles (caused by aggregations of lymphocytes) may be seen, especially in the lower fornices. Viral conjunctivitis is most often bilateral and, unlike acute bacterial conjunctivitis, there is often associated tender pre-auricular lymphadenopathy. Corneal involvement can result in photophobia and reduced vision and the condition is then known as keratoconjunctivitis.
Adenoviruses have been implicated in two specific external ocular infections: epidemic keratoconjunctivitis (EKC) and pharyngoconjunctival fever (PCF). EKC is most frequently caused by adenovirus types 8 and 19 and is usually not associated with any systemic symptoms. PCF is associated with adenovirus types 3 and 7. It is commoner in children and associated with an upper respiratory tract infection. Both conditions are highly contagious for a few weeks and can involve the cornea (keratitis). The mode of virus transmission is usually by contaminated fingers, ophthalmic instrumentation eg tonometer tips or swimming pool water.
The treatment of viral conjunctivitis is mainly supportive, such as ocular lubricants for comfort, and it may take several weeks to completely resolve. Occasionally topical steroids are commenced by specialists if there is sight impairing keratitis and topical antibiotics may be indicated if there appears to be a superadded secondary bacterial conjunctivitis.
Topical antiviral agents are indicated in the special circumstance of signs and symptoms suggestive of a primary or reactive herpes simplex infection eg a child with a unilateral conjunctivitis, lymphadenopathy and associated herpetic eyelid vesicles.
Viral follicular conjunctivitis: Multiple pale swellings in the lower fornix due to follicles which represent clusters of lymphocytes and plasma cells. A follicular reaction can occur in other causes of conjunctivitis including chlamydia, molluscum contagiosum and topical drug toxicity.
Chlamydia Conjunctivitis
This is a sexually transmitted disease (STD) caused by Chlamydia trachomatis serotypes D to K and associated with urethritis or cervicitis. It may present as a low grade chronic unilateral follicular conjunctivitis with associated pre-auricular lymphadenopathy. Corneal involvement can occur if left untreated.
Patients with conjunctival scrapings positive for chlamydia should be referred to Genito-Urinary medicine for further assessment and contact tracing. Systemic antibiotics are required for treatment.
Ophthalmia Neonatorum
This term is used for conjunctivitis occurring in babies during the first month of life. Chlamydia trachomatis transmitted from the mother during delivery is one possible cause, but the differential diagnosis includes bacterial, herpetic and gonococcal infections. Specialist opinion is required to establish the aetiology and commence appropriate treatment.
Ophthalmia neonatorum: Conjunctivitis left eye, with a green mucopurulent discharge, in a 3 week old baby
Allergic Conjunctivitis
This type of conjunctivitis tends to present with red, itchy, watery eyes and a “stringy” discharge. Everting the upper lid often reveals a papillary reaction on the tarsal conjunctiva. It may be seasonal ie hayfever conjunctivitis, and is commoner in atopic individuals who are prone to asthma and eczema. A similar condition can present in patients who are hypersensitive to agents being used in contact with the eye eg preservatives in eye drops or contact lens solutions.
If the allergen can be identified it should be withdrawn. Occasionally patch testing may be helpful. The mainstay of treatment is symptomatic relief with topical (or systemic) antihistamines or mast cell stabilisers.
Mild allergic papillary conjunctivitis: Multiple “dot-like” dilated capillaries surrounded by oedema result in a papillary reaction on the tarsal conjunctiva. Papillary conjunctivitis can be associated with other causes of conjunctival inflammation such as contact lens wear and bacterial infection.