Conjunctivitis describes any inflammation of the conjunctiva, most of which are either bacterial (due to the Staphylococcus species, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis) or viral. Bacterial and viral causes are equally common.
Infective conjunctivitis is predominantly seen in children and the elderly.
In newborns, the aetiology may be chlamydia or gonorrhoea infection.
Occasionally, the inflammation is secondary to another eye condition, such as iritis. Rarely it may be due to fungal, toxic, parasitic or allergic agents.
A patient with conjunctivitis presents in UK general practice about 13 to 14 times a year per 1,000 population.
Symptoms include burning or gritty discomfort, itching, minimal photophobia and blurring of vision.
The patient may report that their eyelids were stuck together on waking. Other members of the family may be affected.
Differentiating bacterial from viral conjunctivitis is difficult, but bacterial conjunctivitis is more likely when the eyes are stuck with purulent discharge, there is no itching and no previous history of conjunctivitis.
Enlarged pre-auricular nodes and a history of VRTI suggest a viral cause. A history of exposure to unusual substances may suggest an inflammatory aetiology.
Contact lens wearers are prone to a particular type of infection called giant papillary conjunctivitis, the symptoms of which include excessive itching, mucus production, and intolerance to wearing the contact lenses.
Examination may reveal engorgement of the conjunctival blood vessels, and mucopurulent or watery discharge.
Enlarged pre-auricular lymph nodes are seen in chlamydia and adenoviral infections.
In contact lens conjunctivitis, the giant papillae can be seen by everting the upper eyelid and exposing the palpebral conjunctiva.
Conjunctivitis should be differentiated from serious causes of red eye, which include acute glaucoma, keratitis and iritis.
Features that suggest a serious cause include moderate to severe eye pain, extreme redness, ciliary injection (redness localised around the cornea) and reduced visual acuity.
Investigation is rarely necessary, but an eye swab is indicated in conjunctivitis that fails to respond to treatment.
Allergic conjunctivitis is suggested by bilateral itchy eyes, a history of atopy, and a ‘cobblestone’ appearance of the upper palpebral conjunctiva.
If there is a possibility that the patient has serious eye disease referral should be made for a same-day assessment at an emergency eye clinic.
Acute bacterial conjunctivitis is a self-limiting condition in 65 per cent of patients, but a Cochrane meta-analysis has shown that antibiotic drops are associated with a modest improvement in clinical and microbiological remission.
This effect was more significant when the treatment was given on early presentation (two to five days) rather than late (six to 10 days).
The most recent evidence supports the strategy of deferred prescribing, however. Chloramphenicol is the usual first-line treatment, and the concerns that it may cause aplastic anaemia have largely been allayed.
However, caution should be exercised in patients who are taking myelotoxic drugs and also in pregnant women in the third trimester of pregnancy because of the possibility of ‘grey baby syndrome’.
Comparative trials suggest that fusidic acid is an equally effective alternative.
Whether to prescribe ointment or drops is a matter of personal choice. Many patients prefer drops to ointment, because the latter causes blurred vision; the elderly may find viscous drops easier to use.
If the condition fails to respond to treatment, a swab should be taken to check for bacterial sensitivity and exclude chlamydia.
Sticky eyes in the newborn should always be swabbed.
Gonorrhoea and chlamydia both require immediate hospital referral for systemic treatment. In the newborn, gonorrhoea can penetrate the cornea, and chlamydia can cause pneumonia.
Premature infants can develop meningitis, septicaemia or cellulitis after bacterial conjunctivitis, and children can get otitis media after H influenzae conjunctivitis.
A wide range of topical antihistamines such as azelastine are available and have been shown to be safe and effective in controlled trials.
Mast-cell stabilisers such as sodium cromoglicate, lodoxamide and nedocromil are safe and effective alternatives.
Giant papillary conjunctivitis usually resolves if the patient stops using their contact lenses, but is aided by use of sodium cromoglicate drops.
Steroid drops should not be prescribed for any undiagnosed red eye condition, because they can transform dendritic ulcer into an extensive amoebic ulcer. Infective conjunctivitis resolves itself spontaneously in most patients.
Dr Knott is a GP in Enfield