Infectious Conjunctivitis

Conjunctivitis is the inflammation of the conjunctiva; the thin layer that lines the inside of the eyelid and covers the white part of the eye. Vasodilation of conjunctival blood vessels causes the eye to appear red. Other symptoms may include irritation, itching and discharge. Red eye has a range of causes and it is important to rule out more serious and potentially sight-threatening conditions.

Infectious conjunctivitis may be caused by viruses or bacteria, with viruses thought to be the most common pathogen involved. Non-infectious causes include allergy, irritants, toxicity and inflammation due to immune-mediated diseases and neoplastic processes.

It is difficult to differentiate between acute viral and bacterial conjunctivitis. Purulent or mucopurulent discharge often indicates bacterial conjunctivitis, while a watery discharge is more indicative of viral conjunctivitis. However, many cases are nonspecific, and some studies have failed to demonstrate a correlation between the type of discharge and the cause of conjunctivitis. Predictive factors for bacterial conjunctivitis include bilateral matting of eyelids, lack of itching and no prior history of conjunctivitis.

Viral conjunctivitis, often associated with upper respiratory tract infections, is the most common type of infectious conjunctivitis. Adenoviruses are the cause in 65% to 95% of cases. Conjunctivitis is a highly contagious condition that is usually spread through direct contact with contaminated fingers or swimming pool water. It is important to ensure that a strict code of hygiene is adhered to, with patients encouraged to practice frequent washing of the hands, avoid touching the eye area, and not share face towels or cosmetics. Close contact with other people is not recommended for the first one to two weeks to reduce transmission. Symptoms include red eyes, discomfort, watery discharge, and swelling of the eyelids. The conjunctiva that covers the white of the eye may also be swollen, creating a glassy appearance. Although there is no specific treatment available, the condition is usually mild and resolves after one to two weeks. Symptomatic relief may be obtained from the use of ocular lubricants, cold compresses, and simple analgesics, such as paracetamol and ibuprofen. Topical antibiotics are not indicated as they do not protect from secondary infections and may complicate the situation by causing allergy, adverse effects, or a possible delay in diagnosis of more serious conditions. There is also the potential for these agents to promote resistance. Patients should be referred if symptoms persist for more than two weeks. Other causes of viral conjunctivitis, such as herpes simplex virus, are less common and less likely to spread.

Bacterial conjunctivitis is also transmitted by direct contact with contaminated fingers. It is usually caused by Streptococcus aureus in adults or Streptococcus pneumoniae or Haemophilus influenzae in children. The condition may begin unilaterally however usually develops into a bilateral infection. The eyes may feel gritty and irritated and is often associated with a sticky discharge or crusting on the eyelashes which may cause the eyelids to stick together, particularly in the mornings. Most cases are self-limiting and clear within one to two weeks. Topical antibiotics may provide marginal benefit in reducing the duration of disease, although up to 65% of patients improve after two to five days with no treatment. Due to the often non-specific nature of symptoms, it is thought that almost half of all cases of suspected bacterial conjunctivitis are viral. The use of antibiotics in these patients offers no benefits and is associated with potential resistance and additional expense. The Therapeutic Guidelines recommend a ‘delayed prescription’ approach in the management of suspected bacterial conjunctivitis. If symptoms do not improve within two to three days of supportive treatment, antibiotic therapy may be initiated. Immediate antibiotic therapy may be considered for patients who are health care workers, reside in a health care facility, are immunocompromised, or for children who need to go to school or daycare. Supportive care should be recommended to all patients detailing the importance of proper hygiene to avoid transmission, frequent eye cleansing with sterile water and cotton balls, warm water compresses, and artificial tears for comfort. If topical antibiotics are indicated, chloramphenicol is the preferred agent. If the infection does not improve within 48 hours of antibiotic use, the patient should be advised to seek medical advice.

Conjunctivitis, regardless of its aetiology, is a mild and self-limiting condition. Symptoms such as pain, fever, photophobia or blurred vision may indicate a more serious condition and prompt referral to an ophthalmologist is required. Due to the highly contagious nature of infectious conjunctivitis, a single red eye should be viewed with suspicion. Contact lens wearers should be referred to their doctor and advised to remove their lenses and wear glasses until symptoms resolve.