Author: Dr Julie Fraser, Adelaide, Australia. Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, December 2015.
Conjunctivitis is inflammation of the conjunctiva of the eye. The conjunctiva is the semi-transparent membrane that covers the white part of the eye (the sclera) and lines the inside of the eyelids.
When the conjunctiva is inflamed, the white of the eye appears red. Conjunctivitis is the most likely diagnosis when a patient has a red eye and discharge.
Conjunctivitis caused by bacterial infection is highly contagious.
Bacterial conjunctivitis is spread by direct contact with secretions from an infected individual or by contact with contaminated sufaces. It can also be secondary to viral conjunctivitis.
The most common organisms causing bacterial conjunctivitis are:
Other notable bacterial causes of conjunctivitis include hyperacute bacterial conjunctivitis and chlamydial infections.
Hyperacute bacterial conjunctivitis is usually due to Neisseria species, especially gonococcus (the cause of gonorrhoea). Hyperacute bacterial conjunctivitis is severe and can threaten sight, requiring immediate referral to an ophthalmologist.
C. trachomatis is the most common cause of chronic follicular conjunctivitis (ie, follicular conjunctivitis lasting for > 16–28 days). It causes 3 clinical syndromes:
Trachoma is due to C. trachomatis, serotypes A, B, Ba and C. Conjunctivitis is the major clinical manifestation of active trachoma. It is also known as "granular conjunctivitis", and can cause blindness and other complications.
Inclusion conjunctivitis is due to C. trachomatis, serotypes D–K. In adults, it is a sexually transmitted infection from hand-to-eye contact. In neonates, it develops 5–14 days after birth and is transmitted from an untreated infected mother.
Conjunctivitis is a diagnosis of exclusion. All forms of conjunctivitis are characterised by:
The following "red flags" point to other more serious diagnoses, such as keratitis (inflammation of the cornea), iritis, or angle closure glaucoma:
Pointers to a bacterial cause of conjunctivitis include:
Hyperacute bacterial conjunctivitis is also associated with:
Trachoma is characterised by painful follicles on the underside of the upper eyelid, which break down to cause pitting of the cornea and possible blindness.
Adult inclusion conjunctivitis is associated with:
Most forms of conjunctivitis are self-limiting but in certain cases, severe complications may occur. Pain, loss of vision or photophobia require immediate referal to an ophthalmologist.
Complications from bacterial conjunctivitis include:
Conjunctivitis caused by Neisseria meningitidis (meningococcal disease) can precede meningitis.
Many cases of bacterial conjunctivitis resolve spontaneously within 5–14 days. Antibiotics may shorten the course if given before day 6. Chloramphenicol 0.5% eye drops or framycetin 0.5% eye drops can be used. Complete the course, then throw out the used bottle. Warning: chloramphenicol and framycetin can cause severe contact allergic dermatitis.
Gonorrhoeal and chlamydial infections require systemic antibiotic treatment. Hyperacute bacterial conjunctivitis requires hospitalisation for systemic and topical therapy. Keratitis and perforation can occur.
Topical or systemic glucocorticoids are sometimes used under specialist advice. Warning: glucocorticoids can cause sight-threatening complications, including corneal scarring and perforation, cataracts and glaucoma, when used inappropriately.
Patients should be educated about hygiene measures to reduce the spread of the infection.
See the DermNet NZ bookstore.
© 2019 DermNet New Zealand Trust.
DermNet NZ does not provide an online consultation service. If you have any concerns with your skin or its treatment, see a dermatologist for advice.