What is conjunctivitis?
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 red-eye and discharge.
Conjunctivitis caused by bacterial infection is highly contagious.
What causes bacterial conjunctivitis?
Bacterial conjunctivitis is spread by direct contact with secretions from an infected individual or by contact with contaminated surfaces. It can also be secondary to viral conjunctivitis.
The most common organisms causing bacterial conjunctivitis are:
- Staphylococcus aureus
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis.
Other notable bacterial causes of conjunctivitis include hyperacute bacterial conjunctivitis and chlamydia infections.
Hyperacute bacterial conjunctivitis
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:
- Adult inclusion conjunctivitis
- Neonatal conjunctivitis.
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.
What are the symptoms and signs of bacterial conjunctivitis?
Conjunctivitis is a diagnosis of exclusion. All forms of conjunctivitis are characterised by:
- Redness and discharge in one or both eyes
- Diffuse redness around the globe including the underside of the upper and lower lids
- Adhesion of the upper and lower eyelids on waking
- Normal vision
- Absence of focal pathology (eg, stye or blepharitis).
The following 'red flags' point to other more serious diagnoses, such as keratitis (inflammation of the cornea), iritis, or angle-closure glaucoma:
- Changes in visual acuity
- Ciliary flush — a pattern of injection in which the redness is most pronounced in a ring at the limbus (the border of the cornea and the sclera)
- Photophobia (light sensitivity)
- Severe foreign body sensation that prevents the patient from keeping the eye open
- Corneal opacity
- Fixed pupil
- Severe headache with nausea.
Pointers to a bacterial cause of conjunctivitis include:
- Unilateral involvement
- Most prominent involvement at the lid margins and in the corners of the eye
- Thick yellow, white or green purulent discharge that continues throughout the day.
Hyperacute bacterial conjunctivitis is also associated with:
- Concurrent urethritis
- Rapid progression of symptoms: lid swelling, marked chemosis (gelatinous swelling of conjunctiva)
- Tender preauricular lymph nodes.
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:
- Concurrent asymptomatic urogenital infection
- Persistent follicular conjunctivitis, unresponsive to topical antibiotics
What are the complications of bacterial conjunctivitis?
Most forms of conjunctivitis are self-limiting but in certain cases, severe complications may occur. Pain, loss of vision or photophobia require immediate referral to an ophthalmologist.
Complications from bacterial conjunctivitis include:
- Chronic redness, discharge and irritation
Conjunctivitis caused by Neisseria meningitidis (meningococcal disease) can precede meningitis.
How is bacterial conjunctivitis treated?
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.
Gonorrhoea and chlamydia 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.
- Wash hands often.
- Avoid touching or rubbing eyes.
- Wash discharge from around the eyes using a fresh cotton ball or tissue.
- Discard used make-up, contact lens solution and used disposable contact lenses.
- Wash bed linen and towels in hot water and detergent.
- Avoid sharing cosmetics, bed linen, towels and clothing.
- Avoid swimming in a public swimming pool.