Conjunctivitis

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A comprehensive topic overview

Introduction

Conjunctivitis refers to in
inner surface of the eyelids. 1
It is an extremely common condition and accounts for more than 1% of GP consultations in the
UK.
Symptoms can include a red-eye, chemosis (swelling of the conjunctiva) and epiphora (watering eyes), which is associated
with discharge.
2
The diagnosis of conjunctivitis is usually clinical but further investigations may be required to rule out other causes of a red
eye (e.g. acute angle-closure glaucoma or scleritis).
Conjunctivitis can be classi
2
This article will cover the di
information on other causes of red-eye, see the Geeky Medics guides to painless red-eye and painful red-eye.

Infectious conjunctivitis

Various micro-organisms can cause infectious conjunctivitis. The most common causes of infectious conjunctivitis are
viruses and bacteria, though fungi can rarely be causative organisms.
Viral conjunctivitis
Aetiology
Most cases of viral conjunctivitis are caused by adenovirus, with herpes viruses also contributing to a smaller proportion.
2
Other less frequent causes include measles, mumps and rubella, though these have decreased due to vaccination.
Enterovirus and coxsackievirus can cause a rare type of viral conjunctivitis, known as acute haemorrhagic viral
conjunctivitis.
3
Risk factors
Viral conjunctivitis is extremely infectious and therefore, direct contact with contaminated skin or objects can lead to the
spreading of infection.
2
Clinical features
Viral conjunctivitis tends to a
preauricular lymphadenopathy. It is often associated with a concurrent upper respiratory tract infection.
1
Adenoviral conjunctivitis can cause two presentations in a patient, depending on its serotype\:
3
Pharyngoconjunctival fever\: as the name suggests, patients present with pharyngitis, conjunctivitis and fever (serotypes
3, 4 and 7).
Epidemic keratoconjunctivitis\: more severe, associated with corneal involvement and photophobia (serotypes 8, 19 and
37).Figure 1. Viral conjunctivitis.
5
Investigations
the patient.
Investigations are rarely required as the diagnosis of viral conjunctivitis can be made from the history and examination of
In unusual or treatment-resistant cases, swabs may be taken to aid with diagnosis.
3
Management
Viral conjunctivitis tends to be self-limiting and rarely requires treatment. It is important to adopt simple hygiene measures
to prevent spread (e.g. washing hands regularly and avoiding sharing linen).
4
Complications
Viral conjunctivitis is unlikely to cause any complications and the prognosis for patients is excellent.
Bacterial conjunctivitis
Aetiology
Causative organisms of bacterial conjunctivitis include S t a p h y l o c o c c u s , S t r e p t o c o c c u s and H a e m o p h i l u s .
6
Other important causes include C h l a m y d i a t r a c h o m a t i s , with serotypes D-K being responsible for conjunctivitis. In
neonates, N e i s s e r i a g o n o r r h o e a can cause a particularly exudative form of conjunctivitis (ophthalmia neonatorum),
because of infection from the mother’s birth canal.
6
Both bacteria are also causes of reactive arthritis, which classically presents as a triad of arthritis, conjunctivitis and
urethritis.
7
Risk factors
Like viral conjunctivitis, one of the main risk factors is contact with contaminated skin and objects. In cases of chlamydia or
gonorrhoea, unprotected sexual intercourse amongst young people is a key risk factor.
2
Clinical features
Bacterial conjunctivitis tends to a6
rapidly with very in
It tends to develop quite
Gonococcal infections are associated with a very profuse discharge. Due to the discharge, patients with bacterial
conjunctivitis will often state that their eyelids stick together on waking.
2,6
Unlike other bacteria, chlamydial conjunctivitis tends to be associated with follicles and pre-auricular lymphadenopathy.
Figure 2. Bacterial conjunctivitis with
mucopurulent discharge.
8
Investigations
Bacterial conjunctivitis can be diagnosed without investigations. Conjunctival scrapes are occasionally used in patients with
a high risk of atypical organisms, for example, immunosuppressed, post-corneal transplant and sexually active young
people.
Management
For most cases of bacterial conjunctivitis, the treatment is supportive and antibiotic drops (e.g. chloramphenicol) are used
rarely. In cases secondary to chlamydia or gonorrhoea, treatment is usually systemic antibiotics such as azithromycin.
6Complications
Unlike viral conjunctivitis, bacterial conjunctivitis carries a higher risk of complications. Certain bacteria such as N e i s s e r i a
have a propensity to invade the cornea, which can lead to keratitis and endophthalmitis. 2
These conditions can
subsequently cause reduced vision or blindness if not treated promptly.

Non-infectious conjunctivitis

Non-infectious causes of conjunctivitis include allergy, chemicals and irritants.
Allergic conjunctivitis
Aetiology
Allergic conjunctivitis is the most common cause of non-infectious conjunctivitis and occurs secondary to a type I
hypersensitivity reaction to a particular trigger.
9
Risk factors
A personal or family history of atopic conditions, such as asthma and hay fever, increases the risk of allergic conjunctivitis.
2
Clinical features
The distinguishing feature of allergic conjunctivitis is the presence of itching. As it is driven by a systemic process, both
eyes are usually a
2
Examination of the eyelid will reveal papillae, which if large can give a ‘cobblestone’ appearance (Figure 3).
Figure 3. Cobblestone appearance in
allergic conjunctivitis.
11
There are multiple subtypes of allergic conjunctivitis\:
2,10
Seasonal allergic conjunctivitis\: secondary to hay fever, therefore most common in summer months due to the presence
of pollen
Perennial allergic conjunctivitis\: caused by allergens such as house dust mite
Vernal keratoconjunctivitis\: most common in young males living in hot dry climates
Atopic keratoconjunctivitis\: most common in middle-aged men
Investigations
A history of atopy or recurring conjunctivitis in response to a trigger or changes to the weather is strongly suggestive of
allergy conjunctivitis.
Conjunctival scrapes may be performed and will reveal the presence of eosinophils, typical of a type I hypersensitivity
reaction.
9
Management
Treatment includes allergen avoidance, topical and oral antihistamine as well as topical mast-cell stabilisers and
occasionally, mild steroids.
10
Complications
Allergic conjunctivitis does not result in complications. However, the use of steroids in managing
of herpes infection, glaucoma and cataracts.
Chemical and irritant conjunctivitisChemical eye injury can also result in conjunctivitis and if severe, in
cause more signi
agent to penetrate structures easily.In contrast, acids denature and precipitate proteins in the cornea, which in turn forms a barrier and prevents further
penetration of the acid.
12
Chemical eye injury is an ophthalmic emergency and requires urgent irrigation of the eye to limit the damage.
1,12
Irritants such as smoke, dust, fumes and even chlorine in swimming pools can also cause conjunctivitis.
1,4

Summary table

Table 1. Summary of the clinical features of conjunctivitis.
Bacterial Viral Allergic Chlamydial
Laterality Unilateral Bilateral Bilateral
Discharge Mucopurulent Watery Watery Mucopurulent
Preauricular
lymphadenopathy
No Yes No Occasionally
Lid

References

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[LINK]
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Reviewer

Consultant Ophthalmologist

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