IV INFECTIOUS CONJUNCTIVITIS
Marek E. Prost
Infectious conjunctivitis is one of the three leading causes of red eye (the other two are aller- g i c c o n j u n c t i v i t i s a n d d r y e y e s y n d r o m e ) . T h e r e f o r e , p a t i e n t s w i t h t h e s e d i s o r d e r s a r e f r e q u e n t l y
seen by general practitioners in their every-day practice. Most cases of infectious conjunctivitis are self-limiting but some of them may progress and may cause severe ocular complications or they may be associated with involvement of other organs. The aim of this chapter is to present, in a concise form, the most important information on how to establish the proper diagnosis of infectious conjunctivitis and differentiate it from other red eye causes, how to choose appro- priate therapy and help to make decisions about which cases can be treated by general practi- tioners and which should be referred for treatment by ophthalmologists.
Infectious conjunctivitis is an inflammation of the conjunctiva caused by infective agents. Almost any microbial organism can cause infectious conjunctivitis. Most frequently it is caused by bacteria, viruses and chlamydia. Rarely, conjunctivitis is caused by acanthamoeba and very rarely, by fungal infection. These inflammations are usually secondary to keratitis.
Infectious conjunctivitis is one of the most frequent causes of red eye. According to a recent- ly published study, performed in nine Eastern European and Middle Eastern countries, red eye
patients account for 15 % of all consultations performed by ophthalmologists and 6 % of visits to general practitioners.  Among these patients, infectious conjunctivitis was the most fre- quent cause of red eye seen by ophthalmologists (31.3 %) and the second largest cause in general medical practitioners practices (25 % – the most frequent diagnosis was allergic con- junctivitis: 56 %). 
CLASSIFICATION AND CLINICAL PICTURE
BACTERIAL CONJUNCTIVITIS This is usually caused by Streptococcus and Staphylococcus species and less frequently by Haemophilus influenzae and enteric gram-negative organisms. [8, 9, 10, 12] In children,
Haemophilus influenzae may be the most common cause. [10, 16] The sources of the infection
are usually a skin or respiratory tract pathogen or, in neonates, vaginal delivery by an infected
mother. Usually, one eye is involved but infection of the second eye may develop in a few days.
Bacterial conjunctivitis can present as an acute, subacute or chronic condition. Acute bacterial conjunctivitis usually begins suddenly in one eye with hyperaemia and mode- rate to copious purulent or mucopurulent discharge (Figure 1 and Figure 3, Chapter I), but infection of the
second eye may develop in a few days.  Patients initi- ally complain of unilateral then bilateral tearing and vague irritation. Associated mild to moderate eyelid oedema and erythema may give the appearance of pseu- doptosis. Purulent discharge may accumulate on the eye- lashes, resulting in the eyelids sticking together in the morning on waking. Some bacteria are able to cause con- junctival membranes or pseudomembranes (beta hemo- lytic streptococci, Bordetella pertussis – diphtheria).
Figure 1 – Acute bacterial conjunctivitis with purulent discharge and conjuctival hyperaemia.
In subacute or chronic conjunctivitis patients present with moderate purulent discharge, mild conjunctival hyperaemia and crustings on the eyelids and/or eyelas- hes (dried purulent discharge). [1, 9] (Figure 1) Some- times a conjunctival papillary reaction may be seen in chronic bacterial conjunctivitis. [8, 9] (Figure 2)
Corneal involvement is very rare in bacterial conjunctivi- tis. The duration of infection is on average 5 – 7 days and is usually mild and self-limiting, but in children it may rarely progress to keratitis and infection of orbital tissue (preseptal cellulites).  Pre-auricular lymph nodes are not enlarged.
Figure 2 – Conjunctival papillary reaction in chronic bacterial conjunctivitis.
The most typical sign of bacterial conjunctivitis is purulent discharge and eyelids sticking to- gether in the morning upon waking. In neonates and infants it is necessary to exclude naso- lacrimal duct obstruction as a cause of bacterial conjunctivitis. A very rare but sight threate- ning form of bacterial conjunctivitis is hyper-acute conjunctivitis (see addendum).