The word conjunctivitis is usually taken to mean a brief infection of the eye surface. Conjunctivitis may be due to bacteria for example Staphylococcus, Streptococcus or Haemophilus or viruses for example Adenovirus. The symptoms are redness, discomfort, a discharge (usually thick and sticky if bacterial, watery and clear if viral), swollen eyelids, feeling generally unwell and sometimes slightly blurred vision. Often both eyes are involved. The patient may have a cold or sore throat as well as conjunctivitis, caused by the same organism infecting the nose, throat, chest etc. Bacterial infections usually respond well to antibiotics, but generally will last 1-2 weeks if untreated. Viral infections usually last 2-3 weeks whether treated or not. Some cases of conjunctivitis are caught from relatives or work colleagues, who may have colds rather than conjunctivitis.

The diagnosis is made from the symptoms, the clinical appearance of the eyes and swabs sent to the laboratory for examination. Conjunctivitis is highly infectious and precautions must be taken to avoid spreading it, for example using separate towels. In most cases of bacterial infection I prescribe chloramphenicol or ofloxacin eye drops although sometimes a different antibiotic is needed. Viral infections do not respond to antibiotics. Steroid eyedrops reduce the symptoms of viral conjunctivitis but not the duration of infection - in fact they sometimes prolong the infection. I therefore assess whether steroid eyedrops are appropriate on an individual basis.

Conjunctivitis normally gets better quickly and does no damage. However viral conjunctivitis sometimes damages the cornea, the clear 'front window' of the eye. The damage usually clears but if there is permanent scarring, laser treatment may be necessary to remove it.