The role of antibiotics

Despite common expectations, antibiotics are required in only a minority of conjunctivitis cases. Their use should generally be reserved for situations where symptoms are more severe, discharge is persistently purulent, symptoms fail to improve after several days, or discomfort significantly interferes with daily activities.

National Institute for Health and Care Excellence (NICE) guidance recommends reserving topical antibiotics for people with severe symptoms or where rapid resolution is clinically required.

In other cases, a delayed treatment strategy may be appropriate. This involves advising patients to monitor their symptoms and to initiate antibiotic drops only if there has been no improvement after around three days.

Evidence suggests that antibiotics shorten the duration of symptoms by only one to two days, and unnecessary use risks contributing to antimicrobial resistance.

Chloramphenicol (as 0.5% eye drops) is the antibiotic most commonly supplied under PGDs. Its broad spectrum of activity, low resistance rates and minimal systemic absorption make it suitable for short-term use in uncomplicated bacterial conjunctivitis.

PGDs typically specify an initial period of more frequent dosing, followed by a reduced frequency once improvement is seen. 

In practice, this usually involves instilling one drop every two hours while awake for the first 48 hours, followed by one drop every four hours thereafter.

Treatment is continued for a short period after symptoms resolve, with a maximum total duration of around five days. This stepped approach aims to achieve early symptom control while limiting unnecessary antibiotic exposure.