Hordeolum

**Definition:** An acute focal infection usually by Staphylococcus aureus involving the eyelash follicle and its associated meibomian and Zeis glands. If the principal focus of infection is the follicle, it presents with a painful boil which discharges pus at the eyelid margin (external hordeolum or stye). If the infection is centred on the meibomian gland (internal hordeolum) then suppuration onto the conjunctival surface occurs.