An acute purulent infection of the sebaceous glands of Zeis at the base of the eyelashes, of the apocrine sweat glands of Moll or the meibomian sebacious glands often caused by staphylococcus infections. Hordeola can either occur as Hordeola externa affecting the sebaceous glands of Zeis or the apocrine sweat glands of Moll or as Hordeola interna affecting the meibomian sebacious glands. In contrast to chalazia, hordeola are extremely painful and can cause extreme local swelling.