A chalazion, also known as a meibomian gland lipogranuloma, is a cyst in the eyelid that is caused by inflammation of a blocked meibomian gland, usually on the upper eyelid. Chalazia differ from styes (hordeola) in that they are subacute and usually painless nodules. They may become acutely inflamed but, unlike a stye, chalazia usually point inside the lid rather than on the lid margin. A chalazion or meibomian cyst can sometimes be mistaken for a stye. Topical antibiotic eye drops or ointment (e.g. chloramphenicol or fusidic acid) are sometimes used for the initial acute infection, but are otherwise of little value in treating a chalazion. Chalazia will often disappear without further treatment within a few months and virtually all will re-absorb within two years.
Contributions by Davidruben, Trigaranus, and 22.214.171.124.