What is a chalazion?

A chalazion is defined as a cyst or nodule that forms on the eyelid due to the obstruction of a meibomian gland. These glands are responsible for secreting oils that help to lubricate the eye and prevent tear evaporation. When the gland becomes blocked, the fluid can accumulate, leading to swelling and the formation of a firm lump on the eyelid. Typically, a chalazion is painless and can resolve on its own or may require treatment if it persists.

The other options describe different conditions affecting the eye or eyelid. Inflammation of the conjunctiva is known as conjunctivitis and is characterized by redness and swelling of the eye's outer surface. The turning in of the eyelash margins refers to entropion, where the eyelashes rub against the eye, potentially causing irritation. An increase in intraocular pressure is associated with glaucoma, a serious condition that can lead to vision loss. Each of these conditions differs from a chalazion in terms of causes, symptoms, and implications for eye health.