Chalazion is a round, slowly emerging, localized swelling, in the form of a cyst located on the lower or upper eyelid. (Chalazion is the Greek word for “hailstone” which represents the size of the lump that makes up the cyst.) The usually painless, grainy (granulomatous) mass is due to inflammation, obstruction, and retained secretions of one of the glands that lubricates the edge of the eyelids. These glands secrete sebum, an oily, protective fluid. If one or more of the ducts that drain these glands is blocked, the sebum accumulates under the skin to form a cyst.
In rare cases, if the cyst is large, blurred vision may result due to pressure on the cornea, the front, clear portion of the eye through which light passes. In some affected individuals, chalazia may disappear spontaneously. However, in other cases, treatment may be required. Individuals with chronic inflammation of the eyelids (blepharitis) may be prone to recurrences.
View images of chalazion/stye: