A chalazion is a hard bump that forms on the eyelid.

Chalazion
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A chalazion can form when the duct leading from a gland of the eyelid becomes blocked. This gland produces an oily substance that lubricates the margins of the eyelid and the front of the eye. When the duct becomes blocked, the oily substance can harden. This causes a chalazion to form near the edge of the eyelid. This condition can recur.