What is a chalazion?

A chalazion is a lump on the upper or lower eyelid caused by a blockage in one of the meibomian glands in the lid. It may be soft and fluid-filled if it is recent, or, it may be firmer if it has been long-standing. A chalazion can also be referred to as a meibomian cyst, tarsal cyst, or a conjunctival granuloma.

What are these glands?

The meibomian glands may also be referred to as palpebral glands, tarsal glands, or tarsoconjunctival glands. There are 30 to 40 of these glands in each of the upper and lower eyelids. The upper lids contain a tarsal plate, a small piece of cartilage that gives the lid shape and protection. The meibomian glands line the lid on both the inside and outside portions of the plate. These glands produce a thick liquid secretion that is discharged into the tear film of the eye. This liquid is called sebum and is a mixture of oil and mucin. The liquid is secreted through the gland openings just behind the eyelashes at the lid margins, and acts to lubricate the surface of the eye.
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