Chalazion, also known as meibomian cyst, is a small cyst or lump in the eyelid caused by inflammation or blockage of the meibomian gland. Meibomian glands are sebaceous glands on the eyelid that produce an oily substance that prevents evaporation of the eye’s tear film and lubricates the eye. A most common condition resembling chalazion is the stye. The major difference between the two is that chalazion forms away from the eyelid margin and is painless, while a stye forms at the eyelid margin and is painful.