A chalazion (; plural chalazia or chalazions) or meibomian cyst is a cyst in the eyelid usually due to a blocked meibomian gland,  typically in the middle of the eyelid, red, and not painful. They tend to come on gradually over a few weeks.A chalazion may occur following a stye or from hardened oils blocking the gland. The blocked gland is usually the meibomian gland, but can also be the gland of Zeis.A stye and cellulitis may appear similar. A stye, however, is usually more sudden in onset, painful, and occurs at the edge of the eyelid. Cellulitis is also typically painful.Treatment is initiated with warm compresses. In addition, antibiotic/corticosteroid eyedrops or ointment may be used. If this is not effective, injecting corticosteroids into the lesion may be tried. If large, incision and drainage may be recommended. While relatively common, the frequency of the condition is unknown. It is most common in people 30–50 years of age, and equally common in males and females. The term is from the Greek khalazion (χαλάζιον) meaning "small hailstone".
Signs and symptoms
Painless swelling on the eyelid
Eyelid tenderness typically none-to-mild
Increased tearing
Heaviness of the eyelid
Redness of conjunctiva

Complications
A large chalazion can cause astigmatism due to pressure on the cornea.As laser eye surgery involves shaping the cornea by burning parts of it away, weakening its structure, post-operation people can be left predisposed to deformation of the cornea from small chalazia.Complications of corticosteroid injection include hypopigmentation and fat atrophy which is less likely to occur in conjunctival approach of injection.A chalazion that reoccurs in the same area may rarely be a symptom of sebaceous carcinoma. Diagnosis
A chalazion or meibomian cyst can sometimes be mistaken for a stye. Differential diagnosis
Sebaceous gland adenoma
Sebaceous gland carcinoma
Sarcoid granuloma
Foreign body granuloma

Treatment
General treatment
Chalazia will often disappear without further treatment within a few months, and virtually all will resorb within two years.Healing can be facilitated by applying a moist warm compress to the affected eye for approximately 10–15 minutes, 4 times per day. This promotes opening, drainage, and healing by softening the hardened oil that is occluding the duct. In addition, it is helpful to scrub the lid margin (at the base of the eyelashes) with a washcloth and mild (baby) shampoo, which removes oily debris.Topical antibiotic eye drops or ointment (e.g., chloramphenicol or fusidic acid) are sometimes used for the initial acute infection, but are otherwise of little value in treating a chalazion.If they continue to enlarge or fail to settle within a few months, smaller lesions can be injected with a corticosteroid. Larger ones can be surgically removed using local anesthesia.