It is an abnormal accumulation of fluid in the tissues of the inner surface of the eyelid, which causes a swelling that prevents the complete opening of the eye, it can also affect the conjunctiva. The most common causes are allergic: local allergy (contact sensitivity) or systemic allergy (e.g., angioedema, systemic allergy associated with allergic rhinitis). The most common cause is a chalazion, the dangerous causes are orbital cellulitis and cavernous sinus thrombosis (rare). In addition, it may be the result of a) disorders that can affect the eyelid, but do not produce edema unless they are very advanced (e.g., eyelid tumors, including squamous cell carcinomas and melanomas). b) Disorders that produce swelling that begins and is usually more severe in the structures near the eyelid, but is not part of them (e.g., dacryocystitis, canaliculitis). c) Disorders in which swelling occurs but is not the presenting symptom (e.g., skull base fracture, burns, trauma, post-surgery).
