Rarely cysts can become secondarily infected.
Periorbital cellulitis is caused by an infection anterior to the orbital septum. It does not cause visual impairment, limited or painful eye movements, oedema of the conjunctiva or protrusion of the eyeball. There may be associated fever and malaise.
Orbital cellulitis is an infection involving the deep soft tissue surrounding the eyeball, located posterior to the orbital septum. It usually presents as an acute onset of unilateral eyelid oedema, with a red and painful eye. It is often associated with severe pain, blurred vision, double vision, limited and painful eye movements, protrusion of the eyeball, headache, fever, and malaise. It is a medical emergency, which can progress rapidly and lead to loss of vision and cerebral complications (such as meningitis and cerebral abscess).