Orbital cellulitis is an infection of the soft tissues within the orbit, posterior to the orbital septum. It is often due to spread from local sinus disease.
Orbital cellulitis is characterized by a red, swollen, tender eyelid. Extraocular movements are limited because of pain or muscle edema. There are vision changes and diplopia. If the patient is a child, they will have a fever and ill appearance.
Loss of extraocular movements is called ophthalmoplegia. Orbital cellulitis is a severe infection presenting with proptosis and ophthalmoplegia. It requires hospitalization and IV antibiotics to prevent vision loss.
Preseptal cellulitis is an infection of eyelid tissues around the orbit, often with local skin defect. It is also characterized by a red, swollen, tender eyelid. However, the extraocular movements are completely intact (i.e. EOMI). There is also NO vision changes.