What is the most likely diagnosis for a patient presenting with decreased vision, pain with ocular movement, proptosis, and eyelid erythema and edema?

The presentation of decreased vision, pain with ocular movement, proptosis (protrusion of the eyeball), and eyelid erythema and edema is highly indicative of orbital cellulitis. This condition involves inflammation and infection of the fat and muscle contents within the orbit, often resulting from a sinus infection, particularly when the infection spreads from the ethmoid or maxillary sinuses.

In orbital cellulitis, the inflammation can cause a range of symptoms, including significant ocular pain, decreased visual acuity, and restricted eye movement due to the involvement of the extraocular muscles. Proptosis occurs as the accumulated fluid and inflammation push the eyeball forward within the bony orbit. Furthermore, patients typically exhibit swelling and redness of the eyelid, known as eyelid edema and erythema, due to the inflammatory response.

The urgency of diagnosing orbital cellulitis lies in its potential complications, including vision loss and the spread of infection to the surrounding tissues or even intracranially. Therefore, prompt medical intervention is crucial for managing this condition effectively.

In comparison, preseptal cellulitis, while also presenting with eyelid swelling and redness, is confined to the area anterior to the orbital septum and generally does not affect vision or cause propt