Hi. I'm online and happy to answer your question today.
pre-septal cellullitis is an infection of the tissues in front of the orbit that has not extended past the septum behind and around the eye. It is correctly treated with oral antibiotics and warm compresses as you doctor has prescribed
Even though you say that the eyelid has started to sag more it is good that the swelling under your eye has improved. If you were not on the correct antibiotic things would be worse now then they were this morning.
I believe what you are experiencing is just a shift in the location of the edema due to gravity. As long as things continue to look better, and not get worse, I think you would be safe to continue with the same treatment. From what you have told me I do not feel you need to rush to the ER right now.
Does this make sense to you?
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