I had an mri due to swollen optic nerves...paranasal sinuses: no fluid levels. small right maxillary mucous retention cyst. should i be worried? no other significant findings. what else could be causing swollen optic nerves?

This will not do it. Some have an idiopathic cause. idiopathic is Dr. talk for we do not know what it is. Discuss with your Drs. Can be difficult to figure out the cause.

If your optic nerves are truly "swollen", bilaterally, this could be secondary to a number of causes, and rather than list these as a speculative approach, suggest seeing an ophthalmologist and perhaps neurologist. Regardless of outcomes, sinus issues would not ordinarily affect the optic nerves unless there were a cavernous sinus thrombosis, which is rare indeed.