I think your doc probably meant you have an infection in you maxillary sinuses. Sometimes significant sinus infections can cause vision changes.

Some people do have more side effects with generic drugs because the inactive ingredients in them are different than the ones in brand name drugs...
I wouldn't even try to find out if there was a difference with the brand name med cuz they are sooooooo expensive. I would probably switch meds if the s/e were really bad.