I'm not familiar with any residency where Ophtho residents work weekends unless they're on call. How often one is on call varies with the program. Also keep in mind that unlike medicine residents you'll be taking call at night during the week and you'll still have a busy day of clinic/OR the next day. Sometimes you're up from 11PM-5AM dealing with an open globe, getting the patient to the OR, scrubbing into the surgery with the attending, etc... and the next day still starts at 7AM.
So don't be misled; it ain't all roses for us eyeball surgery residents.