Our program (perhaps one of the busier ones, but representative of many of the ones out there) has q6 (weeknights and weekends) call for both first and second years. Weekends are Friday night until Sunday night at 5pm, then someone else takes over.
Call is very hit or miss in terms of business. We pretty much always get called in at least once. I tell people the "rule of 3's" which is that about 1/3rd of the time, we have a manageable night, where we are home by 9pm or earlier, about 1/3rd we are busy until midnight but get to sleep after that, and about 1/3rd we are called in after midnight (or never get home at all), and it sucks. In all reality, it's probably a little busier than that.
One of the major things that sucks about "home call" is that you never get the day off after call. Our resident manual says we are supposed to go home the day after an all-nighter, but no one ever does it and the attendings don't ask.
Bottom line: ophtho call is much busier than your friends in other specialties think it is, especially at the decent programs. In fact, my pager just went off, so I have to go (no kidding).