I'd agree; it depends on how fast you can learn material. Some people who recently had similar classes in undergrad and are generally fast learners study a few hours before each test. That's very rare, though; most people study at least a few hours every night, and some study more (4+ hours a night and weekends).
Use your undergrad biology classes as a guide because it's more of the same. At UHCO, the first-year classes that take the most time are Advanced Human Anatomy, Physiology, and Neuroanatomy. Optics is just geometry, although the homework takes some time. Vision Science and Optometry are much lighter subjects. Plus there are labs for all of them, although if you study for class you shouldn't have to study labs too much because they cover the same material. There's also variability in teachers, notes, etc that will matter.
The good news is that you see many ideas multiple times. The sympathetic nervous system and spinal cord tracts come to mind; we've covered them in all 3 bio classes, so it gets easier each time.
For me, it's a little less free time than what I had during undergrad when I had lots of biology classes and a lot less free time than when I was taking more economics, history, philosophy, etc classes that took less studying.
On average, I'd say maybe an hour or two of free time per weekday and then most of the weekend free (although, depending on the school, there are classes and clinics on the weekends).
Of course, consider the long-run, too. Any professional program will suck up most of your free time for 4 years, and you'll probably have to put in another 5-10 years of fairly hard work to pay off loans and get settled, but after that you'll probably have more free time than most people. I know plenty of MDs, ODs, and DDSs that work 3-4 days a week by the time they're, say, 40, and making more money than most people still working 5 days a week. Plus, many plan on retiring by 55 and not working as a greeter at Wal-Mart to make ends meet afterwards. So, short-term sacrifice for long-term payoff.