Ask HN: eye care.. how long do you wear your contacts, etc

Hey HN, just got back from the eye doctor. I've got perfect peripheral vision and pressure, but the doctor is taking extra precautions to make sure the slightly enlarged nerves in my eyes are not a precursor to glaucoma. He compared pics of my eyes from two years ago and it has grown a tad bit. I told him I'm usually on the computer and wear my contacts up to 18 hours per day. I'm too young for glaucoma (22), but there are always exceptions. So the point of this post is to see how you guys deal with being on the computer 24/7. How do long do you keep your contacts/glasses on, how do you deal with eye stress et cetera. My vision isn't terribly bad, -1.5, but I should probably take better care/precautions considering my career revolves around working on computers.