CRT screens probably aren't the safest things in the world to have sitting a few feet in front of your head. After all, the electron guns inside that thing are pointed right at you
. Actually, they are supposed to be shielded and quite safe, but you never can tell. I've never actually tested a CRT for EM radiation or anything like that, so I could be mistaken and die a slow death from an excruciatingly painful tumor growing right in the center of my brain. LCD screens use an entirely different technology, so they should be safer than a CRT. However, with either type, extended usage over time could degrade your eye's ability to focus at objects of varying distances. Somebody could build a monitor or glasses designed with optics that would keep the screen readable while changing the focal point that your eyes focus at. While this could save your vision, it would probably be distracting to the point of madness.