No matter what kind of screen you're using, you're staring into the equivalent of a 60W* light bulb. Which is the reason that you should work in
well-light areas, just like when watching TV. So can it affect your eyes? Yes. Extended exposure without intervals of rest can damage your eyes. Is an LCD better for your eyes than a CRT? Again, yes,
as it isn't quite as bright, but don't think you're safe just because of that.
* Average. Depending on brightness settings, you could be staring at anything in the low 20W to high 150W+ range.