I don't think the big screen tv will be good for your eyes although it has high resolution ratio. If you spend long time sitting in front of the big screen tv, your eyes will be hurt badly. In addition, your eyes will be affected by the electric radiation. You should better have the good rest for the eyes after seeing for about forty minutes.
Well, that depends actually. Because as you can see, different types of TV sets would generate and give out different levels of radiation to your eyes, and sometimes advanced TV made with high technology would give out less radiation no matter their sizes you know? Also, you could try to watch less TV or wear some special glasses to reduce that damage.