How can we prevent us from computer radiation?

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My new job is selling cabinets online,everyday I should use computer 8 hours at least, and I am new, I really want to learm more things, so normally I work extra hours, I dont have PC,and the company provide me one, but it is not LCD screen, after working several hours, my eyes are very uncomfortable, I am really afraid that I would be shortsighted, how can I protect my eyes? Thank you!