Help! iMac screen hurts my eyes!

Just upgrade from my macbook pro laptop to a 27" iMac. I love it but after even a few minutes of using it, my eyes begin to hurt. And when I look away from the computer, my vision is a little blurry. My eyes have been fatigued for a few days now because of this. I have perfect vision and never had trouble looking at computer screens before. I've tried adjusting the brightness, the display settings, changing the lighting in my office, everything!

Can anyone recommend a good solution for me? Maybe an aftermarket glare protector?

Thanks!
Fred