I wear bifocals and my new i7 was driving me nuts as I was caught between the top and bottom part of my lenses. If I leaned back to surf the web, I could not get comfortable with either near or far lenses. I visited my friendly ophthalmologist and asked for single vision glasses optimized for about 40 inches from eye to object. Since I had recently paid him a visit, his assistant did the math and fixed me up. What a difference in using my new 27 inch iMac. If you feel like a bobble head doll using your new computer, you will, as they say at the carnival, be amazed. Your distance may vary, check it out.