Why cant I see the computer screen with my reading glasses?
For the same reason that you cant read in TV specs or see TV in reading specs. The laws of physics mean that a lens has a limited range of focus. Reading glasses are focussed for close work and usually have a range that is within 50cm of your nose. Your computer screen will be beyond the range of your reading glasses. We call this the intermediate range. The most appropriate correction to enable you to see your screen clearly and comfortably will depend on a combination of factors including the layout of your desk and workspace and the amount of time you spend using the computer. You may need specific computer glasses, or you might be recommended a pair of bifocals or varifocals.
