Because of the many different screen resolution settings for monitors, you need to print out this eye chart. On a PC, right click and select print. On a Mac, control + click. Then, hold the page approximately 14 inches away from your eyes and begin reading the top line without glasses and read down until you have difficulty. Look at the number on the right, this is the suggested magnification, or diopter, you need. Please remember that this is not a substitute for a professional eye exam and you should have your eyes checked yearly by a licensed optician for glaucoma if you’re over the age of forty.