The conventional Snellen eye chart features three lines of letters below the 20/20 line that are smaller than the letters on the 20/20 line. The letters on the bottom line are half the size of the ones on the top line. The inter-letter distance is equal for all three lines. The visual acuity measured with this method is called "Snellen vision". It indicates how well you see at a specific distance. If you need to know your visual acuity in order to set up an eye exam, ask your doctor or nurse how to read the chart. The American Optometric Association (AOA) recommends using 3 sizes of letters instead of only two sizes for better measuring visual acuity. However, many doctors and clinics still use only two sizes because it's easier to read on the eye chart. Size A of the eye chart corresponds to 6/6 vision or 20/20 vision. A person who can see clearly without wearing glasses or contact lenses should be able to read all the way down the third line of the chart without assistance from someone else. People who can see closer than that usually have some form of assistive device, such as magnifying glasses, telescopes, and so on. Size E of the eye chart represents the visual acuity needed to read a newspaper with the text no more than 50 feet away.