Different types of letter chart

Reading a letter chart

Reading letters on a chart is one of the most familiar parts of an eye examination.

You will be asked to read the lowest line of letters you can see clearly. This helps the optometrist find out how well you see, and also – if you need glasses – how they will work best for you.

The chart will either hang on the wall opposite where you sit, or behind you so that you look at its reflection in a mirror. It may be a fixed chart or it may change to vary the letters shown. It may be on a computer screen or on a screen where the letters are illuminated.

You may also come across charts which use only one letter presented in multiple directions, usually a C, an E or an F.

The standard distance between the patient and the chart is six metres, or 20 feet. However, if space is limited, optometrists can create that distance by reflecting the letters in a mirror.

You can find out more about the history of the letter chart here.