Why Do Some People Need Glasses?

Have you ever had an eye exam ? If so, your doctor has probably asked you to cover one eye and read letters from a special eye chart.

Eye charts usually contain several rows of letters. The top row begins with very large letters. The letters get smaller and smaller the closer the rows are to the bottom of the chart.

What does identifying your ABCs have to do with eyeglasses? Each line of the chart has been assigned a number. During the test, patients read each line of the chart until the letters become too small to read easily.

If you can read the line labeled 20 from a distance of 20 feet, this means you have 20/20 vision.