How to Understand the Strength of Reading Glasses

Written by leslie howerton
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How to Understand the Strength of Reading Glasses
Reading glasses help restore focusing power to your eyes. (Three books with reading glasses image by Sophia Winters from

The eye's lens focuses on objects at different distances, but as you age, the ability of your eyes to focus declines, a condition called presbyopia. Reading glasses can help by providing the focusing power, or dioptres, lost as you get older. The strength of reading glasses is always measured in dioptres at intervals of 0.25 with a plus sign, which just means the lenses take a convex shape. Choosing the right reading glasses depends on your age, and how close you prefer to read. It's always a good idea to test out the glasses before you buy them.

Skill level:

Things you need

  • Computer
  • Internet access
  • Eye chart

Show MoreHide


  1. 1

    Visit the Peepers website and look at the presbyopia test chart. See which sentence you can read clearly from about 12 to 16 inches from the screen, and note the corresponding strength next to it. This is a good way to get a rough estimate of how many dioptres of strength you need. You may also find a chart like this at an optometrist's office.

  2. 2

    Visit a store that sells reading glasses, and try on a pair in the strength you found from the chart. Remember that this strength is just a starting point. It may not be exactly what you need.

  3. 3

    Test the glasses by looking at a few lines of text from a book, magazine or anything with small print. See how far you have to hold the text away from you to focus clearly. If it's more than 16 inches, you need a higher strength.

  4. 4

    Try out a pair of glasses one strength higher and one strength lower to see how well you focus. Hold the text at the distance you usually prefer to read. Choose the pair that is the most clear and comfortable to you.

  5. 5

    Visit an optometrist and ask about bifocals if you already wear glasses. Presbyopia affects everyone, regardless of any previous vision problems, so bifocals are the best option if you wear corrective lenses for nearsightedness or farsightedness.

Tips and warnings

  • Choose reading glasses based on what feels right to you. There is no set strength for everyone.
  • If reading glasses don't help you focus, or you still can't see clearly, make an appointment with an optometrist.

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