What Is Refractive Error?

Eye chart
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Question: What Is Refractive Error?

Answer: Refractive error occurs when the eye doesn’t bend light correctly (refract) as it enters the eye, resulting in a blurred image. There are several disorders that involve refractive error, most of which are likely all too familiar to you.

The following are the most common refractive errors:

  • Nearsightedness: Nearsightedness, or myopia, is a condition in which nearby objects are seen clearly, but distant ones are blurred. Nearsightedness can be inherited and is often discovered during childhood.
  • Farsightedness: Farsightedness, or hyperopia (also referred to as hypermetropia), usually causes distant objects to be seen clearly, but close objects to appear blurred. Farsightedness often runs in families. When someone has higher levels of farsightedness, their distance vision may become blurry in addition to their near vision. Many people mistake farsightedness for presbyopia, the refractive error that usually occurs over 40 years of age.
  • Astigmatism: Astigmatism usually occurs when the cornea has an irregular curvature. The cornea is curved more in one direction, causing blurry vision. Astigmatism can cause blurry vision at all distances, and it often occurs along with farsightedness or nearsightedness. Most people have very small amounts of astigmatism. Larger amounts of astigmatism cause distortion in addition blurry vision. Very high amounts of astigmatism sometimes have a difficult time achieve 20/20 vision.
  • Presbyopia: Presbyopia is the normal aging process of the lens of the eye. It is the loss of elasticity of the lens that occurs with aging, causing difficulty focusing at close ranges. Scientists also believe that in addition to the loss of elasticity of the lens, the muscle that makes the lens change focus, called the ciliary body, also begins to not work as well. Presbyopia usually becomes significant after the age of 40-45 years of age but people between 35-40 may exhibit early signs depending on their visual state, work and lifestyle.

    Refractive errors are amongst the most common vision problems in the United States. Though also amongst the most correctable, many Americans have uncorrected refractive errors. Eye care professionals, such as optometrists and ophthalmologists, can conduct a comprehensive eye exam to determine how to correct refractive errors. Corrective eye wear, such as glasses or contact lenses, can then be prescribed to help improve vision. Refractive surgery can also be used to correct refractive disorders.


    Symptoms of refractive disorders include blurry vision, fatigue, fluctuating vision, difficulty reading or seeing close objects, headaches, squinting and crossing of the eyes in children. 

    If you are experiencing any of these symptoms, contact your eye doctor for a complete exam. For children, do not depend on a pediatric or school vision screening. While pediatricians and school nurses do an excellent job of evaluating overall eye health and vision, some vision problems will not be detected by a vision screening.

    In fact, even if you read 20/20, it does not mean that you do not need corrective lenses. While nearsightedness is difficult to compensate for, farsighted children will often read 20/20 on the eye chart and still have large uncorrected vision problems. 


    ISRS/AAO. American Academy of Ophthalmology, 2009. Accessed: April 2009.

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