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Refractive Errors Of The Eye


What are refractive errors of the eye?

Refractive errors of the eye, or errors of refraction (EOR) are common eye disorders. These disorders happen when there is a problem with how your eye bends and focuses light. EOR are caused by abnormal shape and texture of your eye.

Lateral cut-away of the Right Eye

What increases my risk for EOR?

  • Eye strain: This includes reading in dim light or overworking your eyes.
  • Heredity: Some types of EOR usually run in families. When both parents have EOR, the child has an increased risk of having it.
  • Injury: Eye trauma or previous eye surgery may cause changes or damage to the cornea and lens.
  • Medical conditions: Your cornea may be abnormally thin. Your lenses may be dislocated or unusually small. Conditions such as diabetes can change the shape of your eye.

What are the different types of EOR?

  • Astigmatism: The cornea may not have the normal round shape. The irregular curves makes the eye shaped more like a spoon or football. Astigmatism may be present at birth and may happen along with hyperopia or myopia.
  • Hyperopia: This is also called hypermetropia, or farsightedness. Hyperopia occurs when the eyeball is too short or the cornea is a little flat or less curved. This causes light rays entering the eye to focus behind the retina.
  • Myopia: This is also known as nearsightedness, or shortsightedness. Myopia usually occurs between 5 to 15 years of age. The eyeball is too long or the cornea is too curved or rounded. This causes the light rays to focus in front of the retina.
  • Presbyopia: This is common among those 40 years and older. Presbyopia happens when the lens becomes stiff and less flexible. This causes the lens to lose its ability to bend or change shape. Eventually, the lens cannot move and is not able to bring nearby objects into focus.
  • Esotropia: This is a form of strabismus, also called squint or cross-eyed, where the eyes may not be aligned. One eye may turn inward while the other focuses normally.
  • Anisometropia: This condition happens when you have different bending power between the 2 eyes. One eye may have myopia, the other eye hyperopia.

What are the signs and symptoms of EOR?

The most common symptom of EOR is blurry vision. You may rub, shut or cover one eye, squint, or tilt or turn your head frequently. You may also have eye strain, headache, or fatigue. You may have symptoms based on your type of EOR:

  • Astigmatism: Both near and far objects appear as deformed images. Straight lines may appear wavy.
  • Myopia: Close objects look clear, but far objects appear blurred.
  • Hyperopia: Distant objects are usually seen clearly, but close or near ones are blurred.
  • Presbyopia: Objects are not clear up close. You may need to hold reading material at arm's length in order to read it.
  • Estropia: Your eyes are not looking in the same direction at the same time.

How are EOR diagnosed?

Your healthcare provider may ask about your symptoms, medical history, and medicines. He may do a series of tests where he aims bright lights directly at your eyes. You may also need any of the following tests:

  • Cover-uncover test: This test checks if your eyes are aligned. An object is placed at a certain distance far away from you while one eye is covered. Your healthcare provider carefully looks at the uncovered eye for any movement.
  • Test for fixation: One eye is covered while your healthcare provider moves a small flashlight in front of you. This checks how well your uncovered eye follows the light. He repeats the test on the other eye and compares the results.
  • Refraction test: This test checks the lens of your eyes. You will be asked to look at a chart through a device that has lenses of different strengths. You will be asked if the word or picture is clear as he changes the lenses.
  • Visual acuity test: Your ability to see clearly may also be checked with charts with letters, pictures, and shapes. Your healthcare provider may ask you to read special eye charts placed farther down the room from you. These charts help your healthcare provider check how well you see colors, lines, and at different distances.

How are EOR treated?

  • Eye correction: Contact lenses and glasses help correct the shape of your eyes. This helps light to focus correctly and improves your vision.
  • Eye medicines: You may need eyedrops or ointments. These decrease inflammation, help your eyes focus, and can make your eye muscles stronger.
  • Refractive surgery: You may need surgery to reshape the curve of your cornea. There are different types of refractive surgery to treat EOR. Your vision may be corrected by a laser. Your healthcare provider may also place special tiny plastic rings into the cornea. Ask your healthcare provider for more information on refractive surgery.

What are the risks of EOR?

Your eyesight may become worse. You may have permanent vision loss.

How can I care for my vision?

  • Get regular eye exams: Get your eyes checked at least once a year.
  • Eat healthy foods: Fresh fruits and vegetables that are rich in vitamins A and C may help with your vision. Foods such as sweet potatoes, apricots, and carrots are rich in nutrients good for the eyes.
  • Take care of your contacts or glasses: Store, clean, and use your contacts or glasses as directed. Replace your glasses or contact lenses as often as your healthcare provider suggests.
  • Decrease eye strain: Rest your eyes, especially after you read or sew for long periods of time. Get plenty of sleep at night. Use lights that reduce glare in your home, school, or workplace.

When should I contact my healthcare provider?

  • You have changes in your eyesight.
  • You have questions or concerns about your condition or care.

When should I seek immediate care or call 911?

  • You have a headache that does not go away, even after treatment.
  • You have a sudden loss of vision.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your caregivers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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