Refractive Errors Of The Eye

GENERAL INFORMATION:

What are refractive errors of the eye?

• Refractive (re-FRAK-tiv) errors of the eye, also called errors of refractions or EOR, are common eye disorders. In the normal eye, light rays must be refracted (bent) by the cornea and lens into the retina. The cornea is the clear, smooth, and dome-shaped surface that covers the front part of the eye. From the cornea, light passes through the pupil (black circle in the middle of the eye) and hits the lens. The lens is a clear, flexible disc in your eye that changes shape to accommodate (allow) light. The iris (colored part of the eye) helps the lens to adjust as one looks at objects at different distances. Finally, the retina transforms the light into electrical signals which are sent to your brain. The brain then uses these signals and tells you what you see.
  
  
• With EOR, there is a problem in the refraction of light by the eye. The shape and texture of the cornea may be abnormal or the lens may have become less flexible. When this happens, the cornea and lens fail to bend and focus the light directly on the retina. This may cause different types of EOR and lead to problems with vision (eyesight), such as blurring. Diagnosing and treating EOR as soon as possible, may improve your vision and prevent further eye problems.

What causes EOR? It is not exactly known what causes EOR. Caregivers may think that the following conditions may play a role in developing EOR:

• Environment: Environmental factors, such as reading with dim light or doing too much work that uses the 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: Traumas or previous eye surgery may cause some changes or damage to the cornea and lens.
  
  
• Other eye problems or health conditions: Certain conditions affecting the eye, such as thinning of the cornea or having dislocated or unusually small lenses. Diabetes (high blood sugar level) may also cause changes in the shape of your lenses.

What are the different types of EOR? The following are types of EOR:

• Astigmatism: The cornea in astigmatism may be uneven (not smooth) and curved, and not have the normal round shape. The irregular curves makes an astigmatic eye shaped more like that of 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 makes light rays entering the eye to focus behind the retina.
  
  
• Myopia: This EOR, also known as nearsightedness or shortsightedness, usually occurs between 5 to 15 years of age. With myopia, 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 eye disorder, also called an old man's eyes, is more 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.
  
  
• Others: You may also have any of the following:
  
  
  • Anisometropia: This condition happens when you have different EOR grades between the two eyes.
    
    
  • 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 fixates normally.

What are the signs and symptoms of EOR? Depending on the type of EOR, you may different signs and symptoms. The most common symptom of EOR is seeing blurred images. Sometimes, you may have trouble recognizing faces or things around you. You may rub, shut or cover your eye, squint, or tilt or turn your head frequently. You may also have eyestrain, headache, or fatigue (getting tired more easily). You may also have any of the following:

• Astigmatism: Deformed images of both near and far objects. Straight lines may appear wavy.
  
  
• Myopia: Close objects look clear, but distant (far) objects appear blurred.
  
  
• Hyperopia: Distant objects are usually seen clearly, but close or near ones are blurred.
  
  
• Presbyopia: Trouble seeing things up close. You may need to hold a reading material at arm's length in order to recognize or see what is written.
  
  
• Others: Anisometropia may have one eye nearsighted and the other farsighted. In esotropia, eyes are not looking in the same object at the same time.

How are refractive errors of the eye diagnosed? Your caregiver will take a medical history and do a complete eye examination. He may do a series of tests where he may aim 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 your one eye is covered. Your caregiver carefully looks at the uncovered eye for any movement.
  
  
• Test for fixation: One eye is covered while your caregiver 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 words or picture is clear as he changes the lenses.
  
  
• Visual acuity test: Your visual acuity (ability to see clearly) may also be checked using charts with letters, pictures, and shapes. Your caregiver may ask you to read special eye charts placed farther down the room from you. These charts help your caregiver check how well you see colors, lines, and at different distances. There are special charts that can be used for those who cannot read or speak yet.

How is EOR treated? You may need any of the following depending on the type of EOR or lifestyle you have:

• Corrective lenses: Caregivers may suggest that you wear corrective lenses to help light rays to focus correctly. This may correct problems with the curves and length of your eye.
  
  
  • Contact lenses: These are small, soft, round pieces of plastic put over your eyes. You may choose to wear soft, extended wear, disposable, rigid gas-permeable (RGP) or bifocal contact lenses. Bifocals are a combination of a lower lens for close vision and an upper lens for distance vision.
    
    
  • Eyeglasses: Glasses are simple and easy devices to correct EOR. You may use single-vision reading glasses, bifocals, trifocals, or progressive lenses.
  
  
• Eye medicines: Your caregiver may give you eye drops or ointments to help you see better. These may include treating problems with the eye muscles or problems with focusing. These may also slow down the worsening of EOR or ease eye symptoms, such as swelling, redness, or irritation.
  
  
• Refractive surgery: You may need surgery to reshape the curve of your cornea. There are different available types of refractive surgery to treat EOR. Your vision may be corrected by using laser, a high-energy light that does not produce heat. Your caregiver may also place special tiny plastic rings into the cornea. Ask your caregiver for more information on refractive surgery.

How can I take care of my vision? The following may help take care of your eyes and eyesight:

• Always have your eyes checked regularly, especially if you have other health conditions. Ask your caregiver for more information on how often you should have your vision examined.
  
  
• 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.
  
  
• Practice good eye hygiene. Follow manufacturer's instructions for proper use, cleaning, and storage of lenses. Your caregiver may suggest when your lenses, especially contact lenses, need to be replaced.
  
  
• Use good lighting in your home, school, or workplace. Using lights that reduce glare and are soft on the eyes may decrease the risk for EOR.

Where can I find more information? Having EOR may be hard for you and your family. Contact the following for more information:

• American Academy of Ophthalmology
  7424
  San Francisco, CA 941207424
  Phone: 1-415-5618500
  Web Address: http://www.aao.org/
  

• National Eye Institute, National Institutes of Health
  202 Vision Pl.
  Bethesda, MD 20892-3655
  Phone: 1-301-496-5248
  Web Address: www.nei.nih.gov
  

• Prevent Blindness America
  211 W. Wacker Dr, Ste 1700
  Chicago, IL 60606
  Phone: 1-800-331-2020
  Web Address: www.preventblindness.org
  

CARE AGREEMENT:

You have the right to help plan your care. To help with this plan, you must learn about your health condition and how it may be treated. You can then discuss treatment options with your caregivers. Work with them to decide what care may be used to treat you. You always have the right to refuse treatment.

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