Photorefractive Keratectomy

GENERAL INFORMATION:

What is photorefractive keratectomy?

• Photorefractive keratectomy (ker-ah-TEK-to-me), also called PRK, is laser (high-energy light) surgery to correct refractive errors of the eye. Refractive errors of the eye are common eye disorders that cause blurring of vision (eyesight). These errors occur when there is a problem in the refraction (bending) of light in the eye. Refractive errors are often caused by having an abnormal shape and texture of the cornea. The cornea is the clear outer layer on the front of the eye. PRK may be used to treat refractive errors, such as astigmatism, hyperopia, and myopia. Astigmatism is a condition where there is an uneven (not smooth) and curved cornea. Hyperopia , also called farsightedness, happens when the eyeball is too short or the cornea is slightly flat or less curved. Myopia , also known as nearsightedness, happens when the eyeball is too long or the cornea is too curved or rounded.
  
  
• With PRK, the surface of the cornea is reshaped using an excimer laser. An excimer laser is a cold laser beam that uses ultraviolet light to change the front surface of the eye. Your caregiver precisely removes the epithelium (very thin layers of tissue) of the cornea with the excimer laser. Removing the corneal tissues changes the focus of the cornea so that light rays focus correctly. By having a PRK, your vision may return to normal and you may be able to see better without eyeglasses or contact lenses.

How does PRK work? PRK works by aiming beams of excimer laser to correctly reshape your cornea. This helps light to focus better in the eye and give clearer vision. Both nearsighted and farsighted people can benefit from PRK. In nearsighted people, the cornea that is too curved is flattened, while in farsighted people, a flat cornea is made more curved. PRK can also correct astigmatism by making the cornea smoother.

Who may have PRK? You may be a good candidate for PRK if you want to be less dependent on eyeglasses or contact lenses. Caregivers must also check first if PRK is the right eye treatment for you. It is important that you understand what this kind of eye surgery can and cannot do for your eyesight. Good results from PRK surgery may be different from person to person. Depending on the levels of nearsightedness, farsightedness, or astigmatism, PRK may be used to correct and improve your vision.

Who may not have PRK? PRK should not be done if there is a higher risk of bad effects. Your caregiver may consider one or more of the following before you may have PRK:

• PRK should not be done if the following conditions are present:
  
  
  • Abnormal conditions of the cornea, such as thinning or swelling of the cornea.
    
    
  • Eye problems or diseases, such as glaucoma, cataract, dry eyes, or swelling of the eyelids.
    
    
  • Grade in the error of refraction has changed recently.
    
    
  • Uncontrolled diseases that affect the connective tissues and immune system. The immune system is the part of our bodies that normally fights off sickness and disease. A weak immune system may be caused by diabetes, multiple sclerosis, rheumatoid arthritis, or cancer.
    
    
  • Unrealistic or too high expectations from the patient.
  
  
• Having PRK may be delayed because of the following:
  
  
  • Age is less than 18 years old. You may have to wait until your eyesight stops changing.
    
    
  • Having untreated, active (ongoing) infections.
    
    
  • Pregnant women should wait until after giving birth to have PRK. Those who are breast feeding should also delay their surgery.
  
  
• Ask caregivers whether you may have PRK with any of the following conditions:
  
  
  • Being treated with certain medicines, such as isotretinoin, amiodarone, colchicine, or sumatriptan.
    
    
  • Poorly controlled diabetes mellitus or glaucoma.
    
    
  • Previous eye surgery, trauma, or infection.

What tests are needed before a PRK is done? Your caregiver will take a medical history and do a complete eye examination. He may do a series of tests where he may use special eye instruments or aim bright lights directly at your eyes. These will help your caregiver know what kind of errors of refraction need correction and how much laser beams are needed. You may also need any of the following tests:

• Eye measurement tests:
  
  
  • Computerized corneal topography: A special camera uses a computer to take pictures of your eyes. This test helps caregivers measure the size, shape, and health of your cornea. It also helps caregivers understand other problems about your vision.
    
    
  • Keratometry: Your caregiver uses a special instrument, called a keratometer, to measure how curved your cornea is.
    
    
  • Pachymetry: This test measures the thickness of your cornea.
    
    
  • Pupillometry: This test measures the size of your pupil (black circle in the middle of the eye).
  
  
• Refraction tests: 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.
  
  
• Slit-lamp test: This test uses a microscope with a strong light to look into your eyes. Your caregiver may also check how well you produce tears using this test.
  
  
• 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 from you. These charts help your caregiver check how well you see colors and lines at different distances.

What are the risks and possible side effects of PRK? Although rare, there are still risks and possible side effects of PRK, and these include any of the following:

• Drying of the eyes.
  
  
• Eye injury, especially to the nerve or blood vessels, or infections.
  
  
• Delayed corneal healing.
  
  
• Permanent loss of vision or vision becomes worse, such as in overcorrected or undercorrected refraction.
  
  
• Other eye problems, such as permanent glare, haze, halos, or starburst around lights at night.

Where can I find more information? 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/
  

• 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.

Copyright © 2008 Thomson Healthcare Inc. All rights reserved. Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes.

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.

Link to Page

Print Page

Email Page