Photorefractive Keratectomy


Description:PRK is a type of corrective eye surgery similar to LASIK was first approved by the FDA in 1995.
During the procedure, the surgeon delivers a pulsing beam of ultraviolet light upon the surface of the cornea to reshape it. Instead of cutting a flap and reshaping the inner cornea, PRK reshapes the corneal epithelium with with an excimer laser allowing the cells to regenerate to the desired shape after surgery. Once the cells regenerate, the focal point of the eye will have moved to the desired location, providing vision improvement. The procedure allows for light to travel without interference and more precisely towards the retina to allow for better visual comprehension created by the image through the lens.

PRK Steps:
  • After proper numbing of the eye, the surgeon removes an area of the corneal epithelium with an alcohol solution and typically a blunt surgical instrument as depicted in the video at the bottom of the page.
  • Afterwards, an excimer laser precisely reshapes the curvature of the cornea's surface with the computer controlled, accurate laser that delivers pulses of ultraviolet light to remove microscopic amounts of tissue in a precise pattern.
  • A soft contact lens "bandage" is then placed on the cornea to help protect your eye. New epithelial cells grow back in five days typically, after which the bandage contact lens is removed by your eye doctor.


PRK vs LASIK:
PRK does not create a flap so the eyes structural integrity is greater than that of an eye that has had LASIK surgery. Additionally, many surgeons prefer PRK in situations where a patient has a thin cornea. LASIK patients usually have less pain and obtain their vision back faster than PRK; PRK patients can take anywhere from weeks to months for their vision to improve. While PRK does not use any knives or cutting lasers there may be more pain during recovery compared to LASIK. While the PRK procedure sheds ultraviolet light on the surface of the cornea, LASIK resorts to treating the eye underneath the cornea.

PRK Advantages and Disadvantages
Pros

Cons



Less depth of laser treatment than LASIK

Slower recovery than LASIK
Suitable for patients with a thin cornea

Best vision takes longer to obtain
No risk of corneal flap complications

Increased risk of post-surgery infection, inflammation and haze
Reduced risk of compromised corneal thickness

More eye discomfort during early PRK recovery, compared with recovery after LASIK surgery

PRK has possible side effects consisting of minor eye irritation and watering of the eyes for up to three days post-procedure. Patients are typically 80% recovered by one month after the procedure, and 95%-100% after three months. Unfortunately for patients who receive the PRK procedure, some may still require the use of glasses to obtain the best vision possible.

After the procedure, other possible side effects can include:
  • The loss of their best vision with or without the use of glasses.
  • A mild glare can become permanent depending on the patient's pupil size in dim light.
  • Mild halos around images.

What are the advantages of PRK surgery?
  • PRK is extremely accurate in the case of treating patients who suffer from nearsightedness.
  • Approximately 80% of PRK patients have 20/20 vision without contacts or glasses, one year after surgery.
  • 95%-98% have 20/40 vision without the use of contacts or glasses.
  • Possibility of requiring another surgery or enhancement surgery after the initial procedure.
  • The procedure takes roughly 15 minutes per eye.


Early Complications:

  • Pain(First 24-48 hours)
  • Corneal swelling
  • Cloudy vision
  • Defect in the outer cornea
  • Feeling as if something is in your eyeShadow images
  • Light sensitivity
  • Redness
  • Itching and scratchiness
  • Burning
  • Dryness
  • Enlarged pupil
  • Headaches

Web Resources:Great PRK Resource

Eye Care Source

Photorefractive Keratectomy Eye Surgery

PRK Information Booklet


Related Terminology:
  • LASIK - Laser-Assisted Sub-Epithelial Keratectomy - is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism. LASIK is performed by ophthalmologists using a laser.
  • Cornea - the transparent anterior part of the external coat of the eye covering the iris and the pupil and continuous with the sclera.
  • Retina - the innermost coat of the posterior part of the eyeball that receives the image produced by the lens. It is continuous with the optic nerve, and consists of several layers, one of which contains the rods and cones that are sensitive to light.
  • Corneal Epithelium - Membranous tissue composed of one or more layers of cells separated by very little intercellular substance and forming the covering of most internal and external surfaces of the body and its organs. It acts as a barrier to stop bacteria from entering the lower epithelium.

Citations/References:www.dictionary.com


http://www.allaboutvision.com/visionsurgery/prk.htm

http://www.webmd.com/eye-health/eye-health-photorefractive-keratectomy-pr-eye-surgery

http://www.accessdata.fda.gov/cdrh_docs/pdf/P970056d.pdf

http://www.thefreedictionary.com/Corneal+epithelium

Graphics:
PRK.jpg