PRK

PRK is an abbreviation for Photorefractive keratectomy and is a laser eye surgery procedure that is intended to correct a person’s vision reducing their dependency on contact lenses or glasses. PRK like LASEK permanently changes the shape of the anterior cornera by vaporisation using an excimer laser a small amount of tissue from the front of the eye just under the corneal epithelium. Typically prior to the ablation the outer layer of the cornea is remove. Depending on the brand of laser used a computer tracks the patients eye position around 60 to 4,000/times a second and redirects the laser pulses for precision. Most modern brands of lasers can automatically center on the patients visual axis and can pause if the eye moves out of range and will resume when the patients eye is centered.

PRK versus LASEK
Even when using basically the same technique, there are slight differences between PRK and LASEK. In LASEK epithelium is not removed but an alcoholic solution causes the epithelial cells to weaken, the eye surgeon can then fold the epithelial layer out of the laser treatment area and fold it back into place after the cornea has been reshaped by LASEK. Where in PRK the epithelium is removed and the outermost layer below the epithelium is treated by laser.

PRK versus LASIK
The cornea’s structural integrity is less altered by PRK because it does not create a permanent flap in the deep corneal layers. Where LASIK involves a mechanical microkeratome (metal blade) or femtosecond laser microkeratome to create a flap. PRK does not create the added risk of dislocated corneal flaps which may occur with trauma at any time after LASIK. PRK does not involve a knife, cutting laser of microkeratome but there is ofter more pain and a slower visual recovery for the patient.

PRK surgery complications

  • Possible Scarring
  • Reduced best corrected visual acuity
  • Reduced acuity in low light conditions
  • Increased sensitivity
  • Dry eyes (most common)
  • Longer healing period
  • Post surgery pain
  • Under-correction
  • Over-correction
  • Glare
  • Halos
  • Starburst
  • Aberrations
  • Recurrence of myopia
  • Corneal haze

PRK patient eligibility

  • Aged at least 20 years
  • Not pregnant
  • Assessment of pollen allergies
  • Complete understanding of benefits and possible risks
  • Pupil size less than 6mms in a dark room
  • Stable refraction error correctable to 20/40 or higher
  • Good ocular health

Pre-existing conditions that may complicate PRK

  1. Ocular diseases: glaucoma, dry eye, keratoconus
  2. Collagen vascular disease: corneal ulceration
  3. Systemic disorders: rheumatoid arthritis, diabetes



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