PRK (Photo Refractive Keratectomy)
PRK was the first procedure performed using the Excimer laser. It corrects vision by reshaping the cornea. The difference between LASIK and PRK is that with LASIK a corneal flap is created and the laser is applied to the inner tissue of the cornea. With PRK, the epithelium (or outer skin of the cornea) is removed and a laser is applied to the surface of the cornea.
PRK can be used to correct low to high levels of nearsightedness, farsightedness and astigmatism. PRK is preferred for patients with thin corneas.
PRK vs. LASIK. Because PRK does not create a permanent flap in the deeper corneal layers (the LASIK procedure involves a mechanical microkeratome using a metal blade or a femtosecond laser microkeratome to create a ‘flap’ out of the outer cornea), the cornea’s structural integrity is less altered by PRK.
The LASIK process covers the laser treated area with the flap of tissue which is from 100 to 180 micrometres thick. This flap can mute the nuances of the laser ablation, whereas PRK performs the laser ablation at the outer surface of the cornea. The use of the anti-metabolite mitomycin can minimize the risk of post-operative haze in persons requiring larger PRK corrections.
PRK does not involve a knife, microkeratome, or cutting laser as used in LASIK, but there may be more pain and slower visual recovery.