Photorefractive keratectomy (PRK)
PRK uses a laser to sculpt the cornea for the treatment of low to moderate degrees of nearsightedness and farsightedness, with or without astigmatism. The outer layer of the cornea, the epithelium, is first removed and the excimer laser then reshapes the cornea. A temporary contact lens is then placed over the cornea. As the cornea heals and a new epithelium is made to cover the area reshaped by the laser, there may be some discomfort and blurred vision. After the epithelium is healed within a few days, the contact is removed, it may take several months before the best vision is obtained.
Laser in situ keratomilieusis (LASIK)
LASIK is a popular surgical procedure that also uses the excimer laser to reshape the cornea. This procedure has been approved by the FDA for nearsightedness, farsightedness and mild to moderate amounts of astigmatism.
This technique first creates a thin corneal flap using an instrument called a microkeratome, and then reshapes the underlying cornea with a laser. The flap is then replaced in its original position to cover the cornea. No contact lenses are generally needed and the improvement in vision is much more rapid than PRK. There will be some discomfort for a few hours after the procedure and patients are generally very comfortable the next day.
Advantages over PRK:
Laser-assisted sub-epithelial keratomilieusis (LASEK)
This is a variant of PRK where the corneal epithelium is loosened by the use of alcohol and then the PRK is performed. The epithelium is then folded back onto the cornea and a bandage contact lens is placed over the eye. This may help in healing compared with the PRK but will be slower than the LASIK procedure.