PRK is short for photorefractive keratectomy. PRK is a laser vision surgery procedures intended to correct eye vision by changing the shape of the anterior central cornea using an excimer laser.

Before the vision surgery, the patient’s corneas are examined with a pachymeter to determine their thickness and other irregularities in the shape of the cornea, and with a topographer to measure and draw their surface contour map. This process before PRK also measures astigmatism for the vision surgery. Using this information, the eye doctor calculates the amount and the locations of corneal tissue to be removed during the vision surgery.

In the process of PRK, the first step is to create a flap of the outer layer of the cornea in the middle section of the cornea, with a hinge left at one end. Then a small amount of tissue from the corneal stroma just under the corneal epithelium is ablated by an excimer laser. During this step of PRK, a computer system is used to help redirecting laser pulses for precise placement 60 to 4,000 times per second. The last step of the vision surgery is to fold back the flap made in the first step is carefully over the treatment area after the laser has reshaped the cornea.

As with other forms of refractive vision surgery, Lasik, Epi-Lasik, Lasek and so forth, the complications of dry eyes is the most commonly occurred after PRK and can be permanent. Some patients after having PRK surgery have suffered glare, halos, and starburst aberrations, which may be the result of postoperative corneal haze that may develop during the healing process. And about 1~3% of the cases, loss of best corrected visual acuity (BCVA) may occur. Compare with PRK, other laser vision surgery procedures are more stable, such as LASIK and LASEK.

• Previous Entry: The brief introduction of EyeMasters
• Next Entry: Lenses for prescription sunglasses