PRK (or photorefractive keratectomy) is the second most popular laser vision correction procedure. Like LASIK, PRK uses an excimer laser to reshape the cornea. But in PRK, the surgeon doesn't first create a corneal flap. Instead, the thin outer layer of corneal cells (the epithelium) is removed and the laser treatment is applied to the underlying corneal tissue (the stroma). After the laser treatment, the cornea is covered with a bandage contact lens. Within days, the removed epithelium grows back and the bandage contact lens is removed.

PRK offers results that are similar to those achieved by LASIK, but it involves more post-operative discomfort and longer healing times. PRK is often recommended for patients whose corneas are too thin for LASIK.


The PRK procedure

The steps in PRK surgery are:

1. Anesthetic eye drops are applied to the eye to prevent pain during the surgery.
2. The outer layer of corneal cells (the epithelium) is removed. This may be done with a laser or it may be removed manually after being softened with a dilute alcohol solution.
3. An excimer laser is used to reshape the underlying corneal tissue.
4. Antibiotic and anti-inflammatory drops are applied to the eye, and the eye is covered with a bandage contact lens.
5. Two or three days later (after the epithelium has had a chance to grow back), the bandage contact lens is removed.

Considerations after PRK surgery

• There is more post-operative discomfort after PRK compared to LASIK. This may last for a week or more.
• It can take 3 to 6 months to achieve optimal vision after PRK. Blurred vision, glare and sensitivity to light are common for several days or longer after the procedure.
• Due to the potential for blurred vision for a time after PRK, surgeons will often perform PRK one eye at a time (performing PRK on the other eye later, after vision in the first eye is acceptably clear).
• You may be required to use medicated eye drops for up to 6 months after PRK to prevent or reduce corneal haze or scarring.

Risks and complications of PRK

As with LASIK and other types of refractive surgery, there are risks and possible complications associated with PRK. Potential complications of PRK are similar to those of LASIK, and include:

• Dry eyes.
• Vision problems, such as poor night vision, glare, halos and haze.
• Incomplete or inaccurate vision correction.
• Infection following surgery.

There may be a slightly greater risk of eye infection, scarring, glare and unpredictable healing of the cornea after PRK compared to LASIK. But serious complications following PRK are rare.


Other information about PRK

Since there is no corneal flap in PRK surgery, it can be used to treat corneas that are too thin for LASIK. And because PRK eliminates the possibility of a flap complication during the surgery, it frequently is the procedure of choice for the re-treatment of eyes that have already undergone a prior refractive surgery procedure.

Though the visual outcomes of PRK and LASIK are quite similar 6 months after surgery, PRK is not as popular as LASIK because of its associated post-operative discomfort, short-term blurred vision and longer healing time. By comparison, LASIK patients experience little or no discomfort and frequently see quite well the following day.

PRK has been around longer than LASIK. It gained U.S. FDA approval for the correction of nearsightedness in 1995 and it was approved for the treatment of farsightedness in 1998.

PRK is typically used to correct up to -7.00 diopters (D) of nearsightedness and up to +6.00 D of farsightedness, with or without astigmatism. During PRK, the excimer laser can be programmed to deliver a standard laser treatment (ablation) or a wavefront-guided custom ablation, just like that used for wavefront-guided LASIK.

The cost of PRK is comparable to the cost of LASIK surgery.