Photorefractive keratectomy (PRK) is a laser vision-correction procedure that reshapes the cornea to correct mild-to-moderate conditions of myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. It is the second-most-common type of laser eye surgery after LASIK. During LASIK, a flap is created to access the cornea; during PRK the entire epithelial layer of the cornea is removed and later allowed to grow back. During both processes, the cornea is reshaped to provide vision correction.
Advantages of Photorefractive Keratectomy
Compared to LASIK, PRK provides the surgeon with greater control over the location and amount of tissue being removed, which permits more precise results. PRK gently sculpts the cornea rather than cutting it, maintaining corneal strength as it corrects vision.
Other advantages of PRK include the following:
- Less depth of laser treatment
- No corneal-flap complications
- Can be used on thin corneas
PRK offers distinct benefits to those whose activities put them at elevated risk of eye injury (boxers, for example), and for patients whose corneas are too thin, or whose pupils too large, to permit LASIK. PRK also avoids the complications from corneal flaps, as well as a serious complication of LASIK known as corneal ectasia, which can result in distorted vision or permanent vision loss.
Disadvantages of Photorefractive Keratectomy
Although PRK may be preferable to LASIK surgery for some patients, it does have disadvantages, including the following:
- More discomfort for the first few days after surgery
- Longer recovery period
- Greater risk of postsurgical eye infection
- Greater risk of temporary or permanent haziness of the cornea
Both LASIK and PRK have comparable rates of vision improvement and carry some of the same risks, so consultation with an ophthalmologist is necessary to determine which surgery will be most beneficial for a particular patient.
The Photorefractive Keratectomy Procedure
Before PRK begins, the eyes are numbed with anesthetic eye drops. The surgeon then uses an excimer laser, with targeted laser energy, to reshape the cornea. Throughout the procedure, the surgeon has complete control over the laser, which provides a highly precise and customized result that gives each patient the best vision possible.
The entire procedure takes only a few minutes to perform. Because of the potential for blurred vision for a time after PRK, it is often performed on only one eye at a time, with the surgeon waiting to schedule the second eye until the vision in the first has adequately cleared.
After the procedure, the eyes are bandaged with a soft contact lens to protect the cornea. New cells grow back over the next few days to replace the cells that were removed. The contact lens is removed by the surgeon in a follow-up examination.
Recovery After Photorefractive Keratectomy
Post-PRK, eyeglasses may have to be worn until vision has stabilized. Eye drops are prescribed to prevent infection, and keep the eyes moist.
While vision may improve immediately after PRK, full results may take several days or weeks to become apparent. Strenuous exercise should be avoided for at least a week because it can interfere with the healing process. A patient will likely be able to see well enough to drive a car after 2 to 3 weeks.
Results After Photorefractive Keratectomy
The results of PRK are considered comparable to those of LASIK. Some patients may achieve only 20/40 vision, and still need glasses or contact lenses. PRK does not correct presbyopia, a natural change in the eyes that affects people over the age of 40. Patients who require glasses for reading will continue to need them after surgery. It is important for patients to maintain realistic expectations of the results of any laser surgery if they are to be satisfied with the results.
Risks of Photorefractive Keratectomy
As with any type of surgery, there are certain risks, including the following, associated with PRK:
- Postsurgical infection
- Adverse reaction to anesthesia
- Inaccurate vision correction
- Sensitivity to light
- Problems with night vision, such as halos
- Hazy vision
- Dry eyes
Many of the complications that arise following PRK are similar to those that occur after any type of refractive surgery.