Photorefractive keratectomy, more commonly known as PRK, is a type of laser eye surgery for correcting vision problems. The procedure uses an excimer laser, a cool ultraviolet light beam to precisely 'ablate' or remove corneal tissue to reshape it. The laser sculpts an area around 5 to 9 mm in diameter in the eye surface.
The new shape of the cornea allows proper refraction of light which gives the seer clearer vision. Unlike LASIK, surface skin cells of the cornea are removed in PRK. No incisions are made, and at this thickness the integrity and structure of the cornea is maintained.
Conditions that are treated with LASIK surgery are often also treatable by PRK. These include nearsightedness, farsightedness, and astigmatism. Nearsightedness is the result of a cornea that is too steep. PRK is used to flatten the too-steep cornea, restoring normal vision. In farsighted patients, where the eyeball is too small or has a very weak focusing power, PRK is used to sculpt a steeper cornea. PRK can also smoothen out an irregular cornea to restore the vision of people with astigmatism.
Pre-operative Preparation
If you are planning to have this procedure done, it is important that you consult a doctor who is qualified and experienced in this type of surgery. Your doctor will need to do a thorough assessment to determine if you have other conditions that may disqualify you from the procedure. These include diseases affecting the immune system as well as eye conditions like dry eyes. Your doctor will also take into consideration the extent of your visual problem. People with severe farsightedness may not be good candidates for this surgery since results are harder to predict and complications are more likely to occur. In some patients, the procedure might only need to be postponed until a particular condition is treated.
Patients are advised not to wear make-up or apply eye creams the day before surgery to minimize the risk for complications. Patients who wear contact lenses are also advised to start wearing glasses full time a few months before consultation since contacts can also distort the shape of the cornea.
During the Surgery
Patients are often given a mild sedative to keep them relaxed throughout the procedure, as well as anaesthetic eye drops to numb the pain. The patient is positioned under the laser and a retainer is placed around the eye to keep it open. The patient is asked to stare at a beam of light during the entire procedure. A small clicking sound may be heard as the laser is beamed on to the cornea. Some patients may experience an acrid odour, similar to burning hair, during the procedure.
After the procedure, patients are often advised to rest. Pain medications may be given, although some patients can tolerate the mild discomfort and scratchiness that comes afterward without any medications. A few days of rest is recommended by doctors, although patients can see normally within the next day.
Outcome (Prognosis)
Patients can often achieve 20/20 vision after PRK, although some patients may still need to use glasses after the surgery, depending on the severity of the vision problem that they previously suffered from. Eye drops may have to be applied regularly for a couple of months to correct excessive eye dryness.
Risks
Although PRK has relatively fewer risks compared to LASIK, potential complications may still occur. The most common are undercorrection and overcorrection. Undercorrection happens when too little corneal tissue is removed, although this can be easily corrected by retreatment. Overcorrection is a result of the removal of too much corneal tissue and is harder to correct.
Some patients may also experience a difficulty seeing at night. Some may start to see gray halos especially when viewing bright lights at night. Dry eyes are also a common complaint after surgery. These conditions may go away after a few applications of eye drops, although surgery may be the only option in some cases.
There is always the risk for infection in PRK, as with any other surgery, although the risk is relatively smaller compared to that with LASIK.
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