Photorefractive Keratectomy (PRK)
PRK (photorefractive keratectomy) involves the removal of the top surface level of the cornea called the epithelium. This exposes the inner cornea so that a cool ultraviolet laser can re-sculpt it to alter the curvature of the eye. For nearsighted people the surgeon flattens the steep cornea and for farsighted people he or she makes the cornea steeper. The laser can also correct astigmatism by smoothing an irregularly shaped cornea. This allows the eye to better focus light onto the retina and provides clearer vision.
PRK was once the most common laser correction procedure for vision until LASIK surpassed it. LASIK is generally able to correct more severe visual acuity with less recovery time and with decreased risks of infection haze and scarring. PRK involves some discomfort following the surgery a gradual improvement of vision and a higher incidence of dry eye. It is however the procedure of choice if a patient has a thin cornea certain corneal scars or a large pupil. No needles or incisions are involved in the procedure.
Before the Procedure
If you are considering PRK the first step in the process is to know how to choose a refractive surgeon. Once this is decided the surgeon will examine your eyes to determine exactly what kind of vision correction you need. A computer creates an extremely detailed map of your cornea and calibrates the laser to your prescription.
During the Procedure
PRK is an outpatient procedure. You walk into the surgery centre have the procedure done and walk out. It is not advisable to drive home. You should make other arrangements for transportation. The surgery itself usually takes less than five minutes per eye to complete although preparation time makes the procedure longer. You are awake the entire time. A few anesthetic drops numb the eye and prevent pain.
After lying down and properly positioning your eye under the laser the surgeon will place an eyelid holder in your eye to keep it open and immobile throughout the procedure. The surgeon will then calibrate the laser to your prescription and using the laser will gently remove the eye s protective layer of cells called the epithelium. This will reveal the next layer of corneal tissue. The area will then be smoothed and an application of computer-controlled pulses of cool laser light will delicately reshape the curvature of your eye. The deeper cell layers remain virtually untouched.
The surgeon has complete control of the laser and can turn it off at any time. When the procedure is finished you will rest for a little while. If the operation is on both eyes the same day the surgeon will probably do the other eye shortly after the first. Many people choose to have their second eye done another time.
Following the Procedure
When the procedure is finished the surgeon places a soft contact lens over the eye as a bandage to help the outer layer of corneal cells regenerate and to prevent infection. During this time it is normal to experience some discomfort and blurred vision as most of the pain sensors in the cornea are located on its surface. Within 2 to 5 days after the surgery the contact lens can be removed. Avoid rubbing your eyes for the first few days. Some people are able to return to work the following day but your surgeon may advise you to rest for a few days instead.
Patients normally take pain medication for a day or two following the surgery to reduce discomfort. To promote healing and reduce swelling the surgeon might prescribe anti-inflammatory and antibiotic eye drops for three to four months following the procedure.
Although PRK dramatically improves vision and reduces dependence on corrective eyewear its goal is not to eliminate glasses and contacts. Some people achieve 20/20 vision or better while others may achieve only 20/40. This prescription is satisfactory for driving without corrective lenses. While eye prescription levels will be much lower than before these patients may still require corrective eyewear following the procedure. In addition PRK does not prevent the onset of presbyopia an age-related vision condition that affects near vision and is that occurs when the eye’s lens stiffens and becomes less flexible.