PRK (photorefractive keratectomy) is a type of refractive surgery
to correct myopia(nearsightedness), hyperopia (farsightedness) and astigmatism.
PRK was the first type of laser eye surgery for vision correction and is the predecessor to the popular LASIK procedure. Though PRK recovery takes a bit longer than recovery from LASIK eye surgery, PRK is still commonly performed and offers advantages over LASIK for some patients.
Like LASIK and other types of laser eye surgery, PRK works by reshaping the corneausing an excimer laser
, allowing light entering the eye to be properly focused onto the retina for clear vision.
The main difference between PRK and LASIK is the first step of the procedures.
In LASIK, a thin flap is created on the cornea with a microkeratome or a femtosecond laser
. This flap is lifted to expose the underlying corneal tissue and is replaced after the cornea is reshaped with an excimer laser
In PRK, the thin outer layer of the cornea (epithelium) is removed and discarded prior to reshaping the underlying corneal tissue with an excimer laser. The epithelium repairs itself (grows back over the corneal surface) within a few days after surgery.
A variation of PRK, called LASEK, also is available.
Instead of removing the outer epithelial layer of the cornea as with PRK, LASEK involves lifting the epithelial layer (using a surgical instrument called a trephine), preserving it during surgery and then replacing it on the eye’s surface at the end of the procedure.
LASEK has decreased in popularity due to the slower recovery of vision compared with PRK, as the replaced epithelial layer takes longer to recover in LASEK than the growth of a new epithelial layer in PRK.
PRK vs. LASIK
The final results of PRK surgery are comparable to LASIK outcomes, but initial PRK recovery is slower because it takes a few days for new epithelial cells to regenerate and cover the surface of the eye.
There also is a slightly increased risk of eye infection and haziness of vision in the first few days after surgery. LASIK patients generally have less discomfort, and their vision stabilizes more quickly, whereas vision improvement with PRK is gradual and the final outcome can take several weeks.
PRK, however, does offer some distinct benefits.
Because PRK surgery does not create a corneal flap (which contains both epithelial and the deeper stromal tissues), the entire thickness of the underlying stroma is available for treatment.
This is of particular benefit if the cornea is too thin for LASIK or if you have undergone LASIK previously and therefore have a thinner residual cornea. There also is no risk of flap complications, and the risk of removing too much of the cornea with the excimer laser is reduced.
How is PRK performed?
First, your eye surgeon removes a central area of corneal epithelium with an alcohol solution, a “buffing” device or a blunt surgical instrument.
Next, an excimer laser is used to precisely reshape the curvature of your cornea’s surface. This computer-controlled, highly specialized laser delivers pulses of cool ultraviolet light that remove microscopic amounts of tissue in a precise pattern.
A “bandage” soft contact lens is then placed on the cornea to help protect your eye. New epithelial cells grow back in about four or five days, after which the bandage contact lens is removed by your eye doctor.
What to expect from PRK surgery
Your first step is to choose an eye surgeon who experienced in PRK surgery.
You will then undergo a thorough eye exam to ensure your suitability for laser eye surgery. This will include:
- Measurement of the size of your pupils
- A check to make sure you don’t have dry eyes that could affect your PRK outcome
- Precise measurements and mapping of the shape of your cornea
- Measurement of the thickness of your cornea
Your eye doctor also will assess your general health as well as any medications you are taking, to determine if you are a suitable candidate for LASIK and PRK.
If you wear contact lenses, you may need to stop wearing them for a period of time before your eye exam, as contacts can change the natural shape of your cornea. Your eye doctor will discuss this with you during your exam and consultation.
PRK is an ambulatory procedure, meaning it is performed on a walk-in, walk-out basis. The actual surgery usually only takes about 15 minutes (total time for both eyes).
You will be awake during the procedure, but your eye surgeon may give you a mild oral sedative to help you relax.
Numbing eye drops will be applied to your eyes, and an instrument called a lid speculum will keep your eyelids wide open. Your surgeon then directs the excimer laser over your eye, which is programmed for your exact prescription.
You will be asked to look at a target light for a short time while your surgeon watches your eye through a microscope as the laser sends pulses of light to your cornea.
The laser energy removes microscopic amounts of tissue and reshapes the cornea. Most people do not feel any discomfort, although you may feel some pressure on your eye. Your surgeon has full control of the laser and can turn it off at any time.
After the treatment, your surgeon will cover your cornea with a bandage contact lens. Within days, new epithelial cells grow back, and the bandage contact is removed.
Immediately after PRK
You will be asked to rest for a short period after your surgery, after which you can return home (someone else must drive you).
Your surgeon will prescribe topical antibiotics as well as anti-inflammatory and pain medications to reduce post-operative discomfort, minimize any swelling and expedite healing.
As with any other surgery, it’s very important that you follow your doctor’s instructions to help ensure optimum results. You will need to attend frequent follow-up appointments with your doctor over the next several weeks to monitor the healing process.
PRK recovery takes longer than recovery from LASIK surgery. It may be days or a couple of weeks before your eyesight improves, and even longer for your vision to stabilize completely.
Most people who have PRK surgery can resume driving a car within a week or two after surgery. But it can take three to six months before vision is completely clear and stable.
Long-term results of PRK
Outcomes of PRK and LASIK are very similar. Most people achieve 20/20 vision after the procedure, and nearly all patients achieve 20/40 visual acuity or better.
If you are dissatisfied with your vision after your eyes have healed fully, you may elect to have a follow-up (“enhancement”) procedure to further sharpen your eyesight.
Another option is to wear eyeglasses for particular tasks as needed.
If sensitivity to light is a problem after PRK, eyeglasses with photochromic lenses often can provide relief.
Also, if you have minor residual refractive error after surgery, low-power prescription lenses with anti-reflective coating often can sharpen your vision for activities like night driving.
Post-operative PRK and LASIK complications are rare and can include infection and starbursts or halos around lights at night.
Reading glasses also may still be required after PRK surgery once you hit your 40s, due to an age-related loss of near vision called presbyopia.
While LASIK is by far the most popular laser vision correction surgery, it’s important to follow the guidance and judgment of your eye surgeon regarding whether PRK or LASIK is the best procedure for your individual needs.