Home / Laser refractive surgery / PKR/LASEK
PRK (photorefractive keratectomy) is a type of refractive surgery intended to correct either myopia, hypermetropia and/or astigmatism.
PRK was the first breakthrough in refractive laser surgery, coming before the popular LASIK technique. Despite the fact that the recovery time for PRK is longer than it is for LASIK, it is still a choice method, offering undeniable advantages to certain patients.
Like LASIK surgery, PRK is based on the concept of sculpting the cornea with an excimer laser, so that the light entering the eye focuses right on the retina and vision is improved.
Who are the best candidates for PRK ? All myopics, hypermetropics and/or astigmatics for whom LASIK is contraindicated.
Length of the procedure: +/- 10 minutes per eye
Usual results: 20/20 vision without glasses or contact lenses
Recovery time: From a few days to a few weeks
Common side effects: transient dry eyes (less frequently than with LASIK) and halos around objects in the dark.
The main difference between PRK and LASIK is the first step of the procedure.
During LASIK surgery, a thin flap is created in the cornea using a femtosecond laser or microkeratome. The flap is then lifted to expose underlying corneal tissue, so that it can be re-sculpted using an excimer laser. After this process, the flap is returned to its place.
During PRK, the thin outer layer of the cornea (the epithelium) is removed and eliminated. Next, the surgeon uses the excimer laser to sculpt the surface of the corneal tissue directly. The epithelium grows back over the cornea within a few days after the procedure.
There is also a variation of PRK called LASEK. The epithelium, instead of being eliminated, is put back on the cornea at the end of the procedure. The concept initially seemed interesting, but LASEK surgery is less popular than PRK because visual recovery is slower.
|The cornea is not sculpted as deeply||Slower recovery than with LASIK|
|Sometimes the only option available
to patients with thin corneas
|Greater risk of post-operatory infection, inflammation, and blurry vision (“haze”)|
|No risk of complications related to the flap||The first post-operatory days are less comfortable than after LASIK|
|A greater safety margin
in relation to residual corneal thickness
How is PRK practiced?
PRK is outpatient surgery. The procedure takes about 20 minutes. Topical local anaesthesia is used in the form of eye drops and the doctor will give you a tranquilizer pill to help you with the pre-surgery anxiety.
First, a small instrument which keeps the eyelids open is gently placed on the eye.
Next, your surgeon removes the central epithelium using a weak alcohol solution and a spatula. Then the excimer laser is applied to the eye, to sculpt the curve of your cornea to within a micron. Aimed at the cornea, the laser beam pulsates at ultra high frequency, guided by a computer which can detect the slightest micro-movements of your eye, no matter how small they may be. The laser power and aim instantaneously adjust to these micro-movements. However, if the movements are too extreme, the device stops.
Lastly, a “bandage” contact lens is placed on the eye to protect it. The epithelium will grow back within 3 to 5 days, and the surgeon can then remove the “bandage lens.”
Right after the procedure, you will have time to rest for a little while before you go home. Your surgeon will have prescribed antibiotic and anti-inflammatory eye drops to prevent infection and speed recovery. Just as you would after any surgical procedure, the doctor’s orders must strictly be obeyed to guarantee a good result. Several check-up visits will be scheduled after the procedure, to make sure that you are recovering well.
Long-term results of PRK
PRK has been practiced since 1980. We can therefore say that over35 years down the road, it yields excellent results. Since it was first introduced, the procedure has been perfected considerably. Today, the results can be said to be similar to those obtained with LASIK. Most patients attain 20/20 visual acuity, and nearly all of them have uncorrected vision of at least 20/40 (the minimum requirement for driving without glasses). With modern lasers, it is not rare for post-operatory eyesight without corrective lenses to be even sharper than pre-operatory vision with corrective lenses.
Post-operatory complications are rare, and side effects such as dry eyes or halos around sources of light at night are usually transitory.
In rare cases, vision may change over time and require surgical retouching. In cases of presbyopia (aging of the eye after 40), a pair of reading glasses may be necessary.