PRK (photorefractive keratectomy) is a type of laser eye surgery that can correct myopia, hyperopia and astigmatism. The first PRK was performed in Germany in 1987 by Dr. Theo Seiler of the Free University Medical Center in Berlin.
PRK permanently changes the shape of the anterior central cornea. An excimer laser is used to ablate (vaporize) microscopic amounts of tissue from the corneal stroma.
The stroma is located under the corneal epithelium in the eye. Before the ablation takes place, the surgeon removes and discards the epithelium. This will then rapidly grow back in the days after surgery.
In order to prevent complications, it is important to follow the recommended procedures for post-operative care. Most clinics prescribe eye drops that are both antibiotic and anti-inflammatory. Use these eye drops according to the prescription, even if your eyes feels great soon after surgery. Moisturizing eye drops may also be needed to prevent dry eyes. Post-operative care will also involve resting the eyes a lot and using dark sunglasses to protect the eyes from bright lights.
After surgery, a protective contact lens is placed on the eye to protect it while the epithelial cells grow back.
The procedure
Prior to the procedure, numbing eye drops will be administered. You may also get a mild oral sedative to help you relax.
- A lid speculum is used to keep your eyelids open during the procedure.
- The surgeon will use an alcohol solution to remove the central area of the corneal epithelium.
- You will be instructed to look at a target light as the surgeon directs the excimer laser over your eye. The laser is programmed for your prescription.
- The laser removes microscopic amounts of tissue and reshapes the curvature of the cornea’s surface. The laser is used on the surface of the cornea, not further down. (This is an important difference between PRK/LASEK and LASIK.)
- The surgeon will place a special contact lens in the eye to protect it for a few days while the epithelial cells grow back.
Risks
PRK is a medical procedure and there are always a risk of side effects and complications, or that the surgery doesn’t produce the high degree of visual correction desired. Just as with LASIK, problems such as pain, dry eyes, halos and glare can be temporary or permanent.
It is not always possible to obtain 20/20 vision through PRK. The risk of needing glasses or contacts even after the procedure is higher for patients that had very large refractive errors before the surgery.
The first PRK procedure was performed in 1987. This means that we can not know much about the really long-term effects of PRK / LASEK.
What to expect after PRK surgery
Since the epithelial cells needs to regrow, you can expect the eye to be irritated and watery for a few days after the procedure. It can also be painful and extremely sensitive to light.
Dry eyes can contribute to pain and irritation, so make sure you use enough eye drops during the healing process. As mentioned above, you will probably have been prescribed antibiotic and anti-inflammatory eye drops, but you may need ordinary moisturizing eye drops as well.
It is not unusual for the eyes to need up to three months of healing to obtain their maximum vision after the surgery.
Dark sunglasses should be used to protect the eyes from bright lights while healing.
Alternatives to PRK
LASEK
LASEK is a variant of PRK where the outer epithelial layer of the cornea is lifted with a trephine and preserved during surgery. When the surgery is over, it is returned to the eye.
Recovery time is usually shorter for LASEK than PRK.
LASEK = Laser-Assisted Sub-Epithelial Keratectomy / Laser Epithelial Keratomileusis
The term LASEK for laser epithelial keratomileusis was coined by Italian surgeon Dr. Massimo Camellin in a scientific report published in 1998.
LASIK
During LASIK, the corneal epithelium is not removed. Instead, the surgeon cuts through the corneal epithelium and Bowman’s layer with a microkeratome or a femtosecond laser to create a flap. The flap is lifted to give the excimer laser access to the stroma. After the stroma has been remodeled, the flap is folded back.
The healing after LASIK is typically less painful then after PRK and LASEK. Also, vision usually recovers sooner after LASIK.
You can read more about LASIK in our LASIK article on this site.
Important differences between LASIK and PRK
- A permanent flap is created by LASIK, but not by PRK.
- The epithelial is removed and discarded during PRK and must grow out again after the procedure. This is not the case for LASIK and LASEK.
- With LASEK / PRK, the laser is used on the surface of the cornea. LASIK goes deeper.
- You can expect more pain, irritation and watering of the eyes during the first few days after PRK compared to LASIK.
- After LASIK, the eyes will typically reach their maximum vision well within a week. The process tend to be slower for LASEK / PRK. Having them at 80% of their maximum vision after one month and 95%-100% of their maximum vision after three months is typical for LASEK / PRK.
PresbyLASIK
This is a special type of LASIK developed for eyes with presbyopia. More information is available in our article about LASIK.
Wavefront-guided LASIK
With Wavefront-guided LASIK, the surgeon will make a spatially varying correction. More information is available in our article about LASIK.
Epi-LASIK
Epi-LASIK is a fairly new method that has borrowed aspects from both LASIK and LASEK.
Instead of using a fine blade to cut the cornea’s outer layer, the Epi-LASIK surgeon will use a blunt oscillating blade made out of plastic.
Instead of loosing the epithelial sheet with alcohol, most (but not all) Epi-LASIK surgeons use a plastic blade.
After Epi-LASIK, a special contact lens is placed in the eye and it should be kept in there as protection while the epithelial cells grow back.
Phakic intraocular lens
A phakic intraocular lens (PIOL) is implanted surgically into the eye without having the natural lens removed or altered. This method is chiefly used on patients where the refractive error is too strong for LASIK or LASEK. It can also be used when the cornea is too thin for LASIK or LASEK.
Radial keratotomy (RK)
During radial keratotomy (RK), a diamond knife is used to make incisions that reach deep into the cornea. This method is unusual today, except for the treatment of astigmatism in certain patients.