Photorefractive Keratectomy (PRK)
PRK laser eye surgery, or Photorefractive Keratectomy is part of a family of procedures called “surface ablations” because the laser is applied directly on the surface of the cornea rather than under a flap, as with LASIK.
The PRK surgery is done under topical anesthesia and takes about 5 minutes per eye.
Surgeons worldwide have performed PRK for over 20 years now. It’s continued popularity is a testimony to the long term stability and efficacy of the procedure observed over this time period. While a Major in the US Air Force, Dr Stetson (formerly Chief of the US Air Force Academy laser eye clinic) studied surface healing on PRK patients using many different methods to remove the epithelium such as alcohol and laser-assisted, before it became clear that using a rotational brush offered the most efficient and consistent surface preparation of the corneal surface in his hands. As a result, Diamond Vision uses a rotating brush (Amoils Brush) to gently and safely remove the surface cells in the treatment zone in just about 10 seconds! Though more expensive for us, this is far faster then alcohol-assisted removal, and allows us to maintain better control over the duration of the surgery while minimizing anxiety for our patients by reducing their time under the laser.
We also use mitomycin C (MMC) for our PRK laser eye surgery treatments which require the removal of more than 30microns of tissue. MMC has been shown to reduce the risk of corneal haze/scarring in many peer- reviewed studies while having a good track record of minimal adverse effects. For more on why we use the Amoil brush for our primary PRK treatments, and MMC in our larger PRK surgery treatments, and to review references to related studies, click below.
The Amoils brush also allows us better control of what epithelial tissue we remove and what we leave behind. For a large astigmatic correction, the laser produces and ellipse, so it makes sense that the surface removal should occur in the same ellipse. This is not possible when using the laser to remove the surface cells nor is it possible using a circular well with alcohol . Therefore we can save a great deal of surface cells that would otherwise be removed.
In contrast of the 7–10 seconds it takes to remove the surface cells with the Amoils brush, one large cohort study of over 1200 eyes found that using alcohol-assisted surface removal took an average of 96 seconds, and such a long elapsed time can allow for the cornea to become dehydrated, which may lead to less predictable outcomes, something we are not willing to risk. It’s interesting to note that even in this study where a much less precise mechanical removal of the corneal epithelium with a blade took place, 93.3% of these 593 patients enjoyed uncorrected visual acuity of 20/20 or better compared to 90.9% in the alcohol group was shown to be In addition, in the same study the healing time for mechanical debridement (removal of surface cells directly with an instrument, just as we do with the brush) was an average of 3.8 days versus an average of 4.2 days in the alcohol-assisted group. Though the above study did not find a statistically significant difference here, we have also seen healing times generally improved by at least 1/2 a day to 1 full day with our alcohol-free Amoil brush method. It has been postulated that using the Amoils brush may allow more rapid healing because it avoids alcohol’s toxicity to neighboring epithelial cells and corneal stroma. Several studies have also shown that post operative pain and inflammation may be reduced by avoiding the use of alcohol or the additional energy of using the laser to remove the epithelium.2
In a rabbit model, it was shown move all of the epithelium by mechanical methods created the least amount of inflammation whereas the use of the laser resulted in the most (p=0.0001) Further, The greatest loss of keratocytes (corneal cells) was observed using alcohol to remove the epithelium whereas mechanical removal resulted in the least damage (P=0.009) 3
Finally, a study out of the Army in 2014 analyzed visual acuity and haze (scarring) results in moderate to high myopes following PRK, versus, PRK with MMC, versus LASIK. The results showed that less haze (in fact no significant haze) was found in the MMC group whereas the other 2 groups had a small number of patients who developed clinically significant haze. Visual acuity salts or similar across the board and no complications arose from the use of mitomycin. This study’s results reflects the majority of the literature available over the last 10 years on the subject.4
1. Ghoreishi, M. et al. j Ophthalmic Vis Res, 2010;
2.Comparison of postoperative pain in patients following PRK versus advanced surface ablation. Blake CR et al. J Cat Ref Surg 2005; 31:1314–1319;
3.Campos, M. et al. Ophthalmology, 1994;
4.The US Army Surface Ablation Study: comparison of PRK, MMC-PRK and LASIK. Sia, RK et al. J Refractive Surg, 2014.
How does PRK compare to LASIK?
Advantages of PRK:
- You keep more corneal tissue than with LASIK, ensuring the long-term stability and integrity of your eyes.
- You are also better able to have a “touch up” procedure if necessary
- There is no risk of flap-related complications.
- You are at less risk for dry eyes, because there is no disruption in the nerves that tell your eyes to produce tears.
- PRK is more comfortable during the procedure.
Disadvantages of PRK:
- Recovery takes longer after PRK. Most people do not work for at least 2 days after surgery to allow their eyes to rest. In a Diamond Vision survey of patients who have had surface ablations, seventy-five percent were back to work after 3 days.
- Compared to LASIK, PRK is not as comfortable for a few days afterwards. However, advances in follow-up care have considerably improved the comfort of PRK. When patients in our Diamond Vision study were asked to rate their discomfort from zero to four, the majority (56%) said their discomfort was zero or one.
What should I expect after PRK?
Once the eye is corrected, the surgeon will place a soft contact lens to protect your eye while the healing takes place. During the healing time – 5 to 7 days – it is normal to experience blurry or fluctuating vision, light sensitivity, dryness and/or a foreign body sensation. It is common for one eye to heal faster than the other, so do not be alarmed if your vision is better in one eye compared to the other. You will be given oral pain medication if necessary, along with topical eye drops. You may find that you do not feel confident driving while the protective lenses are in.
At your one-week visit the contact lenses are removed and your vision will slowly improve. Drops will be given to use for several weeks, which will aid in healing and prevent inflammation.
Although it can take a few weeks to a few months for patients to fully reach their optimal vision, your visual outcome will be the same as if you had LASIK. However, the long-term safety and stability of your eyes will be higher than if you had LASIK. A few days or weeks of patience will be rewarded by a lifetime of better vision.
What is better for me, LASIK or PRK?
In most cases, PRK is recommended for patients who have thinner corneas, slightly irregular corneas, or are at risk for dry eyes or other conditions. Your Diamond Vision doctor will be able to make a recommendation for you based on extensive testing.
In other cases, patients who are candidates for LASIK chose to have PRK instead, because they prefer a flapless or bladeless procedure.
Why is PRK more expensive than LASIK?
PRK is a specialty procedure, meant to address the needs of people with unusual eye measurements. Compared to LASIK or the old PRK, the new PRK offered at Diamond Vision uses more sophisticated and expensive intra-operative eye drops such as Mitomycin-C, and improved surgical instruments such as the Amoils rotary epithelium brush. The new Lotemax gel drops are also used at Diamond Vision for post-operative care after PRK.
Why is PRK becoming more and more popular?
Many studies show that LASIK and PRK produce the same visual results after a few weeks or month. Now that the disadvantages of the “old PRK” have been conquered, doctors like the extra long-term safety afforded by PRK in many patients.
How do I learn more about PRK?
If you would like to discuss the procedure with patients who have had PRK (or a very similar procedure, LASIK), please ask our staff for a list of patient phone numbers. As always, we encourage you to speak to our knowledgeable doctors for any questions regarding this procedure
Or call 888–678-4341