Photorefractive Keratectomy – The difference between PRK and LASIK
Photorefractive Keratectomy (PRK) is a type of laser vision correction surgery that predates LASIK and SMILE. The overall goal of PRK is the same as LASIK: to correct refractive errors and reduce dependency on glasses and contact lenses. PRK and LASIK both use a laser to reshape the cornea. Correct curvature allows the light entering the eye to focus correctly on the retina.
The main differences between the PRK Surgery and LASIK are the creation of a corneal flap in LASIK, and the recovery time and process.
What is Photorefractive Keratectomy (PRK)?
PRK, sometimes also referred to as Surface LASIK, is the original type of laser eye surgery. It is a two-step process. First, the ophthalmologist gently removes and discards the outer skin layer of the cornea, exposing the area to reshape. Then, the excimer laser reshapes the underlying tissue. “Excimer” simply refers to a specific type of laser that uses ultraviolet light pulses. After the procedure, the surgeon places a “bandage” contact lens on the eye. Leave it in for 4-5 days to allow the outer skin layer of the cornea time to repair itself.
Refractive errors are commonly caused by a misshapen cornea. Through PRK, we are able to fix myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. To correct myopia with PRK surgery, we reduce the curvature of the cornea. For hyperopia correction with PRK surgery, we increase the curvature. To correct astigmatism with PRK surgery, the cornea is made more spherical instead of football shaped.
Photorefractive Keratectomy cannot correct presbyopia, the eventual hardening of the crystalline lens inside your eye that causes many people over the age of 45 to need reading glasses. This is part of the natural aging process, and as a result, with PRK surgery and LASIK alike, you might still require reading glasses later in life.
How is PRK different from LASIK?
The purpose and end result of PRK and LASIK are very similar. PRK and LASIK both seek to correct refractive errors and allow for a life without the hassle of glasses or contact lenses. They differ in the initial step before reshaping the cornea and the recovery process.
During LASIK, the femtosecond laser creates a flap of the outer layer of the eye to reveal the corneal tissue underneath. Whereas, during PRK your surgeon removes the outer layer completely to access the corneal tissue underneath. As a consequence, it takes longer for your vision to improve after PRK surgery (4-5 days with PRK versus a few hours with LASIK). However, because we let the outer layer grow and repair itself with PRK, instead of replacing the preexisting tissue, PRK patients tend to experience less dry eye following the procedure.
What are the benefits of PRK Surgery?
PRK surgery, like LASIK, offers a chance to experience clear vision without any of the added frustrations of glasses or contacts. Note that PRK, like all laser vision correction, is designed to reduce your dependency on glasses and contacts. It does not guarantee you will never need glasses or contacts again. Many things change as we age – many people develop presbyopia which generally requires reading glasses.
That being said, there is a good possibility that you will have vision that is as good as or better than your vision with corrective lenses or glasses before the surgery.
Aside from the freedom to live your life without wearing glasses or contacts every day, PRK offers the following benefits as compared to LASIK:
- No corneal flap: Performing laser vision correction without creating a flap makes PRK an option for individuals that have thin corneal tissue – either naturally or because they previously had a LASIK procedure.
- More surface level treatment: As mentioned before, some people refer to PRK as Surface LASIK. Simply removing a small portion of the outer layer of the eye instead of cutting a flap allows the laser to reshape the cornea closer to the surface, maintaining more of your corneal thickness than LASIK.
- Active military personnel or commercial pilots: There are regulations regarding which refractive surgery options are available to individuals in these industries. PRK may be the only type of refractive eye surgery permitted. Please confirm with the appropriate authorities before scheduling a procedure.
Ideal candidate for PRK Surgery
As with other laser vision correction procedures LASIK or SMILE, candidates for Photorefractive Keratectomy (PRK) should:
- Want freedom from glasses and contact lenses
- Be 21 year of age or older
- Have a stable prescription
- Have healthy eyes free from a history of disease
- Understand and be willing to accept the risks associated with PRK surgery
PRK candidates in comparison to candidates for other refractive eye procedures such as LASIK, SMILE, or Refractive Lens Exchange generally:
- Have thinner cornea with less amount of corneal tissue
- Are older – as our eyes age and change, PRK may become a better fit than LASIK
- Are active military personnel or in other professions that require PRK for refractive eye surgeries such as MMA or wrestling
- Have had previous refractive surgeries such as LASIK or other types of trauma to the cornea that make creating a flap risky
- Do not want a corneal flap
What to expect after PRK Surgery?
Immediately after the procedure your vision with be hazy or blurry, but should still be an improvement from before the procedure. Your eyes might be a bit bloodshot or light-sensitive.
As the anesthesia wears off, you will probably feel some irritation, ache or dryness in the operative eye. You should use sterile, preservative-free artificial tears, and your medicine as prescribed to reduce any discomfort.
The bandage lens helps your eye heal comfortably. Do not attempt to take the lens out. If somehow it does fall out or move, call your physician immediately. Do not attempt to place it back in your eye.
The first day you should try and rest your eyes as much as possible to help promote the healing.
The day after PRK surgery you should notice an improvement to the clarity of your vision. It might not be perfectly crisp yet – complete healing takes time. It is also possible that if both eyes had PRK surgery on the same day, one may appear sharper than the other. Results, although predictable, vary from patient to patient and eye to eye.
The eyes should be more comfortable.
In the weeks or months following PRK surgery, your vision should continue to recover and become clearer. This change is most notable earlier on in your recovery. Fluctuations from day to day and morning to night are not uncommon. It should stabilize anywhere from 3 to 9 months after surgery – it all depends on your eyes and your overall health.
You may experience some difficult driving at night (halos or starbursts around lights) in the short term, but these effects are usually temporary and only last for a few days – weeks at most.
Photorefractive Keratectomy (PRK) is a tried and true method of laser refractive surgery. It works by removing the outer layer of your cornea and then reshaping the cornea with a laser. A bandage contact lens is then placed on the eye to promote healing. The results and goals are comparable to the more well-known type of laser vision correction, LASIK. Patients who have thinner corneal tissues or previous refractive surgeries are generally better candidates for PRK than for LASIK.
If you are interested in any type of vision correction surgery, think PRK might be the choice for you or just want more information please contact us here or call 800.EYE.EXAM to speak with one of our LASIK counselors.
You can also view this video to learn a bit more about PRK.