PRK Laser Eye Surgery: LASIK Without a Flap
PRK (or photorefractive keratectomy) is the second most popular laser eye surgery in the United States, behind LASIK. The question of PRK Vs LASIK is common for consumers interested in laser vision correction.
Like LASIK, PRK uses an excimer laser to reshape the cornea. But in PRK, no corneal flap is created with a microkeratome or femtosecond laser prior to the corneal reshaping.
Instead, the central portion of the thin outer layer of the cornea (the epithelium) is removed from the eye, usually after being loosened with a dilute alcohol solution. The excimer laser treatment is then applied to the underlying corneal tissue (the stroma) to reshape the eye.
After the laser treatment, the cornea is covered with a bandage contact lens. Within days, new epithelial cells grow back and the bandage contact is removed.
Pros and Cons of PRK vs. LASIK
PRK has one distinct advantage over LASIK: because no corneal flap is created, there is no risk of flap complications during or after the procedure.
This may be important for people who are engaged in activities that put them at risk for eye injuries (and potentially, LASIK flap dislocations) after surgery. Boxing and martial arts are good examples.
PRK also can be performed safely on corneas that may be too thin for LASIK. Since no LASIK-style flap is required, the entire thickness of the underlying corneal stroma is available for treatment. A person who has PRK surgery rather than LASIK will have a thicker residual "stromal bed" after the excimer laser treatment.
In LASIK, on the other hand, the corneal flap contains both epithelial and stromal tissues, so the underlying corneal stroma is reduced in thickness. The same amount of excimer laser reshaping with LASIK leaves less residual stroma under the corneal flap, which may affect the biomechanical strength and stability of the eye in some cases.
Excimer laser treatments that cause too much reduction in the residual stromal bed have been indicated as a potential cause of a serious LASIK complication called corneal ectasia, which can severely distort vision and cause permanent vision loss.
It's important to know that PRK causes more discomfort than LASIK the first few days after surgery, and complete visual recovery after PRK surgery can take a few weeks longer than LASIK recovery time.
There also is a greater risk of eye infection immediately after PRK compared with LASIK, and a greater risk of temporary or permanent haziness of the cornea that may affect vision.
The PRK Procedure
The basic steps in PRK surgery are:
- Anesthetic eye drops are applied to the eye to prevent discomfort during surgery.
- A central area of corneal epithelium is removed either with a laser or manually after being softened with a dilute alcohol solution.
- An excimer laser is used to reshape the underlying corneal tissue.
- Antibiotic and anti-inflammatory drops are applied to the eye, and the eye is covered with a bandage contact lens.
Two or three days later (after the epithelium has had a chance to grow back), the bandage contact lens is removed.
Considerations After PRK Surgery
Before consenting to PRK surgery, be aware that:
- PRK causes more post-operative discomfort than LASIK. This may last for a week or longer.
- It can take three to six months to achieve optimal vision after PRK. Blurred vision, glare and sensitivity to light are common for several days or longer after the procedure.
- Due to the potential for blurred vision for a time after PRK, surgeons often perform PRK on one eye at a time (waiting several days or weeks to perform PRK on the other eye, after vision in the first eye is acceptably clear).
- You may be required to use medicated eye drops for up to six months after PRK to prevent or reduce corneal haze or scarring.
PRK Risks and Complications
As with LASIK and other types of refractive surgery, there are risks and possible complications associated with PRK. These risks and complications of PRK are similar to those of LASIK, and include:
- Dry eyes
- Vision problems, such as poor night vision, glare, halos and haze
- Incomplete or inaccurate vision correction
- Infection following surgery
There may be a slightly greater risk of eye infection, scarring, glare and unpredictable healing of the cornea after PRK compared to LASIK. But serious complications following PRK are rare. Although ectasia, a thinning and bulging of the cornea (similar to keratoconus), is a risk of PRK, it is very rare for LASIK patients and even more so after PRK. New treatments are currently being evaluated for post laser eye surgery ectasia, including collagen corneal cross-linking.
The cost of PRK is comparable to the cost of LASIK eye surgery. Like LASIK and other laser vision correction surgery, PRK is considered an elective procedure and therefore costs associated with the surgery typically are not covered by health insurance.
You can lower your PRK costs by setting up a Health Savings Account (HSA) at your bank or contributing to flexible health benefits program at work.
Many refractive surgeons also offer financing programs that allow you to pay for PRK and other vision correction procedures over time at attractive interest rates or interest-free.
Other PRK Facts
Here are a few other PRK surgery facts to consider:
- PRK has been performed longer than LASIK. It gained FDA approval for use in the United States for the correction of nearsightedness in 1995 and for the treatment of farsightedness in 1998.
- Studies show the visual results of PRK and LASIK six months after surgery are comparable. (But vision returns to normal faster after LASIK, with less post-operative discomfort.)
- PRK typically is used to correct up to -7.00 diopters (D) of nearsightedness and up to +4.00 D of farsightedness, with or without astigmatism.
- Just like LASIK, PRK can be used as a type of presbyopia laser surgery for treatment of age-related nearsightedness (presbyopia).
- During PRK, the excimer laser can be programmed to deliver a standard laser treatment (or ablation) or a customized, wavefront-guided ablation, like that used for wavefront LASIK.
Because PRK eliminates the risk of flap complications, some refractive surgeons prefer PRK to LASIK for many patients, especially those with marginally thin corneas.
PRK also is recommended by many surgeons to improve vision after cataract surgery. When PRK and cataract surgery are combined it is sometimes called refractive cataract surgery. (It is important to note that the laser used for PRK is different than that used for laser cataract surgery.) PRK can also be recommended to improve vision after previous refractive procedures on the same eye, including radial keratotomy (RK), refractive lens exchange (RLE) and phakic IOL implantation.
Note: This information is for general education purposes only. It is not to be used as a substitute for medical advice from your eye doctor or refractive surgeon.
Take Home Points
- There is more post-operative discomfort after PRK compared to LASIK. This may last for a week or more.
- It can take 3 to 6 months to achieve optimal vision after PRK. Blurred vision, glare and sensitivity to light are common for several days or longer after the procedure.
- You may be required to use medicated eye drops for up to 6 months after PRK to prevent or reduce corneal haze or scarring.