What is photorefractive keratectomy (PRK)?
Photorefractive keratectomy (PRK) is a procedure used to reduce the need for corrective eyewear by reshaping the cornea of the eye with a laser, thereby changing the way the eye focuses light. An excimer laser is used to ablate (remove) a thin layer of the cornea, changing the cornea's refractive (focusing) power.
LASIK is a similar procedure except a flap is created within the cornea with either a laser or a blade. There are pros and cons to weigh in choosing between LASIK and photorefractive keratectomy. In terms of cost, photorefractive keratectomy is usually less expensive than LASIK. Post operative discomfort is typically less of an issue with LASIK. Ultimately, the choice comes down to which procedure will produce the most reliable outcome, and this is largely determined by factors such as corneal health and degree of refractive error.
What vision problems are treated with photorefractive keratectomy?
Photorefractive keratectomy can treat a variety of refractive errors including myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. It can also be used to correct other irregularities of refraction in some individuals.
Who is a good candidate for photorefractive keratectomy?
The ideal candidate is someone whose corneal tissue is well suited for the procedure. Several criteria must be met first. For example, corneal thickness is important. Larger corrections require more tissue ablation. The surgeon will calculate if there will be sufficient residual corneal tissue for the ablation to be performed safely.
Ideally the eyes should also be free of underlying diseases or conditions that might affect the cornea's stability, clarity, or ability to heal well. The eye doctor reviews the medical history and performs a complete eye examination to look for any such condition which might affect the outcome.
Age is another factor. If a candidate's eyes are still growing (for example, in childhood and in the teen years) the refractive error may not have stabilized. Undergoing photorefractive keratectomy too soon may result in an undercorrection.
Photorefractive Keratectomy and Other Eye Surgeries
What Is Laser Vision Surgery?
Excimer laser refractive surgery, commonly known as laser vision correction, has been around for the past 20 years. This procedure is performed to reduce or eliminate the need for glasses or contact lenses.
What are the potential side effects and complications of photorefractive keratectomy?
Common side effects in the days following photorefractive keratectomy include discomfort, dry eye, blurred vision, and glare or haloes around lights. These symptoms tend to resolve as the eye heals.
Long-term undercorrection or overcorrection can result from variable healing rates, inaccuracies in calculations, and unstable refractions such as those of young patients whose eyes are still changing.
Uncommon but potentially serious complications include infection, scarring, and permanent visual blur or distortion. These complications have become less common with improvements in preoperative screening, more sophisticated laser ablation profiles, and better medication regimens for optimized healing.
How do I prepare for a photorefractive keratectomy?
The surgeon first determines if your eyes are suitable for photorefractive keratectomy in the pre-operative screening.
You may be asked to refrain from wearing hard (rigid) contact lenses for up to several weeks or soft contact lenses for several days in preparation for both the preoperative screening and the procedure itself. This is important because contact lenses can temporarily reshape the cornea. You will want your cornea to be in its “natural,” unaltered state when being measured preoperatively and when being treated.
On the day of surgery, do not wear makeup or perfume. Be sure to have your postoperative medications ready and review the instructions for their use.
What happens during the photorefractive keratectomy procedure?
Typically the patient lies on his/her back. A small lid speculum is used to hold the eyelids open. Once the eye is numbed with anesthetic drops, the surgeon removes the outer layer (epithelium) of the cornea either mechanically (with a tiny brush or a sweeping tool) or with laser. Once the epithelium is removed, laser is applied to the surface of the cornea to precisely ablate (remove) a thin layer of corneal tissue based on the amount of correction desired. A clicking or tapping sound might be heard as the laser is fired. Once the laser ablation is complete, a contact lens is usually placed. This “bandage” contact lens is usually removed once the epithelium has healed, typically a few days later (about 3 to 5 days).
What follow-up care is needed after a photorefractive keratectomy?
At the completion of your procedure, you will need someone to do the driving for you. You can expect to be very light sensitive, so be sure to have sunglasses with you.
You will be instructed to use prescription medicated eye drops afterwards. The drops are very important for healing well. They serve to control inflammation and prevent infection, as well as to minimize discomfort.
Close monitoring of the healing process is also very important. Be sure to keep all scheduled follow-up appointments. The number and frequency of follow-up visits will depend on how quickly the eye heals. It may take from about several weeks to 3 months to reach your best corrected vision (stable refraction).
What is the prognosis after a photorefractive keratectomy?
Generally the success rate is very good. Assuming there are no underlying medical conditions that could adversely affect the healing process, the surface of the eye is usually healed in a few days and a stable refraction is achieved in the weeks and months following the procedure.
Over time there may be a need to use corrective eyewear again, either because some of the corrective effect regresses, or because the underlying refractive error was still in flux and had not stabilized completely prior to the procedure. Re-treatment with further photorefractive keratectomy is often possible at a later date.
Patients under the age of 40 who correct their distance vision with photorefractive keratectomy will still need to use reading glasses when presbyopia sets in. Presbyopia is the inability to see well close up due to age-related changes in the eye. Patients over 40 who already have presbyopia can opt to have one eye corrected for distance while having the other eye corrected for near. This is called “monovision.” The eye doctor will discuss these options with you in the preoperative screening.
Medically reviewed by William Baer, MD; Board Certified Ophthalmology
O'Brart, D. P. "Excimer laser surface ablation: a review of recent literature." Clinical & Experimental Optometry 97.1 (2014): 12-17.
Woreta, F. A., et al. "Management of post-photorefractive keratectomy pain." Survey of Ophthalmology 58.6 (2013): 529-535.