What is photorefractive keratectomy (PRK) eye surgery?
All laser vision correction surgeries work by reshaping the cornea, or clear front part of the eye, so that light traveling through it is properly focused onto the retina located in the back of the eye. There are a number of different surgical techniques used to reshape the cornea. During PRK, an eye surgeon uses a laser to reshape the cornea. This laser, which delivers a pulsing beam of ultraviolet light, is used on the surface of the cornea, not underneath a corneal flap as in LASIK.
How do I prepare for photorefractive keratectomy (PRK) surgery?
Before your PRK surgery, you will meet with a doctor and a coordinator who will discuss with you what you should expect during and after the surgery. During this session, your medical history will be evaluated, and you will have your eyes tested. Tests will include maps of the corneal shape and measurement of the refractive error in each eye. Your surgeon will answer any further questions you may have. Afterwards, you can schedule an appointment for the PRK procedure.
If you wear rigid gas permeable contact lenses, you should stop wearing them at least 3 weeks before the date of your screening visit. Other types of contact lenses shouldn't be worn for at least 3 days prior to evaluation. Be sure to bring your current glasses so your prescription can be reviewed.
On the day of your surgery, eat a light meal before coming and take all of your usual prescribed medications. Do not wear eye makeup or have any bulky accessories in your hair that will interfere with positioning your head under the laser. If you are not feeling well that morning, call the doctor's office to determine whether the procedure needs to be postponed.
What happens during the PRK procedure?
The PRK procedure is done under local anesthesia and takes about 10 minutes to treat both eyes, slightly less time than LASIK. During PRK, an eye surgeon removes the corneal surface cells, then uses a laser to reshape the cornea. A clear contact lens is usually placed at the end of surgery to reduce irritation during the healing process.
Risks / Benefits
What are the advantages of PRK?
- PRK can accurately correct nearsightedness. Approximately 90% of PRK patients have 20/20 vision without glasses or contact lenses one year after the surgery. Over 95% have 20/40 or better without glasses or contacts.
- PRK may be preferable to LASIK in certain patients with thinner corneas or with corneal surface irregularity since PRK disrupts less corneal tissue than a comparable LASIK surgery.
- PRK is technically simpler than LASIK and utilizes the same modern laser treatment systems. For this reason, some refractive surgeons prefer PRK to LASIK.
What are the disadvantages of PRK?
- Mild discomfort, including eye irritation and watering, that may last several days following the procedure. This is due to the need for the corneal surface cells (epithelium) to regenerate. These cells are removed by the surgeon right before the corrective laser treatment is performed.
- Longer time to reach stable vision. Typically, vision is about 80% improved at 1 month after surgery and about 95% by 3 months after surgery. LASIK, in contrast, provides a more rapid visual recovery.
- The outcome is not completely predictable due to variations in individual wound healing, and a small number of patients may still require glasses or additional surgery to achieve their best vision.
When both eyes are treated, many patients take off work for up to one week to allow the irritation and vision to improve to a more acceptable level.
What are the potential side effects of PRK?
Many PRK patients experience some discomfort in the first few days after surgery, and almost all experience sensitivity to light. Other rare but potential side effects may include:
- Loss of best vision achievable with glasses.
- Glare symptoms related to light scattering or halos around images. These symptoms are less common with modern laser technology, and usually temporary.
- Corneal haze related to abnormal wound healing after PRK. This is rarely a source of vision problems and usually improves with time. A medicine called mitomycin C is sometimes used during surgery to minimize the risk of haze after PRK.
- Corrections for larger amounts of farsightedness and astigmatism may be more prone to regression (partial loss of the treatment effect) after PRK than after LASIK. This may depend on the laser system used, and adjustments are often made in the targeted correction to account for historical trends with that particular laser system. Your surgeon will be able to provide guidance based on your particular situation.
Other potential side effects include delayed surface healing or mild corneal irregularity that could affect the best vision achieved with glasses. Usually, the quality of vision long-term is as good as that achieved with LASIK.
Recovery and Outlook
What should I expect after PRK surgery?
The bandage contact lens is usually worn for the first several days to allow the surface of the eye to heal. You should expect to visit your eye doctor 2 or 3 times during the first three months after surgery, with the first visit being 1 to 3 days after surgery. Once the surface of the eye is healed, the bandage contact lens is removed.
Your vision may fluctuate between clear and blurry for the first few weeks following surgery. Your eyes may be slightly dry even though they may not feel dry. Your doctor will give you prescription and over-the-counter eye drops to prevent infection and keep your eyes moist. These drops may burn or blur the vision for a moment when applied. Do not use any drops not approved by your ophthalmologist.
Your vision will gradually improve, and usually will be good enough to allow you to drive a car within 1 to 2 weeks following surgery. Keep in mind, however, that your best vision may not be obtained for up to 6 weeks to 6 months following surgery.
Will I still need reading glasses to correct presbyopia after I have had PRK?
Presbyopia (loss of focus on nearby objects) eventually affects all patients over the age of 40 and can be managed with reading glasses or with a blended approach to laser refractive surgery called monovision. Monovision can be simulated before surgery by using a pair of trial glasses or contact lenses. In monovision, the non-dominant eye is corrected for computer or reading distances (slightly nearsighted) and the dominant eye is corrected for distance.
Presbyopia is not actually reversed by monovision PRK, but your dependence on reading glasses can be reduced by incorporating monovision into the treatment plan. An in-office trial of monovision during your screening exam can help you assess the benefits and compromises associated with a monovision approach.