Photorefractive Keratectomy (PRK)
Like LASIK, Photorefractive Keratectomy (PRK), is a laser vison correction surgery to improve vision, and to reduce, and in some cases eliminate, the need for eyeglasses or contact lenses. PRK can treat both nearsightedness (myopia) and farsightedness (hyperopia) with or without astigmatism ((blurry or distorted vision). PRK received Food and Drug Administration approval in 1995, and although PRK is an older laser surgery technique than LASIK, it is still used in cases where patients are not candidates for LASIK.
About Standard PRK Surgery
In PRK surgery, an excimer laser reshapes the cornea in a precise and controlled fashion to change its focusing power. Some patients are not candidates for LASIK, either because of an underlying eye condition, such as chronic dry eyes, or because a cornea flap (which is part of LASIK surgery) is counter indicated. This is why PRK is also called Flapless-LASIK.
Another main difference between PRK and LASIK is recovery time. After PRK, immediate recovery is usually one to two weeks. However, while most of the vision improvement happens in the first month, there is still gradual improvement over the next few months after the initial procedure. The PRK procedure offers patients the following benefits and advantages:
- No blade or incision
- Safe and effective treatment for patients who don’t qualify for LASIK
- Better alternative for patients whose job or lifestyle cannot accommodate a corneal flap
- Minimal to no haze, glare, and halos
What Happens During Standard PRK Surgery?
- Measuring your eye: The treatment during standard PRK surgery is based on measurements of a patient’s vision prescription. During your consultation, your ophthalmologist will perform a detailed eye exam, or a refraction, to measure your prescription for eyeglasses or contact lenses. These measurements will guide the surgeon during the procedure. You have to stop wearing your contact lenses for at least two weeks prior to this appointment to ensure your eyes are in best condition for testing.
- Preparing your eye: After numbing the eyes with eye drops, the surgeon removes the protective surface layer, called epithelium. The amount of tissue removed is about the thickness of the human hair. The epithelium will regrow within five days.
- Delivering your personal treatment: Once the epithelium is removed, the surgeon positions an excimer laser beam over the eye, directing light pulses to shape the eye to achieve the desired correction. An excimer laser (STAR S4 IR Excimer Laser) is an ultra-precise medical laser that creates a highly focused beam of cool ultraviolet (UV) light to gently reshape the cornea. Your refraction measurements will guide the excimer laser reshaping procedure, called photoablation, and it generally takes less than 60 seconds. The procedure is completely painless.
About Wavefront-Guided or Custom PRK
Wavefront-guided PRK treats common vision irregularities, like nearsightedness, farsightedness, and astigmatism, as well as higher-order abnormalities, in order to achieve better vision than possible with contact lenses, eyeglasses, or conventional PRK.
The main difference between standard PRK and wavefront-guided procedure, is that custom PRK creates a personalized 3D map of a patient’s visual pathway from the front of the cornea to the back of the retina. These measurements are obtained with an instrument called a wavefront aberrometer during your initial preoperative exam. This 3D mapping is extremely detailed, producing more personalization than conventional PRK, which is based only on the eyes’ refractive error. It allows the surgeon to reshape the cornea based on a patient’s unique anatomy. As a result, the procedure can offer superior results, bringing patients closer to 20/20 vision or better.
What Happens During Wavefront-Guided PRK Procedure?
- Creating your eye map: A detailed 3D map of the visual imperfections of the eye is created using wavefront eye-mapping technology that is 25 times more precise than the measurements used to write standard prescriptions for eyeglasses or contacts. This step takes place during your pre-surgical consultation, when your surgeon will perform a detailed eye exam and mapping. You have to stop wearing your contact lenses for at least two weeks prior to this appointment to ensure your eyes are in best condition for testing.
- Preparing your eye: After numbing the eyes with eye drops, the surgeon removes the protective surface layer of the cornea, called epithelium. The amount of tissue removed is about the thickness of the human hair. The epithelium will regrow within five days.
- Delivering your personal treatment: In the final step, the Star S4 IR excimer laser gently reshapes the cornea to the desired curvature, based on the digital information from the personalized eye map measurements (using Wavefront technology). Our Laser Vision Correction Center uses the STAR S4 IR® Excimer Laser System, which features VSS technology (Variable Spot Scanning) and VRR (Variable Repetition Rate) pulse-packing algorithm. This laser lessens the thermal effects on the cornea, which lets the doctor perform wavefront-guided procedures more efficiently with maximum patient safety. The procedure is completely painless.
What to Expect After PRK Surgery?
The recovery process for patients, whether they had standard or custom PRK, is the same:
- Once the shaping is complete, a soft contact lens is applied to serve as a bandage during the healing process. This contact lens will be removed within five to seven days of the procedure.
- The recovery period typically lasts one to two weeks, and patients may experience blurry vision and mild to marked discomfort during this time.
- Most of the improvement in vision is noticed throughout the first month after surgery, but gradual improvement continues over the course a few months following the procedure.
- Since PRK healing is slower, you eye drop regiment will be longer.
- Because vision will improve gradually over time, your ability to see clearly will be compromised (driving is not allowed during the healing process).
- You will need several post-surgery check-ups with your ophthalmologist to make sure the eyes are healing properly.
- The results of PRK are irreversible. In those rare cases when the laser surgical procedure may over- or under-correct, a second procedure may be required to adjust the first surgery.
A thorough preoperative exam and consultation with a board certified ophthalmologist is the best way to determine if you are a candidate for PRK. The initial pre-operative eye exam will measure the curvature of the eye, and check corneal thickness, pupil size, tear production, and stability of the refractive error. All of these factors are taken into consideration when determining if a patient is a candidate for laser eye surgery, as well as which procedure is best for their individual case. Patients should use this opportunity to ask questions and discuss any lifestyle changes they need to make during their recovery period.
It is likely you are an excellent candidate for the PRK procedure if you meet the following conditions:
- Being at least 21 years of age and having a refractive error.
- Acceptable refractive errors: near-sighted up to -12.00 or far-sighted up to +6.00. Your level of astigmatism may be as high as 6.00 diopters.
- Having healthy eyes that are free of eye disease or corneal abnormality (scars, infection, abnormal thinning, etc.).
- Having a stable eye prescription (with documented evidence that your refraction did not change by more than 0.50 to 1.0 diopter for two years prior to your preoperative examination).
- Chronically dry eyes or thin corneas.
- Have a job or participate in activities (like sports) where a corneal flap is contraindicated.
- Not being pregnant or nursing.
PRK should not be performed on people with:
- An unstable (changing) refractive error.
- A history of autoimmune disease (such as lupus erythematosis, HIV, etc.) because it has been shown that these patients may heal poorly following treatment and have an uncontrolled reaction to the surgery.
- A history of corneal dystrophy (inherited degenerations of the cornea).
- Past viral infection by herpes simplex or herpes zoster (shingles).
- Advanced glaucoma.
- Uncontrolled diabetes.
Your ophthalmologist will be able to advise what procedure may be right for you based on your eye and overall health.