Laser Vision Correction
with PRK and LASIK
PRK
Photorefractive Keratectomy is an outpatient surgical procedure used to treat myopia, hyperopia and astigmatism. With PRK, an excimer laser is used to sculpt the cornea, permanently changing its shape to improve the way the eye focuses light onto the retina
To be a candidate for PRK, you must have a stable and appropriate refractive error, be free of eye disease, be at least 18 years old, and be willing to accept the potential risks, complications and side effects of PRK. You should not have significant skin or systemic disease that could affect healing. You should also not have a history of excessive scarring. If you meet these requirements, PRK may be appropriate for you to correct your refractive error. If you are considering refractive surgery, PRK may be a better choice if you have dry eye or thin corneas, either of which may prevent you from having some other forms of refractive surgery, such as LASIK.
Before you have PRK surgery, your ophthalmologist will give you a complete, preoperative eye exam to measure your prescription and check for any conditions that might effect the procedure. Your doctor will determine if you are a good candidate for PRK based on this examination. When you arrive on the day of surgery, anesthetic eye drops are put in your eyes. An eyelid speculum is placed on the eye to keep your eyelid open during the procedure. The other eye is patched.
The PRK procedure takes only about 15 minutes. The epithelium, the outer layer of the cornea, is usually removed with a special brush, though a blade, alcohol or laser can also be used. Once the epithelium is removed, an excimer laser is used to remove a thin layer of corneal tissue. Your doctor guides the laser with a computer, and the laser beam sculpts the surface of the cornea, decreasing the steepness of curvature for nearsightedness or increasing the steepness of the curvature for farsightedness. To treat astigmatism, the laser is programmed to selectively reshape specific portions of the cornea more than others. The laser flattens areas that are steeper than normal and steepens areas that are flatter than normal. PRK corrects your refractive error and eliminates or reduces the need for eyeglasses or contact lenses. Because no incisions are made, the procedure does not weaken the structure of the cornea..
Immediately following surgery, a "bandage" contact lens is placed on the eye to promote healing, and you will need to use eye drops for up to a month. You should have someone drive you home following surgery, and your surgeon may suggest that you take a few days off from work. Your surgeon may also ask that you avoid strenuous activity for up to a week, as this could slow the healing process. You may experience some discomfort immediately following surgery, lasting for two to three days. Over-the-counter medications usually control the pain. Occasionally, some patients may need topical anesthetics or other prescription medications for pain control.
Like any other surgery, PRK has risks and complications that should be carefully considered. Possible complications of PRK include undercorrection or overcorrection, both of which can often be improved with eyeglasses, contact lenses, or an additional laser surgery. Other possible complications of PRK include: glare and halos around lights, particularly at night; corneal scarring and corneal haze; corneal infection. Most complications can be treated without any loss of vision. Permanent vision loss is very rare. There is an extremely small chance that your vision will not be as good after the surgery as before, even with eyeglasses or contact lenses. This is called a loss of best-corrected vision.
Initially, your vision is blurry following PRK. The healing process takes three to five days, during which time your vision will gradually improve, though it may take a month or longer to achieve your best vision. It is important that anyone considering PRK have realistic expectations. PRK allows people to perform most of their everyday tasks without corrective lenses. However, people looking for perfect vision without eyeglasses or contact lenses run the risk of being disappointed. Recent studies show that over 90% of people who have PRK achieve 20/40 vision or better without glasses or contact lenses. If that procedure results in an undercorrection or overcorrection, your surgeon may decide to perform a second surgery, called an enhancement, to further refine the results. PRK cannot correct presbyopia, the age-related loss of close-up focusing power. Almost everyone will need reading glasses by the time they reach the age of 40 or 50, including those who have had PRK. Some people choose a vision correction method called monovision, which leaves one eye slightly nearsighted. The nearsighted eye is used for close work, while the other eye is adjusted for distance vision. Although monovision is acceptable for most people, some may not be comfortable with this correction. To determine your individual needs and your ability to adapt to this correction, you may wish to try monovision with contact lenses before surgery. If 20/20 vision is essential for your job or leisure activities, consider whether 20/40 vision would be good enough for you. You should be comfortable with the possibility that you may need a second surgery or that you might need to wear eyeglasses for certain activities, such as reading or driving at night.
LASIK
Laser in situ keratomileusis, or LASIK, is an outpatient surgical procedure used to treat myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. With LASIK, your surgeon uses a laser to reshape the cornea (the clear covering of the eye) to improve the way the eye focuses light rays onto the retina. LASIK may decrease your dependence on glasses and contacts or, in some cases, allow you to do without them entirely. According to the American Academy of Ophthalmology, seven out of 10 LASIK patients achieve 20/20 vision, but 20/20 does not always mean perfect vision. If you have LASIK to correct your distance vision, you'll probably still need reading glasses by around age 45. Therefore, it is important for you to consider the possibility that LASIK may not give you perfect vision.
LASIK is not for everyone, and your doctor will advise you about certain conditions that may prevent you from being a good candidate for this procedure. For instance, the ideal candidate for LASIK is over 18 years of age, not pregnant or nursing, and free of any eye disease. You should not have had a change in your eye prescription in the last year and should have a refractive error within the range of correction for LASIK. You must also be willing to accept the potential risks, complication and side effects associated with LASIK. You should discuss these issues with your surgeon, carefully weighing the risks and rewards. If you are happy wearing contacts or glasses, you may want to forego LASIK surgery.
Your doctor will perform a thorough eye exam to measure your prescription and check for any abnormalities that might affect the procedure. Your doctor will check your eyes for unusual dryness, which could cause dry eye symptoms postoperatively, or unusually large pupils, which could affect night or low-light vision.
LASIK is performed with the patient reclining under the laser in an outpatient surgical suite. First, the eye is numbed with a few drops of topical anesthetic. These drops may sting. An eyelid holder (called a speculum) is placed between the eyelids to keep them open and prevent you from blinking. A suction ring placed on the eye lifts and flattens the cornea and helps keep your eye from moving. You may feel pressure from the eyelid holder and suction ring, similar to a finger pressed firmly on your eyelid. From the time the suction ring is put on the eye until it is removed, vision appears dim or goes black. Your surgeon may use an automated microsurgical instrument called a microkeratome to make a flap in your cornea. This device is attached to the suction ring. As the microkeratome blade moves across the cornea, you will hear a buzzing sound. The microkeratome stops at the preset point, far enough from the edge of the cornea to create a hinged flap of paper-thin corneal tissue. The microkeratome and the suction ring are removed from your eye, and the flap is lifted and folded back. Some ophthalmologists use a specific laser instrument instead of a bladed microkeratome to make the flap in your cornea. With this technique, tiny, quick pulses of laser light are applied to your cornea. Each light pulse passes through the top layers of your cornea and forms a microscopic bubble at the specific depth and position within your cornea. Your surgeon then creates a flap in the cornea by gently separating the tissue where these bubbles have formed. the corneal flap is then folded back. As the flap is moved aside, your vision gets blurrier. Then a special laser for sculpting the corne - preporgrammed with measurements customized to your eye - is centered above the eye. In most cases, a pupil tracker will be used to keep the laser centered on your pupil during surgery. You will stare at a special pinpoint light called a fixation light or target light while the laser sculpts the exposed corneal tissue. The laser makes a clicking sound you can hear during the procedure. After the laser has completed reshaping the cornea, your surgeon places the flap back into position and smoothes the edges. The flap adheres on its own in two to three minutes.
To help protect your cornea as it heals, your surgeon may place a see-through shield over your eye, if needed, or may ask you to wear a shield at night. It is normal for your eye to have a burning sensation or feel "scratchy." This usually disappears in a few hours. Plan on going home and taking a nap or just relaxing after the procedure. You will be given eye drops to help the eye heal and to alleviate dryness. Healing after LASIK is usually more comfortable than with other methods of refractive surgery because the laser removes tissue from the inside of the cornea and not from the more sensitive corneal surface.
LASIK, like any other surgery, has risks and complications that should be carefully considered. LASIK can sometimes result in undercorrection or overcorrection. Fortunately, these problems can often be improved with glasses, contact lenses, or an additional laser surgery. Most complications can be treated without any loss of vision. Permanent vision loss is very rare. There is a chance, though extremely small, that your vision will not be as good after the surgery as before, even with glasses or contacts. This is called a loss of best-corrected vision. Some people experience temporary side effects after LASIK that usually disappear over time. In rare situations, they may be permanent. These side effects may include:
- discomfort or pain;
- hazy or blurry vision;
- hazy or blurry vision;
- scratchiness;
- dryness;
- dryness;
- glare;
- halos or starbursts around lights;
- light sensitivity;
- small pink or red patches on the white of the eye
It is important that anyone considering LASIK have realistic expectations. LASIK allows people to perform most of their everyday tasks without corrective lenses. However, people looking for perfect vision without eyeglasses or contact lenses run the risk of being disappointed. Over 90% of people who have LASIK achieve somewhere between 20/20 and 20/40 vision without glasses or contact lenses. If the procedure results in an under or overcorrection, your doctor may decide to perform a second surgery, called an enhancement, to further refine the results. LASIK cannot correct presbyopia, the age-related loss of close-up focusing power. With or without refractive surgery, almost everyone who has excellent distance vision will need reading glasses by the time they reach the age of 40 or 50. Some people choose a vision correction method called monovision, which leaves one eye slightly nearsighted. The nearsighted eye is used for close work, while the other eye is adjusted for distance vision. Although monovision is acceptable for most people, some may not be comfortable with this correction. To determine your individual needs and your ability to adapt to this correction, you may wish to try monovision with contact lenses before surgery. If 20/20 vision is essential for your job or leisure activities, consider whether 20/40 vision would be good enough for you. You should be comfortable with the possibility that you may need a second surgery or that you might need to wear eyeglasses for certain activities, such as reading or driving at night
SUMMARY
LASIK and PRK procedures are performed at
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