LASIK (laser-assisted in situ keratomileusis) is an outpatientrefractive surgery procedure used to treat nearsightedness,farsightedness and astigmatism. A laser is used to reshape the cornea — the clear, round dome at the front of the eye — to improve the way the eye focuses light rays onto the retina at the back of the eye.
With LASIK, an ophthalmologist (Eye M.D.) creates a thin flap in the cornea using either a blade or a laser. The surgeon folds back the flap and precisely removes a very specific amount of corneal tissue under the flap using an excimer laser. The flap is then laid back into its original position where it heals in place.
For people who are nearsighted, LASIK is used to flatten a cornea that is too steep. Farsighted people will have LASIK to achieve a steeper cornea. LASIK can also correct astigmatism by shaping an irregular cornea into a more normal shape.
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 glasses or contacts run the risk of being disappointed. More than 90 percent of people who have LASIK achieve somewhere between 20/20 and 20/40 vision without glasses or contact lenses. If sharp, detailed 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 (called a retreatment or enhancement) or that you might need to wear glasses for certain activities, such as reading or driving at night. Also, you should be aware that LASIK cannot correct presbyopia, the age-related loss of close-up focusing power.
How the LASIK procedure works
LASIK is performed while the patient reclines under a surgical device called an excimer laser in an outpatient surgical suite.
First, the eye is numbed with a few drops of topical anesthetic. An eyelid holder is placed between the eyelids to keep them open and prevent the patient from blinking. A suction ring placed on the eye lifts and flattens the cornea and helps keep the eye from moving. The patient may feel pressure from the eyelid holder and suction ring, similar to a finger pressed firmly on the eyelid.
From the time the suction ring is put on the eye until it is removed, vision appears dim or goes black. Once the cornea is flattened, a hinged flap of corneal tissue is created using an automated microsurgical device, either a laser or blade. This corneal flap is lifted and folded back. Then the excimer laser preprogrammed with the patient’s unique eye measurements is centered above the eye.
The surgeon checks that the laser is positioned correctly. The patient looks at a special pinpoint light, called a fixation or target light, while the excimer laser sculpts the corneal tissue. Then the surgeon places the flap back into position and smoothes the edges. The corneal flap sticks to the underlying corneal tissue within two to five minutes, and stitches are not needed.
A LASIK surgery procedure
The patient should plan to have someone drive him or her home after the procedure and then take a nap or just relax. To help protect the cornea as it heals, the surgeon may place a transparent shield over the eye(s) to protect against accidental bumps and to remind the patient not to rub the eye(s). The patient may need to wear the shield only when sleeping. The surgeon will provide eyedrops to help the eye heal and relieve dryness.
It may take three to six months after LASIK surgery for the improvements in a person’s vision to fully stabilize and any side effects to go away.
LASIK risks and side effects
LASIK, like any surgery, has potential risks and complications that should be carefully considered. LASIK has now been performed on millions of patients in the United States for more than 10 years, and the overall complication rate is low, between 0.2 and 2 percent of all patients. Infection and inflammation are possibilities, as with any surgical procedure, and usually can be cleared up with medications.
Problems with the corneal flap after surgery sometimes make further treatment necessary. There is a chance, though small, that vision will not be as good after the surgery as before, even with glasses or contacts.
Some people experience side effects after LASIK that usually disappear over time. These side effects may include hazy or blurry vision; difficulty with night vision and/or driving at night; scratchiness, dryness and other symptoms of the condition called “dry eye”; glare, halos or starbursts around lights; light sensitivity; discomfort or pain; or small pink or red patches on the white of the eye. In a small minority of patients, some of these effects may be permanent.
Sometimes a second surgery, called a retreatment or enhancement, may be needed to achieve the desired vision correction. This is more likely for people who were more nearsighted, farsighted, or had higher astigmatism before LASIK — those whose vision originally needed more intensive correction. Approximately 10.5 percent of LASIK patients in the United States require a retreatment.
Considering LASIK? Learn more
Before choosing to have LASIK, it’s important to do your homework to ensure you are a good candidate, understand the potential risks and benefits, and have realistic expectations about what your vision will be like after surgery and for years to come. To ensure the best possible outcome, be a well-prepared and informed patient by reviewing the resources below before you have LASIK. If these materials raise any questions for you, be sure to discuss these questions with your Eye M.D.
Is LASIK For Me? A Patient’s Guide to Refractive Surgery (PDF 303K)
This guide, produced by the American Academy of Ophthalmology, offers straight-forward facts about what makes a good LASIK candidate, the risks and benefits of the surgery, how to choose a surgeon and an introduction to the informed consent process.
LASIK Surgery: Why All Patients Need the K Card (PDF 650K)
If you have decide to have LASIK, it is important to keep a record of your pre-operation and post-operation eye information. Your Eye M.D. may need this information if you have other eye surgery later, such as cataract surgery. Bring this “K Card” with you to your Eye M.D. appointment to have it completed and keep it for future use.
Questions to Ask When Considering LASIK
If you are considering LASIK, you should discuss with your Eye M.D. the benefits and risks — including quality of life issues — that could result from correcting vision with surgery rather than eyeglasses or contact lenses.
Today’s refractive surgery options for vision correction range from corneal reshaping with lasers to surgical insertion of artificial lenses. Following are some of the alternative refractive surgery procedures to LASIK.
Before surgery, the excimer laser is programmed with each patient’s wavefront data to prepare it to perform a very precise “sculpting” of each unique cornea. In conventional LASIK, this programming is based on the patient’s vision correction prescription (the same as used for the patient’s glasses or contacts.)
In wavefront-guided LASIK, computer imaging technology creates a very detailed three-dimensional “map” of the patient’s cornea that looks a bit like a miniature mountain range. This “map” is used to program the excimer laser for surgery. Wavefront technology can measure very subtle abnormalities in the surface of the cornea, enabling wavefront-guided LASIK to achieve vision correction beyond what is possible with glasses or conventional LASIK.
Also, wavefront LASIK has been shown in several studies to reduce side effects, such as problems with night vision and contrast sensitivity (the ability to clearly see objects against a background, such as black letters on a white page), and also to increase the percentage of patients who achieve 20/20 vision. Wavefront technology may also be used in PRK procedures, for similar reasons and with similar results.
PRK: Another Path to Laser Vision Correction
Photorefractive keratectomy (PRK) uses the excimer laser in the same way as LASIK, and patients’ vision correction results are similar. The main difference between PRK and LASIK is that in PRK there is no flap — only the very top (epithelial) layer of the cornea is removed (or moved aside) before the excimer laser sculpts the cornea.
Many PRK surgeons use a blunt, gently vibrating microkeratome to remove the epithelial layer. LASEK and Epi-LASIK, described below, are other PRK techniques. New approaches, such as advanced surface ablation in which the cornea is cooled either before or after surgery, help reduce the discomfort that may occur after PRK. The patient may also be given topical antibiotics and anti-inflammatory medications and oral pain medications to reduce discomfort and speed healing after surgery. A “bandage” soft contact lens is used to promote epithelial healing, which takes about four days.
While LASIK patients often report clear, improved vision by the day after surgery, it may be a few days before vision stabilizes for PRK patients. The cornea’s epithelial layer re-grows during this time. The thicker corneal flap created in LASIK is not made in PRK, so if there is a concern about potential flap complications, the surgeon may recommend PRK. If the patient’s corneas are too thin to meet LASIK standards, if he or she had LASIK previously, or if other eye health factors are involved, the surgeon and patient may decide that PRK would be a better choice.
Wavefront-guided PRK offers additional vision correction, similar to wavefront-guided LASIK. Though thousands of wavefront-guided PRK procedures have been safely and effectively performed in the United States, the FDA approval process has not yet taken place, so wavefront-guided PRK is considered an “off-label” use of the technology. Professional medical standards permit Eye M.D.s to use this and other “off-label” procedures and medications.
A microsurgical instrument called a trephine is used to create a flap of epithelial corneal tissue, and an alcohol solution is used to loosen the epithelial cells. Once the epithelial flap is created and moved aside, the procedure is the same as PRK. After corneal sculpting, the epithelial flap is repositioned and smoothed with a small spatula, then secured with a “bandage” soft contact lens to promote epithelial healing, which takes about four days.
A special microkeratome, the Epi-keratome, is used to precisely separate a very thin sheet of epithelial tissue from the cornea. This thin sheet is lifted to the side and the cornea is treated as with PRK. Then the thin sheet may be moved back into place to re-adhere to the cornea or removed. A “bandage” soft contact lens is applied and used for about four days to help the epithelial layer heal.
Conductive Keratoplasty (CK)
CK is a noninvasive, thermal refractive surgery procedure used to correct mild to moderate farsightedness (hyperopia) in people over age 40. With CK, your Eye M.D. uses a tiny probe that releases controlled amounts of radio frequency (RF) energy, instead of a laser, to apply heat to the peripheral portion of the cornea. The heat then causes the peripheral cornea to shrink and tighten like a belt. This increases the curvature (steepness) of the central cornea, improving the optical power of the central cornea. This refocuses light rays on the retina and enhances vision.
CK can be used to achieve “monovision” (blended vision). With monovision, CK can be used to improve close-up vision in a presbyopic eye with good vision but poor near focus. To maintain good distance vision, usually only one eye is set to near focus (the non-dominant eye), while the other is left or set at good distance vision. CK does not offer permanent correction; for some people, farsightedness may return over time.
Phakic Intraocular Lenses (IOLs)
Phakic IOLs are designed for people with high degrees of refractive errors that cannot be safely corrected with corneal-based refractive surgery. The phakic IOL, sometimes referred to as an implantable contact lens, or ICL, is surgically implanted inside the eye in front of the eye’s natural lens. The eye’s natural lens is not removed, so patients can retain their pre-existing ability to focus.
During the phakic IOL procedure, your Eye M.D. places the phakic IOL either in front of or behind the iris of the eye. Once the IOL is properly positioned inside the eye, it provides the necessary correction to redirect light rays precisely onto the retina.
Refractive Lens Exchange (Clear Lens Extraction)
With refractive lens exchange (RLE) — also called Clear Lens Extraction or CLE — an artificial lens is used to replace your eye’s natural lens in order to improve vision. The procedure is performed much like cataract surgery.
As is an option in cataract surgery, RLE may employ multifocal or accommodative intraocular lenses (IOLs). These lenses allow the ability to focus at all distances.
Some people who have early stage cataracts may choose to have RLE instead of waiting for their cataracts to progress to the point where they should be removed. This is because the lens implants generally provide them with better uncorrected vision at that point, particularly if they currently need vision correction.
RLE may also be an option for people with severe hyperopia (farsightedness), for whom LASIK is not recommended.
RLE is not FDA-approved, however, ophthalmologists legally may choose to perform this procedure in what is called an “off-label” use.
Dr. Carlson and the Duke Center For Vision Correction can be reached at 919 681 4089 for more information and to schedule a personalized consultation.