LASIK or Lasik (laser-assisted in situ keratomileusis) is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism. LASIK is performed by ophthalmologists using a laser.LASIK is similar to other surgical corrective procedures such as photorefractive keratectomy, PRK, (also called ASA, Advanced Surface Ablation) though it provides benefits such as faster patient recovery. Both LASIK and PRK represent advances over radial keratotomy in the surgical treatment of vision problems, and are thus viable alternatives to wearing corrective eyeglasses or contact lenses for many patients.
The LASIK technique was first made possible by the Colombia-based Spanish ophthalmologist Jose Barraquer, who, around 1950 in his clinic in Bogotá, Colombia, developed the first microkeratome, and developed the technique used to cut thin flaps in the cornea and alter its shape, in a procedure he called keratomileusis. Barraquer also researched the question of how much of the cornea had to be left unaltered to provide stable long-term results.
The first patent for LASIK was granted by the U.S. Patent Office to Dr. Gholam A. Peyman on June 20, 1989, "the surgical procedure in which a flap is cut in the cornea and pulled back to expose the corneal bed. The exposed surface is then ablated to the desired shape with an excimer laser, after which the flap is replaced.
Dr. Pallikaris theorized the benefits of performing PRK after the surface was raised in a layer to be known as a flap performed by the Mikrokeratome developed by Barraquer in 1950. The blending of a flap and PRK became known as LASIK, which is an acronym. It quickly became very popular, since it provided immediate improvements in vision and involved much less pain and discomfort than PRK.
Today, faster lasers, larger spot areas, bladeless flap incisions, intraoperative pachymetry, and wavefront-optimized and -guided techniques have significantly improved the reliability of the procedure compared to that of 1991. Nonetheless, the fundamental limitations of excimer lasers and undesirable destruction of the eye's nerves have spawned research into many alternatives to "plain" LASIK, including LASEK, Epi-LASIK, sub-Bowman’s Keratomileusis aka thin-flap LASIK, wavefront-guided PRK and modern intraocular lenses.
LASIK may one day be replaced by Femtosecond laser intrastromal vision correction via all-femtosecond correction (like Femtosecond Lenticule Extraction, FLIVC, or IntraCOR), or other techniques that avoid permanently weakening the cornea with incisions and deliver less energy to surrounding tissues. FEMTEC laser has also recently been used for incisionless IntraCOR ablation on several hundred human eyes and achieved very successful results for presbyopia, with trials ongoing for myopia and other conditions.
There are several necessary preparations in the preoperative period. The operation itself involves creating a thin flap on the eye, folding it to enable remodeling of the tissue beneath with a laser. The flap is repositioned and the eye is left to heal in the postoperative period.
Patients wearing soft contact lenses are usually instructed to stop wearing them 5 to 21 days before surgery. One industry body recommends that patients wearing hard contact lenses should stop wearing them for a minimum of six weeks plus another six weeks for every three years the hard contacts have been worn. Before the surgery, the patient's corneas are examined with a pachymeter to determine their thickness, and with a topographer to measure their surface contour.Using this information, the surgeon calculates the amount and the locations of corneal tissue to be removed during the operation. The patient is prescribed an antibiotic beforehand to minimize the risk of infection after the procedure.
The operation is performed with the patient awake and mobile; however, the patient is sometimes given a mild sedative and anesthetic eye drops.
LASIK is performed in three steps. The first step is to create a flap of corneal tissue. The second step is remodeling of the cornea underneath the flap with the laser. Finally, the flap is repositioned.
A corneal suction ring is applied to the eye, holding the eye in place. This step in the procedure can sometimes cause small blood vessels to burst, resulting in bleeding or subconjunctival hemorrhage into the white (sclera) of the eye, a harmless side effect that resolves within several weeks. Increased suction typically causes a transient dimming of vision in the treated eye. Once the eye is immobilized, the flap is created. This process is achieved with a mechanical microkeratome using a metal blade, or a femtosecond laser microkeratome that creates a series of tiny closely arranged bubbles within the cornea. A hinge is left at one end of this flap. The flap is folded back, revealing the stroma, the middle section of the cornea. The process of lifting and folding back the flap can sometimes be uncomfortable.
The second step of the procedure is to use an excimer laser (193 nm) to remodel the corneal stroma. The laser vaporizes tissue in a finely controlled manner without damaging the adjacent stroma. No burning with heat or actual cutting is required to ablate the tissue. The layers of tissue removed are tens of micrometres thick. Performing the laser ablation in the deeper corneal stroma typically provides for more rapid visual recovery and less pain than the earlier technique, photorefractive keratectomy (PRK). During the second step, the patient's vision will become very blurry once the flap is lifted. They will be able to see only white light surrounding the orange light of the laser, which can lead to mild disorientation. Currently-manufactured excimer lasers use an eye tracking system that follows the patient's eye position up to 4,000 times per second, redirecting laser pulses for precise placement within the treatment zone. Typical pulses are around 1 millijoule (mJ) of pulse energy in 10 to 20 nanoseconds.
After the laser has reshaped the stromal layer, the LASIK flap is carefully repositioned over the treatment area by the surgeon and checked for the presence of air bubbles, debris, and proper fit on the eye. The flap remains in position by natural adhesion until healing is completed.
Patients are usually given a course of antibiotic and anti-inflammatory eye drops. These are continued in the weeks following surgery. Patients are usually told to sleep much more and are also given a darkened pair of shields to protect their eyes from bright lights and protective goggles to prevent rubbing of the eyes when asleep and to reduce dry eyes. They also are required to moisturize the eyes with preservative-free tears and follow directions for prescription drops. Patients should be adequately informed by their surgeons of the importance of proper post-operative care to minimize the risk of complications.
Higher-order aberrations are visual problems that cannot be diagnosed using a traditional eye exam, which tests only for acuteness of vision. Severe aberrations can cause significant vision impairment. These aberrations include starbursts, ghosting, halos, double vision, and a number of other post-operative complications.
There have always been concerns about LASIK because of its tendency to induce higher-order aberrations. The advancement of the LASIK technology has helped reduce the risk of clinically significant visual impairment after surgery. Still imperfections are inherent in the procedure and a reason why patients experience halo, glare, and starburst, even with small naturally-dilated pupils in dim lighting.
Wavefront-guided LASIK is a variation of LASIK surgery in which, rather than applying a simple correction of focusing power to the cornea an ophthalmologist applies a spatially varying correction, guiding the computer-controlled excimer laser with measurements from a wavefront sensor. The goal is to achieve a more optically perfect eye. Surgeons claim patients are generally more satisfied with this technique than with previous methods, particularly regarding lowered incidence of "halos."
The surveys determining patient satisfaction with LASIK have found most patients satisfied, with satisfaction range being 92–98 percent.
Some patients with poor outcomes from LASIK surgical procedures report a significantly reduced quality of life because of vision problems or physical pain associated with the surgery. Most experienced and reputable clinics do a full-dilation medical eye exam prior to surgery and give adequate post-operative patient education care to minimize the risk of a negative outcome.
The following are some of the other complications of LASIK:
LASIK and other forms of laser refractive surgery (i.e. PRK, LASEK and Epi-LASEK) change the dynamics of the cornea. These changes make it difficult for your optometrist and ophthalmologist to accurately measure your intraocular pressure, essential in glaucoma screening and treatment. The changes also affect the calculations used to select the correct intraocular lens implant when you have cataract surgery. This is known to ophthalmologists as "refractive surprise." The correct intraocular pressure and intraocular lens power can be calculated if you can provide your eye care professional with your preoperative, operative and postoperative eye measurements.
Although there have been improvements in LASIK technology, a large body of conclusive evidence on the chances of long-term complications is not yet established. Also, there is a small chance of complications, such as haziness, halo, or glare, some of which may be irreversible because the LASIK eye surgery procedure is irreversible.
There are rare incidences of macular hole, retinal detachment, choroidal neovascularizationand uveitis post LASIK.Although the cornea usually is thinner after LASIK, because of the removal of part of the stroma, refractive surgeons strive to maintain the maximum thickness to avoid structurally weakening the cornea. Decreased atmospheric pressure at higher altitudes has not been demonstrated as extremely dangerous to the eyes of LASIK patients.
Myopic people generally require reading glasses or bifocal eyeglasses at a later age than people who are emmetropic (those who see without eyeglasses), but this benefit may be lost if they undergo LASIK. This is not a complication but an expected result of the physical laws of optics. Recently, a variation of the laser ablation pattern called PresbyLASIK, has been developed to reduce or eliminate dependence on reading glasses while retaining distance vision
Patients considering LASIK are adviced to avoid over-wearing their contact lenses. Usually, it is recommended that they discontinue wearing contact lenses days or weeks before the LASIK eye surgery.