LASIK, an acronym for Laser-Assisted in Situ Keratomileusis, is a form of refractive laser eye surgery procedure performed by ophthalmologists intended for correcting myopia(near sightedness), hyperopia(long sightedness), and astigmatism(cylindrical vision).Many patients choose LASIK as an alternative to wearing corrective glasses or contact lenses.
The LASIK technique was made possible by Jose Barraquer (Spain), who around 1960 developed the first microkeratome, used to cut thin flaps in the cornea and alter its shape, in a procedure called keratomileusis
In 1981, Rangaswamy Srinivasan discovered that an ultraviolet excimer laser could etch living tissue in a precise manner with no thermal damage to the surrounding area.
LASIK surgery was developed in 1990 by Lucio Buratto (Italy) and Ioannis Pallikaris (Greece) as a melding of two prior techniques, keratomileusis and photorefractive keratectomy. It quickly became popular because of its greater precision and lower frequency of complications in comparison with these former two techniques. Today, faster lasers, larger spot areas, bladeless flap incision, and wavefront-optimized and -guided techniques have significantly improved the reliability of the procedure as compared to that of 1991.
Patients wearing soft contact lenses typically are instructed to stop wearing them approximately 7 to 10 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 had been worn. [2] 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 low-power lasers, a topographer creates a topographic map of the cornea. This process also detects astigmatism and other irregularities in the shape of the cornea. Using this information, the surgeon calculates the amount and locations of corneal tissue to be removed during the operation. The patient typically is prescribed an antibiotic to start taking beforehand, to minimize the risk of infection after the procedure.
The operation is performed with the patient awake and mobile; however, the patient typically is given a mild sedative (such as Valium) and anesthetic eye drops.
LASIK is performed in two steps. The first step is to create a flap of corneal tissue. A corneal suction ring is applied to the eye, holding the eye in place. The 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 (procedure known as IntraLASIK) that creates a series of tiny closely arranged bubbles within the cornea.[3] 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 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 adjacent stroma by releasing the molecular bonds that hold the cells together. No burning with heat or actual cutting is required to ablate the tissue. The layers of tissue removed are tens of micrometers thick. Performing the laser ablation in the deeper corneal stroma typically provides for more rapid visual recovery and less pain.
During the second step, the patient's vision will become very blurry once the flap is lifted. He/she will be able to see only white light surrounding the orange light of the laser. This can be disorienting.
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. The energy of each pulse is usually in the milliwatt range Typically, each pulse is on the order of 10–20 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 discontinued in the weeks following surgery. Patients are also given a darkened pair of goggles to protect their eyes from bright lights and protective shields to prevent rubbing of the eyes when asleep.
The incidence of refractive surgery patients having unresolved complications six months after surgery has been estimated from 3% to 6%. The following are some of the more frequently reported complications of LASIK:
Dry eyes
Overcorrection or undercorrection
Visual acuity fluctuation
Halos or starbursts around light sources at night
Light sensitivity
Ghosts or double vision
Wrinkles in flap (striae)
Decentered ablation
Debris or growth under flap
Thin or buttonhole flap
Induced astigmatism
Corneal Ectasia
Epithelium erosion
Posterior vitreous detachment
Macular hole
Complications due to LASIK have been classified as those that occur due to preoperative, intraoperative, early postoperative, or late postoperative sources
Various surveys have been performed to determine patient satisfaction with LASIK. These surveys have found most patients to be satisfied, with anywhere from 92–98% of respondents describing themselves as satisfied.
Some patients with poor outcomes from LASIK procedures report that they have significantly reduced quality of life due to vision problems, and have expressed concerns over the way that LASIK is marketed to potential patients.Patients who have suffered LASIK complications have published websites in an effort to educate the public about the risks, and to provide forums where prospective and past patients can discuss the surgery.
The reported figures for safety and efficacy are open to interpretation. In 2003, the Medical Defence Union (MDU), the largest insurer for doctors in the United Kingdom, reported a 166% increase in claims involving laser eye surgery; however, the MDU averred that these claims resulted primarily from patients' “unrealistic expectations” of LASIK rather than “faulty surgery”.A 2003 study reported in the medical journal Ophthalmology found that nearly 18% of treated patients and 12% of treated eyes needed retreatment.The authors concluded that “higher initial corrections, astigmatism, and older age are risk factors for LASIK retreatment.”
Why is it so popular? LASIK has advantages over other procedures, including a relative lack of pain afterward and the fact that good vision is usually achieved by the very next day.
The surgeon folds the flap back out of the way, then removes some corneal tissue underneath using an excimer laser. The excimer laser uses a cool ultraviolet light beam to precisely remove ("ablate") very tiny bits of tissue from the cornea to reshape it. When the cornea is reshaped in the right way, it works better to focus light into the eye and onto the retina, providing clearer vision than before. The flap is then laid back in place, covering the area where the corneal tissue was removed.
Both nearsighted and farsighted people can benefit from the LASIK procedure. With nearsighted people, the goal is to flatten the too-steep cornea; with farsighted people, a steeper cornea is desired. While this is not widely recognized by consumers, excimer lasers also can correct astigmatism by smoothing an irregular cornea into a more normal shape.
In order to decide whether you're a good candidate for LASIK, your eye doctor will examine your eyes to determine their health, what kind of vision correction you need, and how much laser ablation is required.
Your doctor will also look for signs of dry eye disease, which must be treated and cleared up before LASIK can be performed.
Also, a corneal topographer is usually used; this device photographs your eye and creates a kind of "map" of your cornea. With new wavefront technology associated with custom LASIK, you also are likely to undergo a wavefront analysis that sends light waves through the eye to provide an even more precise map of aberrations affecting your vision.
Finally, the doctor will find out from you any health problems you have or medications you take. Some health conditions will disqualify you altogether for LASIK, but others may just postpone the procedure until a later date...
