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LASIK,an acronym for Laser-Assisted in Situ Keratomileusis, is a form of
refractive laser eye surgery performed by ophthalmologists intended for correcting
myopia, hyperopia, and astigmatism.The procedure is usually a preferred
alternative to photorefractive keratectomy, PRK, as it requires less time for full
recovery, and the patient experiences less pain overall. Many patients choose LASIK
as an alternative to wearing corrective glasses or contact lenses.
Technological development
The LASIK technique was made possible by Spanish ophthalmologist Jose Barraquer,
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 1980, Rangaswamy Srinivasan working at IBM Research Lab discovered that an ultraviolet excimer laser could etch living tissue in a precise manner with no thermal damage to the surrounding area. He named the phenomenon Ablative Photodecomposition (APD). Srinivasan and his co-inventors ran tests using the excimer laser and a conventional, green laser to etch organic matter. They discovered that while the green laser produced rough incisions, damaged by charring from the heat, the excimer laser produced clean, neat incisions. In 1983, Srinivasan collaborated with an ophthalmic surgeon to develop APD to etch the cornea.
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. 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 all-femtosecond correction (Femtosecond Lenticule EXtraction, FLIVC), LASEK, Epi-LASIK, sub-Bowman’s Keratomileusis aka thin-flap LASIK, wavefront-guided PRK, and modern intraocular lenses.
Procedure
Preoperative
Patients wearing soft contact lenses typically are instructed to stop wearing them
approximately 10 to 15 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.
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.
Operation
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. 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 (procedure known as IntraLASIK) 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 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 (than the earlier PRK (?) ).
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.
Postoperative 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.Lasik surgery,lasik new york,lasik dallas,lasik nyc,lasik vision institute,new lasik,lasik, laser eye surgery, lasik eye surgery,
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