LASIK Eye Surgery animation

LASIK (laser-assisted in situ keratomileusis) is a type of refractive laser eye surgery performed by ophthalmologists for correcting myopia, hyperopia, and astigmatism.[1] The procedure is generally preferred to photorefractive keratectomy, PRK, (also called ASA, Advanced Surface Ablation) because it requires less time for the patient's recovery, and the patient feels less pain, overall; however, there are instances where PRK/ASA is medically indicated as a better alternative to LASIK.
The LASIK technique was made possible by the Colombian-based Spanish ophthalmologist Jose Barraquer, who, around 1950 in his clinic in Bogotá, Colombia, developed the first microkeratome, used to cut thin flaps in the cornea and alter its shape, in a procedure called keratomileusis. Stephan Schaller assisted. Barraquer also provided the knowledge about how much of the cornea had to be left unaltered to provide stable long-term results.



Later technical and procedural developments included the RK (radial keratotomy), started in the '70s in Russia by Svyatoslav Fyodorov , and the development of PRK (photorefractive keratectomy) in the '80s in Germany by Theo Seiler. RK is a procedure where radial corneal cuts are made typically using a micrometer diamond knife, and has nothing to do with LASIK

In 1968, at the Northrup Corporation Research and Technology Center of the University of California, Mani Lal Bhaumik and a group of other scientists, while working on the development of a carbon-dioxide laser, developed the Excimer laser, where molecules that do not normally exist come into being when xenon, argon or krypton gases are excited. This formed the cornerstone for LASIK eye surgery. Dr. Bhaumik announced his discovery in May of 1973 at a meeting of the Denver Optical Society of America in Denver, Colorado. He would later patent it.
The introduction of Laser in this refractive procedure started with the developments in Laser technology by Rangaswamy Srinivasan. In 1980, 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). Dr. Stephen Trokel published a paper in the American Journal of Ophthalmology in 1983, outlining the potential of using the excimer laser in refractive surgeries.

The first patent for LASIK was granted by the US Patent Office to Gholam A. Peyman, MD on June 20, 1989, US Patent #4,840,175, "METHOD FOR MODIFYING CORNEAL CURVATURE", describing the surgical procedure in which a flap is cut in the cornea and pulled back to expose the corneal bed. This exposed surface is then ablated to the desired shape with an excimer laser, following which the flap is replaced.

Using these advances in laser technology and the technical and theoretical developments in refractive surgery made since the 50's, 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 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
There are several necessary preparations in the preoperative period. The operation itself is made by creating a thin flap on the eye, folding it to enable remodeling of the tissue underneath with laser. The flap is repositioned and the eye is left to heal in the postoperative period.

Preoperative

Patients wearing soft contact lenses are usually instructed to stop wearing them approximately 5 to 7 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 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 is given a mild sedative (such as Valium) 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.


Flap creation

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.


Laser remodeling

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. 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 technique photorefractive keratectomy (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. Typical pulses are around 1 mJ of pulse energy in 10 to 20 nanoseconds.


Reposition of flap

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 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 have 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 post-surgical complications.

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