Lasik (Laser-Assisted in Situ Keratomileusis), commonly referred to as laser eye surgery, is a type of refractive surgery for the correction of myopia, hyperopia, and astigmatism. The LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye's cornea in order to improve visual acuity. For most (99%) patients, LASIK provides a permanent alternative to eyeglasses or contact lenses.

Preoperative procedures

Contact lenses Patients wearing soft contact lenses are instructed to stop wearing them 5 to 21 days before surgery. Patients wearing hard contact lenses should stop wearing them for a minimum of six weeks.

Pre-operative examination and education In the USA, the FDA has approved LASIK for age 18 and over. More importantly the patient's eye prescription should be stable for at least 6 months prior to surgery. The patient may be examined with pupillary dilation and education given prior to the procedure. Before the surgery, the patient's corneas are examined with a pachymeter to determine their thickness, and with a topographer, or corneal topography machine, to measure their surface contour.

Operative procedure

Flap creation A soft 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 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, A hinge is left at one end of this flap. The flap is folded back, revealing the stroma, the middle section of the cornea.

Laser remodelling The second step of the procedure uses an excimer laser (193 nm) to remodel the corneal stroma.

Repositioning of the 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 care Patients are usually given a course of antibiotic and anti-inflammatory eye drops. These are continued in the weeks following surgery. Patients are told to rest and are given dark eyeglasses to protect their eyes from bright lights and occasionally 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.

Customised LASIK Customised LASIK is a variation of LASIK surgery in which, rather than applying a simple correction of focusing power to the cornea (as in traditional LASIK), 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, though the final result still depends on the physician's success at predicting changes that occur during healing and other factors that may have to do with the regularity/irregularity of the cornea and the axis of any residual astigmatism.

Patient satisfaction Surveys of LASIK find rates of patient satisfaction between 92 and 98 percent. In March 2008, The American Society of Cataract and Refractive Surgery published a patient satisfaction meta-analysis of over 3,000 peer-reviewed articles from international clinical journals. Data from the prior 10 years revealed a 95.4 percent patient satisfaction rate among LASIK patients.