LASIK

LASIK or Lasik (/ˈleɪsɪk/; "laser-assisted in situ keratomileusis"), commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hypermetropia, and astigmatism. LASIK surgery is performed by an ophthalmologist who uses a femtosecond laser or a microkeratome to create a corneal flap to expose the corneal stroma and then an excimer laser to reshape the corneal stroma in order to improve visual acuity.

LASIK is very similar to another surgical corrective procedure, photorefractive keratectomy (PRK), and LASEK. All represent advances over radial keratotomy in the surgical treatment of refractive errors of vision. For people with moderate to high myopia or thin corneas which cannot be treated with LASIK or PRK, the phakic intraocular lens is an alternative.

As of 2018, roughly 9.5 million Americans have had LASIK and, globally, between 1991 and 2016, more than 40 million procedures were performed. However, the procedure seemed to be a declining option as of 2015.

In March 2009, the FDA officially recognized the new LASIK standard from The American National Standards Institute (ANSI), entitled "Laser Systems for Corneal Reshaping".

A detailed pre-operative screening will assess corneal thickness, shape, and refractive error, ensuring the patient is a suitable candidate. During the surgery, a surgeon uses a femtosecond laser or a microkeratome blade to create a thin corneal flap, which is then carefully folded back to expose the underlying tissue. An excimer laser precisely reshapes the stromal layer of the cornea, removing microscopic amounts of tissue to correct refractive errors. This step is guided by a pre-determined surgical plan tailored to the patient's specific visual needs. After the cornea is reshaped, the flap is repositioned, serving as a natural bandage that adheres without the need for stitches. The entire procedure typically takes 10–15 minutes per eye and offers minimal discomfort and rapid recovery, allowing most patients to return to normal activities within a day or two.^{[citation needed]}

In the United States, the US Food and Drug Administration (FDA) has approved LASIK for people 18 years of age and older, but the American Academy of Ophthalmology recommends people wait until age 21 because vision needs to stabilize. More importantly the patient's eye prescription should be stable for at least one year 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. Using low-power lasers, a topographer creates a topographic map of the cornea. The procedure is contraindicated if the topographer finds difficulties such as keratoconus. The preparatory process also detects astigmatism and other irregularities in the shape of the cornea. Using this information, the surgeon calculates the amount and the location of corneal tissue to be removed. The patient is prescribed and self-administers an antibiotic beforehand to minimize the risk of infection after the procedure and is sometimes offered a short acting oral sedative medication as a pre-medication. Prior to the procedure, anaesthetic eye drops are instilled. Factors that may rule out LASIK for some patients include large pupils, thin corneas and extremely dry eyes.

LASIK permanently changes the shape of the cornea, the clear covering of the front of the eye, using an excimer laser. A mechanical microkeratome (a blade device) or a laser keratome (femtosecond laser) is used to cut a flap in the cornea. A hinge is left at one end of this flap. The flap is folded back revealing the corneal stroma, the middle section of the cornea. Pulses from a computer-controlled laser (excimer laser) vaporize a portion of the stroma and the flap is replaced.

Performing the laser ablation in the deeper corneal stroma provides for more rapid visual recovery and less pain than the earlier technique, photorefractive keratectomy (PRK).