LASIK

= LASIK =


 * Description: ** LASIK stands for Laser-Assisted In Situ Keratomileusis, and is a surgery used to correct vision and reduce a patient's dependence on glasses or contacts. LASIK is a type of refractive surgery, similar to Radial Keratotomy (RK) and Photorefractive Keratectomy (PRK), involving reshaping the cornea to improve vision. The cornea is the transparent dome-shaped tissue at the front of the eye. The desired result of LASIK eye surgery is to bend (refract) light rays so they focus more precisely on the retina, rather than at some beyond or in front. The main difference between LASIK and the other options is the creation of a corneal flap with the LASIK procedure. LASIK typically has the least risk and shortest recovery time of the refractive surgeries, but some patients are better candidates for the alternatives.


 * Applications: **LASIK is an out-patient surgery is performed by an eye surgeon. This procedure can correct nearsightedness ("Myopia"), farsightedness ("Hyperopia"), or an astigmatism. A person who is nearsighted has a corneal lens which is too long, while someone who is farsighted has a cornea shape that is too flat. Astigmatism means a patient's cornea curves or flattens unevenly. These differing cornea shapes result in the eye focusing on a point which is in front of or behind the retina. LASIK corrects this by cutting a pattern into the cornea tissue and changing its shape which corrects the focal point of the retina and thus alters the patient's vision. A patient may be recommended by their eye doctor, but typically they will elect to receive this type of surgery in order to see without contacts or glasses.


 * Procedure: ** Typically, LASIK is a two-step process. Surgeons may use a microkeratome blade or a kerotome laser to cut a flap in the patient's cornea. Underneath the flap, they use an excimer laser to remove a section of the cornea tissue determined previously as the right size to reshape the cornea which will alter a patient's vision. The size of the cornea that is removed is determined beforehand using a pattern for the individual patient based on his needs for the LASIK. After the tissue has been cut to its appropriate size, the corneal flap that was created is then re-smoothed to the main part of the cornea and it heals back into one.


 * Results: ** Most patients respond positively to the results of LASIK. However, LASIK does not always result in 20/20 vision. In a 2003 study in the medical journal Ophthalmology, nearly 18 percent of treated patients and 12 percent of treated eyes needed retreatment. After the surgery, eyes will be dried out, and prescribed eye drops will be needed to keeps the eyes moist and prevent infections. Healing of the eyes occurs very quickly, and visions is usually only blurry for a day or two. The patient will have a follow-up with the eye doctor within a few days and may need to schedule regular checkups within the first six months.

**Risks:** As with any surgery, there are several risks to consider before undergoing LASIK eye surgery. These include:
 * **Undercorrections.** Undercorrections are most common for people with nearsightedness and occur when the laser does not remove enough tissue. Another surgery may be needed to better correct the patient's vision.
 * **Overcorrections.** Removing too much tissue from the eye results in overcorrections. These are much more difficult to correct.
 * **Astigmatism.** Astigmatisms can be created by uneven tissue removal and may require additional surgery.
 * **Glare, halos and double vision.** These problems typically arise after surgery when trying to see at night. Sometimes they can be treated with eye drops, but another surgery may be required.
 * **Dry eyes.** Dry eyes are common after the surgery and can inhibit vision. In severe cases, another surgery can be done to prevent tears from draining away from the surface of the eye.
 * **Flap problems.** Since a flap is created in the eye during surgery, complications may include: infections, excessive tears and swelling. Another problem is the outermost corneal tissue layer (epithelium) could grow abnormally during the healing process.

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 * Web Resources: **
 * Related Terminology: **
 * Cornea
 * Myopia
 * Hyperopia
 * Astigmatism


 * Citations/References: **
 * http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/SurgeryandLifeSupport/LASIK/ucm061366.htm
 * http://www.mayoclinic.com/health/lasik-eye-surgery/MY00376
 * http://www.webmd.com/eye-health/lasik-laser-eye-surgery?page=2
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 * Graphics: **

1. Anatomy of the eye.

2. This is an image depicting the different steps involved in a LASIK procedure.