LASIK :laser-assisted in situ keratomileusis

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, 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 people, LASIK provides a long-lasting alternative to eyeglasses or contact lenses.

LASIK is most similar to another surgical corrective procedure, photorefractive keratectomy (PRK), and both represent advances over radial keratotomy in the surgical treatment of refractive errors of vision. For patients with moderate to high myopia or thin corneas which cannot be treated with LASIK and PRK, the phakic intraocular lens is an alternative.[3][4] As of 2011, over 11 million LASIK procedures had been performed in the United States and as of 2009 over 28 million have been performed worldwide.

Effectiveness

"current evidence suggests that photorefractive (laser) surgery for the correction of refractive errors is safe and efficacious for use in appropriately selected patients. Clinicians undertaking photorefractive (laser) surgery for the correction of refractive errors should ensure that patients understand the benefits and potential risks of the procedure. Risks include failure to achieve the expected improvement in unaided vision, development of new visual disturbances, corneal infection and flap complications. These risks should be weighed against those of wearing spectacles or contact lenses."[7] The FDA reports "The safety and effectiveness of refractive procedures has not been determined in patients with some diseases.

Risks

Higher-order aberrations

Higher-order aberrations are visual problems that require special testing for diagnosis and are not corrected with normal spectacles (eyeglasses). These aberrations include 'starbursts', 'ghosting', 'halos' and others Some patients describe these symptoms post-operatively and associate them with the LASIK technique including the formation of the flap and the tissue ablationThey can be measured in micrometers (µm) whereas the smallest laser beam size approved by the FDA is about 1000 times larger, at 0.65 mm. In situ keratomileusis effected at a later age increases the incidence of corneal higher-order wavefront aberrations.

Dry eyes

Some people experience dry eyes following surgery Although it is usually temporary it can develop into dry eye syndrome.Underlying conditions with dry eye such as Sjögren's syndrome are considered contraindications to Lasik

Dry eye syndrome

Dry eye syndrome (DES), also known as keratoconjunctivitis sicca (KCS), is the condition of having dry eyes.Other associated symptoms include irritation, redness, discharge, and easily fatigued eyes. Blurred vision may also occur. The symptoms can range from mild and occasional to severe and continuous.Scarring of the cornea may occur in some cases without treatment.

There is no way to prevent keratoconjunctivitis sicca. Complications can be prevented by use of wetting and lubricating drops and ointments

Patent

A number of patents have been issued for several techniques related to LASIK. Stuart I. Brown and Josef F. Bille filed a patent on surgical lasers in 1988 Samuel E. Blum, Rangaswamy Srinivasan and James Wynne filed a patent application on the ultraviolet excimer laser, in 1982, issued in 1988 In 1989, Gholam A. Peyman was granted a US patent for using an excimer laser to modify corneal curvature. It was,"A method and apparatus for modifying the curvature of a live cornea via use of an excimer laser. The live cornea has a thin layer removed therefrom, leaving an exposed internal surface thereon. Then, either the surface or thin layer is exposed to the laser beam along a predetermined pattern to ablate desired portions. The thin layer is then replaced onto the surface. Ablating a central area of the surface or thin layer makes the cornea less curved, while ablating an annular area spaced from the center of the surface or layer makes the cornea more curved. The desired predetermined pattern is formed by use of a variable diaphragm, a rotating orifice of variable size, a movable mirror or a movable fiber optic cable through which the laser beam is directed towards the exposed internal surface or removed thin layer." The patents related to so-called broad-beam LASIK and PRK technologies were granted to US companies including Visx and Summit during 1990-1995 based on the fundamental US patent issued to IBM (1983) which claimed the use of UV laser for the ablation of organic tissues.