Monday, April 27, 2009

Laser Lasik Vision Correction Eye Surgery

 Laser lasik vision correction  involves creating a corneal flap so that midstromal tissue can be ablated directly and reshaped with an excimer laser beam. The procedure allows the ophthalmologist to surgically reshape the cornea in an attempt to obviate the need for corrective lenses. LASIK is a modification of Colombian José Barraquer’s ingenious innovations. In 1949, Barraquer first described his technique, and in 1964 he published clinical results of his attempts to achieve emmetropia by shaving and reshaping the cornea. With Barraquer’s technique of keratomileusis (i.e., carving the cornea), a lamellar button (lenticule) of the patient’s cornea was excised with a manual microkeratome.

Barraquer then reshaped the lenticule so that the central corneal curvature was flattened and the refractive power of the cornea decreased. He then replaced the lenticule in position, either with or without sutures. Barraquer’s specific attempts to correct myopia were called cryolathe keratomileusis, because they involved freezing and reshaping the removed lenticule with a cryolathe. Troutman and Swinger introduced cryolathe keratomileusis to the United States in 1977. While keratomileusis produced good results when performed by experienced surgeons, the procedure was technically very difficult and the results were therefore variable. Innovations to this procedure, however, eventually led to the creation of the more highly refined procedure of LASIK. The introduction of the “excited dimer” (excimer) 193 nm UV laser allowed for the development of LASIK. The argon–fluoride excimer laser is capable of precise ablation of corneal tissue with minimal disruption of adjacent tissue. The excimer laser’s effect on the cornea was first studied in animal models in 1983 . In 1989, Peyman first used a laser to remove corneal stroma from a lamellar bed in animals. Shortly thereafter, similar attempts were made in human eyes . This early work supported the theory that in situ keratomileusis was better than surface ablation because it induced less activation and proliferation of stromal keratocytes, thereby avoiding both haze and regression. In addition, the excimer laser allowed for more accurate tissue removal, thereby eliminating one of the main deterrents to lamellar surgery.
The LASIK procedure, in its current refined state, involves increasing the eye’s intraocular pressure to at least 65 mmHg with a suction device, and then using a microkeratome to create a corneal flap that is at least 6 mm in diameter and 150 microns thick. This flap, which allows the Bowman’s-layer epithelial complex to remain intact, is then carefully lifted to expose the layers of the cornea that will be reshaped by the excimer laser. The size of the optical zone and the depth and profile of the laser ablation will determine the correction achieved .