The surgeon then uses a specially designed instrument to separate and remove the lenticule through the incision, leaving the anterior lamellae of the cornea intact. No excimer laser is used in the "ReLEx-procedures". Surface procedures
The excimer laser is used to ablate the most anterior portion of the corneal stroma. These procedures do not require a partial thickness cut into the stroma. Surface ablation methods differ only in the way the epithelial layer is handled. Photorefractive keratectomy (PRK) is an outpatient procedure generally performed with local anesthetic eye drops (as with LASIK/LASEK). It is a type of refractive surgery which reshapes the cornea by removing microscopic amounts of tissue from the corneal stroma, using a computer-controlled beam of light (excimer laser). The difference from LASIK is that the top layer of the epithelium is removed (and a bandage contact lens is used), so no flap is created. Recovery time is longer with PRK than with LASIK, though the outcome (after 3 months) is about the same (very good). More recently, customized ablation has been performed with LASIK, LASEK, and PRK. Transepithelial photorefractive keratectomy (TransPRK) is a laser-assisted eye surgery to correct refraction errors of human eye cornea. It employs excimer laser to ablate outer layer of cornea, epithelium, as well its connective tissue, stroma, to correct eye optical power.
It involves cutting a flap in the cornea and pulling it back to expose the corneal bed, then using an excimer laser to ablate the exposed surface to the desired shape, and then replacing the flap. The name LASIK was coined in 1991 by University of Crete and the Vardinoyannion Eye. 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. In 1991, J.T. Lin, Ph.D. (a Chinese Physicist) was granted a US patent for a new technology using a flying-spot for customized LASIK currently used worldwide. The first US patent using an eye-tracking device to prevent decentration in LASIK procedures was granted to another Chinese Physicist, Dr. S. Lai in 1993. Techniques
Flap procedures
Excimer laser ablation is done under a partial-thickness lamellar corneal flap. Automated lamellar keratoplasty (ALK): The surgeon uses an instrument called a microkeratome to cut a thin flap of the corneal tissue. The flap is lifted like a hinged door, targeted tissue is removed from the corneal stroma, again with the microkeratome, and then the flap is replaced. Laser-assisted in situ Keratomileusis (LASIK): The surgeon uses either a microkeratome or a femtosecond laser to cut a flap of the corneal tissue (usually with a thickness of 100–180 micrometres).