The three surgical procedures most often used to improve eyesight are:
• PRK (photorefractive keratectomy). Laser energy is used to reshape the cornea. High-energy ultraviolet electrons vaporise corneal tissue. A central, flattened, anterior corneal surface is created, reducing the refractive, or light-bending, power of the cornea to reduce dependence on optical eyewear.
• LASIK (laser in situ keratomileusis). Uses the same kind of laser as in PRK, but first a hinged corneal flap is cut with a sharp corneal blade. The flap is then rolled back out of the way and the laser is applied to the deeper corneal tissues that are exposed. The flap is then laid back down over the laser treatment site. A central flattening still occurs, but now it is beneath a superficial corneal flap.
• RK (radial keratotomy). Well-known since the 1970s, RK was the first such procedure to become prominent in the West. Four to 16 radial incisions are made extending through 90% of the corneal thickness and run from the edge of the optical zone to the corneal periphery to induce flattening of the corneal surface.
Source: Flight International
