Advances in LASIK Excimer Laser Technology
Reviewed by Jason Jacobs, M.D.
Advances in Excimer Lasers for LASIK Eye Surgery have brought continued improvements in the safety, efficacy and predictability of LASIK to patients. Since the initial Food and Drug Administration (FDA) approval of the use of the Excimer Laser for Laser Vision Correction in October of 1995 there have been many advances in Laser Eye Surgery, especially in LASIK. The first Excimer Lasers used to perform LASIK surgery utilized what has been called "broad beam" technology. That is that they delivered the laser energy to reshape the Cornea in a wide coherent beam of light-often 6.0-7.5 mm in diameter-in an attempt to achieve the entire optical correction within the diameter of the beam width. Delivering the 193 nm high-energy ultraviolet laser beam with such a broad "spot" size, and doing it consistently, requires a great deal of technological hardware and software. Moreover, delivering the high-energy beam through a complex set of optical mirrors and lenses causes significant degradation of these lenses and mirrors. Broad beam Excimer Lasers were commonly known to "eat their own optics". This created a constant service and calibration burden, which was both costly, and a nuisance. Beginning in 1998 the FDA began approving a series of Excimer Lasers for LASIK that utilized "small beam scanning tracking" delivery systems. These LASIK lasers typically delivered the laser energy using a tiny "spot" of light-often 1.0 mm or even less in diameter-projected in a calculated pattern across the cornea to achieve the desired curvature change and thus correction of nearsightedness, farsightedness or astigmatism. In order to use this "scanning" delivery method it required coupling it with a "tracking" system so that the laser software could both determine the position of the eye and then deliver the necessary energy to the correct location on the eye. By using sophisticated hardware and software of "scanning and tracking" Excimer Laser Systems for Laser Vision Correction, patients undergoing LASIK have had the benefit of being able to rely o the technology to deliver the exact amount of laser energy necessary to exactly the correct place on their eye to achieve the best optical correction. LASIK surgeons have had the benefit of creating much less "wear and tear" on the optics of their lasers as well as a technology based system to assist and relax patients during their LASIK surgery as the laser itself was responsible for accurately finding the right location to place the energy spots, rather than relying solely on the patient "holding still" during their treatment.
Another significant advance in LASIK laser technology has been the use of very high-speed ultra fast laser energy delivery systems. In the early 1990's it was fairly typical for the laser portion of the LASIK procedure to require 30-90 seconds of energy delivery, depending on the degree of prescription to be corrected. While this seems like a relatively short time, keep in mind that LASIK is a "lamellar" procedure and is performed between the layers of the cornea. The longer the internal layers of the cornea are exposed to the ambient environment, the greater the chance of variability in the results-so shorter laser times tend to produce more predictable results. Today, LASIK can be performed with treatment times for the application of the laser energy of 2-30 seconds by using some of the more advanced laser systems. These advanced LASIK Excimer Laser systems are capable of tracking the eye 400 times per second and delivering 200-400 laser pulses per second. This ultra fast scanning tracking provides greater predictability and makes the LASIK procedure quicker and more comfortable for the patient.