In 1967, Kelman 7a introduced ultrasonic phacoemulsification for cataract removal. His goal was to find a safer and more efficient way of removing the lens. To date, Dr. Kelman and many others have made significant improvements in technology and technique. Modern cataract extraction by way of phacoemulsification can be accomplished quickly under topical anesthesia, through a 3-mm corneal incision. Today, more than 85% of ophthalmic surgeons in the United States perform ultrasonic phacoemulsification. Despite the high level of technologic achievement, however, modern ultrasonic phacoemulsification is not a perfect procedure, with recognized drawbacks. Phacoemulsification is difficult to learn and can be associated with high complication rates among beginning surgeons. 18 Capsule rupture has been reported to occur in 5% to nearly 20% of early cases with beginning surgeons. In addition, the ergonomics of the ultrasonic handpiece are not ideal. Compared with a common pencil or ink pen, the phacoemulsification handpiece is somewhat bulky and awkward to use, particularly when operating from a temporal approach where the surgeon's hand support is less than optimal. Furthermore, minimization of the size of the ultrasonic phaco handpiece is limited by the piezoelectric motor, which drives the tip at ultrasonic frequency. Phacoemulsification also delivers a great deal of extraneous ultrasonic energy into the eye. This may be as much as 40 W of energy at 100% power, equivalent to placing a 40-W lightbulb into the eye. 2 Much of this energy is converted to heat, and there is great potential for damage at the corneal entrance wound, and to the corneal endothelium, iris, and posterior capsule. In ultrasonic phacoemulsification, the buildup of heat within the eye is limited by the constant flow of irrigating fluid. Current surgical trends that use smaller and tighter entrance are designed to minimize the leakage of fluid out of the eye. This minimizes the volume of fluid used and stabilizes the anterior chamber during surgery. The risk of these tight wounds is that inadvertent occlusion of the aspirating tip stops all fluid flow into the eye, and the temperature can rise quickly. The cornea may be burned within a matter of seconds. Despite the ease in which a skilled surgeon appears to use the ultrasonic phaco, these factors make ultrasonic phacoemulsification difficult to learn for residents beginning cataract surgery or ophthalmologists in transition to small incision surgery. Interest in laser cataract surgery stemmed from a desire to find a more precise and safer method of lens removal, where the handpiece could be brought closer to the capsule without rupturing it. The goal was to find a laser that efficiently and precisely disrupted the lens and a laser whose wavelength could be delivered by way of an optical fiber. A laser fiberoptic handpiece void of moving parts would be smaller and more ergonomically favorable than the current ultrasonic handpieces. Along with the potential for greater precision and safety, this too could improve on the ultrasonic phacoemulsifier.
Read full abstract