Flexible and rigid viewing scopes have changed medicine in ways many Americans have encountered. The repair of a torn meniscus in the knee is usually performed using a rigid arthroscope, through which a number of surgical tools are passed. This technique has changed knee surgery from an inpatient procedure to an outpatient one with reduced pain and convalescence. The colonoscope is used routinely to examine patients for possible colon cancer. The resulting early detection of colon cancer is often life-saving. Many gynecological procedures have become less invasive through the use of a laparoscope, which passes through the abdomen to allow access to the uterus. Laparoscopic techniques also enable numerous other procedures, such as gall bladder removal, which is discussed later in the section on minimally invasive therapy.

Medical applications spread from ophthalmology into the general area of surgery, with these applications generally developing around the most readily available lasers. It is important to note that lasers can emit either short pulses of light (pulsed lasers) or a beam of light that is always on (continuous-wave, or cw, lasers) because the effects of pulsed and cw laser light can be quite different. These were primarily the pulsed ruby laser; the cw argon ion and carbon dioxide (CO2) lasers; the Nd:YAG (neodymium-doped yttrium-aluminum-garnet) laser, primarily in the cw mode; and the cw dye laser. The ability of the cw CO2 and Nd:YAG lasers to cut tissue while producing coagulation led to their use as general surgical lasers. Many companies entered the medical laser marketplace, often without a strong scientific understanding of the effects of lasers on tissue. In addition, the role of the Food and Drug Administration (FDA) in the regulation of new laser devices was not as well established as it is today, allowing the introduction of medical laser systems with unproven efficacy.

Since the early 1980s a number of changes in the nature of medical laser research have occurred. There was an increasing interest in the mechanisms of laser-tissue interactions, and new clinical applications based on these interactions came into use. One of the driving forces behind this change was the initiation of the Medical Free Electron Laser (FEL) Program by the Department of Defense (DOD) in 1985. Although the program was specifically aimed at developing FEL applications, the novel pulse structure of the FEL led to an increased interest in pulsed laser effects, which in turn led to an increased understanding of laser-tissue interactions based on conventional lasers.

Today, the use of optics in surgery and medicine is large and growing. For example, worldwide sales of medical laser systems reached $890 million in 1994, $1,070 million in 1995, and $1,295 million in 1996 (estimated), and they were forecast to reach $1,460 million in 1997

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