Selective Absorption and Control of Thermal Effects: A Comparison of the Laser Systems Used in Otology and Neurotology

Abstract

The surgical lasers available for use by the otologist and neurosurgeon include the CO₂, argon, and neodymium:yittrium-aluminum-garnet (Nd:YAG). Selection of a laser should be based on the principles of power density, radiant exposure, and selective absorption, with a particular application in mind. The history of and relevant literature on lasers in otology are reviewed, and basic research findings are presented. Our conclusions are that (1) lasers are viable for many neurotologic applications; (2) the effect of the CO₂ laser is purely thermal at the tissue surface; (3) the argon and Nd:YAG lasers, both pigment-dependent, may penetrate tissues to variable levels before absorption and conversion to thermal energy; (4) the CO₂ laser can achieve much higher power densities than the argon or Nd:YAG lasers; (5) since there is a discrepancy between focused spot size and actual lesion size, with the argon effect being approximately 5× and the CO₂ effect about 2×, the resulting lesions are essentially equal in size; and (6) no laser is best for all neurotologic procedures and should be evaluated based on the laser's basic physical principles to exploit the advantages and minimize the disadvantages.