Which form of laser-tissue damage is caused by rapid energy deposition leading to mechanical disruption?

• A. Thermal
• B. Photochemical
• C. Photomechanical
• D. Radiation-induced

Answer: (C)

Photomechanical damage is caused when energy is deposited into tissue so rapidly that there isn’t time for heat to diffuse, producing mechanical disruption. Short laser pulses create a rapid thermoelastic expansion and generate pressure waves and cavitation bubbles, effectively tearing tissue apart rather than just heating it. This stands in contrast to thermal damage, which comes from heat diffusion and coagulation of proteins; photochemical damage arises from photons inducing chemical changes; and radiation-induced damage involves ionizing radiation effects, not the rapid mechanical effects from ultrafast laser pulses.