Which form of tissue damage by lasers causes tearing of tissue?

• A. Thermal
• B. Photochemical
• C. Photomechanical
• D. Laser ionization

Answer: (C)

Tearing tissue from a laser exposure is best explained by photomechanical effects. When a laser delivers energy very rapidly, the tissue experiences a swift rise in pressure and rapid expansion, generating mechanical stress such as shock waves and cavitation. These mechanical forces can physically rupture and tear tissue fibers, producing tearing rather than just heating or chemical changes.

Thermal effects, by contrast, mainly cause heating that leads to coagulation, vaporization, or carbonization over time. Photochemical effects involve chemical bond changes driven by photons but don’t necessarily produce the abrupt mechanical rupture that tears tissue. Laser ionization creates plasma and ablation, removing tissue through vaporization rather than tearing due to mechanical disruption.