Which form of tissue damage by lasers can disrupt cell chemistry and may damage DNA?

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

Answer: (A)

Photochemical effects are the way lasers can directly alter the chemistry inside cells. When photons interact with biological molecules, they can initiate chemical reactions or generate reactive oxygen species that attack DNA and other macromolecules. This means the energy from light actually changes chemical bonds and cellular components, potentially causing DNA damage such as base modifications or strand breaks.

In contrast, thermal damage comes from heating tissue and causing protein coagulation or burns, which disrupts function mainly through heat rather than direct chemical alteration. Photomechanical damage results from rapid energy deposition creating pressure waves that mechanically disrupt tissue. Radiation-induced damage refers to ionizing radiation effects, which are not typical of most non-ionizing lasers used clinically.

So, the form of tissue damage most associated with disrupting cell chemistry and potentially damaging DNA is photochemical.