Which adjustment is associated with improved epidermal cooling?

• A. Increase spot size
• B. Increase energy
• C. Increase repetition rate
• D. Increase wavelength

Answer: (A)

Spot size sets the area over which laser energy is delivered. When you increase the spot size while keeping the pulse energy the same, the fluence (energy per unit area) decreases. This lower surface fluence reduces instantaneous heat in the epidermis, making the cooling system’s job easier and more effective at protecting the skin. In practice, a larger spot size also allows the cooling mechanism (like cryogen spray or contact cooling) to cover a bigger area more uniformly, enhancing epidermal protection.

Higher energy would raise surface heat, making cooling harder; a faster repetition rate shortens the cooldown window between pulses, which can reduce cooling efficacy; wavelength changes affect how deeply or how strongly the light is absorbed but don’t directly improve epidermal cooling.