Class III vs. Class IV Lasers

What the classifications actually mean?
Class IIIb:  IIIb lasers are hazardous to the eye when viewed directly.  For visible and infrared
devices emission power is limited to 0.5 W. Protective eyewear, key switch and safety interlock
are required safety features.
Class IV:  Class IV includes all lasers that emit power in excess of IIIB limitations. Eye protection
is needed to limit both direct and diffuse reflected exposure. Key switch and safety interlock are
also required safety features. The majority of scientific, industrial, military, and medical lasers fall
into this category.
Power:  Class IIIb lasers are limited to powers of 0.5 watts and under, Class IV therapy lasers
typically enable the user to select powers of 0.5 W – 15 W.  Increased power enables the
clinician to treat a larger area in a shorter period of time – ultimately resulting in a therapeutic
dose of joules to the target tissue.