What defines Class IV lasers?

Class IV lasers are defined by their power output, which is greater than 500 mW. This classification indicates that these lasers can pose significant hazards to both skin and eyes due to their high energy output. At this power level, the potential for causing serious burns or permanent eye damage is substantial, and proper safety precautions are essential when using such devices.

In contrast, other classifications like Class I or Class II would have much lower power outputs and are generally considered safe under normal operating conditions. For example, lasers with outputs up to 1 mW belong to lower classes where no significant risks are typically associated. The option referring to power output between 5-500 mW would categorize the laser as Class III, which has different safety considerations compared to Class IV. Therefore, the defining characteristic for Class IV lasers is their high power output, confirming the answer choice focuses on the crucial aspects of laser safety and classification.