Which type of classification indicates a laser presents a significant hazard to eye safety?

The classification indicating that a laser presents a significant hazard to eye safety is Class 4. Class 4 lasers are powerful and can cause serious eye injuries from direct exposure or even from reflected beams. These lasers can also pose fire hazards and can cause skin injuries. Such lasers are typically used in industrial applications, research, and some medical procedures, where safety protocols need to be strictly followed to protect personnel and bystanders from the potential hazards they present.

In contrast, lower classifications such as Class 1 and Class 2 represent less hazardous conditions; Class 1 is considered safe under all conditions of normal use, while Class 2 can cause eye injury only under prolonged exposure to the beam, typically requiring protection against direct viewing. Class 3 lasers are less hazardous than Class 4 but can still present a risk to eye safety with limited exposure or specific circumstances. Hence, Class 4 stands out as the classification denoting a significant risk to eye safety.