How does the blink reflex protect against Class 2 lasers?

The blink reflex is an involuntary eye reaction to bright light: the eyelid closes automatically within about 0.25 seconds. With Class 2 lasers (up to 1 mW in the visible range) this time is shorter than the maximum permissible exposure (MPE) for a damage threshold. In practice this means an accidental glance into the beam of a Class 2 laser is harmless because the eyelid blocks the beam in time. Important limitation: the reflex only works for visible light (400–700 nm) and not for prolonged deliberate staring. For UV or IR radiation no blink reflex exists – different protection rules apply.