The rate at which energy (joules per second) is emitted, transferred or absorbed with its measurements described by the unit measurement of watts (W).

Any motion(s) including: eyelid closure, eye movement, pupillary constriction, head movement to avoid exposure to noxious or bright visual light stimulants. In application to visible laser light, its exposure to critical retinal area(s) is established as 0.25 seconds or less.