A measure of how vulnerable the human eye is to damage from a particular Laser source.
This vulnerability is affected by output power and Wavelength of laser lights.
Communication lasers are available in these wavelengths: 780nm, 850nm, 980nm, 1310nm and 1550nm. The eye is sensitive to shorter wavelengths. Wavelengths above 850nm are invisible to the eye, but can still cause damage.
Class I laser devices are the safest, while Class III are the least safe.
Eye safety requirements in the U.S. are specified by CDRH (21 CFR 1040.10 & 1040.11).