Although most lasers are in scientific research laboratories, a growing number are finding their way into field use in the military, and their associated ocular hazards have been of concern. Laser hazards are easier to define and control in the laboratory than in the field. This results from uncertainties introduced by atmospheric effects upon the laser beam and the potential observer's use of optical instruments. These physical uncertainties, coupled with the absence of clear-cut ocular injury threshold data, make exact determinations of hazardous range quite difficult. Therefore, laser range hazard control is generally achieved by the use of backstops and in some instances by the use of protective eyewear.