Pressley Robert J. Handbook of Lasers (with selected data on optical technology)

Cleveland: The Chemical Rubber Company, 1971. — 631 p.Ocular hazards in the vicinity of laser devices include not only the laser itself, but the optical pumps used for excitation, the off-axis spontaneous radiation from gas discharge tubes, and occasionally the blackbody radiation of absorbers used to stop extremely intense beams. Geometrical considerations make the latter two cases a lesser hazard, but obviously do not remove them from inclusion in a safety protocol. Ultraviolet devices of all types must be carefully controlled, as exposure of the cornea to even relatively low levels of irradiation at wavelengths less than 320 nm produces " sunburn " of the cornea, called " photophthalmia." Because a source in this region is not visible, has a cumulative effect, and the extremely dehabilitating " blepharospasm," or " sand in the eye " reaction to the corneal epithelium sloughing off and exposing the nerve tissue does not occur until 30 minutes to 24 hours following exposure (usually in the evening or night after exposure), any source which has a significant ultraviolet component must be used with caution. Figures 1-1 and 1-2, from the work of Pitts and his associates, 1 ' 2 indicate the sensitivity of rabbits and primates to the ultraviolet. The middle infrared (10.6 /i) portion of the spectrum also affects the corneal epithelium as the primary damage site. In this spectral region the damage mechanism is of thermal origin, not abiotic as in the case of the ultraviolet. Thus, the damage mechanism is a function of the time-temperature history within a single exposure interval.