Review of exposure limits and experimental data for corneal and lenticular damage from short pulsed UV and IR laser radiation

Laser exposure limits as promulgated by the International Commission on Non-Ionizing Radiation Protection are compared to relevant experimental animal injury data for cornea and lens exposure in the nanosecond to microsecond pulse duration regime in both the ultraviolet (UV) and infrared spectral ranges. In the UV spectral range, thermal and photochemical damage mechanisms compete and thresholds must be carefully distinguished as a function of wavelength and pulse duration. The thermal UV damage data are compared with levels inferred from CO2 radiation thresholds and it is shown that the reduction factors between experimental data for thermal injury and the corresponding exposure limits appear to be unnecessarily high. The lack of data for nanosecond exposures for wavelengths below 355 nm is identified. Available experimental data for infrared radiation (1.4–4 μm) can be fitted well with an inverse-absorption curve for saline. The exposure limits roughly follow the absorption curve with a varying degree of safety scaling factor. A lack of experimental threshold data is identified for wavelengths around the 3 μm absorption peak for water absorption. The inverse curve for the spectral absorption of water would suggest a rather low threshold for a biological effect at 3 μm.