Potential retinal hazards of visible-light photopolymerization units

We evaluated the potential for retinal damage, both thermal and photochemical, from commercially available visible-light photopolymerization units. The spectral radiance profiles of 11 visible-light photopolymerization units were measured by means of a spectroradiometer and the results weighted according to the American Conference of Governmental Industrial Hygienists (ACGIH) Blue Light Hazard Function and Thermal Hazard Function. The values were then integrated by means of the proposed ACGIH hazard formulae, so that we could determine the maximum permissible exposure (tMAX) duration for each light. This calculation assumed a worst-case condition of direct vision of the light source from a distance of 25 cm. The results indicate that there is no thermal hazard to the retina. The tMAX duration values for the photochemical (blue light) hazard to the retina ranged from 2.4 minutes per day (for the most hazardous unit) to 16.0 minutes per day (for the least hazardous). None of these hazard times is short enough to be of concern unless the individual operator elects to focus on the light source or the reflected output from these visible-light photopolymerization units for an extended period of time.