The potential 'blue light hazard' from LED headlamps

Many dental personnel use light-emitting diode (LED) headlamps for hours every day. The potential retinal 'blue light hazard' from these white light headlamps is unknown. Methods: The spectral radiant powers received from direct and indirect viewing of an electronic tablet, an LED curing light, a halogen headlamp, and 6 brands of LED headlamps were measured using integrating spheres attached to fiberoptic spectroradiometers. The spectral radiant powers were measured both directly and indirectly at a 35 cm distance, and the maximum daily exposure times (t(MAX)) were calculated from the blue weighted irradiance values. Results: The headlamps emitted very different radiant powers, emission spectra, and color temperatures (K). The total powers emitted at zero distance ranged from 47 mW from the halogen headlamp to 378 mW from the most powerful LED headlamp. The color temperatures from the headlamps ranged from 3098 K to 7253 K. The t(MAX) exposure times in an 8 h day when the headlamps were viewed directly at a distance of 35 cm were: 810 s from the halogen headlamp, 53 to 220 s from the LED headlamps, and 62 s from the LED curing light. Light from the LED headlamps that was reflected back from a white reference tile 35 cm away did not exceed the maximum permissible exposure time for healthy adults. Using a blue dental dam increased the amount of reflected blue light, but t(MAX) was still greater than 24 h. Conclusions: White light LED headlamps emit very different spectra, and they all increase the retinal 'blue light hazard' compared to a halogen source. When the headlamps were viewed directly at a distance of 35 cm, the 'blue light hazard' from some headlamps was greater than from the LED curing light (t(MAX) = 62 s). Depending on the headlamp brand, t(MAX) could be reached after only 53s. The light from the LED headlamps that was reflected back from a white surface that was 35 cm away did not exceed the maximum permissible ocular exposure limits for healthy adults.

Automated summary

Many dental personnel use LED headlamps for hours every day, but it is unknown that these headlamps may pose a retinal 'blue light hazard'. This study found that LED headlamps emitted different radiant powers, emission spectra, and color temperatures, all of which increased the retinal 'blue light hazard' compared to a halogen source. Some LED headlamps had a greater 'blue light hazard' than the LED curing light.