The risk of retinal injury from Class 2 and visible Class 3R lasers, including medical laser aiming beams

Abstract

Experimental retinal injury threshold data from the literature and computer model data were used to quantitatively characterize the risk of retinal thermal injury for visible laser radiation that exceeds the exposure limit defined by IEC 60825-1 and the European Directive on Artificial Optical Radiation (AOR). This discussion is of particular relevance for medical laser aiming beams with powers of up to 5 mW. Exposure to 1 mW (Class 2 emissions) does not appear to be able to cause retinal injury for exposure durations of up to about 5 s. Even though there is uncertainty in the experimental threshold data for collimated beams, experience with laser pointers up to 5 mW shows that there is little risk from accidental momentary exposure to these Class 3R lasers. However, injury threshold data indicate that exposure to some pulsed emission Class 3R lasers as well as extended-source Class 3R lasers with powers above 5 mW could induce retinal injury. Recommendations for amendment of the standards IEC 60825-1 and IEC 60601-2-22 are given that should facilitate an agreement of the involved stakeholders on the necessary user safety precautions of Class 3R laser products and medical aiming beams.