Fifth case

In a United States laboratory, an undergrad French student was beginning his internship on a Titanium:Sapphire laser emitting around 800 nm. The student had never been sent to a laser safety course, nor had he been told about laser hazard. His advisor had only told him he must wear safety goggles, without specifying how to choose them or even telling him the meaning of the informations written on the goggles.

Thus, during an experiment, the student, as any good student, took the first goggles he found : they were orange colored. Having not been to any laser safety course, he thought he was protected against every laser radiation, while his safety goggles were in fact only specified for 532 nm radiation.

Then, while aligning the beam of his experiment, the student bent over the desk to look at the beam and placed his eye in the propagation axis of the beam. All along the adjustment, he observed some blue light in his eye due to the non-linear interaction between the 800 nm radiation and the eye. He did not get alerted by this and continued his adjustment likewise.

After his work and while taking the bus to come home, he noticed that he couldn't read the display panel of the bus station any more. The day after, he immediately made a report to his laboratory, which sent him in emergency to do some opthalmologic exams. It revealed that the cristalline lens was partially burned, and that a dark spot had appeared on the fovea – characteristic of the nervous cells destruction.

The student should have been to laser safety courses before he worked on lasers, in order to be aware of their hazard. This formation would have prevented him from making two mistakes. First, he wouldn't have taken the first safety goggles passing by : he would have chosen goggles precisely specified for the near-infrared radiation of the Ti:Sapph laser and for pulsed emission. The second and biggest mistake was to place his eye in the beam propagation axis. If he had been to a laser safety training course, he would instead have used a visualization card or a camera, transforming the invisible radiation into a visible signal. But the worst mistake was made by the advisor, who should have immediately sent the non-specialist trainee to a laser safety training course – thus preventing the following accident from happening.