Dear List,

A urologist working in my Trust has pointed me in the direction of a recently published paper as to why he thinks his eyeglasses are sufficient for laser safety when using a Ho:YAG machine: "Do We Really Need to Wear Proper Eye Protection When Using Holmium:YAG Laser During Endourologic Procedures? Results from an Ex Vivo Animal Model on Pig Eyes" at http://online.liebertpub.com/doi/10.1089/end.2015.0232.  Given that it was only published this year maybe you haven't already come across it but if you have I'd be very interested in having a chat about how you approached the thorny issue of surgeons not wanting to wear laser safe eyewear. 

The paper shows that no ill effects were found in unprotected eyes at distances greater than 8cm from the laser set at its maximum setting of 2J at 10Hz.  It also shows that no effects were shown at any distance in eyes protected by eyeglasses and laser safety goggles using their setup.
  
Upon reading the paper a few things came to mind:
1. The exposure time used was 1s as this was deemed reproducible with some discussion about how the blink reflex would shorten the exposure time in a real life accidental exposure situation.  My problem with this is that the wavelength is not visible therefore using the blink reflex as a limiting factor seems flawed and I'm used to using a 10s exposure for invisible lasers. They do provide a table where they used a worst case scenario of 2J at 10Hz for 5s though.
2. The paper does not provide the divergence of the beam which would have been nice to know and compare with the laser we have here. It also doesn't state a NOHD but I would assume it's 1-2m.
2. The authors used dead pig eyes rather than live pig eyes and admit that further testing is required to see how live eyes would respond.
3. The paper's very last sentence recommends "the use of laser safety glasses or at least eyeglasses" even though "the risk of eye injury is minimal".  So I find myself thinking (again) that the risk may be small but it is real and easily mitigated by wearing safety glasses so my position remains unchanged after reading the paper and advise that laser safety glasses are worn by everyone in the room. And that's without even considering fibre breakage and laser radiation being emitted from an unexpected location mid operation or that the output may be greater than the setting in the event of machine fault.

I would welcome your thoughts and feel free to reply on or off list. 

Kind regards,
Clare.

Clare Joy  |  Principal Clinical Scientist  |  Lead for Non-Ionising Radiation Protection
Radiation Protection, Medical Physics Department, MP 29, Southampton General Hospital
Tremona Road, Southampton, SO16 6YD
 
T: 023 8120 4947
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