To add to Bill's comments
The LPA can argue that the exposure distance for the EN207 eyewear calc can be a reasonable figure,
Eg moving from 10cm to 25 cm reduces the exposure by 1/6 for a some HoYAG fibre, bring the L number down
Also use used treatment figures rather than machine maximum output, can be reasonably argued.
Did have a German laser system where their proposed turnkey PPE used 0.25s as exposure time for invisible treatment beam, using the aiming beam as the eyeblink reflex initiator.
This was rejected on a technicality, the needed PPE wasn't tricky.
However it is a consideration, how often does the aiming beam fail, but some urologists turn it right down due to the scatter.
Perhaps to discuss at a PHE / IPEM / BMLA meeting.
Matt Williamson
Matt Williamson, clinical physics, 01924 541640 07768 987956
----- Original Message -----
From: BMLA automatic digest system [mailto:[log in to unmask]]
Sent: Friday, September 23, 2016 12:09 AM GMT Standard Time
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Subject: BMLA Digest - 21 Sep 2016 to 22 Sep 2016 (#2016-12)
There is 1 message totaling 773 lines in this issue.
Topics of the day:
1. Recent paper questioning need for laser safety goggles in endourology
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Date: Thu, 22 Sep 2016 23:26:32 +0100
From: Bill Davies <[log in to unmask]>
Subject: Re: Recent paper questioning need for laser safety goggles in endourology
Hi all
The general issues set out by Harry need exploring further.
We have all been in the situation where there a measure of conflict between
the need to advise what the safe level of eye protection should be and how
the surgeon may experience difficulty in managing the patient effectively
should protective eyewear be utilised.
In all these situations it is encumbent on the LPA to undertake a thorough
evaluation of both the laser safety aspects of the procedure and the
potential risks to the patient provided by the surgical team.
As you all know The laser safety committee TC76 WG1 takes great care to
examine evidence of optical hazards and incorporate new data into the
tables published in 60825. As better data has become available it has been
possible to review MPEs more conservatively while ensuring a suitable level
of protection for the various personnel who may be exposed. While the MPE
formulae provide deterministic guidance for use in eyewear calculation it
needs to be remembered that a safety factor is included that sets the level
well below the 50 % probit level for visible lesions.
You may well ask where am I going with this! Well I believe that there is
scope for the LPA to make a calculated judgement where it is considered
that the risk is low and there is a clear clinical need to operate in a
lower OD eyewear or no protective eyewear environment. There however needs
to be a clear protocol to cover this situation and strict adherence must be
maintained.
As an alternative we could employ probabilistic risk assessment that is
used to evaluate military laser situations where the judged probability of
eye damage is assessed In relation to an agreed acceptable level of
probability for the particular procedure. While this can be more cumbersome
than using the deterministic MPE levels it would be another avenue to
explore.
Bill
On Wednesday, September 21, 2016, Andy Howe <[log in to unmask]> wrote:
> Dear all
>
> Firstly I have to declare an interest, as my company supplies laser safety
> eyewear.
>
> However, I spent 12 years at R&D at Diomed in Cambridge, so can give a
> manufacturer's / engineer's view on this. All development on our lasers was
> based on risk management. The results were always the same - wear the
> appropriate laser safety eyewear. No ifs or buts.
>
> The laser manufacturer will always state the required level of protection
> somewhere in the IFU and it would be negligent to not follow this
> specification even though the risks can be quite low in reality.
> Personally I always wear laser glasses just for peace of mind, except when
> working on 630 nm red light systems. Some eyewear manufacturers produce
> very ergonomic, light and 'stylish' glasses, albeit at a price premium.
>
> Best regards
> Andy Howe
> Excel Lasers Ltd.
>
>
> On 21/09/2016 12:42, Harry Moseley (Staff) wrote:
>
> Dear Clare,
>
>
> This is a very interesting point. Thanks for raising this issue. I don't
> have access to the journal and so I can only read the abstract.
>
>
> A decision on whether eye protection is required requires a risk
> assessment. In doing this, the emission characteristics of the laser
> (including, as you mention beam divergence) are determined and an estimate
> of worst case exposure level is derived under reasonably foreseeable
> conditions of accidental exposure. This exposure level is then compared to
> the Maximum Permissible Exposure (MPE) level according to 60825-1. If
> eyewear is required, then this should be selected according to BS EN207.
>
>
> There is no zero risk option. If eyewear is uncomfortable and its use
> hinders the performance of the surgeon then requiring its use when it is
> not necessary does not help to promote safe practice. If the laser is
> activated and fired in a closed situation, this should also be taken into
> account, but that is another matter, as the security of the fibre needs to
> be considered as well.
>
>
> The paper seems to suggest that ordinary eyewear confers adequate
> protection against direct exposure to the laser under investigation. This
> is not surprising but the problem is knowing whether the particular pair of
> glasses which the surgeon is wearing in your hospital will provide the same
> level of protection. You could always fire the laser directly at his/her
> glasses to check out that they block the beam and don't cause any damage to
> the lenses! And you would need to do this for each different pair of
> glasses used. As LPA you do not need to comply with the British Standards
> but you need to be able to give a good reason why you choose to disregard
> them and, if necessary, justify your decision in the event of an injury to
> the surgeon.
>
>
> There may be an argument for revising the MPE levels but this would not be
> on the basis of a single investigation, such as the one you mention, which
> seems to be missing some important information.
>
>
> with regards
>
> Harry
>
>
> Prof Harry Moseley
>
>
>
> ------------------------------
> *From:* British Medical Laser Association <[log in to unmask]>
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);> on behalf of Joy,
> Clare <[log in to unmask]>
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);>
> *Sent:* 20 September 2016 17:08:54
> *To:* [log in to unmask]
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);>
> *Subject:* Re: Recent paper questioning need for laser safety goggles in
> endourology
>
> Dear Tom,
>
> Thanks for your email and sorry for my delay in replying. Any insight
> into how other LPAs approach situations like this is greatly appreciated.
>
> I understand how one's personal opinion can be at odds with the stricter
> interpretation of the law. I take on board that the goggles aren't
> comfortable, I've worn them myself though not for as long as the surgeons
> must and this is the very issue that the urologist working here has which
> prompted him to email me the link to the paper I quoted. Apologies, I seem
> to have missed that in my original email and I do indeed sympathise with
> the surgeon.
>
> Long story short, I've decided to continue recommending the wearing of
> laser safety goggles (for now at least). Thank you as well to those of you
> who replied off list, your views were welcome too.
>
> Kind regards,
> Clare.
>
> -----Original Message-----
> From: British Medical Laser Association [mailto:[log in to unmask]
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);>] On Behalf Of Tom
> Lister
> Sent: 01 September 2016 10:46
> To: [log in to unmask]
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);>
> Subject: Re: Recent paper questioning need for laser safety goggles in
> endourology
>
>
> We request users be extra vigilant when accessing their email. Only open
> attachments from known senders and always with caution. Never open an
> attachment if it is in any way suspicious.
> Dear Clare,
>
> Thank you for highlighting this paper and the issue that I am sure many
> are familiar with regarding the use of eye protection in endourology.
>
> I currently recommend the use of laser safety goggles for our surgeons in
> Salisbury. However, I personally think that the probability of an
> accidental eye strike is very low, and the likely consequence in any
> realistic situation is minimal. The problem is that the evidence is not
> strong (including this paper, as you point out), so I feel that there is
> too much uncertainty to base a change of practice upon.
>
> I have worn these glasses for an extended period during a HOLAP procedure
> and they did become uncomfortable on the bridge of my nose, due to their
> weight. I could imagine an entire day list would be quite unpleasant,
> especially where a surgeon is scrubbed up and can't move the goggles for
> comfort during procedures. I noticed that one of our surgeons taped his
> hairnet to his goggles to reduce the weight on his nose. Although lighter
> (plastic) safety goggles are available, they do not offer a very high 'LB
> number'.
>
> Due to this discomfort, I disagree with your point that the risk is
> 'easily mitigated by wearing safety glasses', which I think changes the
> argument for/against the use of goggles.
>
> Overall, I feel that I cannot prove that the risk of harm is high enough
> to warrant wearing goggles. However, my understanding is that there is a
> risk of eye exposure over the MPE, and therefore eye protection should be
> recommended to comply with artificial optical radiations regs.
>
> I would be very interested to get a feel for the consensus opinion on this
> issue amongst UK LPAs.
>
> Best wishes,
> Tom
>
>
>
> -----Original Message-----
> From: British Medical Laser Association [mailto:[log in to unmask]
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);>] On Behalf Of Joy,
> Clare
> Sent: 31 August 2016 14:15
> To: [log in to unmask]
> <javascript:_e(%7B%7D,'cvml',[log in to unmask]);>
> Subject: Recent paper questioning need for laser safety goggles in
> endourology
>
> 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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