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Thread: Photochromic lenses ... should not be worn for lookout duties at night

  1. #1
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    Exclamation Photochromic lenses ... should not be worn for lookout duties at night

    An maritime accident with the yacht Ouzo (in which all three crew members died) prompted an investigation by the United Kingdom's Marine Accident Investigation Branch.

    After the investigation concluded this marine guidance note was circulated:

    MGN 357 (M+ F): NIGHT-TIME LOOKOUT – PHOTOCHROMIC LENSES AND DARK ADAPTATION
    http://www.dft.gov.uk/mca/357_a.pdf

    3. Photochromic lenses

    3.1 Photochromic lenses, even after being in the dark for an extended period and in their most translucent state, can reduce night vision significantly. They should not be worn for lookout duties at night.

    3.2 The MCA’s approved doctors have also been asked to issue this advice to any seafarers they examine who wear glasses with photochromic lenses.
    Here is the report on the investigation of the Ouzo:
    http://www.maib.gov.uk/cms_resources...ile=/Ouzo_.pdf

    It has a lot more information of the photochromic lenses and night adaptation.

    The glasses (from the investigation) were sent to the Institute of Ophthalmology, UCL, London where an expert investigation was done.

    Here are the reports submitted as Annex 1 and 2 in this PDF file:
    http://www.maib.gov.uk/cms_resources...zo_Annexes.pdf

    Report from the Institute of Ophthalmology, UCL, London:
    "Spectral and temporal characterisation of Photochromic eyewear"

    Report from the Institute of Ophthalmology, UCL, London:
    "Report on the potential reduction in visual acuity resulting from photochromic glasses"



    On a related note the Federal Aviation Administration has made this pilot safety brochure:

    Sunglasses for Pilots: Beyond the IMAGE
    http://www.faa.gov/pilots/safety/pil...sunglasses.pdf

    PHOTOCHROMIC
    ... In addition, the faded state of photochromic glass lenses may not be clear enough to be
    useful when flying in cloud cover or at night.
    I hope someone finds the information useful.

    PS: It would be interesting to translate these findings in other critical night vision activities such as driving.

    Best regards,
    Nikolay Angelov
    Last edited by Nikolay Angelov; 03-03-2012 at 04:28 PM.

  2. #2
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    This is an older one, the actual accident was about seven years ago, if I remember correctly. I think the issue was that they were rather old, glass photochromics, and had a bit of a residual tint on them from years of use/age/decay. I wouldn't see it being a problem with the newer T6's and what not, provided they are replaced regularly, and not allowed to go that disgusting yellow colour.

  3. #3
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    Does this mean it's not safe for pilots to wear them either at night?

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    Master OptiBoarder SeaU2020's Avatar
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    wow. Thanks for sharing. It is good to know.

  5. #5
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    I can't see a photochromatic lens being a problem at all if someone has dark adapted. IOW as nightfall comes, the lens lightens up plenty fast enough.

    The only issue I could see is if someone was outside on deck and then walks into a dark room...but then again, if they were outside ondeck with no sunglasses on and they walked inside, they would also have problems suddenly dark adapting.

    This sort of reminds me of the warning employers put out some years ago, that if you view a welder's arc through a contact lens, it will melt the contact lens to your cornea. Hogwash.

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