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Thread: temporary blindness on deco

  1. #1
    RBW Member tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining's Avatar
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    temporary blindness on deco

    Hi all.

    I am looking to find out if anyone has any information or has experienced temporary blindness on deco after a deep dive. A dive buddy of mine conducted a dive to 140m and on the ascent while gas switching from bottom Mix to Tx 32/30 during this switch he temporary lost his vision for around 4 mins. I have no explanation of why this was, the only thing I can find is some information on Retinopathic Oxygen Toxicity.

    Any explanation will be well recieved.

    Happy Days

  2. #2
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    That sounds terrifying to me!


    I think that it is hard to say definitely what the cause would be.

    More information about the dive profile, mixes and switch depths etc might help. What you are describing is very short term total loss of vision in an ascending diver, which was rapidly and completely reversible.


    Firstly there is some experimental evidence in both animals and man that prolonged (several hours) exposure to high (more than 3ATA) partial pressures of oxygen can cause progressive loss of peripheral vision (tunnel vision). This seems to almost always spare the central vision and both visual acuity (eyesight) and measures of intactness of the eye-brain pathways (VER) remain intact. I am uncertain what the proposed mechanism of this effect is. There are reports of individuals who seemed particularly sensitive to this effect. It reverses spontaneously when the subject breathes a lower O2 partial pressure. So that's probably not it.


    Furthermore there is evidence that the photoreceptor apparatus in the retina functions less effectively when exposed to high partial pressure of O2 for prolonged periods of time. So when light hits the retinal cells, they don't fire normally. Again this effect requires many hours at high PPO2, so again probably not the cause.


    The third, and to my mind the most likely possibility would be acute oxygen toxicity. Visual manifestations are commonly described as a prodrome to seizures (in survivors). The putative pathological mechanism is not completely understood but probably relates to excessive free radical production interfering with normal brain cell membrane function. Depending on a whole host of factors, some measurable and some not, it’s possible that whatever PPO2 your buddy was breathing was just a little too high for his poor old brain.


    So…what did you dive? Was it worth the anxiety

  3. #3
    Darlene Starr - DIY Diva Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen's Avatar
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    Quote Originally Posted by tecdivertraining
    Hi all.

    I am looking to find out if anyone has any information or has experienced temporary blindness on deco after a deep dive. A dive buddy of mine conducted a dive to 140m and on the ascent while gas switching from bottom Mix to Tx 32/30 during this switch he temporary lost his vision for around 4 mins. I have no explanation of why this was, the only thing I can find is some information on Retinopathic Oxygen Toxicity.

    Any explanation will be well recieved.

    Happy Days


    What was his bottom mix, and what depth did he switch to the 32/30 at?

    I'm figuring that he had to be running something close to 8/72 or 8/80 on the bottom.

    That's one hell of am O2/N2 slam if he went to 32/30 at around 130'.
    PO2 almost quadruples, .4 to 1.5ata and PN2 doubles, 1 to 2ata ... All at the same time ....

    Can you say, "Chug a pint of tequila and jump up and try to run!

    IBCD certainly has to be considered as well.

    As he lost and then recovered his vision, did everything seem red for a while?

    I don't understand why he wasn't getting on something like 15/55 or 18/45 down in the 200's, wayyyy before the 32/30.


    Was this an OC dive, or a bailout from a RB dive that went south?


    Darlene

  4. #4
    RBW Member tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining is a name known to all tecdivertraining's Avatar
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    Thanks for the replys.

    The dive was as follows:

    TX 10/60 bottom gas (the dive maxed at 130m not 140 having looked back at the profile.)
    TX 18/40 travel & first deco gas
    TX 32/30 at 40m
    EAN 60 at 16m

    the total bottom time including decent was 12 min

    The problem was at the TX32/30 switch. It was an OC dive

    Thanks

  5. #5
    Pedant dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner is a name known to all dteubner's Avatar
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    I agree with Andrew that O2 toxicity is a likely cause.

    Narcosis shouldn't make you go blind.

    DCI is unlikely, especially if the blindness occurred immediately at the gas switch, because total blindness implies loss of quite a lot of the occipital cortex therefore a lot of bubbles and that is not how IBCD seems to work. It would also be unusual for DCI to recover spontaneously after a few minutes.

    Non diving related causes always need to be considered but again it would seem to be an amazing coincidence that it would happen at the gas switch on the ascent from a very deep dive having never happened before.

    Perhaps there was a total eclipse

    Dave T

  6. #6
    Darlene Starr - DIY Diva Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen's Avatar
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    Quote Originally Posted by tecdivertraining
    Thanks for the replys.

    The dive was as follows:

    TX 10/60 bottom gas (the dive maxed at 130m not 140 having looked back at the profile.)
    TX 18/40 travel & first deco gas
    TX 32/30 at 40m
    EAN 60 at 16m

    the total bottom time including decent was 12 min

    The problem was at the TX32/30 switch. It was an OC dive

    Thanks

    That was the missing info from the first post.

    That makes a lot better looking profile, the only bump was with the 18/40, and a smalll one at that.

    I think Andrew has the best guess here with O2 tox issues.

    Was the dive physically challenging, or a strong current present?

    That had to be the scariest 4 minutes ....



    Darlene

  7. #7
    Sebastian Chander Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg's Avatar
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    I've been told that we did have a similar problem here many years ago with and incorrect gas switch at 30m to EAN 80. The diver took a partial breath and isntantly went blind in one eye. But recovered rapidly wehen he got on his EAN 36.

    This though was an extreme case with a Po2 of 3.2 ATA. A jump from .9 - 1.6 seems a reasonable switch, unless the diver was under duress.

    Cheers

    Seb

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