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Thread: O2 induced myopia

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    Question O2 induced myopia

    Hi all,

    I guess most CCR divers have read the few articles about O2-induced myopia after long and repetitive CCR diving.


    But except Howard Hall and his description of his own symptoms, not a lot of observations "from the field"

    So it could be interesting to know if someone here on the RBW has already experimented any symptoms of O2-induced myopia.

    Cheers

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    Shortsightedness (myopia) results from the inability of the lens to adequately change shape (accomodate) to focus distant images on the retina. In the usual setting this is because the eyeball is abnornmally "long", meaning that the distance between the back of the lens and the light sensing layer at the back of the eye (retina) is increased.

    Prolonged exposure to high oxygen concentrations can cause alterations in both the shape and metabolism of the lens, which can cause failure of accomodation and short sightedness.

    This is usually mild and reversible and usually seen in diabetics and the over 50yo, both of whom have other reasons for lens dysfunction.

    By "prolonged exposure" I mean that this is usually seen in patients having protracted courses of hyperbaric treatment with daily 1 to 2 hr exposures to more than 2.0ATA of O2 for weeks or more at a time. There is some animal evidence that myopia may be more severe if the eye itself is exposed to the high PO2, rather than just being exposed by higher arterial PO2.

    Bennett and Elliot quotes a case report of a 48yo mixed gas CCR diver who accumulated 85 hours of diving in a 21 day period at a constant PO2 of 1.3ATA. He developed 1.5 dioptres of myopia which had completely resolved 3 weeks after cessation of diving.


    Extreme exposure to high PO2 may also cause cataracts. There is a study reporting accelerated formation of cataracts in a group of patients who were exposed to 2.0ATA or more daily for periods of 150 to 850 days. All of these patients also developed myopia, most of which had reversed by six months. Half of them had no cataracts before the treatment commenced. The cataracts did not resolve.

    I suspect that in the course of normal CCR diving you are most unlikely to develop this problem, which is mostly reversible if you do.

    If you have developed myopia I would suggest you see an eye specialist.

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