xliii. Blindfolding the blind

9 July 2009 at 00:54 | Posted in Circadian rhythm | 6 Comments
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Blindfolding blind people sounds like an oxymoronic exercise.  But it is clear that some people with no visual light perception, do, in fact, entrain normally.  I believe it was Charles A. Czeisler who, about 1980, discovered that some blind people entrain normally to the 24-hour light/dark cycle while others do not.  

He and colleagues worked with a number of blind people throughout the 1990s, reporting the results in such papers as this one  from 1995 and this one from 1998.

These researchers, as well as others, worked on determining the circadian periods of individuals by the use of forced desynchrony,  so-called constant routines.  Conditions which are impossible to entrain to, allow mapping of body temperatures and melatonin levels. 

The illustration above, from the 1995 paper, shows two days and nights in the lives of a sighted (above) and a blind (below) *person.  They call this the “Melatonin Suppression Test”.   Circadian phase is determined in the first night: the high point of the level of melatonin in the blood corresponding more-or-less to the low point of the core body temperature.  The second night both subjects are submitted to 90 minutes of bright light (the white columns) at the time of their highest melatonin levels the night before.  And the melatonin levels go way down in both subjects! 

In a repeat of the test with the blind person blindfolded, the light had no effect.  Obviously, somehow, the light signal makes it to the body clock in some blind people.  More about how this works, for all of us, in the next post.

* (It seems to me to be not-too politically correct to call healthy volunteers “subjects” and healthy blind people “patients”.  Czeisler et co will have to answer for that.)


Next:  xliv. Rods and cones and the “new” ipRGC



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  1. Hello there,
    I am a Visually impaired person suffering sleep problems. I’ve actually had the DSPS type since childhood but it became aggravated after I lost 97% of my eyesight in the latter half of 1989.

    These days, my natural rhythm has me sleeping somewhere between 4 and 5:30 AM with a wakeup generally in the early afternoon (noon to 2 PM).

    I have tried the sleeping mask bit and leaving the shades up to get full sunlight in the morning (to no avail it seems). i take 10mg of melatonin about 2 hours before i want to sleep (have tried as early as 8 PM). I still won’t get any sleep before 2 AM if I am lucky. I also suffer periodic bouts of “multi-day insomnia” (lasting for upwards of 40 hours).

    So far, I have been unable to find a doctor that knows about DSPS or even how to resolve it.

    I would appreciate some suggestions as to how to build a “light box” and what else I could do. Since my eyesight is so limited, seeing a clock doesn’t help me with time measurement. I may have to acquire another talking clock soon.

    anyway, any help you can furnish would be of great help.

    – Eric

  2. Hi Eric, thanks for commenting. I’d suggest trying a smaller dose of melatonin (1 mg or even less) and experimenting with the timing. It makes me sleepy, for a short while, one and a quarter hr after taking it, if I’m taking it at a reasonable time before my usual bedtime. That is, it can make me sleepy perhaps an hour before I’d otherwise go to bed, but not earlier than that. (My problem is lack of the discipline required to get to bed then, rather than push on through to a second wind.)

    What you call “multi-day insomnia”, I call my 36-hour trick. It was surprising to see it recognized in the literature where they call it “a non-circadian day”. My sleep specialist says that even people who manage their DSPS well, still may do these all-nighters periodically. Seems to be a necessary re-set for some of us.

    I don’t know that building a light box is a good idea. They are available commercially. They commonly give 10000 lux at a prescribed distance and can be used for, for example, 30 or 60 minutes on arising. They also go by the name SAD box or lamp. if you consider getting one, do check how close to it you have to sit; too short a distance from the eyes isn’t practical. Some sellers offer money back within 30 days if a trial doesn’t give results.

    Hope this helps a bit. Good luck!

  3. Welcome, Eric!
    You might want to read one of my previous posts, “Melatonin: Less is sometimes more” .

    It discusses a paper by Al Lewy, one of the experts in treating circadian rhythms, especially in the blind. His group found that some blind people in whom 10mg of melatonin was ineffective actually responded much better to a much smaller dose, 0.5 mg to be exact. I think if you try a small dose like that you may get much better results. The timing may require some trial and error but I suggest taking it 4-6 hours before your current bedtime in order to try to advance it. The effect is gradual so it may take several days, possibly even weeks to see an effect.

    The “multi-day insomnia” may be an indication that your circadian rhythm is not merely delayed but actually free-running with a non-24 hour period. Although rare for sighted people, free-running rhythms are very common among the blind. The days you have the most severe insomnia may be the days your rhythm is 180 degrees out of phase with normal. If you feel sleepy in the daytime on those days that would be more evidence.

    Melatonin would also work for such free-running rhythms, although it may take a bit longer to align the cycle depending on where your rhythms are when you start taking the melatonin.

    Like my co-blogger I am wary of the idea of building your own lightbox because of safety issues. I also think a lightbox is less likely to work than the melatonin. As an experiment, before committing to a lightbox, you could try going out in the sun if possible just after getting up and see if that effects your sleep timing.


  4. thanks you for the responses and suggestions.
    one small problem, I got out in to the bright sunlight, 2 things hppen:
    1. I develop a severe nerve induced migraine the light receptors in my eyes react violently to that much light and
    2. what little eyesight I have vanishes within minutes and doesn’t return for several hours.

    That situation pretty much makes me effectively total for a big portion of the day. I might have to consider a mask over the eyes when going outside. I’ll look into one as soon as I have an extra few dollars to spare.

  5. […] more links: Blindfolding the blind and Rods and cones and the “new” […]

  6. I am not sure what you mean with the 36 hour trick but I do remember when I was back in high school that I also lived on a 36 hour schedule during the vacation which worked quiet well for me. Basically I lived by a 36 hour schedule, staying awake for 24-26 hours and then sleeping for 10-12 hours, I really felt great with this schedule and the advantage was that I was back on society’s day/night schedule for a couple of days a week. I even considered living on that schedule to resolve my sleeping issues but couldn’t do it as I had to be in school during the daytime, I am wondering whether anyone else has tried this?

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