Myopic defocus more potent in the evening?

Apropos nothing in particular, and because my other thread has come to a (non-) conclusion…

I stumbled upon some papers while looking up hyperopic defocus, looking at the effects of time of day. A couple were on chicks, but there was also

Influence of the time of day on axial length and choroidal thickness changes to hyperopic and myopic defocus in human eyes —> author’s copy of the pdf

which found

  • Evening exposure to myopic defocus causes a larger reduction in axial length.
  • Only morning exposure to hyperopic defocus causes an increase in axial length.

Since AF may be related to myopic defocus, perhaps AF is more effective in the evening ?

(Though since AF is actually about resolving myopic defocus, it might be something different.)

Is simply watching a blurred TV in the evening all it takes …?

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And what did they do in this study for activity?

One fact: defocus is greater in the evening. Defocus isn’t only from glasses vs your refractive state. It’s also from light level. So you’re always will get more defocus in tow light when comparing to the better light with the same correction. And remember that all animal study showed that there is no problem with blur adaptation there. So in logic greater defocus = greater reaction. So are humans different animal or is something else blocking axial change? I’m sort of in the second camp.

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I assume it was in a lab, and therefore the illumination was consistent. One hopes the reviewers would have spotted a minor detail like light levels being different if they hadn’t controlled for that. Though I don’t immediately see the details.

Wait they did that with the same light in a building? That does not make any sense, doesn’t it? What would that even tell us from part of the day perspective? Like hours suggesting this was done outdoors or at least with influence of day light. Otherwise we’re talking Moon influence like Hannie was taking about in the morning.

I don’t see any mentioning of activity either.

One hopes the reviewers would have spotted a minor detail

Let’s hope not. Otherwise we can just put overcorrected glasses on.

We’ve been here before. There has even been something on (slight) differences in diurnal patterns between emmetropes and myopes, as I remember discussing this with my daughter and wondering if this had some influence on our very different diurnal patterns. I am an early bird, she is a night owl. I regret not having kept a record of all the studies I found, as @kem suggested some time back. I could go back through all my posts to find them, but this seems more work than it’s worth.
I’m beginning to think it would be useful to have some kind of cumulative reference list of all the studies that have been linked to on the forum. There have been plenty during the time I have been on it, and I am sure many more from before that time. This could probably be done on the wiki, but I would find it more useful on the forum where a lot of the discussion takes place.

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If I understand correctly the measurements was done in a lab setting, but between measurements people were doing whatever they wanted wherever they wanted.

It’s interesting. Instinctively I would dismiss this instantly because why it should matter and there must be some confounding parameter… but other hand there is the general recommendation to go outside before 10 AM and do distance vision from eyesight. Jake says is, mainstream optometrists says it, Bates says is, TCM says it, so… they either got the idea from the same place or there is really some difference :slight_smile:


Found the study on diurnal rhythms again.

I have now at least bookmarked it, so that I don’t have to hunt for it again.

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Yeah but axial length changed while doing this “whatever they wanted wherever they wanted”, and not in a lab. So you’re basically saying the same thing.

This sounds more like plain common sense to me - the eyes are not as tired. :wink:
But as my daughter just struggles awake by 9 in the morning, and I am often up before the birds, our different diurnal rhythms are likely to influence this.


Black line - axial length for emmetropes, black dash line - for myopes

Remember Varakari measurement graph? Does he do it at the exact same hour of the day?

I wonder what disturbing light cycles would do to this stuff.

It’s interesting that they only did this on:

Regular sleep/wake patterns were confirmed through the use of an actigraphy device (Actiwatch Spectrum; Phillips Respironics, Bend, OR, USA), worn for 1 week before the experiment. Specifically, all subjects slept for one period each night with consistent duration, bed time, and wake time across the week. No subjects traveled outside of two time zones in the month before the experiment.

So now you wonder how this graph would look like with someone who has no regular sleep/wake patterns.

Or a night shift worker, or someone with jet lag.

Sorry, yes, I should have guessed. I wonder if it would be useful for the forum to have a separate section for naval-gazing, rather than all the pointless ramblings happening inside the general forum.

Yeah, “a period of 10 minutes of binocular distance viewing … in dim light … was observed to wash out any residual effects of previous visual activities on measurements, as described elsewhere”

I’m sure I’d heard that it was useful to get some early morning sunshine to reset circadian clock, which then helps you to sleep at night. But I’m useless in the morning too. Unfortunately, also at night. (So useless all the time, really…)

Yeah, he mentioned that he always measured after a few hours of waking up, because right after getting up he got funky results. And did not want to do it later to make sure no daily activity interfere with the measurements.

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And does he have regular sleep/wake pattern? From what you’re saying he doesn’t do it on specific hour.

We might need binoculars for that. Sorry, couldn’t resist that, and @lajos will be on me like a hawk on a peaceful dove.


I’m sure I read somewhere or on reddit where a user asks members if they noticed that their eyesight was poor after waking up after 10am. He or possibly she noticed that his/her eyesight was poor that day after waking up after 10am.
I did try this on a Sunday, but noticed not really much of a difference, unless everyday the sunlight changes, or other criteria.

Also, if anyone does wake up for work at 6am Monday-Friday (not having enough sleep), and their eyes were really tired, would their vision increase? (criteria: wakes up before 10am, drives to work before 10am?)… [no time for distance vision without glasses, would Bates method-no glasses but short distance for 30-60 minutes i.e. eating breakfast, brushing teeth etc count?]
Compared to having/not having enough sleep, waking up before 10am, and practising EM. The calculator suggests I am still 3.5 whereas trying on those said glasses gave a headache immediately, and Snellen suggests 20/15.

I would suggest you trust your eyes and not the calculator. I assume you measure on the Snellen with both eyes at the same time. Binocular vision can add quite a bit of clarity. Measure your eyes separately on the Snellen and check on that. I wouldn’t dream of wearing glasses that gave me a headache. Another thing to check is your pupillary distance. Is this really correct in your glasses? The wrong PD can really mess things up. There’s plenty of stuff on the forum for doing this.

Here I go again, diverting the thread! If you want to continue the conversation on PD, there are already other threads on that and we can move there.

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I think this is no real long-term increase or decrease on this graph. These are just normal fluctuations.

Although there is sth weird about this chart. What exactly is causing it to go down and up in such synchronized manner?

It looks like these short-term fluctuation are adjustment to day-night cycle and not reaction to what anybody is doing. Which bring me to my previous question: how would disturbing such cycle affect this?

Btw. this graph is interesting because my vision definitely the worst at around 2 PM. According to this I should be emmetrope :smiley: