Computer Glasses Claim To Protect Eyesight Are Selling Like Hotcakes, But They Probably Aren't Useful (businessinsider.in)

People are increasingly concerned that bright light -- especially "blue light" from computer screens -- is causing harm, making it a potentially dangerous public health issue. Eyewear and screen protector companies have been selling products they say can protect people from these harms. But are they really making any difference? From a report: We do know that blue light at night can interfere with sleep, causing a host of negative effects. But the evidence that the amount of light screen expose us to during the day is harmful is not really there. Furthermore, many experts think these products are unnecessary and could perhaps do more harm than good. [...] The research that companies selling blue-blocking products cite falls into three categories: animal studies, in vitro studies of retinal cells exposed to light, and studies of people exposed to outdoor light. [...] "I think it's largely hype, not science," says Dr. Richard Rosen, Director of Retina Services at New York Eye and Ear Infirmary of Mount Sinai and Ophthalmology Research Director at Icahn School of Medicine. "They want to sell it; they know people get uncomfortable staring at screens all day, so they say, it's because of this [blue light issue]." The report cites insight from several other doctors as well studies to make a case for why these glasses aren't useful.

Comments

DLMO

[epine]

The article has a poor to false understanding of how blue light interacts with DLMO (dim light melatonin onset).

I'm pretty sure the entrainment effect of blue light is via direct neuronal connection to the SCN, and I doubt it involves melatonin, except indirectly.

The homeostatic sleep pressure signal builds up (more or less linearly) for as long as you're awake. On its own, this would mean that you taper into drowsiness all day long. So the sleep system has another mechanism that suppresses response to the sleep pressure signal. I vaguely recall that what happens with DLMO is that melatonin onset signals the body to turn off the suppression switch, so that the body begins to notice the homeostatic sleep pressure signal.

DLMO, however, is easily inhibited by exposure to blue light at a point in time approximately an hour before bedtime. If you're outdoors hunting moose in the bright light of late-evening arctic summer, this is a useful adaptation.

You'll get to bed later, which means you'll sleep a bit later (but not much) and then you will get less blue light early the next morning, which will affect your entrainment, gradually, on the slow-drip program.

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As a rough, empirical ratio, for every extra hour you stay up, you'll sleep about twenty minutes later the next morning. It's not uncommon to stay up for an extra two hours, then barely sleep in for an extra half hour. (We need to ignore here that modern society tends to run a massive, permanent sleep deficit, which can suddenly turn into sleeping four to six hours late at the first opportunity that allows this to happen. That's a different beast entirely.)

I have a circadian rhythm disorder, and I know from decades of sleep tracking that morning wake-up time is about three times more reliable in estimating my sleep phase than time of retirement.

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This is a worthwhile paper from the top of my notes, but it's hard to wade through:

Estimating Dim Light Melatonin Onset (DLMO) Phase in Adolescents Using Summer or School-Year Sleep/Wake Schedules — 2006

I like this paper because it shows how social convention (adolescent schooling) also influences DLMO phase.

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The sleep pressure signal eventually overwhelms the suppression of this signal, regardless of the DLMO mechanism.

James Maas is a good representative of the modern sleep science orthodoxy:

Surefire Strategies to Sleep for Success!

I just love the page break at the end of page 6. But then I'm really into microscopic moments of small page-formatting humour. (It's probably not unrelated to all those long, lonely nights, before I found a viable treatment.)

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Here's a good summary, I just found for the first time.

Phase Response Curve

The reason I only vaguely remember this mechanism is that all the phase response curves in the literature are dose dependent.

There is no PRC I've ever seen that computes the phase response differential to endogenous melatonin levels. No, what you do is administer some dose/formulation (which can include sustained-release components) at staggered times over several weeks, and then you plot the graph averaged over your test population (which thus includes all the metabolic uptake and clearance variability).

There was a time I desperately wanted to consult one of these curves and then to declare "I am here", but it never happened. These are, in effect, better regarded as qualitative curves than quantitative curves.

The model was never predictive enough to be worth memorizing exactly. And thus I remain slightly dim on DLMO when I really shouldn't be after all these years.

instead of glasses use an app

[Kvasio]

A free app, f.lux does the job, https://justgetflux.com/
Set the desired white balance/temperature at night time and you don't need any glasses.

What about optical power?

[TeknoHog]

I'm myopic, and I often read books without glasses, but the computer screen is a little too far for that. So I sometimes find it easier to use my old glasses for computing, compared to my regular glasses with a stronger correction. Around here, "computer glasses"* refer to glasses with the optical power optimized for screen distances. It's something you can get from your employer as a health benefit if you work at a screen all day.

I also use redshift on Linux to tone down the blues (the colour component) during the night, but it's a completely orthogonal issue. Plus if you're worried about computing ruining your sleep, there's also the psychological buzz, so I'm not sure which one dominates in practice.

*(One common term is "päätelasit" meaning "terminal glasses", not necessarily because you're so old they're the last glasses you'll ever need, but because our computing term-inology is ancient and we still think in terms of terminals.)