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Comment by Andhurati | Hacker News Reader

Do books do the same damage to your eyes as screens?

Is that really supported by empirical trials? A short search online seems to point to that being somewhat disputed. I'm all for contradictory evidence though if you have some I missed.

Yeah sure a screen is emitting light which maybe makes it worse for the eyes to look at in some ways and situations than a paper page, but "looking at light" is almost an oxymoron - isn't that what eyes do?

Eyes usually look at diffusely reflected light, which has a different impact than direct light.

A white reflective surface (whiteboard) in direct sunlight is 1.6cd/cm^2. Consumer monitors are ~300cd/cm^2

(I'm not sure how much bearing this actually has on eye health, this is just to illustrate how looking at a monitor and at a piece of paper is significantly different)

>A white reflective surface (whiteboard) in direct sunlight is 1.6cd/cm^2. Consumer monitors are ~300cd/cm^2

Why does it hurt my eyes to look outside after a while looking at a screen in a well lit room? (the sun is not directly visible, just buildings, trees and sky)

Because the sun is an enormous sphere of hydrogen-helium plasma with a core that's undergoing fusion just due to gravity. Even indirect sunlight is still a very large amount of light and energy.

I don't mean to sound flippant, but I think sometimes people forget just how insanely energetic stars of all sizes are.

But GP's point was that a screen is much brighter than a sunlit surface. You can't both be right, or I'm missing something.

Hm, to be honest I find reading a book is direct sunlight quite more challenging than staring at a screen, because the reflected light is quite unbearable.

Your units are wrong. Monitor brightness is measured in square meters not square centimeters. A square centimeter is 10,000 times smaller than a square meter.

I think there is a unit error here. I believe that sunlight on white paper is about 1.6cd/cm^2, while consumer monitors are about 300cd/m^2 (meter not cm). Essentially, you want the brightness to match the environment.

http://www.infocomm.org/filestore/display_specs_and_human_vi...

There is indeed. Oops. I'd delete - no point polluting the Internet with more bad info - but time window has expired.

Thank you for the correction!

As noted, your units are wrong. A white reflective surface in sunlight is FAR brighter than a computer monitor.

cd/m^2, not cd/cm^2

I don't understand. Monitors are intended to be set to the same brightness as the ambient environment. 300cd/cm^2 is max, not average.

Of course shining a monitor in your face at maximum brightness is bad, just like staring at a light bulb all day is bad.

You've got your units wrong. Very obviously so, to anyone who has ever taken a laptop outside in daytime.

Hey, do you have specific examples of the damage you're concerned about?

I've been reading up about this a lot as it is something that concerns me, but so far most of what I've says that longterm damage is mitigated by taking regular eye breaks (ie, starting at something 20+ feet away every 20 minutes for 20 seconds) & getting enough sleep (giving the eyes time to properly rest). Are these mitigation strategies insufficient?

Does that matter? Running damages your knees. Playing tennis damages your elbow. Throwing a ball damages your shoulder. I do the thing I love while staring at the screen. If it damages my eyes that's the price I pay. I'm not going to stop doing it.

Can you provide evidence of where screens cause damage to eyes? My ophthalmologist shared with me that there is general irritation but we haven't been able to prove that screen times degrade eye sight over time.

Staring at anything too close to your eyes for a long period of time isn't good for them. If you are taking appropriate breaks, my understanding is that screen time is harmless.

I've got the same understanding - I asked my ophthalmologist about it as well because my vision is already quite bad and I'm a computer engineer.

For breaks, she recommended the "20/20/20 rule" - focus your eyes on something at least 20 feet away, for 20 seconds, every 20 minutes of screen usage.

Yes, I've gotten that recommendation as well. Apparently more natural light exposure may also decrease the risk for nearsightedness. Having a window near my computer monitor makes it easy to remember to look outside whenever I'm not actively looking at the screen.

I think there is a nuance in reducing screen time versus increasing natural light exposure.

Probably? It's not like screens shoot death rays. It seems very likely that looking closely at patterns within a rectangle has the same effects whether it's made of paper or electronics.

Depends which game you're playing.

CRTs used to emit X-rays, so they actually did shoot death rays.

Any ray is a death ray given sufficient dosage.

And that was the day the Care Bears let their stares full power be known.

They are backlit though, that's a big difference. Not sure if any issues would be caused by this.

Is it a big difference? If you take the reverse of ray tracing, why would a light beam of given intensity and wavelength act differently on my retina because it was directly transmitted vs reflected?

Backlit screens are brighter than a book under typical indoor lighting conditions. (Although this doesn't really support the original point, because the canonical alternative of going outside is much brighter than anything you do indoors.)

If you believe my parents then all the years of reading books at night with almost no ambient light would have destroyed my eyes.

No idea, but I'm not sure it's material to whether "staring at books" is a good description of reading.

probably yes.

At least with [1] tpart of the problem is (very simplified) focusing too long on objects too near (book, screen, ...)

[1] https://en.wikipedia.org/wiki/Near-sightedness

There's always been a strong correlation between near-sightedness and reading books or looking at screens in childhood and early adulthood, and it was assumed for a long time that it was because of what you described (focusing on objects too near), but the latest research suggests something much more interesting is happening.

Children who spend a couple hours per day outside have extremely low rates of near-sightedness, so they think there's something about the eyes being exposed to direct sunlight that's necessary for them to grow properly.

Screens haven't damaged your eyes for a long time. That was only true on the old CRT displays, which literally shot high frequency EM at your eyes.

Yes, it does, especially when reading in poor lighting and poor posture.

It turns out the best way to not damage an organ is to not use it...

Do screens do damage to your eyes? The article lists some side effects, but I wouldn't consider that any sort of eye damage, and it's certainly not permanent.

do screen damage your eyes?

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