E-Readers and Visual Fatigue, compared with iPad

[HarryT]

Originally Posted by DNSB

@HarryT I pretty much agree with 4691mls. The only time I really spend hours concentrating on the screen and not looking away is when I am reading. At work, I can spend most of the day in front of a screen but quite a bit of that time is not spent looking at the screen.

I guess it perhaps depends what job you do. As a programmer, I spend most of my day concentrating on my laptop's screen.

[tomsem]

I would just note that the former paper just references other ‘studies’ and summarizes issues, and the latter paper is over 5 years old and references some pretty ancient devices (the original Paperwhite, probably 2nd generation Fire HD, iPad 1, Sony reader).

Still the first paper is full of some delightful techno-babble:

Blinking and squinting
Blinking aids maintenance of a normal ocular surface, with most blinks instigating a cycle of secretion, dispersal, evaporation and drainage of tears.[32]

Reference [32] turns out to be a paper entitled “Blinking and Tear Break-Up During Four Visual Tasks”. Glad someone is studying this, and not me.

[AnotherCat]

I have never had a problem reading for long periods off LCD/OLED displays and have done so for decades. I do not have perfect eyesight.

When better E Ink devices came along some years back I used them for a few years (and still give newer ones a try in the stores as they have come along since) but found them much inferior to LCD - poor contrast, poor greyscale, no color (important for non-fiction), little user control of display characteristics. Their lack of contrast makes text less distinct, especially in low light levels, so generally read it with larger font, and "dense" fonts become more important.

For some years I have used tablets for all reading - I setup the RGB values to give me a background that just knocks the white away (so like natural paper or a little greyer or sandier) and have screen brightness set up as a screen gesture for easy control (I don't recommend using the devices own native brightness control). Brightness can be set at way lower levels when reading text than one would normally use for browsing, video, etc. and needs to be adjusted according to the environment. The likes of Pocketbook and Moon+ Reader make all of that easy. When people complain of "glare" or "shining in eyes" one knows they have not set the display up correctly because that just does not happen with a correctly setup display.

For me E Ink devices have an advantage of working straight out of the box insofar as screen setup for reading is concerned, but reflective displays (like reflective LCD) have little versatility, however manage for many for displaying plain text and low quality greyscale images. Which I regard as fine if that is all one expects.

Regarding blue light - putting aside possible effects on sleep rhythms if reading at night - any negative effect on eye health of blue light from screens is not an issue if compared to natural exposures. We are bathed in natural blue light all the time if outside during the day - for example, Zeiss (the lens maker) claim that 1 hour of exposure to the light from an overcast sky (so color temperature of around 6,500K) is equivalent to around 30 hours exposure to reading from a screen. Clear blue skies are up around 8,000K, so much higher energy blues from them. Furthermore, natural sunlight extends beyond the very high energy blues into UV which is proven to be dangerous. So if you worry about blue light danger to your eyes from reading on screens then one has to assume that you will never want to go outside where blue level exposure is many times greater.

I have often wondered how many people who worry about blue light exposure from screens then go on to praise E Ink devices because they can read them in bright sunlight .

[rcentros]

Originally Posted by 4691mls

I use a computer at work but I frequently look down at paperwork on my desk, stop to answer the phone, etc .so I am not concentrating on the screen the same way as if I am reading a novel.

Originally Posted by DNSB

@HarryT I pretty much agree with 4691mls. The only time I really spend hours concentrating on the screen and not looking away is when I am reading. At work, I can spend most of the day in front of a screen but quite a bit of that time is not spent looking at the screen.

Agreed. When I do spend too much time on the computer (especially when reading long articles or studies) I will get dry eye (especially in my right eye, probably because I had Bell's Palsy on that side of my face). I don't have that problem when I read for hours on my eInk eReaders. But everyone is different. I know what works best for me and I don't really need a study to confirm it.

[John.Dorrian]

Originally Posted by tomsem

I would just note that the former paper just references other ‘studies’ and summarizes issues, and the latter paper is over 5 years old and references some pretty ancient devices (the original Paperwhite, probably 2nd generation Fire HD, iPad 1, Sony reader).

Still the first paper is full of some delightful techno-babble:



Reference [32] turns out to be a paper entitled “Blinking and Tear Break-Up During Four Visual Tasks”. Glad someone is studying this, and not me.

The three reading devices used in this study: the paper book, the Kindle Paperwhite and the Kindle Fire HD (from left to right).
The experiment consisted of prolonged reading (>1 hour) on each device while eye data were recorded. Subjective and objective visual fatigue measures were collected at the beginning and at the end of each reading session.
Eye data were recorded with a 30 Hz infrared video-based eye tracker (SMI Eye Tracking Glasses - ETG).
experimental evidence indicated that reading on the LCD leads to a larger decrease in the number of blinks, with respect to the other supports. This result is in line with a large number of studies on CVS (for a review see [32]), where the use of backlit displays is usually associated with a decreased frequency of blinking and an increased rate of tear evaporation, each of which contributes to dry eyes. In fact, prolonged display exposure contributes to incomplete blinking provoking tear film instability [44], which is one of the main factors for visual fatigue on VDT [45].
our results showed that participants felt visually fatigued only when reading on the LCD. Such a finding might be attributable to the longer reading sessions employed in our study (on average 73 min, SD 10 min), with respect to previous studies [11], [18].
Although the Kindle Fire HD adopts a last generation LCD with IPS (in-plane switching) technology, advanced polarizing filter, and anti-glare technology, the issues related to backlight technology are still present. In contrast to LCD-displays, which have been associated with impaired reading performance [14] and higher visual fatigue [17], results on E-ink displays are encouraging.
Since visual discomfort and related symptoms occurring in VDT workers have been recognized as a growing health problem [32],


###

Originally Posted by AnotherCat

I have often wondered how many people who worry about blue light exposure from screens then go on to praise E Ink devices because they can read them in bright sunlight .

The concerns I've read being expressed about blue light exposure are related to blue light exposure at night time, when reading outside in bright sunlight would seem to be moot, save in extreme Northern Latitude summers.

[John.Dorrian]

Originally Posted by AnotherCat

Regarding blue light - putting aside possible effects on sleep rhythms if reading at night - any negative effect on eye health of blue light from screens is not an issue if compared to natural exposures. We are bathed in natural blue light all the time if outside during the day - for example, Zeiss (the lens maker) claim that 1 hour of exposure to the light from an overcast sky (so color temperature of around 6,500K) is equivalent to around 30 hours exposure to reading from a screen. Clear blue skies are up around 8,000K, so much higher energy blues from them. Furthermore, natural sunlight extends beyond the very high energy blues into UV which is proven to be dangerous. So if you worry about blue light danger to your eyes from reading on screens then one has to assume that you will never want to go outside where blue level exposure is many times greater.

I have often wondered how many people who worry about blue light exposure from screens then go on to praise E Ink devices because they can read them in bright sunlight .

Thus, LEDs with an emission peak of around 470–480 nm should be preferred to LEDs that have an emission peak below 450 nm. Although we are convinced that exposure to blue light from LEDs in the range 470–480 nm for a short to medium period (days to a few weeks) should not significantly increase the risk of development of ocular pathologies, this conclusion cannot be generalized to a long-term exposure (months to years). Finally, we believe that additional studies on the safety of long-term exposure to low levels of blue light are needed to determine the effects of blue light on the eye.
https://www.ncbi.nlm.nih.gov/pmc/art.../mv-v22-61.pdf

[barryem]

Originally Posted by HarryT

I guess it perhaps depends what job you do. As a programmer, I spend most of my day concentrating on my laptop's screen.

I spent about 35 years as a programmer, beginning well before computers had screens until the mid to late 1990s. I forget what year I retired.

I could read my code on the screen all day long. I sometimes would get a bit of eyestrain but not often and not bad. When I tried reading on my Palm or on my home computer screen I found I was limited to about 20 minutes of reading, after which I could take a minute break and do another 20 minutes. If I didn't take that break I was done reading for a few hours.

Reading means constant focus on the screen. Programming involves looking at the keyboard, at documents, at the guy in the next desk, at my coffee cup, etc. They're really different things.

Barry

[cfrizz]

Sounds like people get so engaged with reading on tablets etc, they forget to blink. That certainly isn't the tablets fault.

I can/do read all day on my pc monitor without a single problem.

[4691mls]

Somebody should do a study comparing people who read on LCD with no problem against people who complain of eyestrain, and see if there are differences in their eyes or vision, or if there are differences in device settings, environment, etc.

[AnotherCat]

Originally Posted by John.Dorrian

Thus, LEDs with an emission peak of around 470–480 nm should be preferred to LEDs that have an emission peak below 450 nm...

One has to keep in mind that for LCD (and OLED) monitors one can set the color temperature of the display, it is user configurable in their menus so it is not correct to rely on the native color temperature of the illuminating LEDs which may have a lot of blue so of very high color temperature (maybe 9,000-9,500K? I haven't checked though). Typically monitors come from the manufacturer with the temperature set as "normal" at 6,500K or there about, so around the same as overcast daylight. Tablets (Android), as far as I know, do not normally provide for natively adjusting color temperature but applications may do so or else provide provision to do so.

I just now did some tests measuring some color temperatures (photographers will be familiar with all this, and I have played around doing this before for reading applications). First, as a check, I measured the temperature of overcast daylight; the result 6,500K as expected.

I then measured the default setting of 2 LED lit LCD computer monitor panels, both were 6,500K approx. I then measured the tablet I currently read on (Samsung TAB A 10.5, current model) at native temperature, it was 6,400K so a little warmer.

I then measured the color temperature with a book open in the Pocketbook reading app with the background color setting of Hex F4E4D4 (Red 245 Green 228 Blue 212) which on my tablet is a very slight sandy tint; it measured as 5,200K so that is much warmer than daylight, or the tablet's default native display temperature, and of the illuminating LEDs. [EDIT: using Wein's law at 5,200K the maximum height of the spectrum curve is around 575nm, so back in the yellow region]

Then in Pocketbook I set the background color to white (so Hex FFFFFF or R255 G255 B255) and the color temperature measured the same as the tablet's display native temperature of 6,400K. Effectively then, one has complete control over color temperature.

For reasons I have never gone into in both Pocketbook and Moon+ Reader the actual rendition of the color depends on brightness, so if one goes to http://www.psyclops.com/tools/rgb/ and enters the above RGB values it renders a color close to bisque on a monitor, whereas on my tablet it renders much paler than that at the low brightness levels suitable for reading.

The outcome, for LCD is it is pointless to talk about LED wavelength and temperature - the panel temperature is a user setting on monitors and within the better reading apps on tablets (and phones) (and TVs too). I think for most people setting up background color for reading will find that the moment they get away from a pure white background they will be hitting the blue down in comparison to green and red so heading towards warmer temperatures.

That because I think most people prefer warmer lighting, in rooms typically around 3,500K (often called "warm white"), and if one has used a cool white compact fluoro, for example, (around 6,500K) as a room light they can be harsh and uncomfortable. Using a reflective reading medium such as a paper book I suspect most people prefer reading in a warm white lit room light (tungsten or the little cooler compact fluoro "warm white") than a "cool white" compact fluoro lit one.

The above means that if one is going to conduct an "reading comfort" experiment with subjects reading from various devices then the devices have to be set up correctly for reading with a good reading app, not just using the device's native settings for display temperature, brightness, etc.

[Plumadona]

I appreciate the offer from Underscore to test different apps, but I really don’t think it’s the app. I’ve also tried to read on iPads using the Kindle and other apps, and it’s the same. No loss for me as I don’t read on the large tablets and not that often on the smaller ones. I used to work for hours using computer screens, but that was years ago. I just have to be kinder to older eyes!

[Plumadona]

That reading requires more concentration on the screen with less looking away compared to working on a comouter sense to me, FWIW.

[kacir]

Originally Posted by HarryT

Many people of course work day in, day out on a laptop or desktop computer with an LCD screen and manage just fine.

I spend most of my workday looking at 24" LCD monitor, with secondary 16" laptop screen on the side. It helps with displaying more info, plus it gives my eyes reason to change focus frequently.
At home I have similar setup and I spend a lot of time looking at one of screens. Plus, when I am in the room there is TV playing with some program for kids or a documentary channel (for me).

I do not think that looking at LCD screen causes problems for me - I wouldn't be able to do that for 10+ hours per day, five days per week for many, many years ;-)

Yet, when it comes to reading books for leisure I strongly prefer my e-ink device with the frontlight at the lowest level.

[DiapDealer]

Originally Posted by 4691mls

Somebody should do a study comparing people who read on LCD with no problem against people who complain of eyestrain, and see if there are differences in their eyes or vision, or if there are differences in device settings, environment, etc.

That could prove interesting. I'm one of those who can read for extended periods of time on any screen type with no physical discomfort. My eink devices have all been retired, but my time spent reading has remained consistent. I will note the brightness settings of my devices are all near the lowest they can go at all times (bright sunlight is not where I do my reading--ever). I don't have perfect vision, but need no glasses/contacts for reading (nearsighted).