Eye strain from LED backlighting in MacBook Pro

I measured the kindle paperwhite at several levels of brightness with a photodiode, and it has no PWM.

Thanks for measuring. I remember somebody here had a problem looking at a certain e-ink reader even without a frontlight, though he did not have trouble with previous e-ink readers. The most plausible explanation then was the new spatial dithering or however it's called. It's not the kind of dithering that results in flicker, but rather in patterns. The dithering is used to create the illusion that there are more shades of grey. I'm not saying this is your problem, but there is a small chance it is. If you are curious, research it more and tell us about your findings! Another idea: why not find somebody who repairs electronics and ask him to remove the frontlight? If it truly is the frontlight's fault, then you would have a usable device after this procedure... and you could be absolutely sure if it's the flicker-free frontlight's fault or not.

I received my other kindle tonight, the old version with no light at all. i will probably sent the paperwhite version back to amazon...i will compare both...

Just to be thurough you should research if any of the two devices use dithering. If the older one doesn't, then it's not a fair comparison.

About dithering: http://kindleworld.blogspot.com/2009/03/are-kindles-16-shades-of-gray-big-deal.h tml

You know whay you could try? Just open some completely white content on your paperwhite and look at it for a few minutes, which you said is enough to feel whether it is tolerable or not. No dothering is done with white content as far as I know.

Here's an excerpt from a medical paper I was just reading about Photophobia, it is interesting information and the whole paper is interesting if you have some time! It helps explain why those here who get migraines are more sensitive to the blue/white spectrum, the info below explains some of why there could be two distinct groups with different reactions to spectrum and flicker. Migraine sufferers probably are sensitive to both while some others who do not get migraines but do get eye irritation and normal headaches may be more sensitive to flicker for a different reason?

The wavelength of light may also affect the photophobia percept. Main et al. (103) found that shorter wavelength (blue) light was more uncomfortable for subjects with migraine than for those with tension-type headache or controls. These investigators also reported that longer wavelength (red) light was also less comfortable for subjects with migraine (103). Good et al. (29) found that visually provoked beta brain activity was suppressed by red light and enhanced with blue light in migraine patients, showing that the two wavelengths have different effects on cortical activity. The reasons for this difference, and the noxious nature of both blue and red light to migraineurs, are unclear. The fact that intrinsically photosensitive retinal ganglion cells are preferentially sensitive to blue light is intriguing (83, 104).

The link to the whole paper here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485070/

Yes that would be me. The cheaper kindle (without the backlight) gave me a strange eye strain while other brand older readers were fine.

I remember that in some other forum a person had the same problem, and the explanation that was provided there by a participant, was dithering. Kindle does that in order to create additional grades of the gray color to show pictures in the Kindle. I remember that the person that made the complaint said that he/she used the previous model of Kindle with no problem.

Unfortunately i cannot find the pages i was reading.

But you still use the old kindle, or the new kindle?

Is that strange eye strain from kindle the same then the eye strain LED gives?

Both kindles to me are note perfect. They dont have enough contrast, they need to much light. A book has a lighter white(page). The new one, the letters are more fuzzy. A book is way, way better. I am trying to understand if the old kindle is good enough to keep.

I dont use a reader at the moment. I have used the Kindle without backlight which i purchased in Oct 13 and returned it due to eye strain.

Previously i owned an old Sony reader which was great, i didn't any experience any problems with it.

Here is another section of the Photophobia report worth sharing, they speak about tinted lens's and why a certain tint called "Fl-41" (Just rose colored tint for the most part) was helpful in reducing migraine frequency when patients were exposed to fluorescent lighting. If anyone here is getting vertigo and migraines from LED/Fluorescent lighting this information points to spectrum being the most dominant culprit. There are sections in this article about dry eye's and normal headaches resulting from photophobia as well, it is a very informative read prepared by Doctors and based on medical science.

One principal treatment is to decrease the dark adapted state. Patients with severe photophobia who wear darkly tinted lenses should be encouraged to reduce dark adaptation. Chronic darkness will increase the perception and pain of light sensitivity. Lebensohn (5) cautioned that “tinted glasses as a symptomatic remedy for chronic photophobia are to be condemned because of both their ineffectiveness and their habit forming tendency”. Wearing sunglasses to an eye clinic has led many physicians to consider the patient to have some type of psychiatric disorder, or at least to predict nonorganic visual loss (118, 119).

Some optical tints have been tried successfully to combat photophobia. Red-tinted contact lenses have been tested in individuals with photophobia due to cone disorders (120–124). However, red tint appears to exacerbate migraine-associated photophobia (103).

Sunglasses do make sense in the bright sunlight for patients with migraine, tension type headaches and those with light sensitivity. Some tints have been successful in migraine. Good et al. (29) found that FL-41 tint, a rose-colored tint, reduced migraine frequency in children by over one-half. Subjects reported a decrease in photophobia and glare in between attacks, but no change in the light sensitivity associated with the migraine attack. FL-41 tint filters 80% of short wavelength 50 or 60 Hz flicker that is seen with fluorescent lights. As flicker stimuli can be particularly noxious to patients with migraine (125), the authors reasoned that flicker reduction contributed to the reduction in headaches.

We studied FL-41 tinted lenses and found that they increased the threshold to discomfort in all subjects (controls, migraineurs, and patients with blepharospasm), but they did not differ from gray tinted lenses in reducing light sensitivity (44). To test whether patients preferred FL-41 tint over gray tinted spectacles, we performed a double cross-over study of subjects with blepharospasm using Gray and FL-41 tint. Patients preferred FL-41 tint over gray spectacles and patients felt that FL-41 significantly reduced their symptoms (70). We also tested the blink reflexes of patients who wore FL-41 tint or placebo pink lenses while reading under a standardized light source. We found that in blepharospasm patients, FL-41 tint greatly reduced the number of blinks and intensity of blinks (70).

Studies using fMRI suggest that there may be different physiological responses to spectrally-specific tints compared to neutral density filtering (which attenuates all wavelengths equally. Huang et al. (126) used precision ophthalmic tints that normalized cortical activation on fMRI, whereas gray lenses did not in patients with migraine. Why would red or pink tinted lenses show this effect? Red tints tend to block blue wavelengths, which more likely may induce photophobia (103).

No mention of yellow tint, I need to research further why yellow tint is not mentioned.

Jesse

Another interesting point here would be how an incandescent light bulb is dominantly red spectrum, interesting.

Also, just in case you are wondering I tried the FL-41 tint and by itself I found it slightly helpful with fluorescent light sensitivity and not at all with LED. However, when Crizal anti-glare coating is added to the tinted lenses it is much more effective, in fact Crizal anti-glare coating by itself seems to be just as effective as the tint. Anti-glare coatings are often applied to lens's these days and now I question if the studies have been done with anti-glare/FL-41 or just the FL-41 by itself? It poses the question of what was really making the difference?

I need to correct one thing about above statement: I meant to say the anti-glare coating is much more effective than the FL-41 tint if you were to use them separately.

Jesse

I was just wondering besides turning the brightness to max Is there anything else you can do to an LED screen to make It not flicker as much? I know you could just smash It and buy a flicker free one but It's at my work and I have no choice but to use It thanks:)

Interesting:

"As the widespread use of smartphones, tablet devices and computers increases the time we face a screen, more and more people suffer from eyestrain symptoms. One cause of this is believed to be the blue light emitted from the display on such devices.

The shorter the wavelength, the stronger energy a light wave has, and this may cause eye fatigue. Blue light, which is next to ultraviolet light on the electromagnetic spectrum, has a shorter wavelength than other visible light. It also tends to be diffused and is believed to cause flickering in the vision."

http://www.nikon.com/about/technology/life/others/bluelightcut/index.htm

I dont understand the relation of blue-light how to tends to be diffused and causing flickering... I dont know if it's just propaganda...

There is a lot of pseudo-science being put forward on here about blue light.