In fact, blue light causes greater eyestrain and fatigue than other colors. It is harder for the eye to focus and causes greater glare and dazzle effects. It can also interfere with our internal body clocks, disrupting sleep patterns. Some researchers believe that even very low levels of blue light during sleep might weaken the immune system and have serious negative implications for health.
The Purkinje shift also noticeably brightens blue or green lights in our peripheral vision under medium to low light conditions, because there are comparatively more rods towards the edge of the retina – hence complaints that blue LEDs are distracting even when they're not the focus of attention.
“Glaring LEDs on displays that you need to see at night... that's poor design,” says Brandon Eash. Remarkably though, it is a mistake that manufacturers continue to make.
We tend to associate blue with coolness, accuracy and clarity. But paradoxically, our eyes cannot focus blue sharply. We actually see a distracting halo around bright blue lights.
“It's well recognized that blue light is not as sharply focused on the retina as the longer wavelengths. It tends to be focused in front of the retina, so it's a little out of focus,” explains Dr. David Sliney, a US Army expert on the physiological effects of LEDs, lasers, and other bright light sources.
The various wavelengths of light focus differently because they refract at slightly different angles as they pass through the lens of the eye – an effect known as chromatic aberration.
For similar reasons, blue scatters more widely inside the eyeball, says Dr. Sliney, who answered questions by phone last year from his office at the US Army Center for Health Promotion and Preventive Medicine in Maryland
The modern human eye evolved to see fine detail primarily with green or red light. In fact, because we are poor at distinguishing sharp detail in blue, our eyes don't really try. The most sensitive spot on the retina, the fovea centralis, has no blue light-detecting cones. That's right: we're all color blind in the most sensitive part of our eyes.
In addition, the central area of the retina, the macula, actually filters out some blue light in an effort to sharpen our vision. Snipers and marksmen sometimes improve on nature by wearing yellow-tinted 'shooters glasses', which block the distracting blue light.
“You throw away a little bit of color information in order to have a sharper view of things,” explains Dr. Sliney.
http://texyt.com/bri...ce health risks
The twin effects of fuzzy focus and blue scatter both make intense blue light from a point source, like an LED, spread out across the retina, obscuring a much wider part of our visual field.
Although our retinas simply don't handle blue very well, nobody told the rest of the eye that. If blue is the strongest color available and we want to see fine detail, then we strain our eye muscles and squint trying to pull the blue into shaper focus. Try to do this for too long and you'll probably develop a nauseating headache. This won't happen in a normally lit scene, because the other colors provide the sharp detail we naturally desire.
A dazzling pain in the eye
By the way, the physical pain some people feel from high intensity discharge (HID) car headlights and particularly intense blue LEDs seems to be a combination of these focus and scatter effects, together with a third. We have a particularly strong aversion reaction to bright blue light sources, including bluish-white light. “Pupilary reflex is down in the blue [part of the spectrum]. The strongest signal to the muscles in the iris to close down comes from the blue,” says Dr. Sliney.
Intense blue light can cause long-term photochemical damage to the retina. Now, nobody is claiming that you're likely to suffer this kind of injury from a normal blue LED (unless you stare fixedly at it from a few millimetres for an hour). However, it is theorized that this may be the evolutionary driving force behind the immediate feeling of pain we get from bright light with a very strong blue component.
Our body's instinctive reaction is to reduce blue light entering the eye by closing down the pupil. This means that blue light spoils night vision. After a brief flash of blue, you can't see other colors so well for a while.
I'm your huckleberry.
One jump ahead of the lawmen
That's all, and that's no joke
These guys don't appreciate I'm broke