Today it’s almost impossible to meet a person without a smartphone, tablet, laptop, etc, which have become an integral part of our civilization. Unfortunately, everything comes at a price. The rapid intrusion of smart gadgets into our lives has dramatically increased eye strain. Of course, this factor worries many people. However, the Internet offers a lot of useful information whose use will partially reduce these risks.
For example, back in 1991 Jeff Anshel OD, FAAO (Fellow of the American Academy of Optometry) developed a simple 20-20-20 rule. It recommends when working with a display, focusing vision on an object 20 feet (6 meters) away from him for 20 seconds every 20 minutes.
Of course, the current list of tips is much wider. Moreover, some aspects have opened new topics for discussion among ophthalmologists. Today, this list includes:
– dependence of eye fatigue on color temperature (blue spectrum);
– dependence on screen resolution (or ppi in smartphones);
– PWM flicker of OLED (AMOLED) displays.
This article discusses the first two factors.
Blue spectrum
Ophthalmologists have long debated the dangers to the eyes of the perception of the “cold” spectrum (high-energy visible light or HEVL range of blue-violet waves).
According to American scientists at the University of Toledo, blue light emitted from displays of phones, tablets and laptops negatively affects vision. According to their data, prolonged use of a phone provokes the generation of toxic molecules in the light-sensitive cells of the eye, which can cause gradual retina macular degeneration.
As known, light is electromagnetic radiation, the visible range of which is characterized by a wavelength of 380 nm (ultraviolet) to 780 nm (infrared radiation).
Unlike green and red, shortwave blue is partially scattered on its way to the fundus with receptors, reducing image clarity and causing additional eye strain. In addition, it has the highest frequency in the visible spectrum. But the photon energy is inversely proportional to the electromagnetic wave length. Therefore, shortwave violet radiation has maximum energy, additionally acting on receptors.
However, some experts are skeptical about these theories. In their opinion, the discomfort when using gadgets is mainly due to digital eye strain. “Most of us blink less when looking at screens, causing eye strain and dry eyes,” for example, says Rahul Khurana, MD, a spokesperson for the American Academy of Ophthalmology.
Circadian rhythm
But he acknowledges the influence of blue light on circadian rhythm.
As known, our brain perceives solar ultraviolet light as information about the daytime, which corresponds to the maximum activity. The correct functioning the circadian rhythm requires the melatonin hormone, the synthesis of which is partially blocked by blue light. In fact, UV light acts on the brain like a cup of coffee. As a result, a person does often experience sleep problems after using electronic gadgets. Unfortunately, the solution to this problem requires that you stop using them at least a few hours before bedtime.
Today companies offer special glasses with filters in abundance.
But opinions about them efficiency are controversial.
Besides, the OS of most modern gadgets already use effective software algorithms to reduce the blue intensity. This list includes Night Shift in iOS and macOS PCs, Night Mode in Cyanogen OS, Blue Light Filter in Samsung devices, Eye Protection Mode in EMUI, Reading Mode in MIUI, etc. Additionally, the internet offers the apps with this function, for example, f.lux for rooted Android devices, or Night Filter for non-rooted gadgets.
But they only reduce blocking the melatonin synthesis.
The discussion about the degree of UV hazard continues. “It’s premature to take preventative action against blue light — there could be unintended consequences,” Rahul Khurana says.
Probably, the shortage of solar UV does not threaten the farmer. But the lifestyle of many modern people in cities precludes spending too much time outdoors in the sun. Wherein, the lack of UV light is also dangerous. For example, not getting enough sun could increase the risk of myopia (nearsightedness) in teens and young adults. In this case, additional limitation of the blue color is hardly advisable.
PPI
As known, image clarity and contrast depend on the resolution and directly affect eye fatigue. But this influence significantly different for phones and TVs due to screen sizes and viewing distances.
The screen resolution is traditionally defined as the number of pixels per unit area. The PPI is ratio of resolution in pixels to diagonal size in inches. Of course, maintaining detail while increasing the screen size requires increasing the actual number of pixels.
But the screen size directly affects the viewing distance. For example, viewing 65-inch TV requires a distance of 5-10 feets. The distance to the smartphone screen rarely exceeds 5-10″. Accordingly, the requirements for its screen resolution are much higher. In addition, the perception of an image depends on many additional parameters, including viewing angles, brightness, contrast, saturation, etc.
Unfortunately, screen resolution estimates are not unified today. For example, Apple measures pixels per degree; other companies use PPI (pixels per inch). Several years ago, Steve Jobs argued that the optimal pixel density is no more than 300 ppi, because the human eye does not perceive its further increase. Today, many manufacturers have already doubled this value, and the pixel density of the Sony Xperia Z5 has reached 806 ppi.
But this factor has lost its significance in terms of eye fatigue, because even budget modern models provide HD resolution and higher.
But according to some physiologists, increasing resolution reduces brain fatigue. Indeed, increasing detail reduces information loss due to increasing the dynamic signal-to-noise ratio. As a result, viewing requires less brain effort to interpolate the lost data. In addition, the level of immersive effect is also enhanced by the high realism of the perceived content. Thus, higher detail reduces the strain on the brain, increasing the immersion effect.
Conclusion
Fierce competition is forcing companies to pay more and more attention to eye protection when using modern gadgets. For example, companies already offer anti-blue-light hydrogel films, develop super innovative quarter-wave AR coating for anti-reflective protection, use innovative DC Dimming technology to protect AMOLED screens from PWM flicker, and efficient blue spectrum intensity reduction algorithms, etc. In addition, improving the overall specs of modern screens has virtually minimized eye fatigue due to poor image quality, including brightness, contrast, resolution, color coverage, etc.
But of course, using the simple tips from ophthalmologists will also reduce the strain on your eyes.
This video contains installation guide of popular Ocushield Blue Light Filter screen protector to monitor.
