Executive Summary
With increased work–from–home requirements, the use of computer and mobile phone screens is rapidly increasing. Long duration exposure to these screens increases strain on the eyes. Simple steps, such as adjusting screen settings, room lighting, and display positioning can help reduce this strain.
Read the full article to know how this eye strain develops, why digital media cause more eye stress than print media, how screen colour temperature affects the eye, and more.
One consequence of the Coronavirus pandemic is increased eye strain.
During the lock–downs, most businesses ask their employees to work from home. That needs one to spend time on digital screens, such as laptops, tablets, and mobile phones.
As newspapers and magazines become unavailable, one has to rely on electronic information. Inevitably, that means news on television, as well as websites and social media on computers and mobile phones.
Finally, as the outdoor entertainment options dry out, people get more and more glued to televisions, computers, and mobile screens.
All these lead to excessive use of electronic screens for reading and viewing. Eye strain is a natural fallout if we don’t take care while using these screens.
Normal Eyesight
All of us know how an eye works. You can search and go through many YouTube™ videos to understand this. Pay special attention to how the eye sees objects that are distant versus those that are close by.
The lens in the eye flattens for us to see objects that are far. In contrast, when we have to view objects that are closer, such as print material and digital screens, the lens needs to become rounder.
Accommodation
The process by which the shape of the eye lens changes is called Accommodation. It involves focusing the light rays coming from any object on to the retina of the eye.
The lens in your eyes is naturally rounder. For it to flatten, some ligaments called Zonule Fibers, have to pull it out radially. These fibers are connected to something called Ciliary Muscles, at their other ends.
Here is a YouTube™ video by Tom Dare that explains how this process of Accommodation works.
By an ingenious arrangement in the eye, when the ciliary muscles are relaxed, the zonule fibers are pulled tightly, flattening the lens. This is the situation when you have to see distant objects, such as the mountains or the car across the street.
For your eyes to read a newspaper or view a mobile screen, the lens needs to become rounder, for which the zonule fibers need to slacken. This is possible only when ciliary muscles contract and stay taut. Thus, as you keep reading or viewing nearby objects, the ciliary muscles in your eyes have to keep working. Eventually, they tire out.
Eye strain
Think of it as if you are flexing, or contracting, your biceps. Thirty seconds; one minute; two minutes. But eventually, your biceps will fatigue out. They can no more contract adequately. You will need to rest them for some time before attempting to flex them again.
The same thing happens to the tiny ciliary muscles in your eyes. Evolutionarily, they were not designed for reading Leo Tolstoy’s book War and Peace cover to cover. They were meant for you to see the berries on the trees, the rivers, the mountains, and the occasional sabre–toothed tiger in the distance.
Seeing a mosquito sitting on your arm, or a potato getting washed properly, needed just a few seconds of eye focus on a nearby object. They did not need any long–duration strain on your eye’s ciliary muscles.
Today, internet is expanding our horizons, but our vistas are becoming narrower. Screens and print media are replacing our outdoor lives. The increased eye strain is a direct consequence of such changes.
Print media
Print media include books, magazines, and newspapers.
The modern print media involve printing a whole bunch of dots on paper to render an image or text. Almost all printing involves 300 dpi, or 300 dots per inch, resolution. At that density, at normal viewing distances, your eyes cannot make out the difference between adjacent dots. That makes the image looks continuous and smooth.
Print media need proper room lighting to read. If there is poor lighting, the eyes find it hard to focus on the printed matter, causing them to fatigue faster. In low light, the eyes blink less often, adding to the problem of dry eyes.
Digital Media
Digital media include computer screens, e–readers, tablets, and mobile screens.
Most modern digital media involve displaying a whole bunch of dots on screen to render an image or text. In the digital world, these dots are called Pixels, a short for Picture Elements.
Earlier screens used 72 pixels per screen inch resolution, which in the digital world was called 72 pixels per inch, or 72 ppi. Read: What is ppi and does it matter?
With modern displays, this number is slowly increasing though many digital screens show images and text at 150-200 ppi.
E-Readers
E-readers, such as Kindle, use 300 ppi as the resolution to make their digital displays as close to paper print as possible in quality. Here is some technical information on e-reader technology: Everything you need to know about e-readers.
In short, digital screens, with the exception of e–readers, have somewhat lower resolution than print media. As a result, to read from digital screens, your eyes need to strain a bit more.
It has also been found that when we read from digital screens, we tend to blink at just about 40% of the normal blink rate. This may cause our eyes to become dry and occasionally, sore.
Ideas for preventing eye strain
Follow the 20—20—20 rule
Every 20 minutes, look 20 feet away from your computer or mobile screen for 20 seconds. Ideally, look at a very distant object. That way, the ciliary muscles in your eyes will get rest for 20 seconds. If you are in a cubicle, simply close your eyes for 20 seconds.
Increase font size
Increase the size of the font (or typeface, in layperson’s terms) in your computer web browser or mobile phone.
On Android phones, go to Settings, tap Display. In the Font section, tap Font Size. Tap the appropriate radio button to select font size you prefer. On an iPhone, go to Settings, tap Display and Brightness, and choose text size you prefer.
For Chrome web browser, select Preferences menu. Then, click on the Appearance menu to view and select font size you want.
Some mobile phones allow you fancy font choices. Avoid whacky looking fonts. They are harder on the eyes for reading.
Change brightness and contrast
You can adjust brightness and contrast of the display to make digital reading easier on the eye.
Ideal screen brightness should be equal to the brightness of the surroundings. For example, if you look at the white background of this webpage, does it look brighter than the outside of the screen? Does it look like a source of lighting? Then, it is too bright.
On the other hand, does the white background of this webpage look duller or darker than the lighting behind and around the screen? In that case, increase the brightness.
The best combination for reading is black text on white background.
Reduce colour temperature
Many displays allow you to adjust the colour temperature of the screen. Now, this has nothing to do with the physical temperature of the screen. It is about the look and feel of the light appearance. Read: Understanding colour temperature.
You may have noticed that at high temperatures, an iron rod looks orange in colour. Heat the rod even more and it becomes whiter. At very, very high temperatures, you will see a bluish tinge in the colour of the rod.
This is what is meant by the temperature of colour. Thus, the orange-ish lights are said to be of lower temperature than the bluish lights.
The blue, or bluish, lights are harsher on the eyes. They can damage the retina over a long–term use. Read on this website: Blue rays: How to protect eyes from this new threat.
So, set the screens to lower colour temperatures, especially at nights.
Obviously, you cannot remove blue colours selectively from a screen display. In such cases, all images will look funny.
In reality, lowering the colour temperature of the screen reduces bluishness from ‘all’ the colours on the screen. That makes the overall image look orange-ish. But for most tasks, such as reading text from the screen, it is fine.
Look at Exhibit 1 above. The image on the right is the actual display. The image on the left is how the screen looks with a lower colour temperature. While it looks a bit orange-ish, no vital details are lost. The sacrifice in colour fidelity is fine, if it reduces eye damage.
Reduce glare
Use an anti–glare filter. This reduces the amount of light reflecting back from your screen on to the eyes.
Position the screens properly
A computer screen should be about 2 feet from your eyes. The top of the screen should be at the level of your eyes. The centre of the screen should be at 15 degrees angle to the eye level.
Mobile screens should be held and read below eye level.
Use good display monitors
Some older monitors may not focus properly causing difficulty in viewing. Modern displays are higher in resolution and so, are better for the eyes.
Use halogen or fluorescent light
For reading print media, use soft, white halogen or fluorescent light in the room. Do not have very bright external or internal lighting.
Ensure air quality is good
Polluted, dusty environments are bad for reading. Pungent odours, very dry air, and fast fans may make reading difficult and strenuous.
Use eye lubricants
Tears are useful for lubricating eye’s smooth external surface. If eyes become dry, focusing becomes difficult. It can give a burning sensation in the eyes, making reading difficult.
Also, as we age, the tear glands produce fewer tears. Use over–the–counter artificial tear drops, if you notice dry eyes.
For some more tips, read: Computer eye strain: 10 tips for relief.
Actionable tips
- Follow the 20—20—20 rule.
Every 20 minutes, look at an object 20 feet away, for 20 seconds. - Adjust screen brightness, contrast, colour temperature and font size.
Large font sizes. Black text on white background. Simple, clean fonts. Low screen colour temperature. - Use anti–glare filters.
Avoid bright lights from outdoors or indoors. - Position the screen correctly.
Top of the screen at eye level. The screen should tend a 30° angle with the eye. - Use proper room lighting.
Use soft white light. Avoid harsh lights. - Use artificial tear drops.
First published on: 30th March, 2020
Image credit: Andrea Piacquadio from Pexels