Time spent staring at a screen of phone, tablet, PC or any other electronic device with a screen has raised concerns after reports were published that excessive screen time can be harmful. Especially, people who read ebooks like to read on an ereader. Kindle, Kobo, Cybook or another device that is designed for reading ebooks comes with a screen. It is, however, a black-and-white E ink display that doesn't emit light (unless the optional front light is turned on). Fortunately, science has something to say about screen time and ereaders.

Studies that claim the bright color screens used in phones, tablets and computers (LCD or LED technology that emits light) are harmful to the eyes frequently make rounds on the internet, as well as reports that prove that screens are not harmful at all. Which truth is the correct one? First, let's look at the big picture.

No matter what you do, take a break every once in awhile

North American Optometrists claim that the key action to avoid eye strain is to take breaks and let the eyes rest. It doesn't matter which media is used for reading. Perhaps you like to read paper books, ebooks on an ereader or ebooks on a tablet - it doesn't matter – as long as you take a break every 20 minutes. Optometrists remind that reading a printed book in dim light causes eye strain, as well as a screen that is too bright.

The fastest medium for reading

Scientists have studied reading speed when the text has been printedon paper, displayed on E ink (e-ereader) screen and LCD (tablet) screen. The research report LCD vs. E-ink: An Analysis of the Reading Behavior comes to the conclusion that there are only minor differences in reading speed and reading behavior when paper, ereader and tablet are compared.

"As we know from earlier studies the reading process when reading on an e-ink-reader is very similar to the reading process when reading a classic paper book (Siegenthaler et al., 2011). Since the results in the present study show that reading on a tablet is not worse than reading on an e-ink-reader we can conclude that reading on a tablet is under artificial light conditions not worse than reading on a classic paper book."

Blue light filter

Some studies argue that blue light emitted by color screens has made some people worry because it supposedly can cause serious diseases, whereas other studies argue that blue light can be a cure for high blood pressure and other physical conditions.

A balanced analysis conducted by a number of scientists, however, doesn't see blue light as harmful. Blue light has always existed, and we have always been affected by it. The sky is blue, which makes most people happy when they see it. Following the natural sleep cycle, and getting enough sleep is more important than panicking because of the alleged effects of blue light.

Screens in some gadgets may come with blue light filters, an even new eyeglasses can be ordered with a blue light filter, but is the filter worth price is another thing.

It is not screen time

If an e-reader is used for reading, it doesn't have to be counted as screen time. Pay attention to the light so that the screen gets enough light. Take a brief break every 20 minutes for the eyes.

If the real reason for screen time restrictions is excessive use of YouTube, Instagram, and messaging, most ereaders are fine, because additional apps can't be downloaded. Some new ereaders, however, are running on Android software, which makes it possible to download apps from Google Play Store.