How long do you spend looking at a computer screen? I bet, if you’re honest with yourself it can easily be an hour a day. “I was only checking my emails.” “Just looking something up.” And this is if you don’t spend your working life in front of a screen. What about a tablet, smart phone or e-reader? How many hours now?
Does it matter? What’s different about a screen compared with a book? How is a reader different from a magazine? The answer to these questions isn’t easy, because it’s the same task, except when it’s different.
When you compare a computer screen to a book, what comes to mind? One is paper, can be moved around fairly easily (unless it is one of the Coffee Table Formula 1 compendiums!), has a fixed print size and doesn’t give off light. The other is fixed in one place, can have the print size changed and does emit light. These are subtle but significant differences.
Let’s first consider the position. When we read, we are much more comfortable with the book at chest height or lower, even on our knees. When we look at a screen, it is straight in front of us.
When we focus on objects that are closer to us, they change their focus and converge (turn in). The eyes are much more comfortable converging when they are looking down, so looking down at a book or a pad feels easier than looking straight ahead at a screen.
The other effect of reading off a fixed screen is that the eye does not move around so much. Some people think that this is one of the major causes of our reduced blink rate when using a screen. Research has shown that whilst we normally blink around 60 times per minute, this can fall to 20 times per minute (or even less) whilst looking at a screen! This has a significant effect on our tear film, making the eyes water, burn and become uncomfortable and bleary.
Another major difference between using a VDU screen and other forms is the fact that the screen and its contents are at a constant distance, so the focusing tends to “lock”. When we read a book or a pad, as we move up and down the page our eyes have to constantly vary the focus, so the focusing lock does not occur.
Then we have to consider lighting. When we look at a reader, pad or a screen (or smart phone), they all emit light. Some emit blue light which can cause problems with sleep (for more details see my previous blog). When the light from the screen falls on the eye it will cause the pupil of the eye to open a little, which will have a small detrimental effect on the image quality – it will be slightly more blurred. When we look at a book, the paper only reflects some of the light from general room illumination, so the pupil enlargement hardly occurs.
When we take all of these factors into account, it’s not surprising that our eyes don’t always feel ccomfortable using modern technology.
In my next blog I’ll be talking about some simple ways to make life easier. If in the meantime you would like any further information please call in to chat to our friendly staff, ring us or drop an email. 01332 666 760 (Spondon) or 01530 832 769 (Whitwick), or email us at email@example.com
Owner and Dispensing Optician