7
If you are reading this from a computer screen, please stop because you will probably only understand about 20 percent of what I am saying. That reading from a computer screen is hard is a phenomena that has brought up more and more lately. When having to read a large piece of text, a lot of people rather print it out to read it from paper. Some even say they don’t really understand what the text is about or can’t find spelling mistakes until they see it on paper. Also even more than once I have heard people complaining about not even recognizing their own writing style when they re-read the emails they have send. Though how is this possible? If you listen to the complaints it almost seems like we are not really paying attention to the text, we are not really reading it. There is something about the design of the computer screen that makes us unable to read for it, and it has all to do with the light.
Though there are two kinds of objects in this case; the reflective objects, the one we just talked about, and luminous objects; these are objects that do not reflect light, but that produce light of their own. Think of objects like the sun, a light bulb or a computer screen! Usually looking straight at a luminous object is not comfortable for the eyes. So subconsciously your brain does not want to look to a computer screen for too long because it knows it will start hurting at one point. Of course this is not only subconsciously, in medical terms your eyes do start hurting from reading the screen because of the constant light that comes into your eyes even though the light is way less bright than the sun. But because your brain already knows that a luminous object will evoke that, it already does not want to focus on it.
To be able to understand what conditions effect this problem, we should first understand how reading from a computer screen works. So let's start by vision itself. How is it even possible we see things? Light is the answer; When you look at an object, the light from it enters your eye through the pupil. The iris changes the size of the pupil, depending on how bright the light is. The lens focuses the light onto the back of the eye where the retina changes it into electrical shocks which will be transported to your brain where it translates it into vision.
(http://www.sciencemuseum.org.uk/whoami/findoutmore/yourbrain/whatareyoursenses/howdoyousee/howdoyoureyeswork.aspx)