The muscles in the eyes end up tired and over taxed.
The eyes were not necessarily designed to focus on one object at the same distance for a long time, rather they are supposed to shift focus from far and near objects.
Nowadays, most of our work and recreation is done up close and our eyes are not given the opportunity to shift focus like they were designed to.
Things such as reading, working at the computer or watching TV require focus and concentration.
You might not even realize it but these tasks put a lot of strain on the muscles in your eyes.
As the muscles in your eyes become tighter they tend to become uncomfortable, dried out and irritated.
If you are feeling these symptoms or have a sensitivity to light then you should go visit your family doctor or optician to have your eyes examined.
The added advantage to doing this is that you can also rule out more serious eye disorders that may be in the early stages.
You can also find out whether or not you need eyeglasses or contact lenses during this visit.
Viewing objects close up tends to strain the eyes more than viewing at long distances.
Lighting also plays a role.
If you are working in an environment that does not have proper lighting then your eyes are working extra hard.
You want to make sure that there is no direct sunlight or ceiling lights entering your field of vision for long periods of time.
It is very common to have eye strain when working at computers for long periods of time.
To make this worse, if there are bright lights bouncing off your monitor screen you are only adding to the problem.
This is because the contrast between what you are looking at and the background are reduced by the light that is being reflected.
Your brain has to work harder to interpret the image because of the glare and ends up forcing you to strain your eyes.
You want to make sure that your desktop, on your computer, is set to a contrast that is close to what you are working on in the window.
What I mean by this is that you do not want a black background with yellow typeset.
Make it colors that are not so different from each other, but not too much the same.
You can buy some over the counter eye drops or artificial tears to temporarily relieve your eye strain.
Try to stay away from prescription eye drops because they are more harsh and have many side effects.
They can even become addictive to your eyes.