Mainly due to decreasing of the blinking rate of eye while working significant effective number of hours with computer screens leads to this phenomenon for anyone irrespective of the age. According to the Medical confirmations, the normal blinking rate in human eyes is 16-20 per minute. It has shown that the blink rate would be caused to decrease to as low as 6-8 blinks per minute for persons dealing with the computer screens regularly.
Computer monitor makes all the graphics and pictures using a large number of prime elements called “pixels”. The video display terminal (VDT) basically the monitor of the computer totally consists of those pixels and different combinations of them would draw these visible pictures on the VDT. Each pixel is brightest in the center, with the brightness decreasing toward the outer edges. This makes very much difficult to maintain the eye focus on them just because the human focusing system would not well response to those kinds of effects. This is the main reason for tiredness of the naked eye.
This leads to dry eyes and eye- tiredness as near focusing effort would strain on ciliary muscles of the eye frequently. After specific time duration, some would suffer with inability of properly focusing on near objects too which can be seen in people aged around 30-40 yrs , leading to a decrease in the accommodative focusing mechanisms of the eye.
Look away from the computer screen to reduce the eye-strain hourly. One of the catch phrases is the "20-20-20 rule"……. every 20 minutes, focus the eyes on an object 20 feet (6 meters) away for 20 seconds. This basically gives a convenient distance & time-frame for a person to follow the advice from the ophthalmologist. Otherwise, the patient is advised to close his eyes (which has a similar effect) for 20 seconds, at least every half hour or even more frequently.
Glare screen filters or anti-reflective coated (AR Coated) lenses of glasses may be helpful for some to control this matter but it will not solve the computer vision problems because they only affect glare from the computer screen.
Place your monitor directly in front of you, not off to one side. It should be about 20 to 26 inches away from you. Make sure your monitor is just right for you, not too high and not too low. And keep your arms in parallel to the floor when you type. Finally, maintain good posture at your desk like, keep your back straight and your shoulders back. Adjust the contrast between the background and the characters on the screen by adjusting the brightness on your computer screen.
This has been happening everywhere to each person to whome dealing with computers overall the world with or without the prior knowledge, hence please make sure to protect your eyes just because, your eyes is absolutely required to continue your life properly, than your computer. :)
and....... BE HEALTHFUL & ENJOY A HAPPY COMPUTING.. ....