On an average a person spends at least 6 hours on a digital device including computers which has an impact on your eyes.
Staring at the computer or a digital device for long hours without a break causes Computer Vision Syndrome (CVS). The best way to prevent this is adjust you seating arrangement and rest your eyes as often as possible.
Switch to LCD screens as they are safer than the CRT screens. Take a break every 20 minutes for 20 seconds and look at an object 20 feet away. Thsi will prevent the onset of near sightedness.
Mobile devices such as e-book readers, iPads and cell phones offer high resolution and magnetic ink images that are devoid of glare. They also have option of increasing font sizes to avoid straining your eyes. Make use of these features to reduce the ill effects.
One last advice to go for regular eye checkups to detect any defects in the early stages.