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The correct answer is: all of the above. Eye strain, headaches, blurred vision, and neck and shoulder pain are common symptoms of CVS.

The correct answer is: 70-75 percent.

Text printed on paper generally has high contrast, and individual characters have well-defined borders that computer-generated text and images often lack. This makes it more challenging for the eye to stay focused on text and images displayed on a computer screen.

The correct answer is: an inability to focus properly on computer images. It's more difficult for our eyes to remain focused on the pixel-generated images on a computer screen, compared with static print in a book or magazine. The constant refocusing required during computer use causes faster eye fatigue, leading to CVS symptoms.

The traditional way of testing distance vision, known as the Snellen Test, does not provide eye doctors with sufficient information to determine the existence of computer eye strain or to decide on the best prescription for use at the computer.

The correct answer is: one-third as frequently. A study* found that normal, healthy adults blinked at an average rate of 15 to 16 times per minute when engaged in conversation, but only about five times per minute when using a computer.

This decreased frequency of blinking during computer use can cause dry eyes, eye strain and contact lens discomfort.

*Characteristics of spontaneous eyeblink activity during video display terminal use in healthy volunteers. Graefe's Archive for Clinical and Experimental Ophthalmology. November 2003.

The correct answer is: about the same. Research shows that comfort and performance at work improve when the brightness of your surrounding workspace is about the same as the background of your computer display. If you work in a very bright office, you could reduce overhead lighting to make your surroundings the same brightness (or slightly dimmer) than the background on your screen.

The correct answer is: true. A study by the University of Alabama at Birmingham School of Optometry found a direct correlation between workplace productivity and accuracy and the proper lens prescription for the computer user (whether or not the individual reported symptoms of computer vision syndrome).

Read more about computer vision syndrome and worker productivity.

The correct answer is: all of the above.

You can reduce your risk for CVS by adjusting the height of your desktop computer display to help you maintain comfortable posture and keeping it approximately arm's length from your eyes to reduce focusing demand.

Also, taking frequent breaks from staring at your display will reduce focusing fatigue that causes eye strain. It's also helpful to get up, stretch, and walk for a few minutes after 20 to 30 minutes of computer use.

And, for some eyeglass wearers, special computer glasses can improve posture, reduce eye strain and decrease muscle strain that can cause head and neck discomfort. Read more about computer ergonomics.