What is CVS (Computer Vision Syndrome)?

R. Kayne

Some experts believe that anyone who stares at a computer screen for more than two hours a day has likely experienced Computer Vision Syndrome (CVS) to some degree. Blurred vision, itchy dry eyes, headaches and neck strain are just a few of the symptoms, according to the American Optometric Association. The problem lies in the difference between images on a computer screen and real-world images. The human eye is designed to focus on real-world objects, which by nature have clearly defined boundaries. Even print on a page, for example, displays sharp borders and high contrast that extends to the letters’ edges.

Staring at a computer too long can cause eye symptoms and headaches.
Staring at a computer too long can cause eye symptoms and headaches.

Conversely, a computer screen creates letters by grouping dots or colored pixels closely together. Zooming in on a computerized letter will reveal that rounded or curved edges are not smooth and solid, but irregular and indistinct. The eyes have a harder time maintaining focus on a computer display for this reason, and involuntarily drift to what is termed “the resting point of accommodation." You might equate this with “going into a daze,” or “staring at nothing,” but on the computer it happens briefly and repeatedly as the eyes strain to regain better focus. The strain becomes greater as more hours pass, leading to fatigue and CVS.

Ask your optometrist for a computer test if you are worried about your vision.
Ask your optometrist for a computer test if you are worried about your vision.

Many of the other symptoms of CVS are by-products of this tendency to attempt to pull computerized letters into better focus. When your eyes are straining to focus, they have a tendency to blink less, which results in dryness and itchiness. Burning, tearing, headaches and sensitivity to light are other symptoms of CVS. Two other contributors to CVS are glare and, if using a cathode ray tube (CRT) monitor, ultra-violet (UV) radiation. Experts now believe glare and overexposure to UV rays can contribute to cataracts as we age.

Luckily, there are steps everyone can take to combat CVS. Many optometrists today offer computer vision tests. This can help people who do not have corrected vision as well. If you suffer from CVS, this test will let you know if you would benefit from simple magnification or a slight prescription. Proprietary computer glasses can relieve much of the fatigue of CVS.

It is important to note that computers sit at a distance that reading glasses and bifocals are not intended to correct, as reading material is held closer. The display also sits higher than reading material held in the hands, making bifocals difficult to use without tipping the head back, creating shoulder and neck strain. By testing for computer vision, your optometrist can give you the perfect prescription for using your computer to reduce symptoms of CVS. When the display is brought into into clearer focus, the eye muscles will not have to work as hard.

Computer glasses, whether they contain a prescription or not, can also be polarized to eliminate glare. If you use a CRT monitor, consider upgrading to an LCD or flat panel display. These displays do not emit UV radiation. If you must use a CRT monitor, include filters for UV blockage in your computer glasses.

After-market display filter screens can also help reduce CVS symptoms by cutting glare and improving contrast. However, the matte finish anti-glare screen has the effect of making the screen less crisp by scattering light off the rough surface. A smooth anti-glare screen that uses a chemical coating to cut glare cuts less glare, but maintains a sharper picture. This type of anti-glare computer screen, along with anti-glare computer glasses, might achieve the best result. The filter screens intended for use with CRT monitors can block a good portion of UV rays as well.

According to some estimates, CVS affects some 125 million Americans. As more people spend longer hours on computers, computer glasses might become as commonplace as sunglasses. If they provide relief from CVS, they are an investment well worth making.

Computer glasses are typically different than reading glasses.
Computer glasses are typically different than reading glasses.

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Discussion Comments


Yeah I think that I'm having CVS problems, going to the eye doctor soon though.


Are you sure LCD panels do not emit UV?


@ Parmnparsley- I would also like to add that you should not forget to blink. You would be surprised at how long someone can stare at a screen without blinking. Making a conscious effort to blink will keep your eyes lubricated and your vision sharp.


@ Pelestears- It is also a good idea to do eye exercises that reduce eyestrain, and to get up and stretch every hour or so. Simply getting up to get something to drink is important in reducing neck and back strain. Sitting in an ergonomic chair will also help reduce hunching which causes excess strain on the neck and back.

You can do a simple exercise to reduce eyestrain in less than three minutes. Hold your hand over one eye and look left, right, up, and down, holding for 15 seconds in each position. When you are doing this exercise, look as far in each direction as you can and focus on one thing for the entire 15 seconds. Cover the other eye and repeat. You will notice that your vision immediately becomes clearer.


I spend a lot of time on the computer and I have definitely experienced symptoms of computer vision syndrome. I have discovered a few things that will prevent some of the symptoms.

One thing I try to do is match my screen brightness to the ambient light. Spending a lot of time glaring into a bright computer screen in a dimly lit room gives me blurred vision and mild tunnel vision. If I either turn on a light or turn down my screens brightness, my eyes last much longer.

I will also look at an object that is far away every half hour or so and try to focus on it for a few minutes. This also helps with the blurred vision.

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