Computer Vision Syndrome

Using a computer has become a normal part of life for most Americans.  Consider these statistics:

  • According to the Bureau of Labor Statistics, over 50 percent of all workers in the United States use a computer at their job.
  • According to the National Center for Education Statistics (NCES), about 90 percent of children and adolescents ages 5 to 17 use computers at school or at home.
  • The NCES also reports that computer use begins at a very early age.   About three-quarters of 5-year-olds now use computers. 
  • About 25 percent of 5-year-olds use the Internet, and this number rises to over 50 percent by age 9 and to at least 75 percent by ages 15 to 17, according to NCES.
  • According to Computer Industry Almanac Inc., over 185 million Americans now use the Internet, making the U.S. the largest user nation of the Internet worldwide.


Unfortunately, most people who use a computer for extended periods of time will experience some degree of vision problems, eyestrain, or general discomfort or fatigue.  When related to computer use, these problems are referred to as computer vision syndrome (CVS).  Though CVS does not cause permanent damage to your eyes, it can be a major cause of discomfort, fatigue, and loss of productivity. 


What is computer vision syndrome?

The National Institute for Occupational Safety and Health (NIOSH) defines computer vision syndrome (CVS) as “eyestrain associated with prolonged computer use.”  The American Optometric Association (AOA) expands on this definition, calling CVS “eye and vision-related problems related to near work which are experienced during or related to computer use.”

Symptoms of computer vision syndrome fall into three categories: vision problems, eye problems, and general discomfort:

Vision problems

Vision problems can include blurred vision (both near and far), difficulty changing focus, double vision, glare, flickering sensations, and temporary changes in color perception.

Eye problems

Eye problems can include redness, burning sensation, soreness, stinging, itchiness, dryness, excessive tearing, eye fatigue, eyestrain, light sensitivity, and contact lens discomfort.

General discomfort

General discomfort symptoms can include headaches, neck tension or pain, shoulder tension or pain, back pain, pain in arms or wrists, excessive fatigue, irritability, and drowsiness.


What causes computer vision syndrome?


Working at a computer requires a number of visual skills.  When you are viewing a computer screen, your eyes must easily converge so they point to the exact same spot on the screen.  As you read the screen, your eyes must move quickly and accurately for sustained periods.  And while maintaining a converged position and moving quickly and accurately across the screen, your eyes must maintain the proper amount of focusing (accommodation).


Focusing on a computer screen is more difficult than focusing on a book or printed page for a number of reasons:

  • The resolution of most computer screens is lower that that provided by ink on paper.  Resolution influences the shape and edge sharpness of characters on a page.  The lower the resolution of the screen, the more difficult it is to maintain comfortable focus.
  • The surface of many computer monitors cause distracting reflections.  This makes focusing more difficult and can lead to eyestrain.
  • Conventional cathode-ray tube monitors cause images to flicker.  Though most computer users are unaware of this flicker, it contributes to eyestrain. (Flat panel LCD monitors eliminate the flicker problem.)
  • Images created on a tube-style computer screen are formed by an electron beam striking a layer of phosphor, generating tiny bright spots called pixels.  Thousands of pixels combine to form characters and words.  Each pixel has a bright center but fades out toward its edges.  This poor edge definition of pixels is present even on high-resolution screens.  Researchers believe that because of this characteristic of pixels, our eyes cannot stay properly focused on the screen and tend to drift in and out of focus, leading to eye fatigue and other symptoms of CVS.


Studies also show that people don’t blink frequently enough when using a computer.  Most people normally blink 16 to 20 times per minute.  But during computer use, blink rates can drop to only 5 to 7 times per minute.  Also, people often perform only partial blinks when using a computer.  Infrequent and incomplete blinking when using a computer can cause eyes to become dry, red, and irritated.  It can also lead to eyestrain and blurred vision.


In addition to the stress it causes on our eyes, prolonged computer use involves sitting in one position for long periods of time.  Many (if not most) people have poor posture when working at a computer.  This may be due to the physical setup of the workstation itself or because the user feels the need to lean closer to the screen over time to see it more clearly.  The longer a person works at a computer, the more likely they are to experience stiffness, headaches, neck and shoulder discomfort, backaches, and arm and wrist pain from poor posture or overuse of certain muscles. 


How common is computer vision syndrome?

The American Optometric Association estimates that 70 to 75 percent of all computer users experience CVS symptoms.  


How is computer vision syndrome treated?


The first step in relieving computer vision syndrome is to have a complete eye exam.  If you use a computer on a routine basis, you should have an annual eye exam.


Tell your eye doctor that you use a computer, and explain what type of computer-related symptoms you are experiencing.  Let your doctor know as much as you can about your work environment, including the distance from your eyes to your computer screen.  Also, let them know whether you typically wear eyeglasses or contact lenses when using a computer.


Most people who use a computer for prolonged periods can benefit from eyeglasses prescribed specifically for computer use.  These eyeglasses will help your eyes maintain proper focus on your computer screen with less eye fatigue.


If you don’t currently wear eyeglasses or you wear eyeglasses with single vision (non-bifocal) lenses, your doctor will likely prescribe single vision lenses that provide added magnification for viewing your computer screen.  These eyeglasses are designed for computer work and other near tasks only.  The lens power in this type of “computer glasses” will make your computer screen clear and more comfortable to read for prolonged periods, but it will make objects that are farther away appear less clear.  Similar lenses can be prescribed to wear over your contact lenses when you are work at the computer.


If you currently wear bifocals or progressive eyeglass lenses, these lenses are typically unsatisfactory for long periods of computer use.  Bifocals require you to tilt your head back to view the computer screen, causing neck stiffness and eyestrain.  Progressive lenses are somewhat better for computer use, but the portion of the lens that contains the proper power for viewing a computer screen is typically too small, requiring frequent head movements to see the screen clearly.


For bifocal and progressive lens wearers, your eye doctor may prescribe a special type of variable focus or progressive lens for your computer work.  These lenses offer a much wider field of view for computer use, with the proper amount of magnification for comfortable viewing of the monitor higher up in the lens.  The lower part of the lens has added magnification for reading smaller printed material on your desk.


A number of different brands of these special purpose “computer progressive” lenses are available, including Cosmolit Office (Rodenstock), Hoyalux Desk (Hoya Lens), Gradal RD (Zeiss), TruVision Technica (American Optical), Access (Sola), Interview (Essilor), and Shamir Office (Shamir Insight).


Like single vision lenses for computer use, these lenses are designed for computer work and other near tasks only.  Distant objects will appear noticeably blurred.  You should keep these eyeglasses near your computer and wear them when you plan to work at the computer for prolonged periods.


All lenses worn for computer use should include anti-reflective (AR) coating.  This vacuum-applied thin film coating keeps light from reflecting off the lens surfaces, thereby preventing an additional source of glare.  Studies show that people who work for prolonged periods at a computer find their eyes are more comfortable if they wear lenses with AR coating (compared to wearing the same lenses without the coating).


In some cases, your eye doctor may also recommend special eye exercises to improve your eye alignment or focusing skills for computer use.


Five things you can do to avoid computer vision syndrome


After you have seen your eye doctor and you have the best possible eyewear for computer use, follow these tips to further reduce your risk of computer vision syndrome:  


1.  Optimize your workstation

  • An improper screen location can cause poor posture.  Position your screen about 24 inches from your eyes, and approximately 6 inches below eye level.
  • Tilt the screen so the top and bottom are the same distance from your eyes and position the monitor directly in front of you, not off to the side.
  • Use a document holder and put your reference material as close to your screen as possible.
  • Check your screen for reflections.  Adjust your desk lighting and window shades or rotate your workstation to eliminate reflections on your screen.  If reflections remain, consider purchasing an anti-reflective screen filter.
  • Most office environments have lighting that is too bright for comfortable computer use.  If possible, reduce overhead lighting to a more comfortable level or use indirect lighting.
  • An adjustable, supportive chair is important.  Sit with your back against the chair and your feet flat on the floor. 


2.  Check your hardware

  • Adjust the contrast and brightness of your screen for greatest comfort. The brightness should be equal to the general background brightness of the room.
  • If possible, increase your screen resolution or purchase a higher quality monitor.
  • Check the refresh rate of your monitor.  Low refresh rates can cause flicker that is barely perceptible yet bothersome to the eyes.  A refresh rate of at least 70 Hz is recommended.
  • If you routinely work with spreadsheets, graphic designs, or long documents, purchase a 17-inch or larger monitor.


3.  Take frequent breaks

  • Rest your eyes frequently by closing them or looking across the room for several seconds.   Do this every 15 to 20 minutes.  Some eyecare professionals call this the “20-20-20 rule”:  Every 20 minutes, take a 20-second break to look at objects that are at least 20 feet away.


4.  Blink often

  • Blink fully once or twice every time you change a page view to help keep your eyes moist and comfortable.  If your eyes still feel dry, use artificial tears or contact lens rewetting drops as often as necessary.


5.  Get up and stretch

  • Every 20 to 30 minutes, get up and stretch.  This relieves muscle tension and increases blood flow. 
  • Be aware of your posture.  Make frequent adjustments to avoid lapsing into cramped positions that can lead to neck, shoulder, and back stiffness or pain.

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