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Computer Vision Syndrome


Computer Vision Syndrome – PowerPoint PPT presentation

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Title: Computer Vision Syndrome

Computer Vision Syndrome
(No Transcript)
What is Computer Vision Syndrome? (CVS)
  • A complex of eye or vision problems which are
    experienced during and related to computer use.

Superior and lateral rectus muscles, optic nerve.
Superior and inferior oblique muscles,
superior,inferior, and lateral rectus muscles,
with eye.
Superior and inferior oblique muscles, medial and
inferior rectus muscles.
Eye with rectus muscle attachments.
Why are we concerned about CVS?
  • 143M American workers work on a computer and
    estimates are
  • - 88 suffer from computer eyestrain
  • 90 of the 143M U.S. workers use computers today
    for more than 3 hours per day.
  • This problem effects productivity by 4 to 19 .

What are the symptoms of CVS?
  • Eyestrain (sore or fatigued eyes)
  • Headache
  • Slowness in changing focusing distance
  • Eye irritation (burning, dryness, redness)
  • Neck, back shoulder pain

The Problem
  • It has multiple causes symptoms.
  • Prolonged viewing is the most common cause and it
    has been proven to be unnatural for the human
    optical system.
  • Humans blink approximately 22 times per minute.
    During computer use humans blink only 4 to 6
    times per minute.

Other Problems
  • Lower blinking rates cause eye moisture to
    evaporate (dry eye).
  • Dry eye causes people to arch their foreheads in
    a effort see better, thus causing headaches.
  • Many people assume awkward, unnatural postures,
    thus causing sore backs, stiff necks hurting

  • What Causes Computer Vision Syndrome?
  • CVS is caused by our eyes and brain reacting
    differently to characters on the screen than they
    do to printed characters.

Our eyes have little problem focusing on most
printed material, which is characterized by dense
black characters with well-defined edges. Healthy
eyes can easily maintain focus on the printed
page. Characters on a computer screen, however,
don't have this contrast or well-defined edges.
These characters (pixels) are brightest at the
center and diminish in intensity toward their
edges. This makes it very difficult for our eyes
to maintain focus and remain fixed onto these
  • Will Glare Screens Prevent CVS?
  • Glare screen filters may help somewhat, but they
    will not solve your computer vision problems
    because they only affect glare from the computer
    screen not the visual problems related to the
    constant refocusing of your eyes when working at
    a computer.
  • Only when your eyes can focus clearly at the
    plane of proper distance on the computer screen
    can they experience relief from the fatiguing
    effects of CVS. An anti-reflective coating (AR)
    is also highly recommended on all computer
    eyeglasses. An AR coating prevents glare and
    reflections on the front and the back of the
    lenses that would interfere with focusing on the

  • Will Computer Eyeglasses Make the Screen Clearer?
  • Yes, because they will eliminate the constant
    refocusing effort that your eyes go through when
    viewing the screen. It has also been proven
    clinically that having the correct prescription
    in computer eyeglasses increases productivity and

  • What About the Tints I've Heard of for Computer
  • If you work in a brightly lit office, you may
    benefit from a light tint applied to your
    computer lenses. This can cut the amount of light
    that reaches your eyes and provide relief in some
    cases. But tints and filters don't address the
    underlying cause of computer eyestrain.

  • Does Every Computer User Need Computer Glasses?
  • More than 70 of computer users need computer
    eyeglasses. In fact, according to a study out
    of the University of California, Berkeley,
    25-30 of children would benefit from computer

  • Will My Reading Glasses Work at the Computer?
  • Not necessarily. In most cases your reading
    glasses are probably not going to do the job. The
    correct computer eyeglasses will optimize your
    comfort and productivity at the computer screen
    while also allowing you to read and see out at
    some determined distance (10-13 feet). Reading
    glasses are usually prescribed to read at a
    distance of 16"-18", but computer glasses are
    usually designed to work at 18" to 28".

  • Can CVS Cause Other Body Pains?
  • Headaches, sore neck, shoulders or back are
    common complaints and there are two main causes,
    one having to do with your vision and one not.
  • Vision
  • So where do the other aches and pains come in?
    These are often caused by trying to read the
    screen through the bottom portion of bifocals, or
    though half-eye reading glasses. You tip your
    head up or lean forward to see and this unnatural
    posture makes you sore.

  • Isn't Ergonomics the Solution to Computer
  • Ergonomics is important changing one's computer
    workstation can certainly help to minimize other
    physical symptoms. But ergonomics cannot fix a
    visual problem. The proper prescription computer
    eyeglasses at the proper computer distance (18"
    to 28") is most important. This can be done only
    with the right computer lens prescription.

10 Steps to Reducing Computer Eyestrain
  • Get a computer eye exam.
  • Use proper lighting.
  • Eyestrain is often caused by excessively bright
    light coming in from outside and excessively
    bright light inside. When you use a computer,
    your ambient lighting should be about half that
    used in most offices. Eliminate exterior light by
    closing drapes, shades, or blinds. Reduce
    interior lighting by using fewer light bulbs or
    fluorescent tubes, or use lower intensity bulbs
    and tubes. If possible, position your monitor so
    that windows are to the side of it, instead of in
    front or back.

10 Steps to Reducing Computer Eyestrain
  • Minimize glare.
  • You may want to install an anti-glare screen on
    your monitor and, if possible, paint bright white
    walls a darker color with a matte finish. Again,
    cover the windows when outside light cannot be
    reduced, use a computer hood. Have an
    anti-reflective coating applied to your glasses.
    This will prevent glare and reflections on the
    back side of your lenses
  • Adjust the brightness of your computer screen.
  • Closely match the brightness of the environment
    with that of your computer screen. Make sure that
    the text size and color are optimized for the
    most comfort.

10 Steps to Reducing Computer Eyestrain
  • Monitor Display Quality
  • Refresh rate how often your monitor redraws
    the content on the screen. A too-low rate can be
    hard on your eyes, and a very slow rate causes a
    noticeable and irritating flicker.
  • Resolution a monitor's pixel density the
    more pixels, the higher the level of detail.
    Generally, the higher the resolution the better.
  • Dot pitch affects the sharpness of the
    display. The lower the number, the sharper the
    image. Most monitors have a dot pitch between
    0.25 mm (millimeters) and 0.28 mm 0.28 or lower
    is desirable.

10 Steps to Reducing Computer Eyestrain
  • Blink more often.
  • Blinking is very important when working at a
    computer it rewets your eyes to avoid dryness
    and irritation. When working at a computer,
    people blink less frequently about five times
    less than normally, according to studies. Tears
    coating the eye evaporate more rapidly during
    long non-blinking phases and cause dry eyes .
    Office buildings may have excessively dry
    environments that also reduce tearing.
  • Also try this exercise Every 30 minutes blink 10
    times by closing your eyes as if falling asleep
    (very slowly). This will help rewet your eyes
  • Exercise and stretch your eyes.
  • An hourly exercise to readjust your focusing is
    to look far away at an object for 10-15 seconds
    and then near for 10-15 seconds, rocking your
    focusing back and forth between near and far. Do
    this 10 times. Both of these exercises will help
    you prevent strained near vision and stretch your
    focusing muscles

10 Steps to Reducing Computer Eyestrain
  • Take frequent breaks.
  • 20/20/20 every 20 minutes look at something at
    least 20 feet away for 20 seconds.
  • Every 50 minutes on a computer, change tasks for
    10 minutes.
  • Modify your workstation.
  • If you need to look back and forth between a
    printed page and your computer screen, this can
    cause eyestrain. Place written pages on a copy
    stand adjacent to the monitor. Properly light the
    copy stand you may want to use a desk lamp, but
    make sure it doesn't shine into your eyes or onto
    the computer screen. Adjust your workstation and
    chair to the correct height. Purchase ergonomic
    furniture to insure proper screen locations and

10 Steps to Reducing Computer Eyestrain
  • Exercise even when sitting.
  • Anyone in a sedentary job, especially those using
    computers, should stand up, move about, or
    exercise their arms, legs, back, neck, and
    shoulders frequently. NIOSH recommends several
    sitting, stretching, and joint rotating exercises
    for computer users

The Solution
  • Keep computer screens slightly below eye level
  • 20-26 inch from the screen
  • Keep contrast brightness at moderate levels
  • Keep screen clean
  • Reduce screen glare
  • Frequent short breaks
  • Purposely blink rapidly

Our eyes involuntarily move to the RPA, and then
strain to regain focus on the screen. This
continuous flexing of the eyes' focusing muscles
creates fatigue and the burning, tired-eyes
feeling that is so common after long hours at the