The Computer Terminal and Your Eyes - Computer Vision Syndrome (CVS)(Monitor
Are you one of the millions of computer-users for communication, entertainment,
business or to access information from around the world? As statistics
would have it, 60-90% of software professionals suffer from visual fatigue
at some time or the other.
It is certainly hard to deny their convenience at home and in the work
place, however, are all of those hours in front of the computer taking
a toll on your health and vision? While working with a computer will not
ruin your eyes, it may well be putting stress on your visual system. Perhaps
you have experienced some of the symptoms of eye stress, strain, or fatigue.
If so, read on to discover what may be causing that fatigue and how to
alleviate some of the symptoms without compromising your computer use.
You're not alone. Over 75% of all computer users report some form of
visual discomfort while using their computers specifically their visual
display terminal (VDT). The symptoms are unpleasant, but the causes, like
improper lighting, glare, and screen brightness, can be easily reduced
Here are some of the common symptoms;
2. Blurry or double vision.
3. Itchy burning eyes/irritation/grittiness.
4. Eye fatigue.
5. Excessive tearing or dry sensation in the eyes.
6. Frequent blinking and/or squinting.
So, what causes these symptoms?
A. In the VDT;
1. Improper lighting, glare, reflections on the VDT.
2. A flickering screen.
3. The size of the displayed characters.
4. Colour, contrast and brightness of the screen.
5. Improper design of the workstation.
B. In the eye;
1. Reduced blink rate.
2. Refractive errors/Presbyopia.
3. Prolonged time spent at the computer terminal.
What is really happening
Six groups of external muscles control the movement of the eye. These
extra-ocular muscles, as they are known, help to move the eye sideways
and up and down, to converge or diverge on an object of focus. An internal
muscle, the ciliary muscle, helps focus the lens of the eye. The external
and internal muscles work in unison with each other.
So what has age got to do with it?
However between the ages of 35 and 45, the lens becomes less flexible
and the ciliary muscles can't adjust the lens focus as they previously
could do for objects at a distance of 12 to 20 inches. This condition
is called Presbyopia and individuals with Presbyopia usually need reading
glasses or bifocals. Even the pupil has a group of muscles which controls
its dilation and constriction. A change in light levels from a white,
brightly-lit page to a dark computer screen can tire these muscles. Over
time and with this stress, the brain can grow fairly tired of trying to
interpret what it is seeing via the optic nerve. All of these factors
contribute to a physical fatigue of the visual system.
If you are over 40, and in some cases under 40 as well, you may be wearing
a bifocal, trifocal or progressive add-on prescription. However, wearers
may have to adjust their heads or bodies to a position where they can
see clearly through the bifocal or trifocal. This may not be comfortable
and can add stress or contribute to fatigue. Also, the portion of the
lens that provides the focus that one needs for a certain distance may
not provide a wide enough viewing area and, therefore, can be unconformable.
To avoid this eye stress, a stiff neck, or back pain, the patient or
computer-user may consider getting a pair of single vision lenses where
the entire lens prescription provides clear vision at the distance of
the computer. Another option is a bifocal in which the top of the lens
is focussed for the computer and the bottom for close reading. You can
discuss the specific demands of your job with your optometrist/eye specialist
and determine the type of glasses or contacts that are right for you.
If your occupation demands long hours at a computer station, you might
ask your employer if your benefits package includes occupational glasses.
Your increased efficiency and satisfaction as an employee will quickly
compensate your employer for his or her investment in your eye comfort.
Look around you. How is your workstation arranged? The number of factors
contributing to the environment of the computer-user is significant, and
all of them could contribute to stress, strain and fatigue.
Is there a remedy for this?
Of course there are several;
1. Eliminate glare by moving lights reflecting in the VDT. (Access the
source of the glare while the screen is turned off).
2. Get an anti-glare screen if you do not already have one. Anti-glare
screens can easily be attached to the front of your VDT much like clip-on
sunglasses can be put over a pair of prescription glasses.
3. Draw shades (curtains) and use lower wattage bulbs, and less fluorescent
lighting near the computer. In a small room, for example, the lighting
should be equivalent to about 60 Watts and the VDT should be perpendicular
to bright light sources.
4. Adjust the contrast control on your monitor so that the intensity
of the characters is comfortable, generally about 5-10 times brighter
than the background. Pay attention also to the size of the fonts in your
programs, increase the size to a comfortable view, or magnify the size
of the text - using zoom if permitted by the program. Black characters
against a white background, as in some of the popular word processors
can cause a lot of eyestrain over a period of time due to the excessive
contrast. Use a more soothing combination, like a dark background color,
and light gray fonts.
5. Adjust the brightness so that the flicker on the VDT is less noticeable.
The brightness of the screen itself should be overall 3-4 times the room
illumination. It may be worth noting that the flicker is more noticeable
with a white background. Move hardware with magnetic fields away from
the monitor (transformers, speakers, etc).
6. The position of the monitor is important as well. If the VDT is placed
at a level so that you do not have to move your head sideways, or far
too high or low, you can work comfortably for a long time.
7. Do get your eyes tested for any refractive errors. Some diseases of
the eye may cause repeated changes in near vision requirements, especially
glaucoma. So if your working conditions are ideal, it is very important
that you get a complete eye check-up done to rule out other eye-related
causes of ocular discomfort.
8. Rest - encourage short breaks, which could be used to either close
or rest the eyes. An effective exercise is to look away from the screen
periodically for a few seconds/minutes.
9. Use of supplementary eye lubricants may be advised by the ophthalmologist
in special cases.
These few changes could make a considerable difference when combined
with other important elements of the workstation, such as location and
general environment and the refractive status of your eyes.
Compiled from various sources, by Dr. Ravin Das, M.S., Ophthalmology.
Date: December 16, 1998. Last modified April 7, 2001.
The term squint to the ophthalmologist
means strabismus, or mal-alignment of the visual axis of the eyes. In
general terms the word is used here not in the medical context, but to
describe a state of screwing of the lids, so as to make the aperture of
the lids narrow, while attempting to see something attentively.
Reduced blink rate is because of a very
simple natural phenomenon. Whenever we observe anything with much curiosity,
or are engrossed with something, the rate at which the eyelids should
blink reduces (the normal blink rate is 14-20 times per minute). This
in turn causes the normal secretions to dry up, which is accentuated by
dry air-conditioning, and also in the dry summer air. This causes the
sensation of dry eye, which may present as a pricking in the eyes, or
even a red eye. On the other hand the eyes may get watery, due to a reflex
excess production of tears.
Refractive errors of the minor types are
easily overlooked, since they do not cause much blurring of vision as
far as near objects are concerned. However there are minor refractive
errors of the type known as astigmatic errors, which cause a lot of strain
with both distance vision and near vision, to the extent of headaches.
Myopia in the young does not cause as much eyestrain as do Hypermetropia
The age at which a person may need Presbyopic
correction varies with the refractive power requirements for distance
vision. A person with normal distance vision (6/6), will require reading
glasses for a comfortable near vision by the age of 40. Whereas, a person
who is previously hypermetropic, may require the near correction at an
earlier age. And someone who is Myopic may not need any correction provided
the myopic correction is in the range of -1 to -2. It is of interest to
note here that the usual correction given for presbyopia is measured at
a distance of 33 CMS, which is the usual distance at which the keyboard
is placed. The monitor may be at a distance greater than 33 CMS, so a
special "intermediate" correction may have to be given. The
later is the origin of "intermediate-near" distance bifocals
for computer users.
Incorrect positioning of the monitor inadvertently
worsens CVS. Keeping the monitor at a level higher than neck aggravates
the problem because in "up-gaze", the exposed eye-surface area
is much larger (almost 2.5 times more) than when the eye is looking down
at the monitor. The more the eyes are covered by the lids, the less the
evaporation - hence wetter the eyes and lesser the symptoms of CVS. These
complaints are often associated with headaches and neck and arm discomfort.
Other factors, like the resolution of
the VDT and the refresh rate are also of importance. But it is a far too
complex topic, which will not be in context here. Briefly, go for a reputed
monitor, take a trial, sit at the monitor for some time before making
a purchase. Black and White or Color? The choice is yours, and depends
on your budget. The color monitors are definitely packed with more features
for more comfortable computing.