Tunnel vision is the condition where the
sufferer has difficulty seeing objects at the edges of the normal field of
vision and can only properly focus on objects in a narrow,
"tunnel-like" field.
The condition has implications on the person’s
freedom of movement, having to turn their head this way and that way just to
avoid stumbling into objects, even in a small room. A person with tunnel vision
may not even be able to drive, and tests of a person’s peripheral vision are
usually a pre-requisite before they can be given a driving license. Some cases
of tunnel vision, if left untreated, could result in total blindness. There are
quite a number of causes of tunnel vision and just about anybody could be
susceptible to the condition.
Tunnel vision, sometimes also called
"peripheral vision loss" is one of those disabilities that could have
fatal implications for the sufferer, and if you have reason to believe that you
have tunnel vision you should seek medical attention as soon as possible. The
chances of tunnel vision being reversed are quite slim in most cases, but if
the treatment is started early, aggravation of the condition to a more severe
stage, or to total blindness may be prevented.
The condition itself cannot kill you, but it
puts you at great risk of being run down when crossing the road, for example,
or if you operate certain types of machinery, and from driving accidents.
The
Causes of Tunnel Vision
Tunnel vision can be caused by a host of medical
and biological conditions ranging from blood loss, alcohol consumption through
to mercury poisoning and a bite from a black mamba (a type of poisonous snake).
The leading causes of the condition are listed below:
Glaucoma
When a person suffers from glaucoma the
condition causes pressure build up inside the eyeball. This fluid pressure puts
a strain on the retina, distorting it or warping it out of shape and the result
is loss of peripheral vision, or tunnel vision. The causes of glaucoma itself
are still unknown, but it can be treated and its impact on the deformation of
the retina slowed or even stopped. This will not cure the tunnel vision that it
leaves in its wake, but it has the effect of "arresting" the
condition and preventing it from getting worse. In addition to causing damage
to the retina glaucoma also may do damage to the optic nerve, and this could
progress into total blindness if the nerve got too badly damaged.
Glaucoma can be treated with eye drops and other
forms of medication and if your tunnel vision has been caused by glaucoma you
should take the treatment of the glaucoma itself as a very high priority. Your
tunnel vision problem could get much worse if you are lax with the glaucoma
treatment.
Eye "Strokes" or Blocking of
Blood Vessels in the Eye
If blood vessels in the eye get blocked
(occluded) blood flow to internal organs in the eye and to the optic nerve gets
interrupted and this can lead to loss of peripheral vision or even permanent
loss of sight.
Strokes Affecting the Brain
A stroke that damages some parts of the brain
can cause tunnel vision by affecting the processing of visual information. The
eye itself will be perfectly okay, but the imaging information it sends to the
brain is only partially processed and this could result in loss of peripheral
vision amounting to tunnel vision sometimes.
A Detached (or Displaced) Retina
The retina inside the eye can get detached from
its supportive layers of tissue if there is injury or shock to the eye or the
head (concussion) and this is a serious condition that could lead to loss of
sight in extreme cases, or to tunnel vision. A surgical operation would then be
needed to re-seat the retina and if this if done early the tunnel vision may be
fully reversed. A person with a detached retina will usually experience warning
signs, such as flashes of light, floating points of light or black and white
spots in your field of vision. In addition you might see shadows and
"curtains" across the field of vision, vertical or horizontal (from
left to right) where you know they should not be.
Alcohol and Hallucinogenic Drugs
Alcohol can affect the ability of the eyes to
focus on the same object and also causes blurring of the vision. In other cases
it can cause tunnel vision. Hallucinogenic drugs can have the same effect as
alcohol, by causing damage to the eyes or the visual processing centers in the
brain. The tunnel vision caused in these circumstances may be temporary or last
for the duration when the drug is still in circulation. But in severe cases of
poisoning of the brain the changes may become permanent.
Severe Cataracts
Cataracts can reduce the area of the external
membrane of the eye (the cornea) through which light can pass to reach the
retina and this usually leads to tunnel vision in one or both eyes.
Wearing Spectacles
Some spectacles can reduce your field of vision
to what amounts to tunnel vision. This is not a condition affecting the eyes
themselves but is the result of the obstruction of the path of light caused by
the lenses. A person in this situation may have to turn their heads every time
they want to focus on an object just a few degrees to the left or right of
center field.
Other Causes of Tunnel Vision
A host of other conditions can cause cases of
tunnel vision that may usually be temporary. Altitude sickness in passenger
aircraft may be the cause of temporary tunnel vision. Very high accelerations
lasting for more than one second can also cause a temporary case of tunnel
vision for pilots or passengers in very fast aircraft.
Situations that cause secretion of high levels
of adrenaline such a physical fight can also cause tunnel vision. Even intense
anger causes the release of high levels of adrenaline and can cause temporary
tunnel vision.
Other situations that cause tunnel vision
include exposure to oxygen at high pressure (such as may happen to divers),
prolonged exposure to air suffused with heated vapor from hydraulic fluids (as
may happen in aircraft for example), extreme fear or anxiety that leads to a
panic attack, etc.
From what has been noted above the conditions,
medical, biological or environmental that could cause tunnel vision are quite
numerous. Anybody could at some point in their lives suffer from tunnel vision
(hopefully the temporary kind!). But the permanent cases of the condition are quite
debilitating, and in some cases could prove fatal. By knowing the causes of
tunnel vision you reduce the risk of developing the extreme cases of the
condition, by knowing when to seek medical attention if you have reason to
believe that you may be getting tunnel vision. Unlike other eye problems tunnel
vision cannot usually be treated by wearing glasses for example, although it
has been tried with spectacles that incorporate prisms to expand the field of
vision. The condition cannot usually be reversed. Where tunnel vision is
concerned the best cure lies in preventing the condition.
