Blindness
The leading
causes of blindness (in America) are different than in under developed
countries. The leading causes of blindness in Africa and other countries are
related to vitamin deficiencies and parasitic diseases that involve the eye. In
America, the leading causes are
á
macular degeneration of the retina in older people,
á
diabetic retinopathy,
á
cataracts
á
glaucoma
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optic nerve diseases
á
injury or trauma
á
strabismus or sensory crossing of the eye.
Diabetes
Diabetes leads to
blindness because delicate blood vessels inside the retina are damaged and
become leaky, allowing blood and lipid and fluid to damage the delicate retina.
Also, the blood vessels become closed off, creating lack of nutrition or
ischaemia to the retina, resulting in growth and proliferation of abnormal or
new blood vessels which then bleed or cause scarring, which leads to traction
or detachment of the retina.
Innovative
surgery in the 90's
There are many innovative
surgeries related to the eye at the present time. New surgeries on the optic
nerve, allow splitting of the sheath of the optic nerve behind the eye that may
be constricting the flow of information from the eye to the brain. The use of
modern vitreous and retinal techniques, now allow surgery of the scar tissues
that grow beneath the retina, and with some people have marked restoration of
vision. Cataract surgery is now routinely performed through tiny incisions,
many times with no sutures. Surgery to relieve nearsightedness is rapidly
progressing through the use of excimer laser and other surgical advances. There
are many other applications of the laser that apply to the diseases of the
retina and now the laser is being used to resurface and smooth the skin around
the eyes.
Causes and
Treatments of Macular Degeneration
Macular
degeneration is usually caused by an aging degeneration of the back layers of
the eye. Proven treatments include laser photocoagulation for leakage and new
blood vessel growth underneath the retina. Promising therapies include
nutritional supplementation and vitrectomy surgery to remove diseased tissue
beneath the retina. Low vision therapy, meaning the proper use of agents that
increase magnification and contrast and utilise proper illumination are also
tremendously important.
Wet and Dry
Versions
Macular
degeneration of the retina is the leading cause of blindness in older
individuals in the western countries today. It almost never causes complete
blindness, but individuals with it may lose the ability to read, drive, and
experience a blackness of their centre vision. The "wet" version is
caused by a leakage of blood, fluid, or fatty material from new blood vessels
growing beneath the retina. The "dry" version is related to an
atrophy of the pigmented layer of the retina and the vascular layer that
underlies it. The wet version is the worse type as it frequently causes a
greater loss of vision but is the only type that is treatable today.
Preventative
measures
It is now recognised
that careful control of one's blood sugar is tremendously important in the
prevention of almost all diabetic complications. All individuals with diabetes
should try to keep their blood sugar normal, their blood pressure normal, their
weight normal, and by doing so may reduce complication rates by 50-70 percent.
Speed of
Progression of Glaucoma
There are many
types of glaucoma. Acute angle closure glaucoma can cause total blindness
within one day, but fortunately its symptoms are extreme pain and blurred
vision so that individuals affected usually seek eye care on an emergency basis
so that blindness may be prevented. The usual kind of glaucoma is slow in
progression, painless, and is a silent thief of vision, taking years to cause
its damage. Blindness occurs most often with advancing age, with half of all
blind people generally considered to be over sixty-five. A significant number
of blind people, however, are children or young adults. There are many causes
of blindness, but the major ones include:
Cataracts - opacities and
clouding of the eye's lens. May form and block the passage of light through the
eye. Some people are born with cataracts, but the incidence increases with age.
They are not painful and the only symptom is blurred, dimmed or double vision.
Not all require surgery, but those large enough to cause serious visual
problems require surgical removal of the lens, implantation of an intraocular
lens and corrective glasses or contact lenses.
Diabetic
retinopathy - the increased lifespan of diabetics has increased the incidence of
this disorder. Changes in the tiny blood vessels of the diabetic's retina can
cause blindness. Abnormal blood vessels are formed, some may burst and the
retina may even break loose from the back of the eye. Laser treatments to
"seal" blood vessels or reattach the retina may help if undertaken
early. Some diabetics do not experience vision loss.
Glaucoma - perhaps one in
every seven or eight cases of blindness is due to this disorder, in which the
transparent fluid inside the forward part of the eye does not drain normally
and excess pressure is built up within the eye. If the pressure is not
controlled, the delicate structure of the eye is increasingly damaged,
resulting in blurred vision, a narrowed field of sight and eventually total
blindness. Early symptoms may include blurred vision, halos around lights and
reduced side vision. In the acute type, there is great pain as eye pressure
rises quickly from blocked drainage canals. In the more common chronic type
there is no pain and vision loss is gradual. Many cases are controlled very
well by medication, but surgery is sometimes necessary. Early detection is
important.
Macular
degeneration - as the inner surface or lining at the back of the eye, the retina functions
a little like the film in a camera. The macula is the part of the retina which
forms the centre of the "picture'' and the sharpest image. Degeneration or
breakdown of the retina may occur, especially with increased age. The disorder
may be slow or rapid, but peripheral vision usually remains good. Magnifiers
may help, and a few people may be helped by laser treatment to seal off blood
vessels which have grown beneath the retina or to repair the macular's weak
spots by removing wornout tissue and allowing new tissue growth.
Retinitis
pigmentosa - frequently beginning as what is called "night blindness,"
this condition brings degeneration of the retina and the choroid (a related vascular
area), usually involving an abnormal development of excess pigment. It is
hereditary, with a variety of patterns of inheritance and development. The most
common pattern of development is that at approximately age ten or twelve, the
youngster begins to experience some difficulty in seeing at night and in poorly
lighted areas. His visual field also begins to narrow, frequently resulting in
what is commonly termed "tunnel vision" although he may not realise
this at first. The visual loss is progressive, so that the individual is
usually legally blind by young adulthood and slowly loses more and more vision
thereafter. Many adults with retinitis pigmentosa have a very tiny field of
vision in which they see well under a good light but which is so small as to be
of little use. Total blindness often results. There is no known treatment.