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Holy diopters! Run for the hills! The sky is falling! We
are threatened with the cure for the scourge of our youth -
myopia - by a gene that can change the destiny of eye care
providers henceforth and beyond.
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The idea of myopes being eliminated from our practices
could certainly have far reaching consequences. In a
nutshell, scientists from the four corners of the world have
announced that they have pinpointed variations in DNA that
make people more likely to develop nearsightedness, our most
common refractive condition. The discovery could lead to
treatment in the next decade via eye drops or tablets that
would halt the elongation of the eyeball, the usual source
of myopia. This refractive condition has reached near
epidemic proportions. Urbanization and increased near vision
requirements, such as intensification of education levels
and increasing dependency on hand-held electronics, have
contributed to the serious regard that our scientists have
relegated to this problem.
About one third of the people in both Britain and the U.S
are affected by nearsightedness. In the Far East it is an
even more formidable problem. Some say about the latter that
this is caused by increased interests in technology at early
age levels, being more prevalent there than in other parts
of the world. In Japan, two thirds of teenagers are already
myopic and in Singapore, eighty percent of 18 year old male
army recruits are myopic compared with 25 percent only
thirty years ago. Successful applicants for fighter pilot
positions were few and far between as a result of their
nearsightedness.
For the past twelve years researchers knew that there was
a strong hereditary or genetic element that influenced both
the incidence and severity of myopia. Professor Terri Young
of Duke University is one of the project's leading authors.
Dr. Young said, "The eye is a great subject for gene
repair. It is an organ of choice because the eye's small
volume and self contained area allows the therapy to remain
inside the eyes in a concentrated dosage," she said.
"In addition, the eyes accessibility allows clinicians
to observe the effect of treatment over a period of time
with non invasive methods that can illuminate and test the
retina and other eye structures." Dr. Young has also
led a team that found a different gene (CTNDD2) which is
related to myopia in Chinese and Japanese populations.
As a result of the search for genes associated with
myopia, scientists discovered a number of variations around
the RASGRF1 gene. This gene is connected with eye growth and
subsequently with the process of preventing myopia or
protecting against it. RASGRF1 provides a novel molecular
mechanism to study so that we can work to prevent myopia.
Linkage studies have identified 18 possible loci on 15
different chromosomes that are associated with myopia.
However, none of these loci are part of the candidate
genes that cause myopia. Instead of a simple one gene locus
controlling the onset of myopia, a complex interaction of
many mutated proteins acting in concert may be the cause.
Instead of myopia being caused by a defect in a structural
protein, defects in the control of these structural proteins
might be the actual cause of myopia. Scientists created mice
that were missing this special gene and as a result the mice
showed distinct changes in their lenticular system.
Researchers now hope to learn how the gene variations affect
the growth of the eye and then develop treatments that
produce the perfect mix of genes.
Dr. Christopher Hammond, of King's College, London, is an
eye surgeon who led the British research project. He said,
"It is not quite the end of spectacles yet, but clearly
the hope is maintained that we will be able to block the
genetic pathways that cause nearsightedness. It will take at
least ten more years before a treatment will be
available." Dr. Hammond believes that eye drops or
tablets administered to children and adolescents could block
those genetic pathways that send signals to stimulate eye
growth. There must be serious testing to explore the
possibilities of side effects. Dr. Hammond adds, "I
think that certainly the number of people needing glasses
would be significantly reduced. But I think that there will
be some people that have rarer genes and they will still
remain myopic. So to say we will eliminate eyeglasses may be
overstating it. We're never going to halt myopia in every
case but we hope to have an impact on the majority."
At birth the eyeball is usually of a farsighted dimension
and assumes a more normal shape at about the age of seven
years. However, much of our youthful years are spent staring
at screens and books which can cause a hypertonicity in the
focal mechanism and set the stage for progressive myopia
through increases in eyeball elongation. Treatment entails
the use of corrective lenses in the form of spectacles or
contact lenses. Certain patients are candidates for
refractive surgery. Lasik surgery can occasionally improve
the vision to the point that further correction is
unnecessary. There are other non surgical approaches to
myopia such as orthokeratology, which is a procedure that
reshapes the cornea and its curvatures. This also can
occasionally eliminate the need for additional corrections.
One can make a comparison with the use of braces to realign
uneven teeth.
There are varieties of nearsightedness which are
considered pathological. These are often linked with retinal
detachment, glaucoma and vision distortion that is not
corrected by normal refractive measures. Most patients with
this form of myopia encounter the condition around the early
adolescent years. Typically, pathological myopia is a
progressive disease and may be accompanied by abnormal blood
vessel growth in the retina. About 2 percent of people are
affected by this condition. There has been very limited
treatment for pathological myopia. One therapy,
photocoagulation, uses heat from a thermal laser to destroy
abnormal blood vessels that are present. Unfortunately, it
tends to damage adjacent healthy retinal tissue. It can
result in some immediate and permanent vision loss.
Recently, new treatments include the use of an injectable
substance to help treat this condition. A drug called
Verteporfin (Visudyne) combined with laser application may
help to stabilize the vision and prevent further
degeneration. This is known as photodynamic therapy.
However, the incidence of this advanced type of pathological
myopia, fortunately, is very rare.
The following question is raised by an interested
observer:
"If we believe in evolution, how can you believe
that millions of years of evolution led to a genetic defect
that affects such a huge number of people? Eyeglasses came
to the rescue to allow them to cope with their environment.
More than half the people in our Asian countries are myopic.
Is it possible that Nature has created a race of handicapped
people? The idea that myopia has advanced so forcefully does
not hold water. How does one explain that among hundreds of
people of Eskimo origin only the young people were myopic.
Old people and middle aged people in that geographical area
had excellent vision. To appreciate this information we must
consider that an important change occurred regarding the
Eskimos in the decades before that study. Their young began
to attend school. They began to abandon their traditional
way of life and started to follow their neighbor's modern
life. Near vision tasks and the strain it causes is believed
to be the real cause of myopia and not genetics."
